Best Development Practices
Conserving Pool-Breeding Amphibians in Residential
and Commercial Developments in the
Northeastern United States
Metropolitan Conservation Alliance
a program of
MCA Technical Paper Series: No. 5
1
Maine Audubon Society, 20 Gilsland Farm Road, Falmouth, Maine 04105
2
Wildlife Conservation Society, 2300 Southern Boulevard, Bronx, New York 10460
Best Development Practices
Conserving Pool-Breeding Amphibians in Residential
and Commercial Developments in the
Northeastern United States
Aram J. K. Calhoun, Ph.D.
Maine Audubon Society
1
/University of Maine
5722 Deering Hall
Orono, ME 04469
Michael W. Klemens, Ph.D.
Metropolitan Conservation Alliance/Wildlife Conservation Society
2
68 Purchase St., 3
rd
Floor
Rye, NY 10580
Cover photo © Michael W. Klemens/WCS
Literature citation should read as follows:
Calhoun, A. J. K. and M. W. Klemens. 2002. Best development practices: Conserving pool-breeding
amphibians in residential and commercial developments in the northeastern United States. MCA Technical
Paper No. 5, Metropolitan Conservation Alliance, Wildlife Conservation Society, Bronx, New York.
Additional copies of this document can be obtained from:
Metropolitan Conservation Alliance
Wildlife Conservation Society
68 Purchase Street, 3
rd
Floor
Rye, New York 10580
phone: (914) 925-9175
fax: (914) 925-9164
printed on partially recycled paper
ii
ACKNOWLEDGEMENTS
This project was made possible through support from the Metropolitan Conservation
Alliance, a program of the Wildlife Conservation Society; the Maine Audubon Society;
the Maine Department of Environmental Protection (104
(b)(3)
EPA funds); the Switzer
Foundation; and Sweet Water Trust.
We are grateful to the following people for their thoughtful reviews and participation in
regional meetings: Al Breisch, Matt Burne, Elizabeth Colburn, Rich Cook, Mark
Ferguson, Frank Golet, Hank Gruner, John Kanter, Ruth Ladd, Carol Murphy, Peter
Paton, and Chris Raithel. We especially thank Bryan Windmiller for his participation in
meetings and for providing us with his unpublished data on the impact of development
around vernal pools.
Our document was greatly strengthened by practical input and review from professionals
in the development community, especially by Michael Divney of Divney Tung Schwalbe,
LLP; Jeffrey Doynow of Fortune Homebuilders, LLC; Beth Evans of Evans Associates;
and Christian Sonne of Tuxedo Park Associates.
We thank David Ladd and Sally Stockwell for critical review of the manuscript. Phillip
deMaynadier also reviewed the manuscript and prepared Figure 4. Nick Miller reviewed
and edited the final manuscript, and assembled Figures 8 and 9. Linda Alverson, Lyman
Feero, and Frank Golet provided practical information on vernal pool photointerpretation
for Appendix 2. Jennifer Schmitz prepared the final layout of the document and provided
administrative support. Becca Wilson and Damon Oscarson also provided administrative
support during the preparation of this document.
iii
TABLE OF CONTENTS
Acknowledgements ........................................................................................................... ii
List of Tables ......................................................................................................................v
List of Figures.....................................................................................................................v
Preface............................................................................................................................... vi
I. Introduction ................................................................................................................1
What is a Vernal Pool?.................................................................................................1
What is Critical Terrestrial Habitat? ............................................................................2
Six Reasons to Conserve Vernal Pool Landscapes ......................................................3
Vernal Pool Animals ....................................................................................................4
II. Planning and Assessment...........................................................................................6
Step 1. Vernal Pool Mapping and Inventory ...............................................................6
Step 2. Ecological Assessment: Prioritizing Conservation Targets ............................7
Vernal Pool Assessment Sheet ..................................................................................9
Translating Science into Conservation.......................................................................10
Step 3. Putting a Conservation Plan into Action .......................................................11
Incorporation into Comprehensive, Development, or Master Plans......................12
Acquisition.............................................................................................................12
Easements ..............................................................................................................12
Overlay Zones........................................................................................................12
Vernal Pool Ordinances .........................................................................................13
Recognition and Voluntary Stewardship Programs...............................................13
Case Study: Jefferson Crossing—Innovative Conservation Design......................14
III. Management Goals and Recommendation ............................................................15
Management Areas and General Recommendations..................................................15
Vernal Pool Depression .........................................................................................15
Vernal Pool Envelope (100 ft. radius) ...................................................................15
Critical Terrestrial Habitat (100-750 ft.)................................................................16
Summary of Management Areas ...........................................................................17
Specific Issues and Recommendations.......................................................................18
Roads and Driveways ............................................................................................18
Site Clearing, Grading, and Construction Activities .............................................20
Stormwater Management.......................................................................................22
Accessory Infrastructure ........................................................................................23
Lighting..................................................................................................................24
Wetland Creation and Alteration ...........................................................................24
Post-Construction Activities ..................................................................................25
iv
Literature Cited ...............................................................................................................36
Appendix 1: Vernal Pool Regulation and Definitions .................................................41
Introduction..................................................................................................................41
Federal Regulation.......................................................................................................41
State Regulation...........................................................................................................42
Connecticut ............................................................................................................43
Maine .....................................................................................................................43
Massachusetts ........................................................................................................44
New Hampshire .....................................................................................................45
New York...............................................................................................................46
Rhode Island ..........................................................................................................47
Vermont .................................................................................................................47
Local Regulation..........................................................................................................48
Appendix 2: Using Aerial Photography to Locate Vernal Pools ...............................50
What Do I Use?............................................................................................................50
What Do I Look For?...................................................................................................51
Common Problems with Photo-Interpreting Vernal Pools ..........................................52
Are National Wetlands Inventory Maps Useful for Finding Potential Pools?.............53
Appendix 3: Resources for Identifying Vernal Pools ..................................................54
Vernal Pool Manuals ...................................................................................................54
Sources for Aerial Photography...................................................................................55
Government Sources..............................................................................................55
Private Sources ......................................................................................................56
Sources for Digital Orthophotography.........................................................................57
National Wetlands Inventory Maps .............................................................................57
Field and Lab Equipment.............................................................................................57
v
LIST OF TABLES
Table 1. Vernal Pool Indicator Species and State Conservation Status ............................5
Table 2. Vernal Pool Facultative Species and State Conservation Status.........................5
Table 3. Recommended Guidelines for Vernal Pools and Surrounding
Management Areas in Developing Landscapes ................................................18
LIST OF FIGURES
Figure 1. Vernal Pool Size and Structure .........................................................................27
Figure 2. Vernal Pool Seasonality ....................................................................................28
Figure 3. Cryptic Vernal Pools .........................................................................................29
Figure 4. Migration Distances
for
Vernal Pool Amphibian Indicator Species .................30
Figure 5. Examples of Vernal Pool Indicator Species of the Region ...............................31
Figure 6. Examples of Vernal Pool Facultative Species of the Region............................32
Figure 7. Mole Salamander (Ambystoma) Life Cycle ......................................................33
Figure 8. Aerial Photography Depicting Vernal Pools and Management Areas in
Varying Development Settings .........................................................................34
Figure 9. Vernal Pool Management Areas and Recommendations ..................................34
Figure 10. Design Schematics for Road and Driveway Construction to Reduce
Impacts on Pool-Breeding Amphibians...........................................................35
vi
PREFACE
Vernal pools and adjacent upland habitats contribute a vast amount of biodiversity to
landscapes of the northeastern United States. However, due to their small size, and a
variety of other issues, these habitats are disproportionately impacted by development
trends associated with regional urban and economic growth. As a result, vernal pools—
and the species that depend on them—are disappearing at a rapid rate. We must come to
terms with the complexities that surround the protection of vernal pools. The Best
Development Practices (BDPs) in this publication present a new approach to accomplish
this goal. This document also outlines steps to identify those vernal pools worthy of
protection. These BDPs are not, and we repeat not, new layers of regulation. They
provide a decision-making pathway that builds upon the strong tradition of home rule
within our region; they add value to that home rule by enabling municipalities to become
more effective stewards of their natural resources. We consider this a win-win solution—
one that should eliminate costly delays in project approval by giving local decision-
makers the ability to reliably identify wetlands worthy of protection and, by default, other
areas where a community can plan for additional growth and development.
As conservationists with real-world experience working in communities throughout New
England and New York, we realize our dual obligation. We need to help those
communities plan for their conservation needs. However, for conservation planning to be
truly effective, we must also provide information to help those communities plan for their
infrastructure and development needs. Ultimately, we view these BDPs as an exercise in
empowering local decision-makers to make better, scientifically credible, and consistent
decisions. In short, we seek to replace site-by-site reactive decision-making with a
framework for making multiple decisions. This is, in essence, planning. We are thankful
to the many people who contributed their time and efforts in the development of these
guidelines, including our colleagues in academia, resource management, municipal
government, and the development community. This is a work in progress. We look
forward to receiving feedback from users of these BDPs as to their effectiveness, and we
welcome suggestions for improvement.
Aram J. K. Calhoun, Ph.D. Michael W. Klemens, Ph.D.
Maine Audubon Society/ Metropolitan Conservation Alliance/
University of Maine Wildlife Conservation Society
1
I. INTRODUCTION
Vernal pools, and the adjacent critical terrestrial habitat used by vernal pool amphibians
during the non-breeding season, often overlap with land slated for residential or
commercial development. These Best Development Practices (BDPs) provide a
pragmatic approach to stewardship that encourages communities to attain a more
complete knowledge of their vernal pool resources, gather the information that enables
them to designate pools that are exemplary and worthy of protection, and then develop
strategies to protect them. Implementing these BDPs will better balance the needs of
vernal pool wildlife with human activities.
Best Development Practices for vernal pools are recommended conservation strategies
for residential and commercial development that minimize disturbance to vernal pools
and the surrounding critical terrestrial habitat. These BDPs:
¾ provide a framework for decision
makers to assess the quality of
individual pool habitats;
¾ have positive effects, or minimize
negative effects, of development on
natural resources;
¾ provide standards based on the best
available science;
¾ were developed with the participation of
state agencies, scientists, resource
managers, and developers in the New
York-New England region (the
Region); and
¾ are offered under the premise that
voluntary compliance, reinforced with
education, is an effective strategy for
protecting natural resources.
What is a Vernal Pool?
Vernal pools are wetlands of great interest to ecologists because, despite their small size,
they are characterized by high productivity and a unique assemblage of species adapted
to breeding in seasonally flooded wetlands (Skelly et al. 1999, Semlitsch 2000). Within
the last decade, interest in vernal pools has increased dramatically because of well-
publicized declines of amphibians, many of which breed in vernal pools and other small
wetlands (Pechmann et al. 1991, Lannoo 1998).
CAUTION! This document addresses only one
element of the vernal pool conservation equation.
Specifically, it targets pools located on privately
owned, relatively small parcels of land (usually
less than several hundred acres) at the suburban-
rural frontier, which have been slated for
development. We recognize that a
comprehensive protection strategy for vernal
pools must also include large tracts of
unfragmented habitat (thousands of acres) with
multiple pools. In New England and New York,
these lands are primarily held by Federal and
state government, and by the timber industry. To
address management of these large habitat blocks
in a working forest landscape, see Forest habitat
management guidelines for vernal pool wildlife
in Maine (Calhoun and deMaynadier 2001).
Owners of small woodlots may also apply the
harvest principles outlined in that document.
2
Plants and animals dependent upon vernal pools vary from state to state, as does the
definition of a vernal pool. The following is an operational definition based on those
common ecological functions identified by all states in the Region:
Vernal pools are seasonal bodies of water that attain maximum depths in
spring or fall, and lack permanent surface water connections with other
wetlands or water bodies. Pools fill with snowmelt or runoff in the spring,
although some may be fed primarily by groundwater sources. The duration of
surface flooding, known as hydroperiod, varies depending upon the pool and
the year; vernal pool hydroperiods range along a continuum from less than 30
days to more than one year (Semlitsch 2000). Pools are generally small in
size (< 2 acres), with the extent of vegetation varying widely. They lack
established fish populations, usually as a result of periodic drying, and
support communities dominated by animals adapted to living in temporary,
fishless pools. In the Region, they provide essential breeding habitat for one
or more wildlife species including Ambystomatid salamanders (Ambystoma
spp., called “mole salamanders” because they live in burrows), wood frogs
(Rana sylvatica), and fairy shrimp (Eubranchipus spp.).
A review of vernal pool definitions either adopted or developed by each state in the
Region is provided in Appendix 1; despite varying definitions, all pools share a unique
ecology. Where available, vernal pool-associated amphibian species are listed for each
state. Some states have not yet developed a definition for vernal pools, while others have
extremely specific definitions. Some definitions focus on physical characteristics of
pools while others are defined by the species of amphibians and invertebrates breeding in
the pools. Vernal pool identification guides are available to help citizens recognize these
habitats. Information about these guides is provided in Appendix 3. See Figures 1, 2, and
3 for images of vernal pools and associated amphibian breeding habitats.
What is Critical Terrestrial Habitat?
Pool-breeding amphibians depend upon both aquatic and terrestrial habitats for survival.
Most adult vernal pool amphibians in the Region spend less than one month in breeding
pools; the rest of their annual cycle is spent in adjacent uplands and wetlands (Semlitsch
1981, 2000). The surrounding forest provides critical terrestrial habitat for adult
amphibians and newly emerged juveniles throughout the year (Semlitsch 1998). In their
upland habitats, both young and adults need areas of uncompacted, deep organic litter;
coarse woody debris; and shade. These elements provide a suitable forest floor
environment for amphibians as they move through the forest, feed, and hibernate
(deMaynadier and Hunter 1995, DiMauro 1998). This dependence on the surrounding
landscape for survival has prompted one researcher (Semlitsch 1998) to refer to this
critical terrestrial habitat around pools as a “life zone,” instead of a “buffer zone.”
Conservation strategies that focus only on protecting breeding pools and associated
wetlands will most likely fail to maintain healthy amphibian populations. Protection of
critical terrestrial habitat must also be a priority (Marsh and Trenham 2001).
3
SIX REASONS TO CONSERVE VERNAL POOL LANDSCAPES
(1) UNIQUENESS
Fish-free pools provide optimal breeding habitat for a specialized group of amphibians that have evolved to
use these wetlands. Vernal pool amphibian eggs and larvae are extremely vulnerable to fish predation.
Even though vernal pool amphibians may breed in wetlands where fish are present, survival of eggs and
larvae in such environments is limited (Petranka 1998).
Many vernal pool amphibians return to breed in the pools where they developed (Duellman and Trueb
1986, Berven and Grudzin 1990, Sinsch 1990) and show little tendency to relocate if their breeding habitat
is disturbed (Petranka et al. 1994). Protecting vernal pools is a critical first step in conserving vernal pool
amphibians.
(2) HABITAT
Small wetlands and vernal pools contribute significantly to local biodiversity by supporting an abundance
of plants, invertebrates, and vertebrates that would otherwise not occur in the landscape (Semlitsch and
Brodie 1998, Gibbs 2000). Many small mammals, birds, amphibians, and reptiles use these wetlands for
resting and feeding. The average travel distance for frogs, salamanders, and small mammals is less than
0.3 km (Gibbs 1993, Semlitsch 1998, Semlitsch and Bodie 1998). The destruction of small wetlands in the
landscape increases the distances between remaining wetlands. Often, these distances are greater than
these animals can travel.
Large mammals (e.g., bear, moose) use these small wetlands as a food source.
Rare wildlife, including state-listed species, may use pools (see Tables 1 and 2).
(3) WEB OF LIFE
Vernal pools contribute a significant amount of food (e.g. amphibians and insects) to adjacent habitats
(Semlitsch et al. 1996, Skelly et al. 1999). This food production is fueled by decaying leaves (organic
matter) that are deposited in these pools each fall. After emerging from the vernal pool, wood frogs and
salamanders may be eaten by a wide variety of forest animals including snakes, turtles, birds, and small
mammals (Wilbur 1980, Pough 1983, Ernst and Barbour 1989). For example, in one Massachusetts vernal
pool, Windmiller (1990) found that the weight of all the vernal-pool breeding amphibians exceeded the
weight of all breeding birds and small mammals in the 50-acre upland forest surrounding his study pool.
He concluded that vernal pool amphibians exert a powerful influence on the ecology of surrounding
forests, up to 0.25 miles from the edge of the pool.
(4) SAFETY NET
Vernal pools are so small that they frequently fall through the regulatory cracks. Because vernal pools are
often small in size and hard to identify, they are inadequately protected by state or local wetland
regulations. An overview of state regulations for vernal pools is presented in Appendix 1.
(5) EDUCATIONAL RESOURCE
A vernal pool is a small ecosystem, easy to “wrap your arms around.” As such, it makes an ideal outdoor
laboratory for school children and adults. Often, a local pool can be visited or people discover that they
have a vernal pool on their own property. These pools are often rich with life and easier to become
intimate with than lakes or rivers.
(6) AESTHETICS
The rich array of moss-covered logs, delicate shades of greens and browns through dappled sunlight, and
the beauty of the vividly marked or masked amphibians that breed in these sylvan gems, are all
inspirations.
4
Amphibians, reptiles, and small mammals also need suitable upland habitat connecting
wetlands. These animals live in small populations or small units that, together, make a
larger population. These small populations often mix through dispersal of juveniles. For
example, small populations may replenish one another with new breeding stock when
natural catastrophes (e.g., drought or freezing) eliminate breeding adults or cause larval
failures in certain pools.
The average distance that a spotted salamander moves from a pool into the surrounding
forest is 386 feet; Jefferson salamanders may travel 477 feet (see Figure 4; Windmiller
1996; Semlitsch 1998; Faccio, in prep.) with as much as half the population, in some
instances, travelling even greater distances. Wood frog juveniles, on average, disperse
approximately 1,550 feet from a breeding pool (Berven and Grudzien 1990). Therefore,
long-term persistence of vernal pool amphibian populations depends on the availability
of habitat that connects local populations and enables dispersal among them (Semlitsch
and Bodie 1998).
Other animals (including reptiles, birds, and small mammals) also depend on these small
wetlands. Beetles and water bugs, for example, that overwinter in permanent water
migrate to vernal pools to breed and feed during the spring and summer. Medium- to
large-sized mammals, including raccoon, skunk, fox, deer, moose, and bear, visit pools to
feed on amphibian eggs and fresh green shoots emerging in spring or, later in the season,
on amphibians and insects. Therefore, the loss of individual vernal pools may weaken
the health of entire wildlife communities.
The bottom line: Connections between pools, through the upland landscape, must be
maintained to accommodate population movements—dispersal to and from pools for
breeding, foraging (feeding), resting, and replenishing locally extinct populations.
Vernal Pool Animals
Many definitions of vernal pools contain language referring to “obligate” or “indicator”
species. Obligate species depend upon vernal pools for successful breeding. However,
many so-called obligate species, such as wood frogs and spotted salamanders, breed in
other wetlands, including roadside ditches, artificial wetlands, and small ponds.
However, in many of these breeding sites, the survival of the eggs and production of
juveniles may be greatly diminished. We suggest using the term “indicator” species as a
more ecologically accurate term. A list of vernal pool indicator species of the Region,
with state conservation status information, is provided in Table 1; images of
representative indicator species are provided in Figure 5.
The term “facultative” species commonly refers to animals that use the pools for resting
and foraging; they might reproduce in vernal pools, but use other habitats for
reproduction as well. A list of vernal pool facultative species in the Region, with state
conservation status information, is provided in Table 2; images of representative
facultative species are provided in Figure 6.
5
Table 1. Vernal pool indicator species and state conservation status
(E = endangered, T = threatened, SC = special concern, P = present, A = absent).
INDICATOR SPECIES
RI CT MA NH VT ME NY
Blue-spotted salamander A
1
T/SC
2
SC P SC P SC
Jefferson salamander A SC SC SC SC A SC
Spotted salamander P P P P P P P
Marbled salamander P P T SC A
3
ASC
Tiger salamander A A A A A A E
Wood frog P P P P P P P
Spadefoot toad T E T A A A SC
Fairy shrimp
4
PPSC
5
PPPP
Featherfoil SC SC P P A T T
1
The blue-spotted salamander is extirpated in Rhode Island.
2
Blue-spotted pure diploid populations are listed as Threatened; the blue-spotted hybrid complex is listed as
Special Concern.
3
Unsubstantiated historic records; no populations have been located (Andrews 2001).
4
Fairy shrimp comprise a group of several related crustaceans throughout the region; “P” indicates presence
of one or more species.
5
In Massachusetts, the Intricate Fairy Shrimp is listed as Special Concern.
Table 2. Vernal pool facultative species and state conservation status
1
(E = endangered, T = threatened, SC = special concern, P = present, H = historical record only, A = absent).
FACULTATIVE SPECIES
RI
1
CT MA NH VT ME NY
Northern cricket frog A A A A A A E
Western chorus frog A A A A E A P
Four-toed salamander P P SC P SC SC P
Spotted turtle P P SC SC E T SC
Wood turtle SC SC SC P SC SC SC
Blanding’s turtle A A T SC A E T
Eastern box turtle P SC SC A A E SC
Eastern ribbon snake SC SC P P SC SC P
Eastern hognose snake SC SC P P A H SC
Ringed boghaunter dragonfly SC E E E A E H
1
For the purposes of this table, we have combined RI’s categories of SI (State Interest) and C (Concern) to
equal Special Concern (SC).
In-depth natural history accounts of pool-breeding amphibians and other species can be
found in Amphibians and Reptiles of Connecticut and Adjacent Regions (Klemens 1993),
Amphibians and Reptiles in Connecticut: A Checklist with Notes on Conservation Status
and Distribution (Klemens 2000), Maine Amphibians and Reptiles (Hunter et al. 1999), A
Field Guide to the Animals of Vernal Pools (Kenney and Burne 2000), A Guide to
Amphibians and Reptiles (Tyning 1990), and Salamanders of the United States and
Canada (Petranka 1998). See Figure 7 for examples of various stages within a mole
salamander (Ambystoma) life cycle.
6
II. PLANNING AND ASSESSMENT
This section complements Section III; Management Goals and Recommendations, by
providing step-by-step guidelines to develop a locally based conservation plan for vernal
pools. Conservation of vernal pool-breeding amphibian habitat is often most effective at
the local level where neighbors, planners, and other concerned citizens play an active
stewardship role. The planning process will take time and many hands to develop and
implement, and should not take the place of, or delay, the application of management
recommendations to individual projects as they arise.
Effective planning for vernal pool conservation at the
municipal level requires long-term vision instead of short-
term crisis reaction. This enables communities to plan for
the protection of vernal pool resources as a subset of their
overall master planning process. Therefore, it is not viewed
as inconsistent or discretionary, but rather as a legitimate
part of the jurisdiction's accepted and approved development
goals. Three sequential steps for local conservation are
presented: (1) vernal pool mapping and inventory, (2) vernal
pool ecological assessment, and (3) developing conservation
actions.
The goal of municipal-wide inventory and mapping exercises is to identify exemplary
pools or pool clusters in each community. This enables decision-makers, developers, and
citizens to understand which sites are considered to be of special significance as a
community resource.
Step 1. Vernal Pool Mapping and Inventory
Identifying vernal pools in your town might at first seem like a daunting task. In this
section we present some simple steps to get you started. Further tips and details for
identifying and mapping vernal pools are provided in Appendices 2 and 3.
Some vernal pools can be located by using aerial photography and National Wetland
Inventory (NWI) maps (see Appendix 2 for details). Inventory methods will vary
according to the availability of resources, the region of interest, and level of expertise. A
primer on identifying and mapping vernal pools using aerial photography and Geographic
NOTE: Clustering development
away from vernal pools and other
key resources is an important
planning tool. It not only
conserves open space, but also
reduces impervious surfaces and
accessory infrastructures.
CAUTION! The absence of a local vernal pool inventory and assessment should not forestall
implementation of Management Recommendations for individual projects and small scale
conservation initiatives. To address development and conservation concerns at individual
vernal pools, proceed to Section III: Management Goals and Recommendations.
7
Information Systems is available in the publication Massachusetts Aerial Photo Survey of
Potential Vernal Pools (Burne 2001).
Pre-inventory checklist:
Towns should consider the following issues before beginning the inventory process:
¾ Assess the status of wetland and vernal pool mapping in your town. It is possible
that outside contractors or researchers have already located vernal pools for
various projects.
¾ Is aerial photography available for your town? Is it appropriate for the mapping
project? (See Appendix 3 for aerial photo resources.)
¾ Do you have skilled volunteers for photo-interpretation and field identification of
vernal pools (using whatever criteria are applicable to your State or town)?
¾ What is the availability of funding (Federal or State) for conducting an inventory
or for contracting professionals to photo-interpret vernal pool resources?
¾ Is there a local university, land trust, or non-profit environmental organization
willing to offer guidance or other support?
Conducting the inventory:
1. Locate vernal pools through mapping, ground surveys, or a combination of both.
If possible, use a Geographic Positioning System (GPS) to obtain coordinates, so
that a vernal pool data layer can be created in a Geographic Information System
(GIS).
2. Mark locations of pools on tax maps, topographic maps, and, if available, in GIS.
3. Identify clusters of pools.
4. Conduct a biological inventory/field verification of as many pools as possible (see
Ecological Assessment steps, below).
5. Identify pools or pool complexes of conservation interest and work to develop a
protection strategy (see details provided later in this document).
Step 2. Ecological Assessment: Prioritizing Conservation Targets
Towns will not be able to protect every vernal pool. Therefore, it is important to know
which pools have the greatest ecological significance, and thus merit greater protection.
This can be accomplished by examining pools in the field and collecting biological data
to determine each pool's relative local importance. The following “Vernal Pool
Assessment Sheet” provides a means for doing this. Issues associated with such
assessments are described in the text below.
8
Vernal pools, or clusters of pools within a town, may vary tremendously in quality or
ecological significance. In general, towns should focus their conservation efforts on:
1. ecologically significant pools along size and hydroperiod (length of time the pool
holds water) gradients in order to protect a wide diversity of pool-breeding
invertebrates and amphibians;
2. pools with intact critical terrestrial habitat;
3. pools with long-term conservation opportunities (e.g., pools on public land, not-
for-profit lands, or in large tracts of relatively undisturbed private ownership); and
4. maintaining or restoring the adjacent terrestrial habitat for pools in agricultural or
suburban lawn/landscaped settings where the amount of forest cover is limited.
(Note: Although forested landscapes are preferred habitat, unfragmented
agricultural lands support dispersal of many amphibians and have the potential to
become even more valuable following old field succession or reforestation.)
Rating the ecological significance of an individual vernal pool is not a simple process.
For this reason, we provide general guidance for assessment of vernal pool ecological
significance based on two parameters: (1) biological value of the vernal pool, and (2)
condition of the critical terrestrial habitat. Assessment of a pool’s biological value
factors in species abundance, species diversity, and pool vulnerability. Assessment of the
critical terrestrial habitat includes the integrity of the vernal pool’s envelope (land within
100 feet from the pool’s edge) and critical terrestrial habitat (land from 100 to 750 feet
from the pool’s edge).
Note: The egg mass thresholds and critical thresholds of development around the pool
are based on current available science. Egg mass numbers may vary regionally
(Calhoun et al., unpub. data). We urge you to complete your own biological inventory
and assess egg mass densities that indicate important breeding pools in your area. These
numbers may be influenced by whether pools occur in clusters or are isolated. Low
numbers in clustered pools do not make the pool less valuable; instead, they may indicate
that the population has dispersed its breeding among all the pools.
We identify pools with 25% or less developed area in the critical terrestrial habitat as
having high priority. The few studies that have been conducted on this topic suggest that
development pressures (buildings, impermeable surfaces, roads, lawns) higher than 25-
30% cause declines in breeding populations (see “Translating Science into
Conservation,” below). See Figure 8 for examples of vernal pools and critical terrestrial
habitats under varying development scenarios.
9
VERNAL POOL ASSESSMENT SHEET
A. Biological Value of the Vernal Pool
(1) Are there any state-listed species (Endangered, Threatened, or Special Concern) present or
breeding in the pool?
Yes______ No__________
(2) Are there two or more vernal pool indicator species breeding (i.e., evidence of egg masses,
spermatophores [sperm packets], mating, larvae) in the pool?
Yes______ No__________
(3) Are there 25 or more egg masses (regardless of species) present in the pool by the
conclusion of the breeding season?
Yes______ No__________
B. Condition of the Critical Terrestrial Habitat
(1) Is at least 75% of the vernal pool envelope (100 feet from pool) undeveloped?
Yes______ No__________
(2) Is at least 50% of the critical terrestrial habitat (100-750 feet) undeveloped?
Yes______ No________
NOTE: For these purposes, “undeveloped” means open land largely free of roads,
structures, and other infrastructure. It can be forested, partially forested, or open
agricultural land.
Cumulative Assessment
Number of
questions
answered
YES in
category A
Number of
questions
answered
YES in
category B
Tier
Rating
1-3 2 Tier I
1-3 1 Tier II
01-2Tier III
1-3 0 Tier III
CAUTION! This rating system is designe
d
s
trictly as a planning tool, not as an officia
l
assessment tool. It will enable you to
determine the relative ecological value o
f
p
ools within your community. A Tier I
rating—which will most likely apply to only
a
minority of sites—denotes exemplary pools;
Management Recommendations should be
applied at these sites. For pools rated as Tie
r
II, proceed with care; you need more
information! Tier II pools will probably
constitute the majority of your vernal pool
resources; Management Recommendations
should be applied at these sites to the
maximum extent practicable. Tier II pools
might also be likely candidates for restoration
efforts (e.g., reforestation of the critical
terrestrial habitat).
10
TRANSLATING SCIENCE INTO CONSERVATION
Very little published research has addressed conservation concerns as they relate to vernal pool
habitats and wildlife. Therefore, the recommendations made in this document are based
primarily upon decades of field observations made by the authors. Those observations have
repeatedly demonstrated that pool-breeding wildlife populations experience precipitous
declines in response to developments within vernal pool envelopes and critical terrestrial
habitats.
Vernal pool research conducted in Massachusetts by Bryan Windmiller (unpub. data)
corroborates the authors’ conclusions. In one study, 25 acres (10 hectares) of upland forest
adjacent to a vernal pool in an urban setting was almost completely cleared. Within two years,
the pool’s wood frog population was extirpated (i.e., wood frogs became locally extinct). This
occurred despite the maintenance of an untouched 150-foot wide buffer of forested upland
around the pool and a forested wetland corridor adjacent to the pool. These findings
underscore the fact that narrow buffers alone—which are usually less than 150 feet—are
insufficient to protect wildlife populations.
In a second study, Windmiller tracked large populations of spotted salamanders, blue-spotted
salamanders, and wood frogs over a five-year period at two vernal pool breeding sites located
in close proximity. The land surrounding one of the pools remained largely intact throughout
the five years. At the second pool, approximately 25% of the existing forested upland within
about 1,000 feet (300 meters) was cleared for residential development after the first year of the
study. That development also greatly fragmented the remaining forested upland, although a
100-foot wide buffer was left untouched.
Within four years of the beginning of construction, spotted salamander numbers declined by
53%; the wood frog population was reduced by 40%. Blue-spotted salamander numbers also
declined over a two-year period following initial construction but subsequently recovered to
pre-development levels. In contrast, there was no reduction in amphibian breeding population
sizes at the undeveloped pool.
This study demonstrated that even a relatively small degree of development—covering
approximately 25% of the surrounding critical terrestrial habitat—can negatively impact vernal
pool wildlife. As in the first study, these impacts occurred despite the maintenance of a
forested buffer.
The recommendations in this document would limit the footprint of development to <25% of
the area surrounding productive vernal pools. This is a relatively conservative
recommendation, given the results of the second study. However, this threshold may be less
detrimental to resident amphibians if impacts are further reduced by following site-specific
recommendations made in Section III of this document.
11
Step 3. Putting a Conservation Plan into Action
From Awareness to Action
Informed with the results of a town-wide vernal pool survey and assessment, local
decision-makers can begin targeting for protection those significant vernal pools and
vernal pool clusters identified by their inventory and assessment. The advantage of such
a proactive planning exercise is that it replaces the site-by-site debate, which is focused
on individual pools, with an objective, scientifically informed process that can be applied
to all of a town's vernal pool resources. From a developer’s perspective, it provides
certainty as to where locally important or significant resources are located. This should
replace the status quo of vocal opposition to almost every development near a vernal
pool, regardless of the relative ecological viability of the pool.
Why is it important to simplify the presently confused process? Concern for vernal pools
has risen dramatically over the last decade. However, unless clarity and fairness become
integral parts of the decision-making process, we risk creating a backlash that could undo
all that has been achieved in heightening public awareness of these vital resources. With
increased knowledge and authority comes a responsibility to act in a consistent and fair
manner.
The most difficult task will be to determine from the Assessment and Mapping Exercise
where a community should focus their efforts. We recognize that it is impossible to
protect every vernal pool and its critical terrestrial habitat. Therefore, each community
should prioritize its efforts based on the results of its inventory and assessment. The
driving impetus for this priority-setting exercise is that a smaller number of well-
protected vernal pools (ideally those with intact envelopes and 75% undeveloped critical
terrestrial habitat) is far preferable, from a conservation standpoint, to a greater number
of pools “protected” in name only but lacking a sufficient envelope and critical terrestrial
habitat to sustain populations of vernal pool species. Once conservation priorities are
established, there are a variety of mechanisms local jurisdictions can employ to achieve
these goals.
CAUTION! The priority-setting exercise will focus conservation efforts on certain
p
arcels of property, and de-emphasize the importance of others. Because of the political
and emotional nature of such decisions, this priority-setting should be conducted with
maximum public input, so that the community understands the reasoning behind this
exercise. Priorities set by a small group, in the absence of broader public involvemen
t
and understanding, are likely to be challenged, and will ultimately be ineffective.
12
Incorporation into Comprehensive, Development, or Master Plans
Community Master Plans should incorporate the goals of these vernal pool protection
strategies, justification for those goals, and locations of exemplary pools that have been
targeted for stewardship. There are two primary reasons for doing this.
¾ Clarity: It is very important that all stakeholders (property owners, citizens,
developers, and local decision-makers) are aware of the goals of vernal pool
protection and which properties are considered essential to achieving those goals.
This provides some level of certainty in what is now a chaotic case-by-case
debate.
¾ Security: If a community clearly articulates its goals and objectives in a written,
publicly adopted document, and then consistently follows those guidelines, it is
less susceptible to legal challenges. Legal challenges against municipal decisions
are most successful if it can be demonstrated that those decisions are capricious,
without reasoned basis, and therefore inconsistent with a community’s articulated
goals and policies.
Acquisition
Acquisition is expensive and therefore not often feasible for communities. It is important
to spend limited acquisition dollars wisely. However, under certain circumstances it
might be possible for a community or land trust to acquire key properties. We
recommend acquisition measures for individual vernal pools only if they receive a Tier I
rating during the Vernal Pool Assessment Exercise; this acquisition should include at
least 750 feet of land from the vernal pool depression in all directions. In addition,
acquisition efforts are appropriate for large blocks of open space with clusters of pools of
any Tier.
Easements
Easements provide another mechanism to protect pools and their contiguous critical
terrestrial critical habitat. On subdivision projects where open space with vernal pools is
reserved we recommend that the developer convey a conservation easement to a local
land trust, the municipality, or a conservation or scientific not-for-profit organization. In
our experience this conservation strategy is far superior to reliance on a homeowner’s
association to protect these resources. The holder of the easement would be responsible
for ensuring that the terms of the easement are being met, and for informing the
neighbors about the stewardship needs of the property.
Overlay Zones
A resource overlay zone specifically designed to protect vernal pools can be adopted by
the town. This would be particularly effective where clusters of Tier I and Tier II pools
occur. While leaving town zoning in place, additional standards, requirements, and
13
incentives are applied in the overlay zone. It is recommended that a town adopt a
resource overlay zone to encompass those vernal pools and critical terrestrial habitats that
have been designated as protection priorities. The zone could provide a mix of
regulations and incentives to conserve vernal pools and preserve economic equity
including (but no limited to):
¾ minimal lot-clearing restrictions within the zone, allowing for more dense
clustering of development;
¾ density bonuses for tightly clustered, conservation-oriented subdivisions;
¾ reductions in road width standards including cul-de-sac radii, and prohibiting hard
90 degree, vertical curbing;
¾ establishment of a transfer of development rights (TDR) program where a
landowner gets credits in a developable portion of town in exchange for giving up
development credits in the overlay zone. TDRs are complicated to set up,
because one needs a sending district (the overlay zone) as well as a receiving
district (an area where development can be intensified). Therefore, this may not
be an appropriate strategy for many towns. However, towns could incorporate
some, if not all, of the practices recommended in this document as standards to
guide development in an overlay zone.
Vernal Pool Ordinances
Some municipalities have developed ordinances specifically to protect vernal pools and
their associated terrestrial habitat. Some of these use rating systems that place undue
emphasis on number of species present or on larger vernal pools. A better approach
would be to develop a local ordinance that incorporates both the assessment and best
development practices presented herein.
Recognition and Voluntary Stewardship Programs
Programs that encourage vernal pool stewardship could be set up to provide technical
advice and recognition to landowners who voluntarily protect and manage these
resources. Similar programs to register natural areas on private property have been
successful both as conservation strategies and in raising public awareness. Another
approach would be to publicly recognize those developments that incorporate vernal pool
Best Development Practices. Apart from demonstrating that it is possible to develop
responsibly, such recognition may be an important marketing tool. In Farmington,
Connecticut, a small development has been created that has turned a vernal pool and its
resources into the centerpiece of the development and its marketing (see Case Study:
Jefferson Crossing—Innovative Conservation Design for a Subdivision, page 14).
For other ideas for forming local partnerships for vernal pool conservation, see Vernal
Pool Conservation in Connecticut: An Assessment and Recommendations (Pressier et al.
2001).
14
CASE STUDY
Jefferson Crossing
Innovative Conservation Design for a Subdivision
On Talcott Mountain—a trap-rock ridge lying west of Hartford, Connecticut—a unique
conservation subdivision was created, incorporating many of the design principles
contained in this manual. Unlike most subdivisions, where natural resources are expected
to "fit" around a pre-conceived development pattern, Jefferson Crossing was designed with
great sensitivity to the site's natural features. The subdivision is named for the rarest
vernal pool breeding amphibian found on the site, the state-listed Jefferson salamander,
and for the fact that the salamanders will be able to cross freely through the site to their
breeding pool. To accomplish this, all structures and infrastructure were placed outside of
the vernal pool envelope. In addition, the design of the site maximized protection of the
critical upland habitat zone through a combination of conservation easements and lot-
clearing restrictions. Finally, the design allows for unimpeded movement of amphibians
and other wildlife throughout the forested site.
The execution of this novel design required a commitment from the developer to engage a
team of professionals to simultaneously integrate design, engineering, and natural resource
protection. For example, the proposed entrance road (using an existing access from a
demolished single family house) was determined to be too close to the vernal pool. The
developer acquired an additional lot of land specifically to enable relocation of the
entrance road well beyond the vernal pool envelope. The houses were clustered several
hundred feet away from the vernal pool; this, combined with lot clearing restrictions (no
more than 50% per lot) and conservation easements, resulted in 75% of the site being
protected in its natural state.
The roadways internal to the site have "Cape Cod curbing" to allow salamanders to move
freely. Stormwater is handled through swales and a single catch basin. To minimize
mortality of amphibians and other wildlife caught in the catch basin system, the water
moves through a grassy swale and into an open, biofiltration wetland. By using low
gradient curbing and eliminating the need for hydrodynamic separators, amphibian
mortality is minimized. Additional restrictions govern the design of individual driveways;
the use of pesticides, herbicides, and salts; and exterior lighting.
Jefferson Crossing will incorporate its unique conservation design as part of its marketing
strategy. The location of the homes tucked amongst the hemlock trees and nestled
between trap rock outcrops will attract a distinctive type of buyer, one that is looking to
live in greater harmony with the natural world. Ms. Anitra Powers, who developed this
property on the site of her family homestead, rejected conventional development patterns.
Her vision has turned what many would consider a liability into an asset.
15
III. MANAGEMENT GOALS AND RECOMMENDATIONS
Management goals are described below for each of three vernal pool management areas:
the vernal pool depression, the vernal pool envelope
(100 ft. from spring high water), and
the critical terrestrial habitat (100 to 750 ft from spring high water).
See Figures 8 and 9
for schematics of vernal pool management areas and recommendations.
Management Areas and General Recommendations
Vernal Pool Depression
Description and Function:
This area includes the entire vernal pool depression up to the spring high water mark.
Due to seasonal fluctuations in water levels, the vernal pool depression may or may not
be wet during the period when a development review is initiated. During the dry season,
the high-water mark generally can be determined by the presence of blackened leaves
stained by water or silt, aquatic debris along pool edges, water marks on surrounding
trees or rocks, or a clear change in topography from the pool depression to the adjacent
upland. The pool basin is the breeding habitat and nursery for pool-dependent
amphibians and invertebrates.
Desired Management:
For all Tiers, maintain the pool basin, associated vegetation and the pool water quality in
an undisturbed state.
Rationale:
Creating ruts or otherwise compacting substrates in and around the pool can alter the
pool’s water-holding capacity, disturb eggs or larvae buried in the organic layer, and alter
the aquatic environment. Excess slash, construction debris, or channeled stormwater in
the pool basin can hinder amphibian movement and alter water quality. Removal of pool
vegetation reduces the availability of egg-attachment sites.
Vernal Pool Envelope
(area within 100 feet of the pool's edge)
Description and Function:
The envelope consists of a 100-foot area around the pool, measured from the spring high
water mark. In the spring, high densities of adult salamanders and frogs occupy the
habitat immediately surrounding the pool. Similarly, in early summer and early fall,
large numbers of recently emerged salamanders and frogs occupy this same habitat. This
zone also maintains the water quality of the pool depression and provides a source of
leaves, which constitute the base of the pool food web.
16
Desired Management:
¾ Maintain an undeveloped forested habitat around the pool, including both canopy
and understory (e.g., shrubs and herbaceous vegetation).
¾ Avoid barriers to amphibian dispersal (emigration, immigration).
¾ Protect and maintain pool hydrology and water quality.
¾ Maintain a pesticide-free environment.
Rationale:
The integrity of the forest immediately surrounding the pool depression is critical for
maintaining water quality, providing shade and litter for the pool ecosystem, and
providing suitable terrestrial habitat for pool-breeding amphibian populations. Juvenile
salamanders are especially vulnerable to drying during the first months after emergence
(Semlitsch 1981). Such desiccation is much more likely where habitat elements
described above (e.g., leaf litter, shade) are lacking.
Critical Terrestrial Habitat
(area within 100-750 feet of the pool's edge)
Description and Function:
The critical terrestrial habitat extends 650 feet beyond the upland edge of the vernal pool
envelope (i.e., 750 feet beyond the edge of the pool). This area provides habitat for
amphibians during the non-breeding season for foraging, dispersing, and hibernating.
During the breeding season, adults migrate to pools through this zone.
Desired Management:
¾ Maintain or restore a minimum of 75% of the zone in contiguous (i.e.,
unfragmented) forest with undisturbed ground cover.
¾ Maintain or restore forested corridors connecting wetlands or vernal pools.
¾ Provide suitable terrestrial habitat for pool-breeding amphibian populations by
maintaining or encouraging at least a partially closed-canopy stand that will
provide shade, deep litter, and woody debris.
¾ Minimize disturbance to the forest floor.
¾ Where possible, maintain native understory vegetation (e.g., shrubs and herbs).
Rationale:
This area is needed to support upland populations of amphibians that breed in vernal
pools. Juvenile and adult wood frogs and mole salamanders select closed-canopy forests
during emigration and dispersal in managed forest landscapes (deMaynadier and Hunter
1998, 1999). Spotted salamanders often occur under, or closely associated with, woody
debris on the forest floor (Windmiller 1996). Other mole salamanders in the Region have
similar habitat needs. Rutting and scarification of the forest floor may prevent
17
salamanders from traveling to breeding pools by creating barriers along travel routes
(Means et al. 1996). Furthermore, if shallow ruts fill with water, vernal pool amphibians
may deposit eggs in ruts that do not hold water long enough to produce juveniles.
Created treatment wetlands (e.g., detention ponds) that are located near to vernal pools
often cause similar problems.
Roads (and associated development) within this zone limit the amount of terrestrial
habitat available to amphibian populations, fragment and isolate remaining pieces of
habitat, facilitate further development, and directly result in mortality of individuals.
Recent research conducted within Rhode Island has demonstrated that vernal pool-
breeding amphibians may be extremely sensitive to roads constructed within 0.62 miles
(1 km) of the vernal pools in which they breed (Egan 2001; Egan and Paton, in prep.).
Within this area, a mere 16 linear feet of road per acre (12 m/ha) was linked to significant
declines in numbers of wood frog egg masses; only 25 feet of road per acre (19 m/ha)
appeared to cause significant declines in numbers of spotted salamander egg masses.
Beyond these thresholds, even slight increases in road density severely limited the
potential of the areas surrounding pools to serve as nonbreeding habitat. Research by
Klemens (1990) has suggested that actual road configuration and pattern (i.e., “roads to
nowhere” and cul-de-sacs servicing subdivisions vs. linear roads connecting urban
centers), as well as road density, likely factors into amphibian population declines.
Although much of amphibian terrestrial life history is still unknown, researchers have
documented travel distances from breeding pools of juvenile wood frogs and adult mole
salamanders (see Figure 4 and reviews by Windmiller 1996, Semlitsch 1998). These
distances, along with all of the other factors discussed above, demonstrate that pond-
breeding amphibians require significant habitat surrounding pools.
Summary of Management Areas
To ensure successful breeding, vernal pool depressions must be left intact and
undisturbed. Excluding development and minimizing disturbances to the area
immediately surrounding the vernal pool (i.e., the pool’s envelope) will provide breeding
amphibians with a staging ground and will also help to maintain pool water quality.
Additional upland habitats are required during the nonbreeding season; such “critical
terrestrial habitats” can be maintained by limiting development and by applying
Management Recommendations (discussed in the following section). By carefully
considering the recommendations made for each of these three management areas, viable
populations of pool-breeding amphibians may be maintained. A summary of management
areas and desired outcomes is presented in Table 3.
18
Table 3. Recommended guidelines for vernal pools and surrounding management
areas in developing landscapes
Management
Area
(distance from
pool edge)
Area of Managed
Zone
(acres)
1
Primary Wildlife
Habitat Values
Desired
Management
Recommended
Guidelines
Vernal Pool
Depression
(0 ft)
0.2
Breeding pool; egg
attachment sites.
Good water quality
and water-holding
capacity;
undisturbed basin
with native
vegetation along the
margin.
No disturbance.
Vernal Pool
Envelope
(100 ft)
1.4
Shade and organic
inputs to pool;
upland staging
habitat for juvenile
amphibians.
Maintain forested
envelope around
pool; avoid barriers
to amphibian
movement; prevent
alteration of water
quality or pool
hydrology.
No development and
implementation of
Management
Recommendations
for this zone.
Critical Terrestrial
Habitat
(750 ft)
40
Upland habitat for
pool-breeding adult
amphibians (for
foraging, dispersing,
and hibernation).
Partially shaded
forest floor with
deep, moist
uncompacted litter
and abundant coarse
woody debris.
Less than 25%
developed area;
implementation of
Management
Recommendations
for this zone.
1
Approximate area, based on a 100-ft. diameter pool.
Specific Issues and Recommendations
In the following section management recommendations and standards for specific
development issues (e.g., road construction, stormwater management, and locations of
outbuildings) are provided. We encourage application of relevant recommendations.
Roads and Driveways
Conservation Issues:
¾ Road mortality is a major contributing factor in amphibian declines. This occurs by
direct mortality from vehicular traffic as well as increased vulnerability to
depredation and desiccation when amphibians cross roads.
19
¾ A number of studies have shown that roads (and urbanization) limit amphibian
dispersal and abundance (Gibbs 1998; Lehtinen et al. 1999; deMaynadier and Hunter
2000; Egan and Paton, in prep.). Certain species are reluctant to cross open,
unvegetated areas, including roads. Roads create barriers to amphibian dispersal.
Curbs and catch basins act as traps that funnel and collect amphibians and other small
animals as they attempt to cross roads.
¾ Roads are sources of chemicals and pollutants that degrade adjacent aquatic and
terrestrial habitats. These pollutants include, but are not limited to, salts, particulate
matter, and heavy metals. Eggs and larval amphibians are especially sensitive to
changes in water quality. Influxes of sediment can smother eggs, while salts and
heavy metals are toxic to larvae (Turtle 2000).
¾ Roads create zones of disturbance characterized by noise and light pollution. Both of
these pollutants interfere with the ability of amphibians to disperse across the
landscape. Noise pollution can also interfere with frog calling activity, which is an
essential part of their reproductive ecology.
¾ Roads can change hydrology (thus changing vernal pool quality and hydroperiod).
Management Recommendations:
¾ Roads and driveways should be excluded from the vernal pool depression and vernal
pool envelope.
¾ Roads and driveways with projected traffic volumes in excess of 5-10 cars per hour
should not be sited within 750 feet of a vernal pool (Windmiller 1996). Regardless of
traffic volumes, the total length of roads within the critical terrestrial habitat should
be limited to the greatest extent possible (Egan and Paton, in prep.).
¾ Use Cape Cod-style curbing (see Figure 10) or no-curb alternatives on low capacity
roads.
¾ Use oversize square box culverts (2 feet wide x 3 feet high) near wetlands and known
amphibian migration routes to facilitate amphibian movement under roads. These
should be spaced at 20-foot intervals and use curbing to deflect amphibians toward
the box culverts.
¾ Use cantilevered roadways (i.e., elevated roads that maximize light and space
underneath) to cross low areas, streams, and ravines that may be important amphibian
migratory routes.
¾ Cluster development to reduce the amount of roadway needed and place housing as
far from vernal pools as possible.
20
Site Clearing, Grading, and Construction Activities
Conservation Issues:
¾ Site clearing may result in crushing large numbers of amphibians and other animals.
¾ Site clearing and subsequent construction activities reduce terrestrial habitat available
to amphibians by decreasing the extent of the habitat, compacting soil, removing
downed woody debris, diminishing invertebrate food supplies, and decreasing the
number of small mammal burrows used for refuge by salamanders.
¾ Site clearing removes shade trees, which alters local climate, resulting in elevated
vernal pool water temperatures and increased drying of the forest floor. Amphibians
are sensitive to alterations in temperature and are highly subject to desiccation.
Elevated temperatures in vernal pools can increase algal productivity, thereby
reducing oxygen available to developing amphibian larvae and increasing the
likelihood of larval die-offs.
¾ Site clearing and grading increase erosion rates, which may result in sedimentation of
vernal pools. Increased sediment loads stress and kill both amphibian eggs and
developing larvae and can alter the structure and composition of in-pool vegetation
¾ Site clearing and grading create barriers to amphibian dispersal by stockpiling
mounds of soil, altering topographic contours, and creating open areas which
amphibians may be reluctant to cross because of increased vulnerability to predation
and desiccation.
¾ Use of silt fencing to control erosion creates major obstacles to movement of
amphibians and other small animals. Removal of silt fencing is rarely addressed, or
often overlooked in sedimentation and erosion control plans. The prevailing belief is
that more fencing, for longer periods, provides better environmental protection.
Therefore, fences are often left in place indefinitely, impeding the migratory patterns
of tens of thousands of animals. Erosion control structures should be removed within
30 days of final site stabilization. Erosion control berms—a sediment control
measure accepted in some states—are effective sediment barriers when properly
installed and provide less of an obstacle for amphibians and reptiles. Installation of
sediment control barriers to control erosion and sedimentation should be limited to
the down-gradient edge of any disturbed area and adjacent to any drainage channels
within the disturbed area.
¾ Site clearing and grading can de-water vernal pools by altering surface-water
drainage patterns associated with the pool.
¾ Site clearing can create water-filled ruts. These ruts intercept amphibians moving
toward the vernal pool and may induce egg deposition. Often the ruts do not hold
water long enough to allow development of the amphibians and therefore act as
“sinks” that result in population declines.
¾ Perc test holes act as pitfall traps, collecting large numbers of amphibians, turtles, and
other animals. Unable to climb the vertical walls of the perc scrape, these animals
perish.
21
¾ Site clearing and grading creates habitat for the establishment of invasive plants and
facilitates the movement of amphibian predators (edge species) into the forest
interior.
Management Recommendations:
¾ Minimize disturbed areas and protect down-gradient buffer areas to the extent
practicable.
¾ Site clearing, grading, and construction activities should be excluded from the vernal
pool depression and the vernal pool envelope.
¾ Site clearing, grading, and construction activities should be limited to less than 25%
of the entire vernal pool habitat (i.e., the pool depression, envelope, and critical
terrestrial habitat).
¾ Limit the area of clearing, grading, and construction by clustering development.
¾ Minimize erosion by maintaining vegetation cover on steep slopes.
¾ Avoid creating ruts and other artificial depressions that hold water. If ruts are
created, refill to grade before leaving the site.
¾ Refill perc test holes to grade.
¾ Use erosion and sediment control best management practices to reduce erosion.
Stagger silt fencing with 20 foot breaks to avoid disrupting amphibian movements or
consider using erosion control berms. Use combinations of silt fencing and hay bales
to reduce barrier effects. Re-seed and stabilize disturbed areas immediately;
permanent stabilization for revegetated areas means that each area maintains at least
85% cover. Remove silt fencing as quickly as possible and no later than 30 days
following final stabilization. Minimize use of silt fencing within 750 feet of vernal
pools. Erosion control berms can be leveled and used as mulch or removed upon
final stabilization.
¾ Limit forest clearing on individual house lots within the developed sections of the
vernal pool management zones to no more than 50% of lots that are two or more acres
in size. Encourage landscaping with natural woodland, containing native understory
and groundlayer vegetation, as opposed to lawn.
¾ Silt fencing should be used to exclude amphibians from active construction areas. At
Jefferson Crossing (see Case Study), each house construction site was encircled by a
silt fence barrier to keep salamanders away from heavy machinery, excavation, and
stockpiling. However, construction activities should, ideally, occur outside of peak
amphibian movement periods (which include early spring breeding and late summer
dispersal).
22
Stormwater Management
Stormwater management provides an excellent example of how addressing one set of
environmental issues can result in creation of other environmental impacts, as follows.
Conservation Issues:
¾ Systems of curbs, catch basins, and hydrodynamic separators—designed to capture
and treat road runoff—intercept, trap, and kill amphibians and other small animals
crossing roads. These systems can also de-water vernal pools by releasing water into
another watershed, or downslope of a vernal pool. Hydrodynamic separators are
especially problematic because they remove particulate matter from stormwater via
swirl chambers. These devices cannot distinguish between sediments and small
vertebrates; thus, thousands of amphibians can be killed in one unit.
¾ Systems of gutters, leaders, and infiltration systems designed to capture and manage
roof runoff can drain wetlands if the roof water is captured and released in another
watershed, or below the vernal pool area.
¾ Systems designed to capture road and roof runoff can alter how long pools hold water
by transporting additional water into the vernal pool watershed. This is especially
critical in short hydroperiod pools that support fairy shrimp.
¾ Vernal pools and other small wetlands have been inappropriately used as stormwater
detention pools and biofiltration basins. These practices create a degraded aquatic
environment subject to sediment loading, pollutants, and rapid changes in water
quantity, quality, and temperature.
¾ Stormwater detention basins and biofiltration ponds can serve as decoy wetlands,
intercepting breeding amphibians moving toward vernal pools. If amphibians deposit
their eggs in these artificial wetlands, they rarely survive due to the sediment and
pollutant loads, as well as fluctuations in water quality, quantity, and temperature.
Management Recommendations:
¾ Vernal pool depressions should never be used, either temporarily or permanently, for
stormwater detention or biofiltration.
¾ Detention and biofiltration ponds should be located at least 750 feet from a vernal
pool; they should never be sited between vernal pools or in areas that are primary
amphibian overland migration routes, if known.
¾ Treat stormwater runoff using grassy swales with less than 1:4 sloping edges. If
curbing is required, use Cape Cod curbing. Maximize open drainage treatment of
stormwater.
¾ Use hydrodynamic separators only in conjunction with Cape Cod curbing or swales to
avoid funneling amphibians into treatment chambers, where they are killed.
¾ Maintain inputs to the vernal pool watershed at pre-construction levels. Avoid
causing increases or decreases in water levels.
23
¾ Minimize impervious surfaces (i.e., surfaces that do not absorb water) to reduce
runoff problems and resulting stormwater management needs. Use of grass pavers
(concrete or stone that allows grass to grow) on emergency access roads and in low
use parking areas is recommended. Use of phantom parking is also recommended.
Zoning formulae often require more parking spaces than are actually needed. Under a
phantom parking strategy, sufficient land is reserved for projected parking
requirements, but only a portion of the parking area is constructed at the outset.
Additional areas are paved on an as-needed basis.
¾ Examine the feasibility (which varies by location) of reducing the road width standard
to achieve conservation goals (i.e., minimize the footprints of roads). This is often
done in tandem with development clustering, to reduce impervious surfaces and
disturbance areas.
Accessory Infrastructure
Conservation Issues:
¾ In many communities, a different standard is employed when evaluating impacts of
accessory structures and functions (e.g., outbuildings, pools), as compared to homes
and other buildings. There appears to be no legal basis for this distinction, but rather
a discretionary sense that, for example, the construction of a swimming pool in a
regulated area surrounding a wetland is different (i.e., less harmful) than construction
of a house within the same area. For pool-breeding amphibians, there is no
distinction; the siting of accessory structures near vernal pools is a major conservation
issue resulting in the loss of millions of amphibians and other small creatures each
year.
¾ Below-ground swimming pools may function as large animal traps, capturing
salamanders, frogs, small mammals, snakes, and turtles. Trapped animals either
drown or are killed by chlorinated water.
Management Recommendations:
¾ Accessory structures should be excluded from the vernal pool depression and vernal
pool envelope.
¾ Below-ground swimming pools located within the critical terrestrial habitat of a
vernal pool should be surrounded by some sort of barrier. A fine mesh wire at the
base of a picket fence or a one-foot high, 90-degree, curb or barrier would deter
amphibians from travelling into the pool.
24
Lighting
Conservation Issues:
¾ Light spillage in wetlands and woodlands affects a diversity of wildlife species (e.g.,
see www.urbanwildlands.org). Recent increases in the use of security and garden
lighting have intensified problems associated with light spillage. Scientific
experiments and anecdotal evidence suggest that changes in lighting may affect frog
reproduction, foraging, predator avoidance, and social interactions (Buchanan 2002).
Buchanan demonstrated in laboratory experiments that dark-adapted frogs exposed to
rapid increases in illumination may be temporarily ‘blinded’, unable to see prey or
predators until their eyes adapt to the new illumination. Similarly, there is evidence
that salamanders are strongly attracted to light (S. Jackson, University of
Massachusetts, pers. comm.). This behavioral response could divert salamanders
away from breeding sites; it could also make them more vulnerable to predation or
road mortality during migrations. Artificial lights that emit unusual spectra may
especially disrupt these migration patterns (Wise and Buchanan 2002). Research on
the effects of lighting on amphibian behavior and larval development is ongoing.
Management Recommendations:
¾ Exterior and road lighting within 750 feet of a vernal pool should use low spillage
lights—those that reflect light directly downward onto the area to be illuminated. A
variety of products to accomplish this goal are now on the market. Avoid using
fluorescent and mercury vapor lighting.
Wetland Creation and Alteration
Conservation Issues:
¾ Extensive structural complexity (i.e., the arrangement of different layers of trees,
shrubs, and plants in a small wetland) supports a diversity of small vertebrates and
invertebrates. When wetlands are altered through clearing of vegetation,
impoundment of water, or dredging, the microhabitats used by many species of
wildlife are changed or lost. This results in unsuitable breeding habitat for many
amphibians, including vernal pool species.
¾ Wetland creation is another byproduct of development and landscape alteration.
Created wetlands are often mandated as replacement for other wetlands lost during
development; sometimes, they are also incorporated as design features in a
subdivision. Similar to altered wetlands, created wetlands usually lack the structural
diversity, microhabitats, and hydrology to support vernal pool breeding amphibians.
25
¾ Altered and created wetlands often support highly adaptable, widespread, “weedy”
species (e.g., bullfrogs or green frogs). These species prey upon, or successfully
outcompete, vernal pool-breeding amphibians, which reduces or locally eliminates
populations of these habitat specialists.
¾ Created wetlands that do not have the appropriate habitat often attract breeding
amphibians. Eggs laid in these “decoy” pools often do not survive. Such pools serve
to trap breeding amphibians and might result in local population declines.
Management Recommendations:
¾ Alteration of existing conditions within vernal pools and other small wetlands should
be avoided.
¾ Creation of ponds and similar wetlands should be avoided within 750 feet of a vernal
pool.
¾ Redirect efforts from creating low value, generalized wetlands to enhancing
terrestrial habitat around vernal pools. These enhancements could include
reforestation of post-agricultural lands within 750 feet of a vernal pool, restoration of
forest, importing additional cover objects (e.g., logs, stumps), and removal of
invasive plants and animals.
Post-Construction Activities
After a construction project has been completed, there are long-term development issues
that continue to affect vernal pools. Even projects that are designed with ecological
sensitivity can cause problems over time, due to the day-to-day activities of humans.
Many of these longer-term problems can be anticipated and avoided during the overall
design and approval process of the project.
Conservation Issues:
¾ Pest animals are those species that humans encourage by subsidizing food resources
and fragmenting habitats. Raccoons, foxes, and skunks fall into this category. These
artificially inflated mammal populations often prey heavily on vernal pool
amphibians during the breeding season.
¾ Domestic animals, including pets, can threaten pool wildlife through predation or
physical disturbance of habitats.
¾ Protected areas around wetlands, over time, are intruded upon by humans. Impacts
include dumping, forest clearing, dirt biking, introduction of free-ranging dogs and
cats, favoring of invasive plant species, fires, collection of native wildlife, and other
activities that degrade the vernal pool and its envelope.
26
¾ Increased pesticide use is usually associated with suburban landscaping. These toxins
often enter into the vernal pool watershed and compromise the pool’s ability to serve
as a breeding site and nursery for vernal pool species.
Management Recommendations:
¾ Discourage predators by making garbage and other supplemental food sources
unavailable.
¾ Consider keeping cats indoors at all times. This would reduce predation on a wide
variety of species, ranging from pool-breeding amphibians to ground-nesting birds.
Attaching bells to cat collars does not significantly reduce the ability of cats to prey
on small vertebrates.
¾ Mark the edge of a protected area (e.g. the critical terrestrial habitat) with permanent
markers. Well-marked boundaries make enforcement of restricted areas clear to both
homeowners and the local wetlands enforcement agency. For example, granite
monuments or stone cairns could be placed every 10 feet around a protected area. In
cases where intrusion is a concern, small sections of stone wall could be erected;
these walls should be discontinuous, so that they do not impede amphibian dispersal.
¾ Use covenants or deed restrictions to assure that the vernal pool and its envelope are
conserved and that pesticide use, lot clearing, and other degrading activities are kept
out of associated areas. Assign the homeowner or homeowner's association with
responsibility for ensuring that conditions of the covenant or deed restriction are met.
Provisions should also be included to allow a third-party, such as the town or local
land trust, with adequate notice, to enter the property and conduct appropriate
management and remediation, charging the homeowner for these services.
¾ In the case of a homeowner's association or other type of multiple tenant
arrangement, a stewardship manual could be prepared that would educate each
purchaser, or lessee, as to the unique nature of the property they are purchasing or
renting, what their collective obligations to protect the resource entail, and where to
obtain additional assistance or information.
¾ A conservation easement, covering at minimum the vernal pool depression and vernal
pool envelope (and, preferably, including land within the "critical terrestrial habitat"),
could be held by a municipality, land trust, or other non-governmental organization.
27
Figure 1. Vernal Pool Size and Structure
© Michael W. Klemens/WCS
A “classic” vernal pool lying in a basin, or
depression, in deciduous woodland.
Although these habitats are important for vernal
pool-breeding species, only a small percentage of
pools within the Region have this distinctive
signature. Many cryptic (i.e., non-classic) vernal
pools are found within larger wetland systems.
Figure 3 provides some examples of the wide
diversity of these cryptic vernal pools.
© Aram J. K. Calhoun
Small vernal pool.
Most vernal pools are quite small, as typified by
this 0.25-acre pool. This photograph depicts two
important components of vernal pools:
microtopographic complexity (as illustrated by a
patchwork of hummocks, moss, and logs) and
vertical stratification (which consists of a variety
of layers of herbaceous plants, low shrubs, tall
shrubs, and trees). Collectively, these elements
provide a tremendous variety of microhabitats,
which support the rich diversity of life in and
around vernal pools.
Large vernal pool.
Although vernal pools average
considerably less than one acre in size,
some are as large as two acres. Large
vernal pools are not uncommon in the
northern part of the Region.
Aerial view of vernal pool.
Many pools exhibit this concentric,
ring-like pattern of habitat zones.
© Ed Hammer/EPA
© D. Demello/WCS
28
Figure 2. Vernal Pool Seasonality
© Nicole S. Klemens
© Michael W. Klemens
© Michael W. Klemens
Dry vernal pool in August.
Most vernal pools will begin
to refill in the autumn, when
plants become dormant and
use less water. Spotted
salamanders and wood frogs
breed at this site. The pool is
also used by spotted turtles
and box turtles.
Drying vernal pool
in late June.
Low water levels—and
resulting low oxygen
levels—exclude fish from
vernal pools, which would
otherwise decimate larval
amphibian populations.
This site provides breeding
habitat for Jefferson
salamanders, spotted
salamanders, and wood
frogs. Blanding's turtles,
wood turtles, and box
turtles also use this pool.
Snowbound vernal pool in
late March.
Vernal pool levels are
generally highest during
winter and spring. This
pool contains breeding
populations of Jefferson
salamanders, spotted
salamanders, and wood
frogs.
29
Pool with seasonally flooded wet meadow.
Larval amphibians exploit the rich food
resources and warmer water of the meadow. As
the meadow dries, the larvae retreat into the
deeper pool to complete their development. Tiger
salamanders breed here; the site also provides
habitat
f
or box turtles and ribbon snakes.
Red maple swamp with carpet of Sphagnum moss.
Spotted and four-toed salamanders, as well as wood
frogs, breed in deeper pools of forested wetlands.
These water-filled pockets are often created when
trees are uprooted during severe storms.
© Michael W. Klemens
© Laura Tessier
© Michael W. Klemens/WCS
© Michael W. Klemens
Figure 3. Cryptic Vernal Pools
Semi-permanent pool.
Jefferson and spotted salamanders breed
in this wetland. This pool rarely dries up
completely, as opposed to classic vernal
pools, which dry up annually.
Floodplain swamp.
Blue-spotted salamanders and wood frogs
breed in depressions and oxbows within
river floodplains. When floodwaters
recede, these pools become isolated;
therefore, they do not provide breeding
habitat for fish. Four-toed salamanders,
spotted salamanders, and wood turtles
also use this habitat.
30
Figure 4. Migration Distances for Vernal Pool Amphibian Indicator Species*
Adult salamander migration distances are provided as means (and ranges). Two values are reported
for wood frogs (Rana sylvatica)—mean juvenile dispersal distance and maximum adult migration
distance. The number of studies contributing data (n) is listed for each species (sources include:
Windmiller 1996; Semlitsch 1998; Berven and Grudzien 1990; Faccio, in prep.).
*Distances are not to scale.
Wood Frog
Spotted Salamander
Jefferson Salamander
386 ft 477 ft 1550 ft. / 3835 ft
(0-817 ft) (15-2051 ft) n=2
n=8 n=5
31
© Paul Fusco/CT DEP
Jefferson Salamander (Ambystoma jeffersonianum) Spotted Salamander (Ambystoma maculatum)
Wood Frog (Rana sylvatica) Eastern Spadefoot Toad (Scaphiopus holbrookii)
Fairy Shrimp (Eubranchipus sp.) Featherfoil (Huttonia inflata)
Figure 5: Examples of Vernal Pool Indicator Species of the Region
© Richard G. Zweifel/AMNH
© Maine Natural Areas Program
© Leo P. Kenney
© Richard G. Zweifel/AMNH © Richard G. Zweifel/AMNH
32
© Don Sias
© Geoff A. Hammerson
© Michael W. Klemens
© Geoff A. Hammerson
© Geoff A. Hammerson
Four-toed Salamander (Hemidactylium scutatum) Spotted Turtle (Clemmys guttata)
Blanding's Turtle (Emydoidea blandingi) Eastern Box Turtle (Terrapene c. carolina)
Eastern Ribbon Snake (Thamnophis s. sauritus) Ringed Boghaunter (Williamsonia lintneri)
Figure 6: Examples of Vernal Pool Facultative Species of the Region
© Francis C. Golet/URI
33
© Louis N. Sorkin
© Geoff A. Hammerson
© Geoff A. Hammerson© Chris Raithel
© Geoff A. Hammerson
Figure 7: Mole Salamander (Ambystoma) Life Cycle*
*Source: Klemens 2000. Text reprinted by permission of the author and the Connecticut Department of
Environmental Protection.
Male salamanders migrate to vernal pools
under the cover of darkness and deposit
spermatophores on the pool bottoms.
Females enter the pond during nightime
rains, engage in courtship, and are fertilized
by picking up the spermatophores. They
then deposit clumps of jelly-coated eggs.
Bushy-gilled larvae hatch. They are
voracious feeders and develop rapidly for
several months.
Larvae metamorphose. The pattern of this
newly-transformed marbled salamander
metamorph differs markedly from an adult.
Adult patterns appear several weeks
to months after metamorphosis, as
seen here in the adult marbled
salamander (Ambystoma opacum
).
35
Source: Jefferson Crossing, Farmington, CT; Buck and Buck Engineers, Hartford, CT.
Figure 10: Design Schematics for Road and Driveway Construction to Reduce
Impacts on Pool-Breeding Amphibians
36
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41
Appendix 1
Vernal Pool Regulation and Definitions
Introduction
Wetlands are more extensively regulated than any other habitat or landscape unit within
our Region, due in large part to their ecological sensitivity and the number of ecological
services they provide (e.g., flood abatement, water quality improvement, groundwater
recharge). However, despite the vast amount of resources devoted to wetlands—at
Federal, state, and local levels—regulations addressing vernal pools are, for the most
part, ineffective or nonexistent. Most wetland regulations contain lower size thresholds;
therefore, impacts to small wetlands such as vernal pools often “slip under the radar” of
regulatory agencies. In addition, although many regulatory agencies have jurisdiction
over upland “buffers” or “setbacks” surrounding wetlands, such jurisdiction rarely
extends beyond 150 feet from wetland edge—a distance that is insufficient for
maintaining vernal pool wildlife populations. Another hurdle lies in the establishment of
a standardized definition of “vernal pool;” numerous, widely varying definitions exist
within the Region. The following text discusses the details and limitations of wetland
regulations within the Region, as they pertain to vernal pools.
Federal Regulation
Dredge and fill activities in freshwater wetlands are regulated at the federal level through
Section 404 of the Clean Water Act (CWA). The Army Corps of Engineers (the Corps)
oversees this program. However, regulation does not necessarily equal protection. Keep
in mind that the CWA was created to protect water quality, not wildlife habitat. Often,
permits are issued for relatively small impacts; however, vernal pools often fall within the
exempted size threshold. Most states in the Region have Programmatic General Permits
(PGP), which currently replace all Nationwide Permits. PGP’s are intended to expedite
the review of "minimal" impact work in coastal and inland waters and wetlands. General
permits are also supposed to be authorized for activities that are "substantially similar in
nature." Any proposed project that does not qualify for the PGP must then go through the
individual permit review process. A PGP is designed to work in concert with a State's
wetland regulatory program. Ideally, the Corps allows the State regulatory agency to
take the lead on permitting of smaller impact projects. Any of the Federal resource
agencies can "kick out" a project for screening as an individual permit if the agency can
document that the wetland or water body impacts would be more than "minimal," which
really isn't difficult to do. The level of scrutiny and review is generally less for a PGP
project than for an individual permit project. For example, all applicants have to
demonstrate that they have first avoided and then minimized the amount of wetland
impact, but the amount of documentation required by a PGP application is generally quite
a bit less than for an individual permit.
42
Maine—Maine has a "kick out" for vernal pools from Category I of the Programmatic
General Permit.
Connecticut, Vermont and Massachusetts—PGPs require screening reviews for fill in
vernal pools. A vernal pool is defined in the PGP as an “…often temporary body of
water occurring in a shallow depression that fills during spring rains and snow melt and
typically dries up during summer months. Vernal pools support populations of
specialized species, which may include wood frogs, mole salamanders (Ambystoma),
fairy shrimp, fingernail clams and other invertebrates. A feature common to vernal pools
is the lack of breeding populations of fish. Some shallow portions of permanent
waterbodies also provide vernal pool function by supporting breeding populations of
vernal pool species. Old, abandoned, artificial depressions may provide these necessary
breeding habitats."
Another administrative tool is known as the "pre-construction notification" process; this
process allows so-called minor wetland fillings to be reported to the Corps after the fact,
so that the Corps can track acreage lost. The Corps is aware of the limitations of these
approaches, and recently has begun to curtail the use of these programs in areas of
ecological concern, such as the New York City Watershed. However, in many sections
of the Northeast, filling of small wetlands continues; among the hardest hit are those
wetlands supporting vernal pool-dependent species.
Because of a recent Supreme Court decision (SWANCC; January 9, 2001), the Corps no
longer regulates isolated wetlands by invoking the Migratory Bird Act. This ruling puts
even more pressure on individual states to take the lead in protection of these resources.
Other federal agencies involved in wetland permitting include the US Fish and Wildlife
Service, which serves in an advisory capacity on projects that may affect wildlife
resources, and the Environmental Protection Agency, which has veto power over Corps
decisions.
State Regulation
Each state in the Region has a wetland protection statute that regulates activities in
jurisdictional wetlands. The specifics of the regulatory program and permit process vary
from state to state, but small wetlands, including vernal pools, receive the least protection
under most state regulatory programs. For example, New York has a regulatory
minimum-size threshold of 12.4 acres, considerably larger than the majority of vernal
pools. The only vernal pools protected at the state level in New York are those that: 1)
contain a State-listed endangered or threatened species and 2) have been added, through a
public hearing process, to the official map of State-regulated wetlands. Even
Massachusetts, which has led the region with its program of volunteer-driven vernal pool
certification, is unable to protect sufficient critical terrestrial habitat to sustain the
amphibians that breed within those certified pools. In fact, most states do not include the
terrestrial habitat associated with isolated wetlands in their wetland regulations.
43
Note: Under all Federal and state regulations, even where vernal pools are regulated,
the critical terrestrial habitat around them is not. Sometimes a small buffer around the
wetland is maintained, but this does not provide the necessary upland habitat for pool-
breeding amphibians.
Connecticut
Overview:
Legislation passed in 1995 (P.A. 95-313) and included in the Inland Wetlands and
Watercourses Act (originally passed in 1972) expanded the definition of
“watercourse” to include, “all other bodies of water, natural or artificial, vernal or
intermittent.” Regulation occurs at the municipal level via town Inland Wetlands
Commissions. While not specifically defining “vernal pools” this amendment
promoted their inclusion in municipal inland wetland regulations. However, no
towns have developed regulations regarding vernal pools specifically. The
Connecticut Department of Environmental Protection has model regulation and
guidance documents.
Definition:
There is no official definition for a vernal pool. The University of Connecticut
and the Forest Stewardship Program (Donahue 1995) have issued guidance for
identification and protection of vernal pools. They recommend the following
physical features and the presence of one or more obligate species:
a. water for approximately 2 months during the growing season,
b. a confined depression that lacks a permanent outlet stream,
c. no fish, and
d. dries out in most years.
The following definition of a vernal pool was prepared by the Connecticut Vernal
Pool Working Group: “seasonal or permanent watercourse in a defined
depression or basin, that lacks a fish population and in most years supports
breeding and development of amphibian or invertebrate species recognized as
obligate to such watercourses.
Proposed obligate species:
fairy shrimp, spotted salamander, eastern spadefoot toad, Jefferson salamander,
marbled salamander, wood frog.
Maine
Overview:
In organized towns, wetlands are regulated by the Department of Environmental
Protection (DEP) through the Maine Natural Resources Protection Act (NRPA
44
1996). Vernal pools generally meet Federal and State wetland definitions and are
subject to regulation. However, the degree of environmental review in Maine
depends upon the size of the impact to the wetland. Impacts to wetlands that are
less than 4,300 ft
2
(approximately 0.1 acres) require no reporting. Impacts
between 4,300 ft
2
and 15,000 ft
2
(approximately 0.3 acres) require the lowest
level of review, Tier 1, and have an expedited 30-day review process with no
requirement of compensation for wetland loss. Tier II (impacts >15,000 ft
2
to 1
acre) and Tier III (impacts > 1 acre) require greater documentation and require
input from professional delineators.
In the unorganized towns and plantations, the Land Use Regulation Commission
(LURC) regulates activities in wetlands. LURC’s language on vernal pools is
consistent with the statutory provisions in NRPA. However, LURC’s regulatory
authority over vernal pools is tied to the Maine Department of Inland Fisheries
and Wildlife’s (MDIFW) ability to define and identify vernal pools. In
unorganized towns, MDIFW is relying on a voluntary, cooperative strategy for
protecting vernal pools.
“Significant vernal pools" (SVPs) were listed as “Significant Wildlife Habitat” in
Maine’s 1995 revision of the NRPA. Designation of SVP’s is pending formal
adoption of a definition of “significant vernal pools” and development of a system
to pre-identify vernal pools.
Proposed definition:
The following definition has been approved by the Maine Vernal Pool Working
Group, and will be incorporated into the Natural Resources Protection Act.
"Vernal pools are naturally-occurring, temporary to permanent bodies of water
occurring in shallow depressions that typically fill during the spring and fall and
may dry during the summer. Vernal pools have no permanent or viable
populations of predatory fish. Vernal pools provide the primary breeding habitat
for wood frogs, spotted salamanders, blue-spotted salamanders and fairy shrimp,
and often provide habitat for other wildlife including several endangered and
threatened species. Vernal pools intentionally created for the purposes of
compensatory mitigation are included in this definition."
Indicator species:
wood frog, spotted salamander, blue-spotted salamander, fairy shrimp
Massachusetts
Overview:
The Massachusetts Wetlands Protection Act Regulations (310CMR 10.00, 1996)
include measures for the regulation of vernal pool habitat, as long as it is located
within another category of wetland regulated by the Act, and as long as it has
45
been certified by the Massachusetts Division of Fisheries and Wildlife (MDFW)
prior to the filing of a Notice of Intent by an applicant. A vernal pool must be
certified and mapped by the Natural Heritage and Endangered Species Program
(NHESP) prior to permitting of a wetland impact. Criteria are available through
NHESP.
Definition:
The Massachusetts Wetlands Protection Act Regulations (310 CMR 10.00,1996)
define vernal pools as “confined basin depressions which, at least in most years,
hold water for a minimum of two continuous months during the spring and/or
summer, and which are free of adult fish populations, as well as the area within
100 feet of the mean annual boundaries of such depressions.”
Obligate species:
fairy shrimp, spotted salamander, blue-spotted salamander, Jefferson salamander,
silvery salamander, Tremblay’s salamander, marbled salamander, wood frog
New Hampshire
Overview:
In New Hampshire, there is no minimum size limit to projects that require a
wetland permit. Vernal pools are regulated in New Hampshire only if they are
located within other regulated wetlands (Wetlands Board Code of Administrative
Rules 1993); they have traditionally been assessed as low-value wetlands.
New Hampshire Fish and Game (NHFG) developed a vernal pool identification
manual (Tappen 1997) to initiate local conservation efforts. Following
documentation, the information is supposed to be forwarded to NHFG and the
local conservation commission for informational purposes. However, there are no
state or local regulations that give added protection to documented vernal pools.
Definition:
There is no official regulatory definition of a vernal pool. New Hampshire Fish
and Game defines a vernal pool as “A temporary body of water providing
essential breeding habitat for certain amphibians and invertebrates and does not
support fish.” For a pool to be documented, it must be demonstrated that:
a. the pool occupies a confined depression without a permanently flowing
outlet;
b. the pool contains water for at least two months in the spring/summer;
c. the pool dries up and therefore does not support fish;
d. indicator species are present (i.e., there is evidence of amphibian breeding
or the presence of certain invertebrates in a flooded pool)
46
Indicator species:
fairy shrimp, spotted salamander, blue-spotted salamander, Jefferson salamander,
marbled salamander, wood frog
New York
Overview:
Vernal pools are not specifically recognized and would only be subject to
regulation under the following conditions (NYS DEC Article 24 Freshwater
Wetlands law):
1. greater than 12.4 acres,
2. demonstrating unusual local importance for one or more of the specific
benefits set forth in subdivision seven of section 24-0105,
3. contain a State-listed endangered or threatened species and have been added,
through a public hearing process, to the official map of State-regulated
wetlands, or
4. located within Adirondack park (minimum regulated size 1 acre).
An act to amend the environmental conservation law was introduced in February
2000 (A9561) that specifically describes vernal pools and recommends lowering
the State regulated wetland size from 12.4 acres to 3 acres.
Definition:
There is no regulatory definition of a vernal pool. Ecological Communities of
New York State (Reschke 1990) describe the natural vernal pool community as
follows:
"…a wetland in a small, shallow depression within an upland forest. Vernal pools
are flooded in spring or after a heavy rainfall, but are usually dry during summer.
Many vernal pools are filled again in autumn. This community includes a diverse
group of invertebrates and amphibians that depend upon temporary pools as
breeding ponds. Since vernal pools cannot support fish populations, there is no
threat of fish predation on amphibian eggs or invertebrate larvae. Characteristic
amphibians include wood frog (Rana sylvatica), mole salamanders (Ambystoma
spp.), American toad (Bufo americanus), green frog (Rana clamitans), and red-
spotted newt (Notophthalmus viridescens)."
Indicator species:
The New York Natural Heritage Program is reviewing the literature and will
produce a list of obligate species, most likely matching those listed in
Massachusetts.
47
Rhode Island
Overview:
The Rhode Island Fresh Water Wetlands Act (RIFWWA) does not specifically
regulate vernal pools but defines pond as a place not less than one-quarter (1/4) of
an acre in extent, natural or manmade, wholly or partly within the state of Rhode
Island, where open standing or slowly moving water shall be present for at least
six (6) months a year.
To ensure enhanced protection for vernal pools, the 1994 rules included a new
wetland category, special aquatic site defined as a body of open standing water,
either natural or manmade which does not meet the definition of ‘pond’ but
which is capable of supporting and providing habitat for aquatic life forms as
documented by:
a) presence of standing water during most years as documented on site or by
aerial photographs; and
b) presence of habitat features necessary to support aquatic life forms of obligate
wildlife species, or the presence, documented use, or evidence of aquatic life
forms of obligate wildlife species (except biting flies).
There is no size minimum but, because most are smaller than 1/4 acre, they do not
meet the definition of "pond"; therefore, there is no protection of the adjacent
upland. DEM can regulate land use within 50 feet of the edge of ponds but not
smaller water bodies. The applicant is expected to recognize special aquatic
sites—based on the presence of aquatic life forms of obligate wetland species or
their habitats—and to put them on plans for proposed development. DEM checks
those sites, and other wetlands, in the field during the project review.
Definition:
None (but see definition of "special aquatic site," above).
Indicator species:
fairy shrimp, spotted salamander, blue-spotted salamander, Jefferson salamander,
marbled salamander, wood frog
Vermont
Overview:
Vernal pools can be protected under Vermont's wetland rules only if they are part
of a Class II wetland or better (i.e., show up on Vermont Significant Wetland
Inventory maps derived from National Wetland Inventory maps). If a Class II
wetland is protected under the wildlife habitat section or any other section, the
maximum protection would be for the wetland and a 50-foot buffer. Class 1
wetlands can be protected with a 100-foot buffer, but there are few Class 1
48
wetlands at this time. Vernal pools are potentially protected under this rule only
if they are within a mapped wetland or are contiguous to such a wetland. Again,
only up to 50 feet of the adjacent land around such a pool could be protected for a
Class II wetlands
Vermont Wetland Rules (Water Resources Board 1990) do not specifically
address vernal pools. Under the rules, Vermont evaluates wetlands based on 10
functions and values, wildlife habitat being one of those. The likely impact of a
project on those functions is then assessed. If it is determined that a pool provides
significant amphibian breeding habitat, this could trigger a larger buffer
requirement or a potential denial of a project.
According to Rule 5.4 c (1), the following considerations are made in designating
wetlands significant for wildlife:
a. The wetland provides habitat that supports the reproduction of uncommon
Vermont amphibian species including: Jefferson salamander, blue-spotted
salamander, spotted salamander, and others found in Vermont of similar
significance;
b. The wetland supports or based on its habitat, is likely to support, breeding
populations of any uncommon Vermont amphibian species including:
mountain dusky salamander, four-toed salamander, Fowler’s toad and others
found in Vermont of similar significance.
Definition:
None.
Local Regulation
Building upon a long tradition of home rule in New York and New England, towns may
adopt more stringent protective wetland regulations than those mandated at the state and
federal levels. There are two specific aspects of vernal pool protection where local
ordinances add considerable value to conservation efforts. First, local laws are able to
extend protection to very small wetlands, including vernal pools that fall beneath the
regulatory threshold of state or federal governments. Second, local laws are able to
protect upland habitat surrounding a vernal pool. The Connecticut towns of Guilford and
Redding have proposed statutory protection of vernal pools by maintaining large areas of
critical upland habitat surrounding vernal pools and the upland connections between
pools.
The downside to this approach is the creation of a patchwork pattern of wetland
protection, varying from town to town. It is not unusual for a wetland that spans two
political jurisdictions to be conserved in one town, and be totally unprotected in the other.
The level of diligence and expertise in enforcing and interpreting local wetland
ordinances also varies from town to town. Even the most comprehensive wetland
49
ordinance is vulnerable to the lack of political will and due diligence by local decision-
makers in its application. Another downside to vernal pool regulation is that groups
opposing development are beginning to use vernal pools indiscriminately—regardless of
their relative biological value—as a tool to thwart applications in the local review
process.
50
Appendix 2
Using Aerial Photography to Locate Vernal Pools
The practicality of using aerial photography to identify vernal pools varies with predominant
forest cover-type, scale, timing, and type of photography. A primer on identifying vernal
pools through aerial photography and using Geographic Information Systems to create a
database is available in Massachusetts Aerial Photo Survey of Potential Vernal Pools (Burne
2001). Aerial photo coverage can provide a landscape overview to aid during
reconnaissance-level (i.e., field) surveys. From aerial photographs one can identify areas
most likely to have pools. For example, topography and breaks in the forest canopy give
clues to vernal pool location.
Use of aerial photography must be followed with ground-truthing. In fact, finding existing
vernal pools in the field and then characterizing the way they appear on aerial photography
(i.e., defining the signature of vernal pools) may help in picking out other potential pools on
photography. NOTE: Even with good aerial photography and experienced photo-
interpreters, many vernal pools are easily missed; this may be due to pool size, forest cover
type, the presence of tree shadows, or because the pools are embedded in other wetlands). It
is critical to ground-truth!
Below are some common challenges and solutions for using photography for pre-
identification of pools based on work done in Maine, Massachusetts, and Rhode Island.
What do I use?
Stereo coverage: Try to obtain aerial photographs in stereo pairs and view them with a
stereoscope. Subtle changes in relief can provide clues to potential vernal pool sites.
Season and ground conditions: Photos taken when the leaves are off the trees, the
ground is free of snow, and water levels are high provide the best opportunity for
identifying vernal pools. Early spring (March-May) is generally the best period for
capturing these conditions, but late fall (November-December) may also provide good
visibility for aerial coverage. Identification of vernal pools is least reliable on photos
taken during very dry years or in the middle of summer when tree canopies obscure
ground conditions.
Scale and film type:
Scale
The larger the scale (e.g., 1:4,800 is a larger scale than 1:12,000), the easier it is to
identify small ground features. Generally, scales at least 1:4,800 to 1:12,000 should be
obtained to identify small pools. However, scales as small as 1:31,680 (2 inches per
mile) have been used successfully to identify vernal pools that are 0.25 acre in size (L.
Alverson, Forest Resource Consultant, pers. comm.). Ultimately, the scale of
photography needed to successfully pre-identify vernal pools will depend on the type of
film, time of year photos were flown, forest cover type, and size of the pool.
51
Film Type
Color Infrared—CIR is the most reliable photography for picking out vernal pools
because water absorbs color infrared light and appears black in contrast to the lighter
colored (pink, magenta, orange, yellow) vegetation. A study conducted at the University
of Massachusetts, Amherst (MacConnell et al. 1992) found that large-scale CIR (1:4,800
or 1:12,000) was the best tool for delineating wetlands, particularly forested wetlands.
Specifically, they found that CIR is very sensitive to water and chlorophyll—key features
for wetland identification. Photo interpretation was faster, more consistent, more
accurate and required less corollary information and field work to maintain a high level
of accuracy. CIR had much finer resolution than black and white film at the same scale,
permitting the use of smaller scale photography. Tiner (1990) and Stone (1992) discuss
the advantages of CIR film in photo-interpreting wetlands. The disadvantage of using
CIR photography is that it is considerably more expensive than black and white
photography.
Black-and-White—A pilot project in York and Penobscot counties evaluating the use of
black-and-white aerial photography at 1:4,800 or 1:12,000-scale found it to be an
effective pre-identification tool in deciduous forests in southern Maine. Pre-
identification using 1:4,800-scale photography resulted in both a higher percentage of
correct predictions and less omissions than did 1:12,000-scale photography. However, in
lower Penobscot valley, pre-identification of vernal pools less than 0.5 acre was not
effective in mixed and evergreen forests (both wetland and upland). In some cases,
known pools could not be identified on the photography (K. Huggins, Champion
International, pers. comm.).
True Color—An evaluation of true color photography and vernal pool pre-identification
has not been conducted. Fall true color photography is effective in picking out red maple
swamps in softwood mosaics. These forested wetlands potentially harbor vernal pools.
True color photography taken under leaf-off conditions, especially in early spring, may
reveal considerable detail of the forest floor. Small waterbodies such as vernal pools may
appear as dark spots, or occasionally as white patches if light is reflected off the water
surface. Spring leaf-off true color at 1:9000-scale is available for much of southern and
central Maine at Maine Forest Service District offices and USDA Natural Resource
Conservation Service offices.
What do I look for?
1. Vernal pools may appear as small openings in the forest canopy on winter or spring
photos; in deciduous forests they can be detected through the canopy.
2. In forests that have not been harvested for 15-20 years, look for a hole or gap in the
canopy that seems larger than the typical shadows caused by individual trees. If the gap
is black with no visible vegetation, it may be a vernal pool.
3. Use signature color and relief when attempting to distinguish vegetated vernal pools
dominated by ferns, sedges, or grasses. Vegetation growing in water or in very wet soils
52
imparts gray shades to black and white photos, grayish green tones in color photographs,
and grayish pink colors in color infrared photos (CIR).
4. Identifying subtle pockets of variation in relief can be especially helpful when
distinguishing vegetated vernal pools in larger wetland complexes. Uneven ground and
shallow depressions can be seen through a stereoscope on aerial photographs.
5. Vernal pools might occur in clusters due to uneven topography and the composition of
the bedrock or soil type (particularly soils with shallow confining layers or shallow to
bedrock). It is often possible to pick out clusters on topographic maps or aerial
photography.
6. In central and southern Maine, vernal pools are commonly associated with red maple
swamps or mixed evergreen-deciduous swamps. Because pools may be included within
larger wetlands, identification can be difficult. If a wetland is in the southern portion of a
photo, there might be enough reflection of light off of water surfaces to highlight vernal
pools. When viewing stands dominated by softwood, a cluster of red maple is sometimes
an indicator of a potential vernal pool (particularly when working with fall true color
photography). Conversely, patches of softwoods in hardwood uplands may indicate
small areas of wet soils that could include vernal pools.
Common problems with photo-interpreting vernal pools
Many features can mimic vernal pools, including:
overstory or superstory trees with large crowns that cast shadows over the top of the
surrounding canopy and appear to be black spots. (This is particularly true of photos
flown in spring or fall when solar angles are low. Looking at photos in stereo may
eliminate some of these tree shadows);
shadows created by narrow pockets in bedrock or streams with deep narrow gorges;
gaps and openings in the canopy from recent forest harvesting operations; or
tree shadows along skid trails and near large openings.
Vernal pools might be difficult to see because:
they are small (often less than 2,000 ft
2
);
tree species typically associated with depressional pools in upland settings
(particularly red maple and hemlock) often extend their branches into the pool opening,
or the pool itself may be forested by flood-tolerant species.
pools associated with forested wetland complexes, particularly in mixed and softwood
stands, may be obscured by canopy cover or hard to distinguish from the overall wetland
complex.
53
Are National Wetlands Inventory (NWI) maps useful for finding potential pools?
Vernal pools range widely in the types and amount of vegetation they contain and the
duration of inundation (i.e., flooding); for that reason, individual pools might be classified as
ponds (POW* or PUB), marshes (PEM, PAB), wet meadows (PEM), shrub swamps (PSS),
or forested wetlands (PFO).
A 1997 pilot study in southern and central Maine was conducted to test the effectiveness of
NWI maps in identifying potential vernal pools. Results from this study suggest:
NWI maps can be used to locate many of the larger natural pools (isolated wetlands with
PUB, PSS and PFO status are often good candidates), but keep in mind that the resolution
of NWI maps is often limited to wetlands ≥ 15,000 ft
2
(~0.3 acres). Many of the PUB or
POW classifications are likely to be permanent ponds (average mapping unit for NWI is
1-3 acres).
Effectiveness of NWI maps for locating potential vernal pools depends on local
knowledge of types of wetlands in which pools occur. For example, in this pilot study,
vernal pool species occurred in some wetlands with temporary inlets and outlets and in
forested wetland complexes associated with other wetland types. Therefore, NWI
categories of PFO, even with outlets, were considered potential sites.
Ideally, NWI maps are used as one of a number of interpretive tools, including aerial
photography.
* National Wetland Inventory classification codes (Cowardin et al., 1979).
54
Appendix 3
Resources for Identifying Vernal Pools
Note: This is a listing of potential resources; it is not an endorsement of these products or suppliers.
Vernal Pool Manuals
Calhoun, A. J. K. 1999. Maine citizen’s guide to locating and documenting vernal pools.
Maine Audubon Society, Falmouth, ME.
Maine Audubon Society
20 Gilsland Farm Road
Falmouth, ME 04105
Colburn, E. A. (ed.) 1997. Certified: A citizen’s step-by-step guide to protecting vernal
pools. Massachusetts Audubon Society, Lincoln, MA.
Massachusetts Audubon Society
Educational Resources Office
208 South Great Road
Lincoln, MA 01773
tel: (781) 259-9506 ext. 7255
Kenney, L. P. 1995. Wicked big puddles. Vernal Pool Association. Reading Memorial High
School, Reading, MA.
Reading Memorial High School
Vernal Pool Association
62 Oakland Road
Reading, MA 01867
http://www.vernalpool.org
Tappan, A. (ed.) 1997. Identification and documentation of vernal pools in New
Hampshire. New Hampshire Fish and Game Department, Concord, NH.
New Hampshire Fish and Game Department
2 Hazen Drive
Concord, NH 03301
55
Sources for Aerial Photography
Government Sources
U.S. Geological Survey (USGS)
U.S. Geological Survey
Customer Services
EROS Data Center
47914 252nd Street
Sioux Falls, SD 57198-0001
tel. (800) 252-4547
http://edcwww.cr.usgs.gov/
U.S. Geological Survey (USGS) Business Partners
http://mapping.usgs.gov
U.S. Department of Agriculture (USDA)
Natural Resources Conservation Service (NRCS)
USDA Natural Resources Conservation Service
East Regional Office
5601 Sunnyside Avenue
Mailstop 5410, Room 1-1290A
Beltsville MD 20705-5410
tel. (301) 504-2300
http://www.nrcs.usda.gov
"Inventory of Aerial Photography and other Remotely Sensed Imagery of New York
State"
a publication available from:
Center for Geographic Information
NYS Office for Technology
State Capitol ESP
PO Box 2062
Albany, NY 12220-0062
tel. (518) 443-2042
County planning departments are also potential sources for aerial photos.
56
Private Sources
James W. Sewall Company
147 Center Street
P.O. Box 433
Old Town, ME 04468-0433
tel. (207) 827-4456
http://www.jws.com
Aerial Survey and Photo, Inc.
Airport Road
P.O. Box 657
Norridgewock, ME 04957
tel. (207) 634-2006
http://www.aerialsurveyandphoto.com
Col-East, Inc.
P.O. Box 347
North Adams, MA 01247
tel. (800) 359-8676
http://www.coleast.com
ADR Associates, Inc.
9285 Commerce Highway
P.O. Box 557
Pennsauken, NJ 08110
tel. (800) 257-7960
http://www.adrinc.com
AirPhotoUSA, LLC
7122 N. 27
th
Avenue
Suite 500
Phoenix, AZ 85051
tel. (866) 278-2378
http://www.airphotousa.com
57
Sources for Digital Orthophotography
Note: Small vernal pools are very difficult to detect consistently on digital
orthophotography, due to pixel resolution issues.
Rhode Island Geographic Information System (RIGIS)
http://www.edc.uri.edu/rigis/
Massachusetts Geographic Information System (MassGIS)
MassGIS
Executive Office of Environmental Affairs
251 Causeway Street, Suite 900
Boston, MA 02114
tel. (617) 626-1000
http://www.state.ma.us\mgis
NYS Statewide Digital Orthoimagery Program
http://www.nysgis.state.ny.us/orthoprogram.htm
National Wetlands Inventory Maps
U.S. Fish and Wildlife Service (USFWS)
http://www.nwi.fws.gov/
for hard copies, contact:
USGS/ESIC
National Headquarters
507 National Center
Reston, Virginia 20192
tel. (703) 648-5920 or (888) 275-8747
Field and Lab Equipment
Forestry Suppliers, Inc.
P.O. Box 8397
Jackson, MS 39284
tel. (800) 543-4203
Ben Meadows Company
P.O. Box 20200
Canton, GA 30114
tel. (800) 241-6401
