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Conservation and Best Management Practices

 

Threats | Conservation | Best Management Practices
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THREATS

Habitat Loss
Seasonal pools are often not identified as wetlands due to their temporary nature.  Pools that are not identified cannot be protected during development activities that would alter or destroy them.  Some estimates state that more than 50 percent of the wetlands in the United States have been lost since European settlement (Vileisis, 1997).  The rate at which seasonal pools have been lost is likely even greater considering that these areas are often overlooked.  Filling seasonal pools, and disturbances to the vegetation and soil around pools from building and road construction, quarries, and logging operations lead to direct mortality of animals and habitat destruction or degradation. 



Habitat Fragmentation
Fragmentation of the landscape by various human activities destroys or reduces the amount of habitat available to seasonal pool animals and reduces their ability to find and colonize new habitats.  Roads are a common form of habitat fragmentation, even in relatively undeveloped areas.  And roads near seasonal pools present a physical obstacle to animals moving from their upland feeding habitats to their seasonal pool breeding habitats.  Many animals are killed as they attempt these crossings.  The presence of roads also provides opportunities for undesirable elements to get into the pools.  Roads bring invasive plant species, sediments, and contaminants to pools through runoff.  During the winter the application of road salt poses a problem for pools located near roads.  As the snow melts, salt-laden water flows into these pools and increases the salinity of the water, making the water less hospitable to wildlife.

Development of extensive agricultural, urban and suburban areas also creates biological “islands” of isolated natural areas.  It can be difficult for animals to move long distances across unsuitable habitat such as open lawns and parking lots and to navigate large obstacles such as highways and fences.  Some highly mobile animals are able to disperse over these obstacles.  Other more sessile animals are unable to move great distances from their preferred habitat.  For those species that can travel large distances, there is increased risk that they will not be able to find suitable habitat at the end of their journey in a fragmented landscape with diminished habitat. 

Just as habitat fragmentation isolates a group of animals on an island of habitat; it also isolates the gene pool collectively held by that group of animals.  When animals cannot make contact with other populations, inbreeding within one population takes place.  This means there is no gene flow between populations and genetic diversity is lost.  As genetic diversity is lost, the ability of that population to adapt to changes in the environment is reduced.  This increases the chances that the population will not be able to survive over the long-term. 

Alteration of Hydrology
Alterations to the natural water regime change many habitat parameters such as inundated area and depth, length of inundation, temperature, dissolved oxygen levels, and types and amounts of vegetation in and around the aquatic habitat.  All of these factors are important in proper development of aquatic eggs and larvae.  Heavy water demand can lead to decreased water tables and decreased water retention in seasonal pools.  Deepening of pools can increase their water retention and can change them from seasonal to permanent aquatic habitats. 

Alteration of Water Chemistry
Many human activities have degraded water quality in aquatic habitats.  Agricultural runoff is a major source of pollutants in Pennsylvania where there are abundant farmlands.  Agricultural runoff is generated as rainwater flows through fields that have been treated with fertilizers, herbicides, and insecticides, and through livestock pastures and feedlots, washing the waste into local aquatic systems. 

Suburban and urban runoff comes from rainwater that flows off rooftops, down streets and parking lots, through industrial zones and garbage disposal sites, and through lawns and golf courses treated with various chemicals.  This runoff contains sediments, garbage, road salt, oil, pesticides, herbicides, and a whole mixed bag of other household and industrial chemicals. 

Testing for a variety of synthetic chemicals and heavy metals that can be toxic to wildlife is an important part of water quality monitoring.  Other important variables used to monitor water quality include temperature, pH, dissolved oxygen, sediment load, nutrient levels such as nitrates and phosphates, and bacterial and algal levels.  The types of plants and animals found living at a site can also be used to evaluate water quality.  Certain species are very tolerant of poor water quality, while others will only be found in clean habitats.  The types of plants and animals living at a site can be monitored for change over time.  If species intolerant of pollution disappear from a site, and species tolerant of pollution increase, this is an indication that there is a problem with water quality.

Seasonal pool animals are adapted to the relatively high acidity levels naturally found in seasonal pools, but they have tolerance limits.  Increased acidification of seasonal pools takes place due to acid rain.  In a review of literature, Hulse (2001) describes one study that showed that embryos living inside eggs of spotted and Jefferson salamanders experience higher mortality at lower (more acidic) pH values.  In a lab setting, no hatching occurred at pH values below 4.5.  Another study showed that natural pools that supported Jefferson salamanders had significantly higher (less acidic) pH values than pools that did not.  Other studies on spotted salamanders found that increased acidity can deform egg membranes and developing embryos and produce a decrease in hatching success and higher levels of larval mortality (Hulse, 2001).

Alteration of Substrate
The term substrate is used here to refer to the environment at the bottom of a seasonal pool.  Substrate requirements can be quite specific for seasonal pool animals.  The amount and composition of materials such as leaves, woody debris, and muck are important factors.  The substrate can be altered by activities such as dumping, dredging and filling.  Gradual non-point effects from runoff can also change substrate.  For example, surface runoff from agricultural fields carries fine sediments.  The silt gets deposited into nearby seasonal pools, eventually filling in the pool basin.

Loss of Vegetation
In-pool and upland vegetation are an important part of the seasonal pool habitat.  Removal or change in composition of vegetation in and around a pool affects which species can use the pool.  For species that lay their eggs in plant material, loss of vegetation eliminates egg-laying sites.  For species that lay their eggs in the water, removal of vegetation reduces shade.  This causes water temperatures and evaporation rates to increase.  These effects are particularly noticeable in small wetlands like seasonal pools.  One cause of mortality of odonate eggs is prolonged high temperatures or periods of drought (Brooks, 2003). 

Climate Change
All aspects of life in a seasonal pool, from amphibian migration to egg and larval development to adult feeding, thermoregulation, and reproductive success, depend on certain environmental cues and conditions.   For example, the migration of salamanders to seasonal pools is in response to environmental cues.  One study showed that salamander migrations started when evening rains occurred with moderate temperatures over 44.6 F during the day and over 40 F at night (Hulse 2001).  In Pennsylvania, migrations can start as early as the end of February and as late as the beginning of April depending on local temperatures and rainfall. 

While predictions of climate change do not agree on the details, evidence shows that changes in average yearly temperatures, minimum and maximum temperatures, rainfall amounts, and other environmental changes are occurring.  These changes are having an effect on wildlife, which respond more quickly to environmental changes than humans, who are able to create a favorable environment inside their home.

There is already evidence that the geographic ranges of plant and animals have been shifting in response to changes in climate.  Climate change is of increasing concern for species of special concern, especially in regard to species that are geographically restricted (Westfall and May 1996). 

Global Warming – Early Warning Signs – References:  http://www.climatehotmap.org/references.html

U.S. Environmental Protection Agency:  Global Warming – Impacts Bibliography http://yosemite.epa.gov/oar/globalwarming.nsf/content/ImpactsImpactsBibliography.html

CONSERVATION

Several important pieces of information are needed when developing conservation and management plans for seasonal pools and the wildlife they support:

1) Research and define the specific habitat requirements of each life stage of the species of concern.

Understanding the life history of seasonal pool wildlife is an area of ongoing research.  From egg to larva to adult, each stage of an animal’s life has certain requirements, and these requirements differ by species.  For example some species ride out the dry phase in a seasonal pool as an egg.  The egg must dry out and freeze before it will respond to environmental cues to hatch.  In other species, the larva or adult waits out the dry phase of a seasonal pool in the moist soil under the leaf litter in the pool basin.  Other species have terrestrial adults that leave the seasonal pool.  These adults have another of set of habitat requirements for their life away from the pool.  Some species need wooded upland habitats while other species require nearby streams or permanent ponds. 

Terrestrial adults that leave the pool also need to find their way back for the breeding season.  Eighty-five percent of seasonal pool amphibians return each year to breed in the same pond where they were born (Colburn, 2004). They will bypass other pools that provide suitable habitat and cross obstacles such as roads and other forms of human disturbance in order to return to the pool of their birth.  This fidelity by individual amphibians to a particular pool is an important consideration when considering how to conserve the species as a whole.

2) Avoid use of certain pesticides and herbicides in and around seasonal pools to maintain the balance that is necessary between predators and their prey.

Larval and adult seasonal pool animals feed on the smaller animals that share their environment such as mosquitoes, midges, gnats, and other flies.  Predators such as amphibian larvae and insects such as dragonfly and diving beetle larvae and adults help control the insect species that are considered pests.  However, when homes encroach upon wetland habitats, municipalities and homeowners often take measures to control mosquitoes and other nuisance insects.  The pesticides used to control these pests have many negative effects on non-target species.  Direct mortality of all insect species occurs when broad-based killing agents are used.   More specific killing agents are available that only harm black flies or mosquitoes, but they indirectly affect the predators by decreasing the availability of their food.

3) Protect the species and habitats within a healthy, functioning ecosystem.

Landscape scale conservation of wetland habitats and the supporting upland habitat is needed for long term survival of healthy seasonal pool plant and animal communities.  Identifying and protecting seasonal pool habitats is a first step towards ensuring the long-term survival of seasonal pool wildlife.  Protection of large tracts of habitats supporting seasonal pool communities from alteration and fragmentation is an attainable goal for Pennsylvania, which has large amounts of public lands and many high quality seasonal pool habitats.  Restoration efforts should strive to restore and recreate seasonal pool habitats in areas where they have been lost.  Restoration of the surrounding uplands to relatively natural conditions in terms of connectivity, hydrology, substrate, vegetation, and water quality will help sustain healthy seasonal pool communities as well.

 

BEST MANAGEMENT PRACTICES AND OTHER CONSERVATION ACTIONS

Best Management Practices (BMP’s) are typically developed by large landowners such as state and federal agencies and forestry industries to optimally manage their natural resources.  Best management practices for seasonal pools address the pool itself and the surrounding habitat.  The goal is to protect sufficient habitat to preserve seasonal pool species while allowing sustainable levels of activities such as logging.  For example, if a tract of land is to be cut for timber purposes, BMP’s might delineate a series of buffer zones around a seasonal pool.  Activities permitted within those buffer zones would be defined, with greater restrictions applied with increasing proximity to the pool. 
Best management practices are needed to establish balance between resource use and protection.  Forestry practices can affect seasonal pools by altering leaf input, ground water flow, sunlight penetration, sedimentation and condition of upland habitat. Ruts created by logging can impede amphibian migration and insecticide usage on the surrounding woodland affects abundance of insect food sources and has been shown to lower reproductive rates of amphibians.        
                
Some best management practices developed in other states include not cutting more than 50 % of the basal area within 50 feet of a pool, not depositing slash into the pool basin and encouraging foresters to avoid creating ruts or disturbances on the land surface that may interfere with water flow in and around the pools (Colburn, 2004).
                       
Land use planning and zoning laws are another way that seasonal pools can be protected.  Like best management practices, land use plans and zoning ordinances can be designed to protect seasonal pools and their surrounding areas while allowing sustainable levels of development activities. 
Best management plants, zoning laws, and other actions such as conservation restrictions and easements, direct land acquisition, and even creating new pools for species to use are important pieces to seasonal pools conservation.  Successful protection efforts will protect individual seasonal pools or pool clusters, their associated upland habitats, and corridors between seasonal pool groups, wetlands and permanent water bodies.

Important questions to consider when developing BMPs and land use plans:

  • What activities are intended for the planning area?
  • What are the potential impacts on seasonal pools?
  • Where are seasonal pools located in the planning area?
  • What are the biological and physical characteristics of the pools?

The following categories are useful when planning management of seasonal pools and the surrounding landscape.  Appropriate activities can be defined for each zone (adapted from Calhoun and deMaynadier, 2004). 

  • Seasonal pool depression:  the area the seasonal pool occupies when it is fully inundated in the spring.   This is the critical breeding habitat for seasonal pool animals.  Important considerations are in-pool vegetation, hydrology, and water quality.

  • Seasonal pool protection zone:  also called the seasonal pool envelope (Brown, 2005), this is the area immediately surrounding the seasonal pool that has a high level of influence on conditions in the seasonal pool itself.  This area also experiences high densities of adult amphibians during breeding season and high densities of recently metamorphosed amphibians leaving the pool in the summer and fall.  Important considerations are forest cover, ground cover and soil quality. 

  • Seasonal pool life zone:  also called seasonal pool terrestrial habitat (Brown, 2005), this is the area utilized by the terrestrial seasonal pool adults for feeding and overwintering.  This buffer should encompass as much of the adult habitat as possible.  Estimates on how far seasonal pool amphibians travel from the seasonal pool vary from 50 meters to 1200 meters depending on the type of disturbance and the species using the pool.

  • Seasonal pool corridors:  connectivity between pools is important for long term conservation of seasonal pool species.  Forested, unfragmented corridors are especially important in areas that support seasonal pool clusters where many pools are found together and occur less than ¼ mile apart.  Important considerations are forest cover, ground cover and soil quality, and connectivity (lack of fragmentation).

 

Additional information on BMPs for seasonal pool habitas can be found in:

Brown, Lesley J. and Robin E. Jung. 2005.  An Introduction to Mid-Atlantic Seasonal Pools, EPA/903/B-05/001.  U.S. Environmental Protection Agency, Mid-Atlantic Integrated Assessment, Ft. Meade, Maryland.  Website last accessed January 20, 2006 at http://epa.gov/maia/html/SeasonalPools_PDF.html.

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.

Calhoun, A. J. K. and P. deMaynadier. 2004. Forestry habitat management guidelines for vernal pool wildlife.  MCA Technical Paper No. 6, Metropolitan Conservation Alliance, Wildlife Conservation Society, Bronx, New York.

Colburn, Elizabeth A.  2004.  Vernal Pools: Natural History and Conservation.  The McDonald and Woodward Publishing Company, Blacksburg, VA. 

Literature Cited