Vernal pools are small, isolated wetlands that hold water on a temporary basis, most often during winter and spring. They are very important to the life cycle of many amphibians, since they are too shallow to support fish that would eat the amphibian eggs or larvae. Vernal pools and their adjacent upland habitats encourage biodiversity, by supporting an abundance of plants, invertebrates and vertebrates not found in other areas.
Species that depend on vernal pools for successful breeding include fairy shrimp; the spotted, marbled and Jefferson salamanders; eastern spadefoot toad; and wood frog. A wide variety of other forest animals, including birds, turtles, snakes, and small and large mammals, also use these pools for feeding and resting. In addition, these “sylvan gems” are aesthetically pleasing, with moss-covered logs, delicate hues of greens and browns, and dappled sunlight shining through forest cover.
However, because they are small, hard to identify, and subject to limited regulation, they are often impacted by development. As a result, vernal pools – and the species that depend on them – are rapidly disappearing.
Many vernal pool amphibians go back to breed in the pools where they were born. If the pool is disturbed or destroyed by development, the amphibians show little tendency to relocate. It is also important to remember that they rely on both vernal pools and connecting upland terrestrial habitats for survival, spending about 11 out of 12 months each year in adjacent uplands, forests and wetlands.
Even a relatively small degree of development (25% of surrounding critical terrestrial habitat) can negatively impact vernal pool wildlife. For example, one study done in Massachusetts found that when 25 acres of upland forest next to a vernal pool was cleared, the pool’s wood frog population became locally extinct, despite a 150 foot wide forested buffer around the pool and a forested wetland corridor adjacent to the pool.
The most valuable vernal pools are ecologically significant due to size and the length of time they hold water, have state-listed or vernal pool species present/breeding, and are surrounded by intact, undeveloped critical terrestrial habitat.
Vernal pools, like Atlantic Cedar Swamps, are critical habitats that we must continue to work together to protect. Mechanisms include acquisition by a conservation organization like a land trust; conservation easements; employment of best management practices to integrate design, engineering and natural resource protection into developments; zoning/ordinances; and last but not least, voluntary stewardship programs by landowners.
Source: 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.