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Vernal Pools in Eastern North America

Vernal pools occur all over the world, and are known by many different names. In the northeastern United States, where the term vernal pool has become popular, they are common and a very important component of natural systems.


Basically, vernal pools are small, seasonal forest ponds that typically dry out at some point during the year. They are usually full in the early spring as snow and ice melt, and dry completely (or at least mostly) by late summer or early fall.


Vernal pools are temporary ponds that cannot sustain reproducing fish populations, and are therefore very important to a wide variety of aquatic organisms that would not successfully reproduce when subjected to fish predation. 

Many organisms with an aquatic stage in their life cycle have evolved to require the temporary but fish-free waters of vernal pools.  These organisms are sometimes known as "obligate" vernal pool species, so called because they do not breed successfully in water that supports fish. They require a temporary pool.


If the obligate species are using a body of water, then that water is a vernal pool. In New England, the easily recognizable obligate species are the fairy shrimp, the mole salamanders and the wood frog. There are additional obligate species many of which are not vertebrate animals.

Vernal pools tend to be remarkably productive habitats, from which significant biomass is created. Frogs and salamanders breed in large numbers, and may produce thousands upon thousands of larvae each year. Upon metamorphosis, tiny frogs and salamanders (aka biomass) hop and crawl their way into the surrounding uplands, extending the food webs of the pool out into the woods around them.


In addition to the animals that use vernal pools for breeding, many species use vernal pools as feeding resources, for breeding, migration, and shelter habitat. These productive wetlands are incredibly important for a wide variety of wildlife.

vernal pool - winter
vernal pool - spring
vernal pool - summer
venal pool - fall
A vernal pool through four seasons. This pool in Reading, MA only occasionally becomes completely dry.
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