Vernal Pools of Massachusetts

Massachusetts is unique in its efforts to protect vernal pools. In 1988, the MA Wetlands Protection Act was amended to include wildlife habitat as a reason to protect wetlands, and in recognition of the value of vernal pools to wildlife, they were defined and included in regulation. Though a bit quirky, vernal pools are actually defined in large part upon their use by certain animals, as opposed to being defined by a set of physical traits as most wetlands are. On this page, we describe the characteristics required for official designation of vernal pools in Massachusetts. There is much more information about this under the Protection page.

Physical description of a vernal pool

A vernal pool is a contained basin depression lacking a permanent above ground outlet. In the Northeast, it fills with water with the rising water table of fall and winter or with the meltwater and runoff of winter and spring snow and rain. Many vernal pools in the Northeast are covered with ice in the winter months. They contain water for a few months in the spring and early summer. By late summer, a vernal pool is generally (but not always) dry. Below are views of the same pool at three different times of the year - note the tree at the foreground and stump near the back of the pool.

Vernal Pool, a hand-colored relief engraving, illustrates the beauty of these special woodland pools (used with permission of artist Abigail Rorer..

Vernal pools are generally small, less than an acre in area and only a few feet in depth. Vernal pools vary in how long they hold water from weeks to many months. They may differ in appearance as determined by the physical and biological surroundings. Below are several vernal pools in Massachusetts. More pools are in Vernal Pool Views.

vernal pool with vegetation indicating depth

Biological description of a vernal pool

A vernal pool, because of its periodic drying, does not support breeding populations of fish. Many organisms have evolved to use a temporary wetland which will dry but where they are not eaten by fish. These organisms are the "obligate" vernal pool species, so called because they must use a vernal pool for various parts of their life cycle. 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. These organisms are recognized as obligate vernal pool species for the purposes of certification of a vernal pool in Massachusetts.

Massachusetts Regulatory Vernal Pool vs Biological Vernal Pool

A vernal pool for regulatory purposes is defined on these pages. In other usage or other locations, "vernal pool" might be defined differently. For example, California vernal pools are defined and dominated by wildflowers. In other locations, amphibians are not as important as are invertebrates. Even in Massachusetts where the spadefoot toad breeds in temporary pools, we do not use the breeding of spadefoots to indicate a vernal pool as the develop in less than two months.