Lathrop’s Vernal Pools

by Barbara Walvoord

(from Lathrop Lamp Post, Feb. 2, 2017)

Vernal pools are a unique and threatened habitat.  Lathrop’s east campus is very fortunate to have two just off the wide woods path, and one just off the southwest corner of the mid-woods meadow (map, see https://lathropland.files.wordpress.com/2014/10/trail-eh.pdf)

A vernal pool, by definition, has no permanent above-ground outlet. It fills with seasonal rains, and it dries up in late summer, at least every few years.  That drying eliminates fish, who otherwise would gobble down small critters like fairy shrimp, wood frogs, and mole salamanders who can survive only in a vernal pool. Many other creatures use vernal pools for food or habitat.  

Jefferson salamander. . Photo by Virginia State Parks staff (SH Jefferson Salamander Uploaded by AlbertHerring) [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons
Jefferson salamander. . Photo by Virginia State Parks staff (SH Jefferson Salamander Uploaded by AlbertHerring) [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)%5D, via Wikimedia Commons
Some creatures spend their whole life in the vernal pool, laying eggs in the bottom that can survive both drying and freezing.  Others spend part of their life cycle in the surrounding forest. Marching to the pool to breed, many are crushed crossing roads.

Wood frog on mid-woods path near vernal pool, 11/16/16 by Barbara Walvoord and Sharon Grace.
Wood frog on mid-woods path near vernal pool, 11/16/16 by Barbara Walvoord and Sharon Grace.

The National Heritage and Endangered Species Program certifies vernal pools. Federal, state, and local governments protect them with laws and urge their preservation.

Because so many species use both the pool and the surrounding forest, building around vernal pools poses special threats.  Mass Audubon urges: “Even if a vernal pool itself is saved from destruction, changes in the surrounding upland may disrupt the habitat and life cycles of the resident species. The removal of the surrounding forest during the construction of houses, driveways, and lawns, for example, may degrade a nearby vernal pool to such an extent that the amphibian population is eliminated.”  http://www.massaudubon.org/learn/nature-wildlife/reptiles-amphibians/vernal-pools/protecting

Most vernal pool creatures try to return to the pool where they were born, so when a pool is destroyed, polluted,  or degraded, its creatures are affected,  even if they were off in the woods at the time.

The State of Maine says, “The loss of vernal pools and the critical terrestrial habitat around them leads to local loss of amphibian species, a decrease in biodiversity, and a decline in food available for many other animals that live in these areas.” http://www.maine.gov/dep/land/nrpa/vernalpools/fs-vernal_pools_intro.html.  More information on vernal pools: http://vernalpool.org/vernal_1.htm

Having three vernal pools in our forest is both a gift and a responsibility for Lathrop, as we seek to “live lightly on the land.”

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