With spring’s official start this week, keep an eye out for one of the subtler signs of its arrival: vernal pools. Vernal pools are ephemeral wetlands that are only filled for part of the year, usually starting in the late winter and spring when snow begins to melt. By summer these special ponds are often dried up and replaced by patches of mud.
Vernal pools play an important ecological role, supporting many species of animals and insects that rely on them for habitat and reproduction. Fish and other aquatic predators can’t survive in vernal pools, so they provide a safe place for these indicator species to lay their eggs. Four of Pennsylvania’s salamanders, two frogs, and a handful of shrimp all require vernal pools to breed.
Amphibians are one of the primary animals that take advantage of vernal pools to reproduce. Many amphibians migrate long distances across roads and other infrastructure to return to their breeding grounds. This results in countless amphibians being hit by cars each spring. Luckily, several programs are in place to help toads, salamanders, and other amphibians travel safely.
This month, the National Park Service announced that through mid-April, River Road in Delaware Water Gap National Recreation Area will close on rainy nights, when amphibians are most active. The portion of the road is closed to protect breeding amphibians each spring.
Organizations like the Schuylkill Center for Environmental Education are taking a more hands-on approach to keeping amphibians safe. Each year from March 1st to June 30th, the Schuylkill Center organizes a “Toad Detour”: on nights with high potential for toad migration, volunteers barricade streets near Roxborough Reservoir in Philadelphia and redirect traffic to help reduce toad fatalities. Hundreds of toads can cross the blocked off roads in one night (check out the Toad Detour predictor here). When driving at night in the coming months look out for amphibians in the road — especially if it’s rainy.
While certain amphibians can only survive with access to vernal pools, many other animals benefit from the temporary wetlands. Certain newts, toads, and tree frogs that can breed in other wetlands or streams sometimes choose vernal pools to lay their eggs. Turtles, snakes, and birds also visit vernal pools as a source of food and water.
Vernal pools are fragile ecosystems. Small changes in rainfall, temperature, and land use can cause significant disruptions. If you have a vernal pool on your property, try to avoid disturbing the pool water, soil, or vegetation around it. The Pennsylvania Natural Heritage Program has many resources on vernal pool conservation here.