Vernal Pools Are the Place to Be for Woodland Critters—as Long as They Last

In early spring, melted snow and rain trickle through forests, forming pools amid the leaf litter. Within these basins, life begins to sing. Frogs and salamanders migrate from winter dens to these waters, where fairy shrimp emerge from dormant eggs.

These small but biodiverse ecosystems are called vernal pools. Though they reappear in the same places each year, the pools are ephemeral: They fill up as winter ends and dry out by late summer. Since these isolated wetlands have no fish or other aquatic predators, they make fantastic nurseries for tiny forest critters and feeding grounds for reptiles, birds, and mammals. “You can hear them sometimes before you even see them, because they’re very active in the spring,” says Abby Pointer of the Michigan Nature Association.

Vibrant as they are, vernal pools tend to go unnoticed. Because of their seasonal nature and modest size, these wetlands often “fall through the cracks,” says Pointer, unprotected by regulations like the Clean Water Act and left vulnerable to threats like development and logging. But over decades, a growing number of community science efforts across the Northeast and Midwest have built massive databases of these small wetlands and the life that flourishes there. These maps are now informing a push to better conserve what ecologist Aram Calhoun describes as VIPs—“very important pools.”

Prior to these projects, vernal pools were largely unmapped and unregulated, Calhoun says. By some legal definitions, they weren’t even considered wetlands, since they’re small—often a quarter-acre or less—and isolated from other waterways. Developers, therefore, were free to build on top of these pools and alter the habitats around them.

In 1999, to show their biological significance and create better safeguards, Calhoun—then a professor at the University of Maine—started one of the first community science efforts to catalog vernal pools that offered significant wildlife habitat. Volunteers explored local forest patches in Maine, where they located and surveyed hundreds of pools in the project’s initial years. They documented the egg masses of sensitive species like blue-spotted salamanders, and noted the other creatures that come to these ponds for food, water, and shelter—including Wood Ducks, Barred Owls, and migratory songbirds like Black-and-white Warblers that stop for rest on their biannual journeys.

Calhoun’s project, along with similar early efforts in the Northeast, provided a model for other states, demonstrating how science could harness the community to gather valuable data. In 2011 Yu Man Lee, a biologist at the Michigan Natural Features Inventory, helped bring that model to the Midwest. Together with a number of government entities in Michigan, Lee ran the pilot year of a monitoring program, finding possible pool sites through exploratory hikes and aerial photography and sending volunteers to check on them. This evolved into the Vernal Pool Patrol, which Pointer now works on, recruiting volunteers to scour Michigan’s forests for pools and count up gooey egg masses within. To date, the program has verified more than 1,000 vernal pools throughout the state that offer important breeding sites for certain indicator or at-risk species.

The data collected on these pools’ lively ecosystems have spurred some states to add more robust protections. Since the late 2000s, regulations in Massachusetts and Maine have protected vernal pools if key species are found breeding there. This year New York extended its wetlands regulations to cover vernal pools, protecting ponds with egg masses of amphibians like spotted salamanders and wood frogs. Meanwhile, local bylaws in certain cities and towns fill in some gaps for pool protections. Such guardrails have become especially important since the 2023 U.S. Supreme Court decision in Sackett v. EPA, which limited the kinds of waterways that are federally protected under the Clean Water Act. Climate change also poses a growing threat, as shifting seasons alter the wet and dry cycles that vernal pool creatures are adapted to.

Bringing community members on board with these efforts has multiple benefits, says Lee. Not only can it open up access to hard-to-reach places on private land, but it also helps landowners understand and value the vernal pools on their own property. Many trainees recall growing up exploring vernal pools, but had no idea that diverse and rare species lived there. Now, many of these landowners contribute important data to conservation efforts—and some have become powerful advocates for pool protection. “The benefit that we weren’t even counting on was the educational aspect of this,” says Calhoun, who is working with some of her former volunteers to push for stronger local bylaws across multiple towns in Maine.

Meanwhile, as a new breeding season gets underway, vernal pools are filling up and brimming with life. Wood frogs croak and grumble. Salamanders lay their gelatinous eggs below the surface. Their fate could be shaped by the next curious community scientist who comes across them. “Everything is connected, even things we don’t always see,” Lee says. “We all have a role to play.”

This story originally ran in the Spring 2025 issue as “Very Important Pools.” To receive our print magazine, become a member by making a donation today.