Understanding and Protecting Vernal Pools

That chorus of frogs you hear erupting from the woods on spring evenings is coming from a special but fleeting place.

One of those songs belongs to the wood frog, just a couple inches long but with a voice that fills the air with a warm reminder winter is over. These frogs hang out among leaves and twigs at the edges of shallow, secluded pools and call for mates with their trademark tune. Females lay their eggs in the water where their tadpoles will hatch and develop into frogs before moving deeper into the forest.

After that, their pond will dry up and disappear as if nothing ever happened there. This is the cycle of a vernal pool.

Michigan Natural Features Inventory describes vernal pools as small, isolated wetlands occurring in forests across the state. These areas are inundated with snowmelt in spring but dry up entirely in summer or periods of drought. Also known as vernal ponds, ephemeral pools or seasonal wetlands — “vernal” meaning spring — they don’t connect to larger bodies of water and lack permanent fish populations.

In Northeast Michigan, vernal ponds are most common in areas with high water tables or where shallow bedrock, clay or muck causes water to pond on the surface. The character of any given pool is the result of local climate, weather, wildfire processes, terrain and the types of plants and animals present, making each one unique. Though easily overlooked, they provide critical habitat for amphibians like wood frogs and many other animals adapted to life in water and on land.

“Vernal pools are important to wildlife that rely on them for annual breeding,” said Julie Crick, Natural Resources Educator for Michigan State University Extension in Roscommon. “Spotted salamanders and wood frogs all make their way back to the same pool each year to breed and migratory birds use them as temporary resting places.”

Because of their small size and fleeting nature, vernal pools are especially vulnerable to certain land-use practices and a changing climate. Little is known about their abundance and distribution in Michigan and they are not well protected under current wetland laws, according to Michigan Vernal Pool Patrol, a citizen science-based mapping and monitoring program.

The Vernal Pool Patrol uses trained citizen scientists, educators and community partners to help identify and map vernal pools and collect information to steer conservation and management efforts.

Monitoring a vernal pool involves visiting the location a couple times in the spring wet season and once in late summer or fall to verify the pool has dried up. During each visit, information is collected about the physical and biological character of the vernal pool, including the types of plants and animals observed. Particular attention is paid to “indicator species” like fairy shrimp, spotted salamanders and wood frogs whose presence — or absence — demonstrates good or poor water quality.

Volunteer monitors receive training through one-day workshops in the field where they are taught how to use tools like dip nets and thermometers, along with their own observations, to collect and record data. According to Crick, this kind of field work helps foster relationships between volunteers and their environment.

“Many people have these places on their own property and may not even know it — maybe they refer to it as the frog pond out back or the ‘wet spot in the yard’ — but they are still vernal pools,” Crick added. “Knowing this deepens the connections people have to their own property and Michigan’s natural wonders.”

Huron Pines is leading an effort this year alongside MSU Extension and Michigan Natural Features Inventory to train volunteer monitors.

“Volunteers are our eyes and ears for focusing on these unique systems across Northern Michigan,” said Emily Vogelgesang, Environmental Education Coordinator for Huron Pines. “Several student groups already conduct this monitoring in Alcona and Roscommon counties each year and I’m excited to see more people joining in.”

Learn more about vernal pools through the Michigan Natural Features Inventory or Michigan Vernal Pool Partnership. Follow Huron Pines on social media or huronpines.org/events for a training event once a date is set. Vernal pool monitoring events are supported in part by the Great Lakes Fishery Trust.

By Chris Engle

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