Vernal Pools: Seasonal Wetlands and Their Importance

If you do any hiking, you’ve likely stumbled upon or had to navigate around a vernal pool. Vernal pools are seasonal wetlands usually found in forests during the spring and late fall. They are pretty inconspicuous – often large puddles that dry up over the course of weeks or months.

I never thought much about these pools until I read about their importance for amphibians and invertebrates. It gave me a new appreciation for them and maybe it will do the same for you.

Ecological Importance

Scientists, Aram Calhound and Phillip deMaynadier, argue that vernal pools may act as keystone ecosystems. A keystone ecosystem is an ecosystem that though small, has a great effect on the surrounding landscape.1 Vernal pools support many species, some of them rare.

These temporary wetlands act as breeding grounds, foraging areas, and damp stopping places for animals on the way to larger wetlands.2 They support “hundreds of invertebrate species…across northeastern North America,” “more than a dozen or so amphibians, handful of reptiles, and a few opportunistic bird and mammal species that breed, feed, or water in pools.”3

Amphibians and Invertebrates

Frogs, toads, and salamanders rely on pools as breeding grounds as they offer refuge from predatory fish.4 That said, these ephemeral wetlands are not without predation. Predation still occurs, but “pool invertebrates’ life histories and behaviour” are “tailored to avoid predation” in pools.5

Examples of invertebrates found in vernal pools include: aquatic insects (dragonfly nymphs, mosquitoes, water beetles), small crustaceans (water fleas, roundworms, aquatic earthworms, leeches), molluscs (snails, fingernail clams), and arachnids (water mites and spiders).6

These invertebrates are “key to energy and nutrient cycling in vernal pools and play important roles throughout the food web, both as prey and predators.”7 Nutrient cycling is the process by which “organic and inorganic material is moved back into the production of living matter.”8 Think of it as nature’s way of recycling.

Threats to the Health of Vernal Pools

Despite their important role in ecosystems, vernal pools face several threats including: chemical contamination, habitat conversion, invasive species, wetland draining, recreational activities, and logging.9

Public education about vernal pools is integral to protecting them. Next time you are hiking with a friend or family member and stumble across one of these pools, you can tell them about their role in the larger ecosystem.

Other Posts You Might Enjoy

Acadian Forest: History, Species, and Biodiversity

Sand Dunes: Their Ecological Importance


1 Aram J. K. Calhound and Phillip G. deMaynadier. 2008. Science and Conservation of Vernal Pools in Northeastern North America.

2 Ibid.

3 Elizabeth A. Colburn, Stephen C. Weeks, and Sadie K. Reed. 2007. “Diversity and Ecology of Vernal Pool Invertebrates.”

4 Calhound and deMaynadiere. 2008.

5 Colburn, Weeks, and Reed. 2007.

6 Ibid.

7 Ibid.

8 Nutrient Cycles.” Siyavula.

9 Parks Canada Agency. 2006. “Recovery Strategy for Multi-species at Risk in Vernal Pools and other Ephemeral Wet Areas Associated with Garry Oak Ecosystems in Canada.” Species at Risk Act Recovery Strategy Series.


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