Conservation Outdoors Sustainability

Sustainability: Vernal Pools

Ambystoma maculatum (Spotted Salamander). Photo by Ben Dalton, NC Wildlife.

Vital Vanishing Habitats

By Winslow Umberger

It is likely that few made note of the first warm, rainy night since last fall. Yet it was a notable night for amphibians. While people slept, wood frogs and spring peepers, in response to the warmish rain, emerged from their winter sleep deep underneath the leaf litter in search of a vernal pool. Males fill these often tiny wetlands with their chorus of seemingly endless peeps, croaks and trills in order to attract a mate, with the result being hundreds of jelly-coated egg masses floating on the surface of the water or submerged underneath.

By summer’s end, these shallow, temporary pools will have served as crucial breeding grounds for many species of amphibians, including gray tree frogs, green frogs and salamanders such as red-spotted newts, and will have served as a nursery for literally thousands of various tadpoles. By mid-summer, the area will be aswarm with miniature young land-dwelling frogs and toads and tiny land-going bright orange-red salamanders called efts, not to mention the endless hordes of often unknown and unseen insects known as macroinvertebrates that serve as high-protein food for aquatic and land animals.

Notophthalmus viridescens (Eastern Newt). Photo by Ben Dalton, NC Wildlife

Vernal pools are an amazing hotspot of biodiversity. “They are temporary, typically lasting for only a few months during mid-winter and into early spring and early summer,” says Carlton Burke of Carolina Mountain Naturalists. “Yet they play a critical role not only in the life cycles of many species but also in the web of life. Salamanders and dragonfly larvae eat mosquito larvae while frogs, toads and dragonflies consume countless insects. These, in turn, become an important food source for many fish, reptiles, birds and mammals.”

The journey to a vernal pool is often fraught with danger. “They access these pools on rainy nights, traveling under cover of darkness and rain, and the temperature can’t be too cold,” says Burke. “A lot of them have to cross and recross highways to get to and from where they are breeding and, unfortunately, many are killed as a result.” Also, they may have made the trek for nothing. Their ancestral pool might have become a parking lot as development impacts wetlands, large and small.

There are different classifications of wetlands, but where there is water there is life. Each species that has an aquatic component in its life cycle relies on a specific type of wetland. Many vernal pools form in woods or along the edge of the forest. Some farm fields have areas where water collects, and tree frogs and toads will also utilize them. Even a small puddle a foot or two wide can become an oasis for a local amphibian population.

While vernal pools are usually temporary, some don’t dry up every year. They may fill up with heavy rainfall, snowmelt or flooding from nearby rivers or streams and last for months or even a few years. “People often fight against flooding which can often form vernal pools because they don’t understand the natural cycle of things,” says Burke. “People may protect larger, more scenic ponds, lakes, marshes and streams, but vernal pools are not normally protected or appreciated.” That is why education about the topic is so important.

Wood frog eggs. Photo by Winslow Umberger

Burke hopes that with awareness will come the desire to protect these essential habitats. “Anywhere water stands can become a vernal pool,” he says. “A true vernal pool that you see from year to year typically occurs at the base of a mountain slope or a low-lying area, but one can also be created in your own backyard.”

It may take a year or two for something to find it, but Nature will eventually populate it if it is located in a proper spot. A simple way to create a backyard vernal pool is to select a site that is part sun/part shade. Water depth in vernal pools can vary greatly, but they are generally shallow, some only three or four inches deep. Creating a pool can be as simple as inserting a non-toxic, preformed pond into the ground atop a thick layer of material to deter roots from piercing holes in the liner. Allow rainwater or snowmelt to fill it. If mosquitoes become an issue, throw in a chunk of mosquito dunk once a month. Then leave it alone.

Anaxyrus americanus (American Toad). Photo by Ben Dalton. NC Wildlife

Pollinator gardens have become popular projects both at home and at schools. Adding a small vernal pool is the next step in restoring another vanishing habitat. The opportunities for observation and learning offered by such a simple project are considerable and the benefit to wildlife immeasurable. While there are plenty of resources to get you started, Sarah Marwil Lamstein’s Big Night for Salamanders might be just the inspiration you need to get out and dig a hole for wildlife!

Winslow Umberger is head of outreach for Appalachian Wildlife Refuge. To learn more, volunteer or donate, visit AppalachianWild.org.

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