Ephemeral Wetlands

Northwestern Salamander (Ambystoma gracile)

As first appeared in BC Outdoors Magazine. Written by Kendall McLaughlin, BCWF Wetlands Workforce Assistant

It’s July and you are thinking of building a cabin somewhere far away from civilization. You come across this beautiful, relatively flat area full of sedges and grasses. The best part is the large pond just a few meters away. You take several photos of the area and plan all the logistics for building the cabin starting in the early spring.

April comes around and it’s time to start construction. You come back to the exact spot that inspired you in the summer, but it looks entirely different; it is now completely covered with water. The area that you thought was flat was a large shallow depression in the topography. Sadly, this place is no longer suitable for your cabin, unless you drained it, but you wonder why there wasn’t any water here in the summer. You inspect the pools and find several egg sacks that look like they belong to some sort of amphibian species, like frogs, toads or salamanders.

What you’ve found is an ephemeral wetland, also known as a vernal pool in some provinces and states. These are seasonal wetlands that fluctuate from dry during the summer to wet throughout more wet seasons. These periodic wetlands are often easily missed due to their natural isolation from any water inlet or outlet and are usually fed by rainwater or spring runoff. When completely dried up, it can blend into the surrounding topography, therefore making ephemeral wetlands very vulnerable to land-use changes.

Ephemeral wetlands are more noticeable during the spring season when the snow starts melting. Coincidentally, it is also the time when many species of wildlife start mating and reproducing – probably not by accident. Since these wetlands dry up, they are not suitable as fish habitat, making them the perfect spot for amphibian breeding with little predator presence, such as the Western toad, a species of concern in British Columbia.

Western Toad (Anaxyrus boreas)

Habitat loss and fragmentation, the division of connected and important habitat features, is one of the main drivers of the decline of amphibian populations. Many amphibian species have evolved to breed exclusively in these temporary pools. When they arrive to find them gone, they have spent too much energy to find another. Having access to these pop-up habitats gives these species a chance to thrive and these temporary wetted areas act as a path to other desirable habitats like the ponds or forests with a lot of security cover from predators.

Salamanders in particular take advantage of these sites. They are very sensitive to any changes in water quality, so their presence in an area is an indicator of good water quality. Their abundance is important for other species as a source of food, such as birds, snakes, fish, and rodents, which then further contribute to the food chain of other, larger predators.

In 2016, the Wetlands Education Program hosted the annual Wetlands Institute’s restoration project at Dewdney Elementary School to remove invasive reed canary grass and Himalayan blackberry from an ephemeral wetland on the school property to increase its habitat value to amphibians, birds, and invertebrates like dragonflies. Invasive species are one of many things that threaten these seasonal wetlands, as well as polluted runoff water, and water diversion or draining.

Dewdney Elementary School before and after restoration work in 2016.

In 2019, the Wetlands Institute brought participants to King George VI Provincial Park to help restore a 2.5-hectare project site that was a cottonwood swamp converted into agricultural lands in the early 1900s. This site has now been restored into a series of ephemeral wetland pools and will follow a trajectory back to a cottonwood swamp. The diversity of swamps is very important to many different types of wildlife species.

King George VI Provincial Park before and after restoration work in 2019.

Restoration projects like these are important for the local ecology. According to some ecologists, these types of wetlands are some of the most at-risk habitats, as their value is often under-estimated by landowners and land managers, or their wet features may not always leave obvious evidence for those that are not trained to look for seasonal fluctuations. You can help save these at-risk habitats by looking for them during the wet seasons, mapping them and informing your local government of their location.

Want to learn how to map wetlands? Come join us at a workshop hosted by the BCWF’s Wetlands Education Program by visiting our website at bcwf.bc.ca/wetlands-program/.

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