New Cootes Drive Vernal Pools Create Critical Habitat for Wildlife

McMaster University
By Johnathan , Restoration & Stewardship Intern
28 March, 2024

In November 2023, five ponding features were excavated in the wet meadow along Cootes Drive with the intention to create vernal pool habitat. Over the course of 2024, native wetland plant species will be planted around these ponds to replace the pre-existing non-native grass species that had taken over this area, promote biodiversity and restore healthy habitat for plants, insects, amphibians, and many other species.

What are vernal pools?

Vernal pools are ephemeral wetlands that are distinguished by the unique community of species that rely on them for survival. Ephemeral wetlands are any wetland that is not permanently flooded, and in southern Ontario ephemeral wetlands generally fill during spring melt and dry up over the course of the summer. This seasonality is crucial to the unique ecology of vernal pools, as it prevents fish from surviving in them. Many fish species are voracious hunters, and vernal pool species cannot survive with these aggressive predators.

What species rely on vernal pools?

In southern Ontario, vernal pools are home to frog, toad, and salamander larvae. Some of these species, such as American Toads, commonly breed in any water body available to them. However, vernal pools can provide a habitat for growing toad tadpoles free of many of their usual predators, affording them increased likelihood of survival. Other species, like Spotted and Jefferson Salamanders, are entirely dependent on fish-free ponds and wetlands to reproduce and their populations cannot survive without these sensitive habitats.

Vernal pools are also the habitat of fairy shrimp, which are small crustaceans that can only survive in these unique ponds. Despite being fully aquatic and unable to leave ponds during the dry season, fairy shrimp survive by laying eggs that must dry up completely before hatching when wet conditions return. These eggs begin a new population of adult fairy shrimp when spring returns (Fairy shrimp).

Beyond the animals that rely on them, vernal pools can be amazing habitat for wetland plants. Beautiful native wildflowers like Cardinal Flower and Swamp Milkweed thrive in the wet conditions in and around these ponds, and vibrant shrubs like Red Osier Dogwood provide habitat for birds above the water level and amphibians below the water level, as well as food for insects.

Vernal pools contribute to more species than just those that live in and around them. Healthy populations of amphibians also boost the populations of their predators, such as snakes, opossums, and fish. Wildflowers growing around vernal pools can support native pollinators, and vernal pools can serve as watering holes for local wildlife.

Why build vernal pools?

Vernal pools are an increasingly rare and sensitive habitat in southern Ontario. Due to rapid urbanization, many vernal pools have been lost to development. Their small size and ephemeral nature means they are often overlooked, despite their essential role in our local ecosystems. Constructing new vernal pools is not a perfect solution, and protecting existing natural vernal pools is essential to maintain the health of our local ecosystems. However, new vernal pools can provide important habitat for struggling species and contribute to overall biodiversity in the surrounding area.