Wild About Keystone Species

The temperate rainforests of British Columbia’s central coast are a complex ecosystem filled with towering trees and lush vegetation. Home to grizzly bears, wolves, and a host of other species, the diversity of this forest depends on one species more than any other: salmon.

Every summer, millions of salmon return to rivers on the central coast, seeking their ancestral spawning grounds. Waiting for them are a host of other species, bears, wolves, eagles, ravens, and even the trees themselves. Salmon are a keystone species, they anchor the ecosystem, playing a role that can’t be duplicated by other other plants or animals. Unlike other keystone species, salmon’s most important contribution comes in a unique way—by dying. 

A male sockeye salmon in full breeding colours of red and green in shallow water. The upper half of the fish is visible above the water.
Male Sockeye Salmon, photo by US Environmental Protection Agency, Public domain, via Wikimedia Commons

If you’ve ever been to a river during the salmon run, you’ll know that it’s the smell that hits first. The cloying, rancid smell of rotting fish lodges in the back of your throat as the water fills with the corpses of salmon. With the decaying fish comes a vast array of nutrients that return to the forest from the ocean. But not all of the dead fish rest in the water. In particular, bears catch fish and drag them into the forest, spreading the nutrients beyond the confines of the river channel, and ensuring the rich growth of the forest. Without salmon, the entire forest ecosystem would suffer.

A young grizzly bear carries a fresh caught salmon out of the river towards the bank.
Brown bear carrying a salmon. Photo by Mark Wipfli, Alaska Cooperative Fish and Wildlife Research Unit. Public domain, via Wikimedia Commons

Keystone species are found in ecosystems around the world. For the North American prairie ecosystems, bison filled this role until their deliberate and systematic extermination in the late 1800s. 

Like salmon, bison are intimately connected with their habitat, and their presence benefits a range of species. Unlike many other herbivores, bison foraging across the landscape causes vegetation to green-up sooner and last longer than expected, improving diversity. The way bison graze native grasslands is unique; although they may seem similar, domestic cattle do not provide the same benefits to the ecosystem. 

While bison have landscape level impacts on prairie ecosystems, their presence also has smaller, more individual impacts on other species, from the bison fur that’s used to line bird nests to the close-cropping of vegetation in prairie dog colonies, which in turn provides habitat for a range of species such as burrowing owls and rattlesnakes. 

A prairie dog pokes its head out of its burrow. In the background, a bison grazes.
Bison and prairie dog. Photo by Steevven1, CC BY 4.0, via Wikimedia Commons

It shouldn’t be a surprise that bison and salmon are fully connected to their ecosystems. After all, they have evolved together for millenia. What is a surprise is that our ‘scientific’ understanding of the complexity and interconnectedness of these systems is a relatively recent phenomena. Our Western desire to separate and classify limits our ability to understand the whole. Once again, we have an opportunity to learn from Indigenous knowledge, which teaches that everything is connected. 

Bison and salmon are also cultural keystone species. Like ecological keystone species, in a cultural context, these keystone species have a significant influence on the cultural and social identity of a people, influencing diet, art, spiritual practices, medicine, and more. While cultural keystone species may also fill the keystone role in an ecological system, that is not always the case.

Cultural keystone species demonstrate something that many of us don’t think about as often as we should. That we are part of these systems as well. We are not separate from the salmon or the bison or from the rainforest or the prairie. Even in our urban neighbourhoods, with our sidewalks and our lawns, we are connected to the environment that surrounds us. Which begs a question. When these species are lost—as happened to the bison in the 1800s and is happening to the salmon today—what happens not only to the environment, but to us?