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What are keystone species and why are they important?

What are keystone species?

And why are they important?

What are keystone species and why are they important?

The Great Bear Rainforest, located along the Pacific Coast of British Columbia, is a great example of a thriving yet vulnerable ecosystem. In this temperate rainforest, over 2,500 salmon runs take place a year. Many species rely on salmon as a seasonal food source, including bears, otters, wolves, orcas, loons and humans. The natural cycles of different species even closely align with salmon spawning season, ensuring their survival. Salmon also nourish trees, insects, algae, mosses and shrubs by enriching the rainforest’s living soil with nitrogen, sulfur, carbon and phosphorus. This process takes place when other larger species, like bears and wolves, drag their carcasses through the forest. Because salmon are at the centre of an essential system taking place in the rainforest, they are often considered a keystone species. 

Brown bear eating salmon in water
By DAPA Images via Canva

What are keystone species?

A keystone species is a plant, animal, fungi, or even bacteria that has a disproportionately large impact on their ecosystem. They play an important role in their natural environments as their impact on other species can reshape entire ecosystems. And without their presence, many ecosystems would look incredibly different, could face collapse, or may not even exist.

So, where did the name ‘keystone’ come from?

Coined in 1966 by the American ecologist, by Robert T. Paine, he used the term ‘keystone species’ to describe the relationship between seastars (predators) and mussels (prey). In architecture, the ‘keystone’ refers to the wedge-shaped stone located at the top of an archway. While its presence within the structure appears relatively minor, if removed, the whole arch would collapse as it locks the structure in place.

Types of Keystone Species

The first type of keystone species are PREDATORS. As a vital part of ecosystems, they help “control the population of prey species,” according to National Geographic. This in turn impacts the whole food web. One of the most well-known keystone species are the grey wolves in Yellowstone National Park. In the 1920s, their population was completely depleted as a result of years of overhunting. Without their presence, the population of prey species exploded. This resulted in a massive decline in vegetation and aspen trees, which in turn degraded parts of the ecosystem. However, grey wolves from Jasper National

Park were reintroduced in 1995. While it took some time, they triggered what’s called a trophic cascade. This ripple effect, which is continuing to unfold to this day, restored the beaver population, increased vegetation, and even brought back rivers. Check out this fascinating video to learn more about this conservation success story.

The second type of keystone species are ECOSYSTEM ENGINEERS. Beavers are a great example of this keystone since they create and modify habitats. To build their dams, they typically use old or dead trees along riverbanks, which helps encourage new tree growth. Their dams also divert the flow of rivers, establishing rich wetland habitat.

The third type of keystone species are MUTALISTS. Bees are a great example of this type of keystone since their interactions with plants is mutually beneficial. For example, as they collect their primary food source of nectar and pollen, they enhance plant growth and potential for fertilization.

Ink and watercolour painting of a salmon
'Salmon', ink with watercolour wash, by Leanne Cadden