What is a KEYSTONE Species?

Keystone species are the glue for their ecosystems and hold everything together. Without them, entire ecosystems collapse. What are keystone species? What do they do? Why do we care?

All species fulfill their purposes but some species are so important that their survival is essential to the ecosystem they live in. Keystone species can determine the success or failure of an ecosystem, and thus are even more important than you might think.

When I first learned about keystone species was right before a trip down the Pacific Coast Highway in California. My husband and I were enjoying our breakfast in the car while watching the sea otters float peacefully in the Morro Bay bay.

Sea otters are one of the prime examples for a keystone species. They are one of the few species that eat sea urchins despite the spines. Morro Bay, like much of California, is home to beautiful and vast kelp forests. The Giant Kelp endemic in Californian waters houses endless species, from tiny critters to sea lions and Giant Sea Bass. Sea urchins eat kelp. Sea otters eat sea urchins. Without sea otters, the urchins take over and destroy the kelp forests. The sea otters are necessary to keep the balance of the ecosystem in check.

Of course, there are plenty of other examples for keystone species.

But what exactly makes a species a keystone species?

There is no formal method for determining a keystone species, so scientists often don’t agree about them. And I agree that it can be a bit of an oversimplification of things. After all, ecosystems are complex webs of interactions. But declaring something a keystone species can drive the point home that a species is essential for an ecosystem to stay in balance.

According to the National Geographic, there are three types of keystone species: predators, ecosystem engineers, and mutualists.

Predators, like our lovely sea otter, keep populations in check. Sometimes, they even favor the weaker organisms and leave the healthier ones alive. So it can be a simple culling or a culling of the weakest links.

Ecosystem engineers, like beavers, change the setup of ecosystems for the better. They chew down old trees for their damns, allowing new growth.

And then there are the mutualists, which live in symbiosis with another species to the benefit of all. Take bees, for example, which feed on the nectar of flowers, trees, and other plants, but also take the pollen and spread them to nearby recipients. This means fruit to feed on later in the year and reproduction, so new growth in the future.

The problem is, that even if a species is declared as a keystone species, protective action is often too slow or too late. We need to do better here. If we realize the importance of a species after it is gone, it is too late to do anything about it and we’ll have to deal with the consequences.

Keep in mind that keystone species are often what makes an ecosystem resilient to human activity or invasive species. Without them, the balance is thrown off and the ecosystem is vulnerable.

Some argue that declaring some species as “essential” takes away from those species not labeled thusly. And while I agree that this is the case, I am not very confident that humanity will wake up in time to save them all, so saving at least some—preferably the ones that keep everything together—seems a necessary evil.

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