What is a Keystone Species?

For anyone who knows anything about architecture, a keystone is common knowledge. However, for those who aren't familiar with the term, a keystone is the block or stone in an arch that basically supports the entire structure. If the keystone fails, the arch falls down. This basic premise is also applied in wildlife biology.

When biologists or ecologists talk about a keystone species, they are talking about one particular species of animal that is at the center of an ecosystem. An animal that all the others rely on in one way or another. A keystone species is critical to the environment and the entire ecosystem. If it's removed, the system will collapse. Conservation biologists have studied keystone species and recognize the importance of them in protecting the ecosystems. One excellent example of a keystone species is the sea otter. The sea otter eats abalone and sea urchins, which limits the population of these creatures. There's a perfect balance that's obtained naturally as the otters eat the abalone and urchins, which eat smaller organisms and the roots of sea kelp. Everything works fine until the sea otters are removed. Once the predators are gone, the abalone and sea urchins will have a spike in their population numbers. This causes a stress on the other organisms or the sea kelp, and then the creatures that rely on the kelp. The balance shifts and the ecosystem collapses.

This happened when fishermen who dive for abalone didn't like the sea otters because they ate the shellfish, so they began hunting and killing off the otters. For a while, they were very pleased because there was a lot of abalone around, but as the abalone flourished, they began to deplete the other organisms in the ecosystem. This caused a spiral and eventually the abalone did not have enough food to eat. The sea urchins ate too much of the kelp, causing the kelp forests to thin out. The fish and shellfish that relied on the kelp for shelter died or moved away. All of this happened because one important species was removed.

This is just one example, there are many others. But just like the keystone in an archway, a keystone species is essential to the health of the ecosystem. Nature has a way of naturally balancing itself out, but when humans become involved, they inevitably mess things up. A keystone species doesn't have to be a large predator, it could be a small insect that eats other insects that might otherwise eat too many of a species of plant. The plant is reduced or eliminated from the ecosystem and then the other insects that used the plant for food die. Understanding how an ecosystem works is very important, but sometimes not enough research is done and nature suffers.