British Sign Language Glossaries of Curriculum Terms

BSL Environmental Science Glossary - Keystone species definition

Definition: A Keystone Species is a species that is important for the maintenance of an environment. For example, prior to the 1900s in the Yellowstone National Park (an area of outstanding natural beauty), the number of wolves began to decline and were eventually wiped out. This was because people hunted and killed them. Consequently the number of deer in the park started to increase and this was because they were no longer being preyed upon and eaten by the wolves. Unfortunately this ever-increasing number of deer had a detrimental impact on the vegetation and meant that birds, beavers and other animals had nothing to eat and either declined in numbers or were forced to leave. This went on until about 1995 when the decision was made to reintroduce wolves back into the park. They started off with about 8, just to see what would happen. The wolves had a massive impact on the environment because the numbers of deer started to fall as they were again being preyed upon by the wolves. Once the number of deer became more stable, the plant life recovered and with it the numbers of birds and animals that had previously left or died out and the environment returned to its more natural state. All of this happened because of the presence of wolves which is why they are a keystone species.