How do you know which organisms are keystone species?

Question

I know that keystone species are those that play a crucial role in an ecosystem, but since all species are interdependent upon each other and each occupy their own niche, aren't they all important? How do you know which organisms are keystone species?

Answer 1

You are correct in saying that keystone species play a critical role in an ecosystem. The "key" distinction is that a keystone species typically plays a disproportionate role compared to its relative abundance compared to there species. Sea otters are a great example of this. The otters feed on sea urchins, which feed on kelp. Although there are far fewer otters compared to sea urchins, the otters play a critical role in the health of this ecosystem. Without the otters, sea urchin populations will increase, which will cause more keep to be consumed. Eventually, the actual kelp forest ecosystem can be so negatively impacted by the sea urchins that the ecosystem collapses. The otters play a critical role in maintaining the entire ecosystem.