Answer:
It is important because it keeps the other animals in check.
Step-by-step explanation:
They keep the animals in check so there isn't an overpopulation of a certain animal.
Let's take sea otters for an example, the sea otters keep the sea urchins in check so they don't eat all the kelp. When there was a massive decrease in sea otters due to orcas eating them, the kelp was disappearing and the sea urchins were growing in population.