How Sea Otters Save the Planet

FOOD CHAIN: kelp → sea urchins → otters → killer whales (orcas)

\ The ecosystem/food chain shown above is called a trophic cascade. It means that the secondary/tertiary consumer affects the entire food chain. Sea otters, while they may not be at the very top of the food chain, affect the entire ecosystem. They are what is known as a %%keystone species%%. Without them, the entire ecosystem falls apart.

Sea otters were hunted often by human because of their thick pelts, and also by killer whales. When they began to disappear from their ecosystems, everything fell apart. The kelp population began to decline at a rapid pace, and the urchin population grew. And, because there was no kelp and no sea otters, the ecosystems started to break down. Acidity levels rose, which was harmful to many species.

\ When sea otters were reintroduced to their habitats, a scientist by the name of James Estes compared ecosystems that had otters versus those without them. The results were fascinating. In ecosystems with sea otters, there was a lot of homeostasis. The kelp forest was thriving, and CO2 levels declined since the kelp was consuming the carbon. However, in ecosystems without sea otters, CO2 levels continued to rise, and sea urchins covered the sea floor.