Kelp Forests Were Quite Different Before The Stellar’s Sea Cow Went Extinct

Using mathematical models, researchers have been able to identify how an extinct mammal – the Stellar’s Sea Cow – likely impacted kelp forests prior to overhunting by European colonizers.

The Stellar’s Sea Cow was a four-ton animal that was closely related to the manatee and occurred along the Pacific coast of North America until the 1700s. It went extinct a mere 27 years after its first encounter with Europeans due to overhunting. And, its disappearance likely altered the kelp forest ecosystems it inhabited.

This study focused on how the Sea Cow’s decline affected kelp forests in the Commander Islands, which are the westernmost Aleutian Islands and are part of Alaska. With the Sea Cow gone, the scientists used dugongs as an analogous species, because of their close relation to sea cows. Because the Sea Cow consumed large quantities of kelp fronds from the canopy, its grazing likely allowed more sunlight through, allowing other photosynthetic species to thrive on the seafloor and greatly reducing the abundance of kelp.

There is no such large mammal in present-day kelp forests that consumes vast quantities on any regular basis, which creates the kelp-dominated systems we see today. In thinking about conserving kelp forests, it is important to consider the conditions they evolved under – especially when trying to protect them from further decline.

“When kelp forests were evolving millions of years ago, there were large marine herbivores like the Steller’s sea cow, which are now extinct. So when it comes to what’s driving their widespread decline, there might be a major component we’re missing,” says Dr. Peter Roopnarine, Curator of Geology and Invertebrate Zoology at the California Academy of Sciences.

Thus, the paper suggests considering a “Past-Present-Future” approach, where ecosystem characteristics that can be deduced from museum specimens and Indigenous science be used alongside contemporary evidence when designing conservation plans for the future of different species.