Sea otters help kelp forests return—but how quickly?

When sea otters return to coastlines, they can help facilitate the growth of kelp forests that sea urchins once destroyed. But their ability to do so is based on a few factors. Managers reintroduced the otters to British Columbia in the 1970s and to Nicolas Island in California in the 1980s. In a study published in Proceedings of the National Academy of Sciences, researchers looked at 30 years of data from community collection studies in both areas. They found that the sites where sea urchins overgrazed due to the absence of sea otters (Enhydra lutris) had kelp forests that grew back. However, it took much longer for kelp to grow back in the Southern California site. The research team found that this was because there was more competition between different urchins, kelp and other species there. “We always thought keystone species control their ecosystem the same way, regardless of where they are or what else is in the ecosystem,” said Ryan Langendorf, the lead author of the study. “A more modern view is that they are still very important, but they can have different effects in different places.” 

Read the study in Proceedings of the National Academy of Sciences.