Sea otters aren’t just unbearably cute; they’re also emerging as key players in keeping the oceans healthy in a warming world, according to new scientific research.
Think of sea otters as the park rangers of coastal kelp forests. The floating thickets of treelike seaweed provide habitat for a plethora of marine life, including seals, sea lions, whales, gulls, terns, and snowy egrets. Like terrestrial forests, kelp forests absorb huge quantities of carbon dioxide that would otherwise be released into the atmosphere. (If you’re a surfer, kelp is cool because great white sharks don’t like to venture into the tangle of seaweed, so it’s safe to ride waves when otters are nearby.)
Sea otters must eat a quarter of their body weight each day to keep warm, and their appetites make them voracious consumers of spiny urchins, according to Rebecca Martone, a marine biologist at the Center for Ocean Solutions at Stanford University.
Left unchecked by otters, spiny urchins would multiply and lay waste to kelp forests, creating oceanic dead zones, Martone and her colleagues said in a presentation on Tuesday at the Ecological Society of America’s annual conference in Sacramento, Calif.
Fortunately for kelp forests and the marine animals that depend on them, the sea otter is one of the few predators that can crack the urchin’s hard shell.
A 2012 study led by Christopher Wilmers of the University of California, Santa Cruz, found that when otters were present, carbon storage in kelp forests from British Columbia to Alaska increased by 8.7 million metric tons. That’s worth about $408 million on Europe’s carbon trading market.
“Sea otters exhibit strong top-down control of grazers, particularly sea urchins, and thus indirectly increase kelp population spatial occupancy and productivity,” Martone and her colleagues wrote in a summary of their research they presented Tuesday.
The scientists studied the impact of otters on kelp forests and marine life off the Canadian coast in British Columbia. They found a greater diversity of marine life in areas where sea otters were present.
“Researchers found that when sea otters arrive in an area from which they have been absent, they begin feasting on urchins,” the Ecological Society said in a statement. “As a result, the kelp forest begins to grow back.”
The bad news is that sea otters are in trouble. Fewer than 3,000 otters are left off the California coast, for instance, and the marine mammal is classified as threatened under the United States Endangered Species Act. (The International Union for Conservation of Nature lists the sea otter as endangered.)
The impact of climate change on sea otters themselves remains uncertain.
“I don't know how vulnerable otters are themselves to climate change,” Martone said in an email. “If their prey populations are shifting in response to climate change, their populations could be affected.”
But she said her research shows the importance of preserving top predators to keep ecosystems in balance.