The return of sea otters to their former habitat in central California estuaries has reduced erosion of stream banks and wetland edges in the region by up to 90 percent, a new study finds.
These carnivorous semi-aquatic mammals were able to slow the rate of erosion through their hunger for plant-eating marsh crabs, according to research published Wednesday. Nature.
“It will cost millions of dollars for humans to rebuild these stream banks and restore these wetlands,” said corresponding author Brian Silliman, a professor of marine conservation biology at Duke University. statement.
“They’re stabilizing the sea otters for free in exchange for unlimited crab food,” added Silliman, who also directs the Duke Wetlands Coastal Center and Restoration Program for Ecosystem Restoration.
The authors note that after fur traders hunted the local otter population to near extinction, the marsh crab population exploded, and the few remaining animals were driven out by agriculture and other human activities. did.
“Crabs feed on salt marsh roots and dig into the salt marsh soil, which can cause salt marsh erosion and collapse over time,” said lead author and Sonoma State University Associate Professor of Biology. Brent Hughes said in a statement.
Scientists decided to study conditions in the estuary waters of Monterey Bay’s Elkhorn Swamp, where sea otter recolonization efforts began in the mid-1980s.
“After several decades, salt marshes and stream banks have become stable again in areas where sea otters have recolonized,” says Hughes, who was previously a postdoctoral fellow in Silliman’s lab at Duke University.
Hughes added that this change occurred “despite rising sea levels, increased amounts of water from inland sources, and increased pollution.”
To determine exactly what role sea otters played in that migration, researchers conducted comprehensive surveys across 13 tidal creeks and smaller-scale surveys at five sites around the estuary over nearly a decade. A field experiment was conducted.
Scientists removed sea otters from some areas and allowed them to recolonize others.
By collecting ground and aerial measurements and observations, the authors confirmed that erosion had slowed by as much as 80 to 90 percent by the study’s conclusion. Some swamps are expanding further, they noted.
“The return of the sea otter did not reverse the loss, but it slowed the sea otter down enough that these systems could re-stabilize despite all the other pressures the sea otter was under.” Hughes said.
Co-author Christine Angelini, director of the Center for Coastal Solutions at the University of Florida, wrote in a separate article: statement The recovery of the otter population appears to have been “achieved without much effort.”
“As a result, we are now unlocking decades of benefits from that single conservation action,” Angelini added.
Silliman also highlighted the important theoretical implications of their study, saying it “overturns the established bottom-up paradigm” that coastal change is controlled by vegetation and physical forces.
“Our findings clearly show that predators also play an important role in controlling the flow of these tidal streams,” Silliman added.
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