Sea Otters Help Save California's Wetlands
2024-02-08
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1At one point, it was nearly impossible to see sea otters along the west coast of the United States.
2The animals were hunted nearly to extinction in the 1800s. People paid for their fur.
3At one point, only about 2,000 remained. Most lived in the waters off Alaska.
4But by the 1980s, the animals started to recover.
5Three programs helped increase their population in northern California.
6First, hunters were banned from killing the otters.
7Next, an environmental program restored the wetlands where the otters once lived.
8And finally, California's Monterey Bay Aquarium began to raise otters and release them into the wild.
9For about 40 years, the animals have been back in the seaside area called Elkhorn Slough.
10It is between Monterey and San Francisco.
11Brent Hughes is studying how the otters' return affected the environment.
12He is a marine ecologist at nearby Sonoma State University.
13He recently published a report in the science journal Nature.
14Hughes and his team looked at a wetland area called a tidal estuary.
15The researchers found that the otters perform a service that keeps the area from eroding -- or wearing away.
16Hughes said the otters feed on a destructive shellfish called the striped shore crab.
17The crabs dig into the mud and sand and bite the roots of a marsh grass known as pickleweed.
18Pickleweed holds the soil in place during coastal flooding.
19The holes the crabs make cause the area to look like "Swiss cheese," Hughes said.
20Swiss cheese is a kind of cheese with many holes.
21For the new study, researchers examined erosion rates dating back to the 1930s.
22The historical data help the researchers understand the effects of sea otters' return to the area.
23The researchers also set up fences that prevented the otters from entering certain areas for three years.
24In the fenced-off section of the estuary, the scientists say the soil eroded much more quickly.
25Hughes said the otters "don't completely reverse erosion but slow it down to natural levels."
26The otter study is one of several research projects that follow what happens to an area when a top predator returns after a long period of time.
27A famous past study looked at the return of gray wolves to Yellowstone National Park.
28The wolves hunted elk and moose that ate small trees along riverbanks.
29With fewer elk and moose, the trees started growing again and the riverbanks did not erode as quickly.
30Something similar happened when the otters returned.
31Johan Eklof is a Swedish marine biologist from Stockholm University who reviewed the study.
32Other studies, he noted, depended only on observation.
33But this new study leaves no doubt that the otters limit erosion.
34Other studies show that otters can be helpful for plants.
35One study said the otters eat sea creatures called urchins that feed on kelp.
36The return of the otters permitted the kelp to grow again.
37Brian Silliman is a coastal ecologist from Duke University in North Carolina. He co-wrote the new study.
38He described the otters as "amazing finders and eaters."
39I'm Dan Friedell.
1At one point, it was nearly impossible to see sea otters along the west coast of the United States. 2The animals were hunted nearly to extinction in the 1800s. People paid for their fur. At one point, only about 2,000 remained. Most lived in the waters off Alaska. 3But by the 1980s, the animals started to recover. Three programs helped increase their population in northern California. First, hunters were banned from killing the otters. Next, an environmental program restored the wetlands where the otters once lived. And finally, California's Monterey Bay Aquarium began to raise otters and release them into the wild. 4For about 40 years, the animals have been back in the seaside area called Elkhorn Slough. It is between Monterey and San Francisco. 5Brent Hughes is studying how the otters' return affected the environment. He is a marine ecologist at nearby Sonoma State University. 6He recently published a report in the science journal Nature. Hughes and his team looked at a wetland area called a tidal estuary. The researchers found that the otters perform a service that keeps the area from eroding -- or wearing away. 7Hughes said the otters feed on a destructive shellfish called the striped shore crab. The crabs dig into the mud and sand and bite the roots of a marsh grass known as pickleweed. Pickleweed holds the soil in place during coastal flooding. 8The holes the crabs make cause the area to look like "Swiss cheese," Hughes said. Swiss cheese is a kind of cheese with many holes. 9For the new study, researchers examined erosion rates dating back to the 1930s. The historical data help the researchers understand the effects of sea otters' return to the area. 10The researchers also set up fences that prevented the otters from entering certain areas for three years. In the fenced-off section of the estuary, the scientists say the soil eroded much more quickly. 11Hughes said the otters "don't completely reverse erosion but slow it down to natural levels." 12The otter study is one of several research projects that follow what happens to an area when a top predator returns after a long period of time. 13A famous past study looked at the return of gray wolves to Yellowstone National Park. The wolves hunted elk and moose that ate small trees along riverbanks. With fewer elk and moose, the trees started growing again and the riverbanks did not erode as quickly. 14Something similar happened when the otters returned. 15Johan Eklof is a Swedish marine biologist from Stockholm University who reviewed the study. Other studies, he noted, depended only on observation. But this new study leaves no doubt that the otters limit erosion. 16Other studies show that otters can be helpful for plants. One study said the otters eat sea creatures called urchins that feed on kelp. The return of the otters permitted the kelp to grow again. 17Brian Silliman is a coastal ecologist from Duke University in North Carolina. He co-wrote the new study. He described the otters as "amazing finders and eaters." 18I'm Dan Friedell. 19Dan Friedell adapted this story for Learning English based on a report by the Associated Press. 20________________________________________________ 21Words in This Story 22extinction -n. the state or situation that results when something (such as a plant or animal species) has died out completely 23affect -v. to produce an effect on something 24certain -n. a known place or area 25predator -n. an animal that lives by killing and eating other animals 26We want to hear from you. Have you ever seen a sea otter up close? What did you think?