sea otters

Otters to the rescue

February 23, 2024 By EarthWise Leave a Comment

California sea otters were hunted almost to extinction in the 19th century. Only a small number survived along California’s central coast. But over time, the otters recovered and increasingly recolonized their former habitats.

Sea otters are playing an important role in safeguarding California’s kelp forests and marshlands against the harmful effects of climate change.

Over much of the 20th century, increasing ocean heat had devastated underwater kelp forests by driving a population explosion of sea urchins that devour kelp. But sea otters eat urchins and as the sea otter population has grown, kelp has flourished. According to a new study published in PLOS Climate, the underwater kelp canopy along the central coast increased by 56% since 2016. Kelp forests have become more extensive and resilient to climate change wherever sea otters have reoccupied the California coastline.

At the same time, sea otters started recolonizing their former habitat in a central California estuary several decades ago and erosion has slowed by as much as 90%. The main reason is that otters love to eat the marsh crabs that were devouring the plants in this coastal ecosystem. The marsh plants establish dense root systems that can withstand waves and flooding. It would cost millions of dollars for humans to rebuild creekbanks and restore these coastal marshes. Instead, sea otters have been stabilizing them for free in exchange for a crab feast.

Sea otters are playful creatures that people enjoy watching. It turns out that they are also very valuable ecosystem engineers that are helping to mitigate the effects of the warming climate.

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How Sea Otters Are Protecting the California Coast Against Climate Change

Photo, posted May 17, 2021, courtesy of Michael L. Baird via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Vanishing Kelp Forests | Earth Wise

June 25, 2021 By EarthWise Leave a Comment

Bull kelp is the dominant species in offshore kelp forests north of Santa Cruz, California along the west coast of North America. Bull kelp has similar physical structures to terrestrial plants; it anchors to the ocean floor with root-like structures called holdfasts, and has stem-like structures called stipes from which leaf-like blades stretch out through the water, absorbing nutrients and sunshine.

These giant seaweeds form lush underwater forests in northern California’s coastal waters and have long provided critical habitat for many species like salmon, crabs, and jellyfish. But now, for much of the California coast, only a few patches of bull kelp remain.

A team from University of California Santa Cruz has studied satellite images of about 200 miles of coastline. They found that starting in 2014, the area covered by kelp has dropped by more than 95%.

The die-off was driven in part by an underwater heat wave that depleted nutrients in the water and made it harder for the kelp to grow. Making matters much worse, populations of purple sea urchins, which eat kelp, have exploded in the region because of overfishing and other reductions in urchin predators such as sea otters. The sea urchins eat kelp holdfasts, creating so-called urchin barrens where their destructive grazing has decimated kelp forests.

Bull kelp is a species at high risk of becoming endangered. In coming decades, more marine heatwaves are expected. These events as well as stronger El Niños will become more common and frequent with climate change. Between these thermal events and the sea urchins, it will be difficult for kelp forests to survive.

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Ninety-five percent of bull kelp forests have vanished from 200-mile stretch of California coast

Photo, posted October 28, 2015, courtesy of Florian Graner/Green Fire Productions via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

The Cockroaches Of The Ocean

December 14, 2018 By EarthWise Leave a Comment

The coast of Northern California is home to underwater forests – huge, sprawling tangles of brown seaweed. Kelp forests play a similar role in the oceans as the one that ordinary tree forests play on land. Like trees, kelp absorbs carbon emissions and provides critical habitat and food for a wide range of species.

Disappearing Kelp Forests

January 9, 2018 By EarthWise Leave a Comment

In recent decades, ocean temperatures in many places have warmed by nearly 3 degrees Fahrenheit. An effect of this warmer water is the decimation of what were once luxuriant giant kelp forests in eastern Australia and Tasmania. There used to be thick canopies covering much of the region’s coastal sea surface, but they have wilted in the intolerably warm and nutrient-poor water.