New in Wildlife Science: Hungry Otters Stabilize an Ecosystem

Otters in California feast on crabs that cause salt marsh erosion; indoor gardening enhances health; lungs help birds soar

By Mark Wexler
Wildlife Science
Dec 18, 2024

Otters Eat Their Way to a Healthy Ecosystem

Nearly exterminated by fur traders in the 1800s, southern sea otters that recolonized California’s Elkhorn Slough after hunting was banned are now thriving (above)—and their recovery shows how a single top predator can rescue a collapsing ecosystem. Following six years of field work in the 7-mile-long estuary, a team of scientists from several U.S. and Canadian institutions reports in Nature that the disappearance of otters had triggered an explosion of the slough’s marsh crab populations. “Crabs eat salt marsh roots, dig into marsh soil, and over time can cause a marsh to erode and collapse,” says lead author Brent Hughes, a Sonoma State University biologist. Otters have a voracious appetite for crabs, and in the decades since they began recolonizing Elkhorn, erosion along its creek banks and marsh edges has slowed by up to 90 percent, the team reports. Today, the estuary is home to the state’s largest concentration of sea otters. “It would cost tens of millions of dollars for humans to restore these marshes,” says senior author Brian Silliman, a Duke University marine biologist. “The sea otters are stabilizing them for free in exchange for an all-you-can-eat crab feast.”

An image of a floral designer preparing the Echeveria subrigida for planting.

Indoor Gardening Enhances Health

In previous studies, scientists unearthed health benefits that gardeners gain by digging in microbial-rich soil outdoors during spring and summer. Now, researchers in Finland find that indoor gardeners (above) can get a similar health boost from soil microbes in winter. For their study, the investigators collected samples from volunteers in two Finnish cities, measuring skin microbe levels along with the stability of the volunteers’ immune systems. In Environment International, the researchers report that just one month of indoor gardening (specifically, growing vegetables in fertile, microbe-rich soil) was enough to increase the variety of skin bacteria, some of which fight infection. They also found higher levels of anti-inflammatory molecules in the indoor gardeners’ blood. (Another group growing the same plants in peat soil that was low in microbes showed no positive changes in blood chemistry.) “Our research emphasizes the dependence of our health on the diversity of nature,” observes lead author Mika Saarenpää, who adds that the results “demonstrate how beneficial microbial exposure may be obtained year-round.”

An image of western gulls flying.

Lungs Help Birds Soar

Some birds use their lungs for more than just breathing. In a groundbreaking discovery reported in Nature, an international group of researchers has identified a specialized air-filled sac attached to the lungs of soaring avian species, including such diverse birds as bald eagles, turkey vultures, brown pelicans and western gulls (above). The structure seems to boost the power of these birds’ flight muscles while soaring, allowing them to remain aloft for long periods without flapping their wings. Called the subpectoral diverticulum, the air sac has evolved only in lineages of soaring birds, note the researchers, who examined computer imaging (CT) scans of birds belonging to 68 species that broadly represent Earth’s living avian diversity. The scientists did not find the air sac in any nonsoaring birds. “This evolutionary pattern strongly suggests that this unique structure is functionally significant for soaring flight,” says lead author Emma Schachner, a University of Florida evolutionary biologist.

An image of energy production at a PV solar ranch.

Microscope

Renewables Powering Up

Driven by steady growth in solar (pictured) and wind development, renewable energy sources generated a record 30 percent of the world’s electricity in 2023, British analysts conclude in the 2024 report Global Electricity Review.