The southern sea otter was once found throughout the Pacific coast of North America, ranging from Oregon to Mexico. However, these cute critters were prized for their fur and hunted to near extinction in the 18th and 19th centuries. By the early 20th century, the population of sea otters in California had dwindled to only 50. Conservation efforts over the last few decades have allowed the Californian sea otter population to partially recover. Today, roughly 3000 sea otters can be found in the region. In a recent study, a team of researchers shed light into the impact of this otter renaissance on the local ecosystem.

Sea otters are a top predator. The scientists hypothesized that the reintroduction of otters would therefore have a large impact on the local ecosystem, as they would prey on other animals, creating ripple effects that trickle down through the food chain. In particular, otters eat crabs, which in turn eat pickleweed. Pickleweed plays an important role in the ecosystem, as its roots keep the creek bank stable and prevent erosion. With no predator to suppress the population of crabs, the crabs eat too much pickleweed, causing the creek banks to erode and eventually resulting in the destruction of the habitat. The scientists were therefore interested to see if the reintroduction of otters led to reduced erosion. To answer this question, they monitored the Elkhorn Slough estuary in central California over four decades. At the beginning of this period, otters were extinct in the region; today, the population totals more than 100. The scientists found that as the otter population increased, the population of crabs was suppressed and erosion was reduced by two thirds. So yes, sea otters do protect coastlines from erosion.

These findings underscore the importance of conservation efforts. While saving endangered species is a noble goal in itself, no species exists in isolation. Animals like the southern sea otter have evolved alongside their ecosystem for countless generations; restoring populations that have been devastated by human activity can therefore create ripple effects that allow the entire ecosystem to thrive.

This study was led by Brent B. Hughes, an associate professor in the Department of Biology at Sonoma State University.

Managing Correspondent: Emily Pass

Press Article: Ecosystem effects of sea otters limit coastal erosion (News from Nature)

Original Journal Article: Top-predator recovery abates geomorphic decline of a coastal ecosystem (Nature)

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