In 2013, California began removing millions of purple urchins from arid reefs; Seven years later, more than 55 acres of kelp forest had returned

Beneath the waves of Southern California, a once lush underwater forest had been reduced to something resembling a desert. The algae that had provided shelter and food for fish, crabs and marine mammals had disappeared, leaving behind rocky reefs covered with hungry purple sea urchins. Then, in 2013, conservationists and fishermen began tackling the problem from the seafloor, one urchin at a time. Seven years later, more than 55 acres of kelp forest had returned, bringing with it marine life, the NOAA Fisheries website reports. Scroll down to read the details.

When kelp forests disappear

Kelp forests are among the most productive ecosystems in the ocean. They provide habitat for fish and invertebrates while supporting marine mammals and other wildlife.But Southern California’s kelp forests have faced years of pressure from environmental damage. A major source of pollution came from the Montrose Chemical manufacturing plant, which discharged contaminants, including DDT and PCBs, into coastal waters between the 1940s and 1970s. The chemicals persisted in sediments along the Palos Verdes ocean shelf and affected marine ecosystems and wildlife. As the algae subsided, another problem arose.

Purple Hedgehogs Take Control

According to the report, sea urchins are normally part of a healthy coastal ecosystem. But when their numbers become excessive, they can consume algae faster than the plants can recover. The result is an urchin desert, a shallow reef where dense populations of purple urchins graze on newly grown algae, preventing the forest from returning. To break that cycle, the Bay Foundation led a partnership involving researchers, conservationists and commercial urchin fishermen. Starting in 2013, the team began removing the overwhelming number of purple urchins from affected reefs. The scale of the effort was enormous. Five commercial fishermen ultimately contributed more than 8,000 hours of underwater work and caught approximately 4.2 million urchins.

Make a barren reef green again

The goal was not simply to eliminate the urchins. It was to give the algae a chance to establish itself and rebuild the habitat. The strategy began to produce visible results. By 2020, restoration efforts had helped recover more than 55 acres of kelp forest. Recovering forests created new habitats for fish and other marine species, transforming areas once dominated by bare rocks and urchins into more complex and productive ecosystems. The project also demonstrated the value of bringing together people with different types of expertise on the same conservation problem. Scientists contributed research and monitoring, conservation groups coordinated restoration, and commercial fishermen brought years of hands-on experience working underwater.

Restoration beyond Kelp

Kelp recovery is part of a much broader effort to repair ecosystems damaged by pollution and oil spills. In San Francisco Bay, restoration funds following the 2007 Cosco Busan oil spill have supported more than 60 projects. The spill contaminated more than 3,300 acres of coastal habitat and affected Pacific herring. Among the projects are efforts to restore subtidal native oyster and seagrass habitat. More than nine acres of eelgrass have been planted, while more than five acres of oyster reef structures have been installed to provide habitat for oysters, fish, crabs, birds and other wildlife.

A bigger lesson from damaged waters

Other restoration work has extended south to Baja California, where conservation teams have worked to rebuild seabird populations affected by pollution and oil spills. On the region’s Pacific islands, a multi-year restoration program used techniques designed to encourage the return of seabirds while reducing human disturbance. Of the 27 seabird populations that had disappeared from the islands, 22 returned over the past decade and four additional species began nesting there. These projects show that environmental recovery rarely occurs through a single intervention. It can require years of monitoring, funding, field work and cooperation between scientists, governments, conservation groups and local communities.Image courtesy: istock