In 2020, California placed more than 70,000 tons of rock on a sediment-covered seafloor; four years later, fish biomass across the restored reef complex had risen 166%

Beneath the waters off California’s Palos Verdes Peninsula, a vast ecological experiment has quietly transformed one of the state’s most damaged marine habitats. In 2020, scientists and engineers dropped more than 70,000 tons of quarry rocks onto a sediment-covered stretch of the Pacific seabed to recreate the rocky reef habitat that was once present and had been buried by decades of landslides and contaminated by historical DDT and PCB pollution. According to NOAA Fisheries , monitoring after four years showed that the restored reef had exceeded expectations, with fish biomass across the entire reef complex increased by 166%, thus highlighting how carefully designed habitat restoration can rapidly revive marine ecosystems.

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