Three women were killed last week while sunning on a beach in Encinitas, California, when the bluff above them gave way.

The sudden tragedy that befell Anne Clave; her mother, Julie Davis; and her aunt Elizabeth Cox, who had gathered at the resplendent coastline in the seaside community north of San Diego to celebrate Cox surviving cancer, made headlines around the world. But cliff erosion continues to imperil people and property around the state. California is falling into the sea piece by piece, and coastal conditions will only grow more dire with worsening climate crisis.

A woman was killed in Santa Cruz county when a cliff collapsed beneath her feet in 2017. A landslide on a San Francisco beach killed another beachgoer in 2019.

Nearly three-quarters of California’s coastlines are actively eroding, putting lives, homes, roadways, railways, utilities and other infrastructure in danger. The cliffs have been crumbling since before the Arctic began melting, but natural geological collapse stands to worsen in the coming years.

Facebook Twitter Pinterest The area of the collapse is taped off in Encinitas. Photograph: Hayne Palmour IV/AP

“We’re always striving to make our beaches safer – safety is a huge part of beach access,” said Jennifer Savage, California policy manager for the Surfrider Foundation, which is dedicated to coastal preservation. “We did not take everything into account when we started building, so now we’re trying to play catch up, and that’s really hard. But the cost in human lives and to the economy will be profound if we don’t start thinking differently.”

Although researchers can’t point to a single cause of any particular cliff failure now, they expect to see more as the climate continues to collapse. “What we can say unequivocally is as sea level rises, these kinds of events will become more common,” said USGS research geologist Patrick Barnard.

Scientists say sea level rise will accelerate cliff retreat, doubling average erosion rates in southern California by 2100, including some of the state’s most heavily populated, tony coastal communities. That’s because sea level rise and more extreme storms mean bigger, higher waves washing away beaches and lapping at the bottoms of the cliffs. California stands to lose two-thirds of its beaches by the turn of the next century, in a wave of coastal economic destruction worse than the state’s most devastating fires to date.

“We expect the higher the sea level, the more the ocean is pounding the base of the cliff, the more frequently we can expect to have failures like the one in Encinitas,” said Barnard.

Coastal residential development, too, contributes to erosion by adding weight to clifftops and changing water drainage routes. And sea walls meant to fortify bluffs and protect communities can actually help scour away protective sand beaches even faster.

Facebook Twitter Pinterest A beach in Santa Cruz. A woman was killed in Santa Cruz county when a cliff collapsed beneath her feet in 2017. Photograph: Dan Tuffs/The Guardian

The stakes are rising along with the ocean. Apartment buildings and homes in Pacifica, south of San Francisco, were condemned and demolished after rapid erosion following an intense 2015-2016 storm season crept under property lines. Several homes in Sonoma, north of San Francisco, have been torn down or have fallen with the cliffs that had once supported them. Sections of California’s famed coastline-hugging Highway 1 have been closed or moved inland, and there are plans to shift more.

One potential adaptation strategy is “managed retreat”, or the unbuilding of communities threatened by erosion and flooding along the coast using buyouts and eminent domain.

“As time moves forward, we have less and less options,” Sara Aminzadeh, a commissioner with the California coastal commission, told representatives of several cities at a July meeting. “I think it’s incumbent on all of us together to change the narrative and make the case for why [managed retreat] is necessary.”

The commission oversees how cities develop and protect their coastlines and has been working to prepare the coast for sea level rise for several years.

Facebook Twitter Pinterest Sections of land are seen missing from coastal properties in Pacifica, California, amid erosion in 2016. Photograph: Josh Edelson/AFP/Getty Images

Perhaps unsurprisingly, several coastal towns are defiant about nature’s inexorable push and instead hope to hold the line by better engineering the natural coastline to withstand more pressure from the Pacific, replenishing sand on the thinning beaches and further armoring cliffs against collapse.

The precarious coastal community of Del Mar, for example, just a few miles south of Encinitas, has largely rejected the notion of moving back from the edge, even as its cliffs are crumbling at a rapid clip. Del Mar’s plan to protect the city, where the average home is valued at $2.5m, largely hinges on building up the beach with imported sand – not unbuilding parts of the town that hang in the balance.

More of the coastline is bound to fall in the meantime, endangering beachgoers and homeowners alike. The deadly incident at Encinitas is a reminder of how much is at stake.

“Just culturally we tend to want to stand our ground as Americans,” said Savage. “The idea of retreat is not who we feel that we are.”