Climate change is transforming the state’s coast but with habitats hemmed in by cliffs, condos and farms, pre-emptive action is needed to preserve biodiversity

The sea otters of Elkhorn Slough float by on their backs, greeting the occasional kayaker with unwanted socializing that can tip a boat. Chubby harbor seals lounge on large rocks and a great blue heron stands tall among hundreds of birds on a sliver of land.

This Monterey Bay estuary south of San Francisco hosts about 20,000 migratory shorebirds a year and is a nursery habitat for fish and shellfish. It’s notable for having bolstered the waning population of the curious southern sea otters, which now exceed 100 and are webcast live daily.

California is one of the most biodiverse states and its coast hosts most of its native species. Estuaries like Elkhorn Slough, where saltwater and freshwater meet, also filter pollution, reduce flooding and erosion and trap greenhouse gases.

But as the seas encroach due to climate change and rising water levels, governments and conservationists are asking themselves: where will the coastal habitats go?

If they retreat farther inland, they will meet cliffs, condos and farms. With intensive planning, minimally undeveloped land could be conserved to accommodate them. Without it, the west coast of the United States could lose a significant number of its unique ecosystems.

“The coast of California that we know today is not going to be the coast of California of the future,” says Walter Heady, a coastal marine scientist for the Nature Conservancy.

More than two-thirds of Californians live in coastal counties, and manmade pressures from development and pollution make it hard enough to protect coastal habitats, Heady said. Sea-level rise will only increase the challenge.

The Nature Conservancy partnered with a state agency, the California State Coastal Conservancy, to assess how a sea-level rise of 5ft (1.5 metres) would threaten the 3,427 miles where land meets water along the coast in the state.

In total, 59% of California’s coastal habitat is at risk, according to the group’s study of 40 different types of habitats, including estuaries, as well as beaches, tide pools and terrestrial areas.

Reserving minimally developed land for those habitats to move into could spare more than half the losses, the assessment concludes.

“We’re not trying to land-grab here, and it’s not my idea that all agriculture or golf courses or minimally developed lands should become habitat,” Heady said. “It’s a really small proportion of that human land use, and it could mitigate 61% of our losses.”

Four state agencies, two regional groups, four counties and two cities have signed on to conservation commitments spurred by the assessment.

“To my mind, this was an incredibly important tool that we need to acknowledge and to take into account and think through in all of our decision-making,” said Deborah Halberstadt, executive director of one of the state agencies, the California Ocean Protection Council.

Halberstadt said until recently ocean and coastal issues have not been a primary focus in the climate change advocacy world. Estuaries in particular tend to be “some of the least-funded geographies”, she said. Halberstadt’s agency advises the governor and legislature on coastal matters and is looking to fund work focused on estuaries.

“The more we can do now, the less expensive it will be in the future because we will have addressed some of the issues, but it’s sometimes harder to get funding prospectively,” she said.

Experts say that is the key problem with conserving coastal habitats: it’s hard to get people to proactively protect the places where those habitats will need to move as the seas rise.

“If you’re a farmer who’s got very productive land, at what point do you pull the ripcord?” said Mark Silberstein, the executive director of the Elkhorn Slough Foundation.

Facebook Twitter Pinterest Torrey Pines beach and coast of San Diego, California. Photograph: Feverpitched/Getty Images/iStockphoto

Silberstein has worked with nearby farms to retire their less productive acres of land that were using millions of gallons of water that would otherwise be buffering aquifers from salt water intrusion.

In Oxnard, a city west of Los Angeles, farmland is likely to become wetlands. Farmers are not allowed to sell their land for development, said Carmen Ramirez, mayor pro tem of the city.

“You can’t really farm on land that’s underwater, particularly saltwater. So it’s little by little going to be converted to wetlands anyway, like it or not,” Ramirez said.

As sea-level rise quickens, local governments can have trouble keeping up.

The state now recommends considering the possibility that if greenhouse gas levels are very high and ice melt increases, seas could rise 10ft by 2100. That would be 30 to 40 times faster than in the last century. While that is an extreme, California guidance says governments can’t afford to not plan for the worst-case scenario.

In Santa Cruz, the projections are looking worse and worse for West Cliff Drive, a seafront street on a bluff that may have to be narrowed or abandoned.

Tiffany Wise-West, sustainability manager for Santa Cruz, said the city will plan based on the state figures, its own vulnerability findings and the Nature Conservancy’s assessment.

“This is the first time we’ve actually had an understanding of which habitats are vulnerable to climate change impacts,” Wise-West said.