As sea levels rise and natural disasters become more intense, homes in low-lying coastal areas or tinder-dry mountains are starting to lose value.

That’s a problem for the finances of Fannie Mae and Freddie Mac, the government-sponsored enterprises that back half of the nation’s outstanding mortgages — and keep the residential real estate market liquid by buying mortgages from banks and repackaging them into securities.

In the first year of the Biden administration, financial regulators seemed to recognize the risk, identifying the mortgage market as one of the main channels through which climate change could destabilize the financial system.

Since then, reports have been published, comments gathered and summits held. But when it comes to insulating the two enterprises and borrowers from climate-related catastrophe, the Federal Housing Finance Agency — which regulates Fannie and Freddie — has issued only vague guidance.

“It came out and I thought, where’s the rest of it?” said Carlos Martín, director of the Remodeling Futures Program at the Harvard Joint Center for Housing Studies.

The issue comes with risk for taxpayers as well, since the federal government took Fannie and Freddie into conservatorship in 2008 after the financial crisis. Fannie and Freddie have reserve capital buffers, but large losses could force the government to intervene.