There are few places to purchase a home in the U.S. that have a greater risk of flooding than on the coast of Florida. But sellers needn’t lose sleep over that. That’s because the Sunshine State doesn’t mandate disclosure of whether a property has previously flooded. Some 21 states have no rules requiring owners to reveal a property’s flood history, according to a newly updated rating by the Natural Resources Defense Council, a New York-based non-profit advocacy group. That’s down only one from 2018, when NRDC did its first disclosure report.

“Too often policy changes only occur after a major disasters and that is not going to be good enough going forward,” said Joel Scata, a water and climate attorney with NRDC. “We need pre-emptive action on flood risk because climate change is increasing risk and the nation can’t afford to keep people in the dark.”

For would-be home buyers, no disclosure means there is often no way to gauge the true risk they are taking on. “Too often, homeowners are shocked years after a purchase because they didn’t know their home carried flood risk,” said Matthew Eby, executive director of the First Street Foundation, a non-profit that is trying to make the impact of climate change more transparent for individual property owners. The foundation recently released maps estimating current and future financial risks to every residential property in the U.S.

Flooding causes billions of dollars in damage in the U.S. every year and many of the costliest bills relate to properties that are built in flood-prone areas that get damaged over and over again.

Nearly 30 percent of Florida is in a high-risk area, and that number is expected to increase over the coming decades as climate change causes sea levels to rise. But that hasn’t stopped the state from protecting its valuable real estate industry. New York is similarly friendly to sellers—for $500 it will allow them to avoid disclosing that a home is located in the 100-year floodplain, the NRDC says.

But even awareness of being in a floodplain is inadequate. That’s because each home has a unique risk based on factors such as the nature of the built environment—for example, whether there is a sea wall or salt marsh nearby that could blunt a storm surge.

“Since so much flooding happens outside of the floodplain, you really need concrete details of each homeowner’s experience to understand flood risk,” said Scata. “And it is really only the seller that has the information.”