Nearly 400,000 homes in the United States will be either permanently inundated by sea level rise or suffer chronic flooding from higher tides and storm surges by 2050 if nations fail to make significant cuts to greenhouse gas emissions, according to a new analysis by the real estate company Zillow and Climate Central. That number could grow to 2.5 million homes — worth $1.3 trillion, equal to 6 percent of the U.S. economy — by 2100 if emissions remain unchecked.

Among the nation’s 150 most-populous cities, Galveston, Texas and Miami Beach, Florida are projected to have the largest share of homes in risk zones by 2050, at 13.1 percent and 10.8 percent, respectively, if emissions go unmitigated, according to Zillow. That’s within the lifetime of a typical 30-year mortgage signed in the next couple years.

The analysis, which combined Zillow’s housing data with Climate Central’s sea level rise and flooding maps, found that moderate emissions reductions roughly in line with Paris agreement pledges would reduce those numbers by 10 percent.

It also found that in more than half of the nation’s coastal states, homes are currently being built in flood risk zones at higher rates than in safer areas — as much as 3 times faster in Rhode Island and New Jersey. This is despite several devastating coastal storms and flooding events in recent years, such as Superstorm Sandy and Hurricane Harvey.

In New Jersey, around 2,700 new homes, worth some $2.6 billion, have been built since 2009 in areas at risk of flooding at least annually within the next three decades. “After Sandy, the main thrust was to put everything back the way it was as quickly as possible,” David Kutner, the planning manager for New Jersey Future, a nonprofit that supports sustainable development, told Zillow. “The byword during that period was ‘stronger than the storm,’ which was the height of hubris. There wasn’t consideration for what we were going to be facing down the road.”