The percentage of the U.S. population living in counties adjacent to coastline has reached nearly 40 percent in recent years, meaning more of us are exposed to extreme — and extremely costly — coastal storms such as Sandy and Isaac, according to a government report released Monday.

These coastal counties account for less than 10 percent of the U.S. land area, excluding Alaska, meaning that this growing population is packing into a finite amount of space, one that’s increasingly threatened by rising seas, storm surge flooding and damaging winds.