A global study of 34,120 amphibian, reptile, bird and mammal species estimates that coastal inundation could reduce suitable habitat for more than 42% of them—about 14,325 to 15,324 species—by 2100, depending on emissions.

The projected share of affected species varies widely: 57%–63% of birds and 47%–52% of mammals could be affected, compared with 28%–36% of reptiles and 20%–24% of amphibians; affected reptiles and amphibians may lose nearly twice the average proportion of habitat lost by birds and mammals.

The consequences could be especially severe for species already classified as threatened, which may lose about five times the proportion of habitat lost by least-concern species; under a high-emissions scenario, the worm lizard, Catalina chuckwalla and Restinga toadlet could each lose about half their habitat.

Island species are particularly exposed because many have small ranges and a large share of island land lies near the sea; migratory birds also face risks across their distinct breeding, nonbreeding and resident habitats.

Southeast Asia is a major hotspot because many threatened and range-restricted species live along its coasts; inundated areas in Peninsular Malaysia, Borneo and Sumatra support nearly three times as many threatened species as the rest of the world.

The Amazon River delta is projected to experience the greatest overall habitat losses, with more than 100,000 hectares of low-lying forest and coastal wetlands potentially inundated by 2050; Central America and southeastern Africa are also at high risk.

The Amazon delta also has the largest number of species whose habitats overlap projected flooding, and more than 1,000 square kilometers of inland area there could be inundated by 2050.

Researchers identified refugia—habitats likely to remain above water—but more than 96% of these priority areas lie outside existing protected areas; Myanmar, Vietnam and Indonesia were highlighted as places to consider expanding protection.

The authors recommend using the maps to guide protected-area expansion and land-use planning, while assessing how coastal defenses could affect wildlife; captive breeding may be needed for some species.

The estimates are conservative because the analysis covers only terrestrial portions of species’ habitats and excludes additional impacts from salt spray, hurricanes and storm surges.

The article argues that cutting emissions must go hand in hand with protecting habitats now, including international support for countries with limited conservation funding and capacity; coastal planning should also let wetlands move inland rather than trapping them behind infrastructure.