Rising Seas Threaten Habitats of Over 40% of the World's Land Vertebrates by 2100

A study published in Science has put a number on something conservationists have mostly discussed in fragments: more than 42% of the world's land vertebrates could lose some of their habitat to the sea by 2100. The researchers overlaid habitat suitability maps for 34,120 species, roughly 90% of all known amphibians, reptiles, birds and mammals, with sea level rise projections drawn from five IPCC climate scenarios, from low to high emissions.

Depending on the scenario, between 14,325 and 15,324 of those species would be exposed to habitat loss from coastal inundation by the end of the century. Yet only 5.9% of them are currently listed as at risk from climate change in their IUCN Red List assessments. Up to 63% of birds, 52% of mammals, 36% of reptiles and 24% of amphibians are likely to be affected. Reptiles, narrow-ranging species and already threatened species stand out as especially vulnerable, and reptiles are expected to lose nearly twice as much habitat as birds or mammals.

The losses grow with emissions and with time. Under the highest emissions scenario, the number of species losing more than 10% of their habitat climbs from 18 in 2050 to 109 by 2100, with more than half of those being reptiles. Three species are projected to lose over half of their global habitat: the Catalina chuckwalla, the Restinga toadlet, and a Brazilian worm lizard, Amphisbaena littoralis. At the 1% threshold, 395 species are affected under low emissions and 1,180 under high emissions, according to co-author Zhong-Wen Jiang of Sun Yat-sen University. Stronger mitigation, she said, could reduce both the number of species exposed and the severity of loss.

The pace of the underlying change is not slow. The World Meteorological Organization reports that global mean sea level rose an average of 4.7 millimeters a year between 2015 and 2024, more than double the rate of 1993 to 2002.

Geographically, the Amazon River delta is expected to see the greatest extent of habitat loss, partly because of its exceptional biodiversity. More than 100,000 hectares of riparian forest and coastal wetland there could be inundated by 2050. Central America and Southeastern Africa are also high-risk coasts. Southeast Asia has proportionally less habitat at risk than the Amazon delta, but many of its coastal species have small ranges and are already threatened. Flooded habitats in Peninsular Malaysia, Borneo and Sumatra support nearly three times as many threatened species as the rest of the world.

The study also mapped refugia, areas within species' ranges likely to stay above water. Ninety-six percent of them lie outside existing protected areas. Myanmar, Vietnam and Indonesia are singled out as places where protection could be extended to such refugia, though Jiang noted that these countries often lack conservation funding and technical capacity, which is why she argues for international cooperation to direct resources there.

The effects are already visible. European shorebirds face habitat loss and flooded nests. In the Bangladesh Sundarbans, the Bengal tiger is expected to lose most of its mangrove habitat by 2070. In 2016, the Bramble Cay melomys, a rodent from a small coral islet in the Torres Strait, was declared the first mammal extinct because of human-caused sea level rise.

The authors call their results conservative. They count only terrestrial habitat, leaving out marine and intertidal zones, and do not account for salt spray, stronger hurricanes or storm surges. Jennifer Magel, a University of British Columbia conservation scientist not involved in the work, said she expects all but a handful of shorebird species to be exposed. Her 2026 review describes "coastal squeeze," where roads, dykes and seawalls stop mudflats, saltmarshes and mangroves from migrating inland. Losing even a few key stopover sites can hurt whole migratory populations. She urges limiting infrastructure and permanent coastal defenses so wetlands have room to move.

The researchers' message is about timing: decisions on where to protect land are being made now, while the refugia are still dry.