Tropical nations will face more coastal inundation from a rise in sea levels due to climate change than other countries, according to new research that also more than doubles the number of people estimated to be impacted.
Using land elevation data gathered by laser pulses beamed by satellite to Earth, scientists identified coastal areas low enough to make them vulnerable to a one-meter rise in sea level – a level the world is on track to see by 2100. Higher water levels will likely lead to more damage and disruption from flooding and storm surges.
The team found that 62% of these low-lying areas were located in the tropics, with a third of the total in Asia, said the study, which was published on Tuesday in the journal Nature Communications.
Today, those vulnerable lands – at elevations that are less than two meters above sea level – comprise about 1 million square kilometers and are home to 267 million people, the team found.
As sea levels rise, the total amount of vulnerable land could million reach 1.46 million square kilometers by 2100, an area on which some 410 people live today.
Already, the global average sea level is rising at more than 3 millimeters per year, accelerating as global warming melts glaciers and polar ice and expands the oceans.
The tropics are particularly vulnerable, with a large number of low-lying river deltas and strong tropical storms.
For some Asian regions, sea level rise is being exacerbated by land subsidence, as major cities including Jakarta and Bangkok pull water up from underground aquifers. Forest loss can also make it harder for land to absorb rainfall.
“There are also man-made factors like loss of forests, drainage for agriculture, poor urban planning that is driving land subsidence,” said study co-author Aljosja Hooijer, an environmental scientist at a Dutch research institute, Deltares, and the National University of Singapore.
The study is the first to use topographic data collected using laser technology for more granular elevation data worldwide at a half-meter scale. That yielded estimates for how many people are living in flood-risk zones that are much higher than previous studies based on radar measurements with a 25-meter resolution.
It is also higher than an October 2019 study, which concluded that by 2100, areas that are currently home to 190 million people or more would be affected by rising sea levels.
The authors of the new study said research was still ongoing and methods were being further improved.
“This global study is a first step and therefore it’s quite coarse. If you go regional or local, you need more refined models,” Hooijer said. “But even with this data, policymakers can start making broad assessments.”