Nearly a quarter of the world’s population is exposed to significant flood risks, new research published Tuesday shows that people in poorer countries are more vulnerable.
Floods from heavy rainfall and storm surges affect millions of people every year, causing billions of dollars in damage to homes, infrastructure and economies.
And the risks are mounting as climate change causes more extreme precipitation and sea levels rise, while exposed populations increase.
The new study, published in the journal Nature Communications, looked at global data on flood risk from the sea, rivers and rainfall, as well as population distribution and poverty estimates from the World Bank.
It found that about 1.81 billion people — or 23 percent of the people on the planet — are directly exposed to floods greater than 15 centimeters (six inches) in floods of 1 in 100 years.
“This would pose significant risks to lives and livelihoods, especially of vulnerable populations,” the study said.
Overall, according to the study, nearly 90 percent of those exposed to flooding live in low- or middle-income countries.
It also concluded that the number of people living in poverty and at serious risk of flooding is “significantly higher than previously thought”.
Researchers found that about $9.8 trillion of economic activity worldwide — about 12 percent of global gross domestic product in 2020 — is located in areas exposed to severe flooding.
But they said focusing only on a monetary value could cause a bias towards higher-income countries and economic centers.
“By taking into account the poverty levels of exposed populations, we show that low-income countries are disproportionately exposed to flood risks, while being more vulnerable to disastrous long-term impacts,” said the study by World Bank’s Jun Rentschler and colleagues.
Overall, the study estimates that most of the people exposed to flooding — 1.24 billion — are in South and East Asia, with China and India accounting for more than a third of the global total. .
About 780 million people living on less than $5.50 a day are at risk of flooding once every 100 years, it found.
The research provides “the first global estimates of the interaction between flood risk exposure and poverty,” said Thomas McDermott of the National University of Ireland Galway, in a linked comment published in Nature Communications.
The authors said previous studies were often limited by geography or the type of flood risk being assessed and that they underestimated how many people around the world are exposed.
“Climate change and high-risk urbanization patterns are expected to further exacerbate these risks in the coming years,” she added.
According to World Weather Attribution, a network of scientists tracking the impacts of climate change, global warming has made extreme rainfall more frequent and intense across most of the world.
This has likely made flooding in these areas more severe, although scientists emphasize that other human factors also play a role, such as decisions about where to build houses and infrastructure.
This month, record flooding in southern China has displaced more than half a million people.
In Bangladesh, the Red Cross said on Tuesday that seven million people were still “desperately” in need of shelter and assistance after some of the heaviest rains in a century swelled rivers to record levels and flooded rural villages.