Around 7.5% of Bangladesh's population could become internal climate migrants by 2050 due to the compounded effects of sea-level rise, water scarcity and agricultural decline, according to a new Asian Development Bank (ADB) report.
The finding comes from the "Asia-Pacific Climate Report 2026: Coastal Risks on the Rise—Actions for a Resilient Future," released today (21 October), which assesses growing coastal climate risks and resilience needs across Asia and the Pacific.
The report also found that in some countries, people exposed to coastal flooding are poorer than their coastal neighbours, creating a double burden of flood risk and deprivation.
This is most visible in Bangladesh, Myanmar and India, where households facing the greatest flood risks have the fewest resources to prepare for, cope with and recover from their impacts, it said.
The report said Asia and the Pacific coastlines are central to the region's economic future, generating around $7 trillion in annual economic output, but face intensifying threats.
It said investments in resilience to mitigate some of these risks could generate benefits up to 20 times greater than the amount invested.
Coastal flood losses set to surge
Coastlines across the region are increasingly exposed to rising seas and intensifying hazards, with the economic costs already mounting.
Without adaptation, annual coastal flood damage in Asia and the Pacific could increase more than sixfold by 2050 and nearly twentyfold by 2100.
Based on estimates across 30 coastal economies, the report projected annual flood damage could reach $172 billion to $199 billion by 2050 and $520 billion to $739 billion by 2100, up from about $27 billion today.
Keeping flood damage near current levels would require an estimated $9 billion to $19 billion a year in coastal protection. Such investment could avoid between $178 billion and $360 billion in flood damage each year, according to the report.
"Coasts are the overlooked engine-room of Asia and the Pacific's growth but are retreating in the face of rising seas and escalating hazards," said Yevgeniy Zhukov, director general of ADB's Climate Change and Sustainable Development Department.
"We are at a turning point and must act now with long-term, adaptive, and risk-informed solutions to create resilient coasts that keep people safe and economies running."
More than 400 million people in the region — or more than one in 10 people in ADB's developing members with a coastline — live within 10 kilometres of the sea.
Coastal areas are also major hubs for ports and trade, as well as tourism and heritage.
The ADB report highlighted that without adequate adaptation measures, larger economies could face some of the highest economic losses in absolute terms, while the relative impacts could be particularly severe in atoll nations.
Under a high-emissions scenario, annual flood damage in atoll nations could reach between 30% and 60% of gross domestic product by 2100.
In major coastal cities such as Bangkok, Jakarta, Kolkata and Mumbai, coastal floods that historically occurred once every 100 years could become annual events by the end of the century.
The report also estimated that about $40 billion to $45 billion is at risk each year from disruptions to ports across the region.
To strengthen coastal resilience, governments need adaptive planning that links near-term actions with long-term development objectives while allowing policies to evolve as risks and circumstances change, the report said.
It recommended four key steps: mainstreaming adaptive planning into development decisions, strengthening institutions and governance, mobilising financing, and sustaining implementation and ownership.
International adaptation finance to coastal economies in Asia and the Pacific roughly doubled from around $5 billion in 2015 to an average of $11.4 billion a year in 2022-23, but the report said a large financing gap remains.
Public finance remains the bedrock of coastal resilience investment, but closing the gap will require expanding fiscal space and mobilising additional public, private and concessional finance for long-term resilience projects, it added.