UN warns Kolkata, Mumbai face immediate home loss risk from rising seas

Unitednations,UPDATED: Sep 1, 2026 18:30 IST

A United Nations report has said millions of people in Kolkata and Mumbai are at "immediate risk" of losing their homes because of rising sea levels and permanent inundation. Released on Monday, the report said sea level rise is no longer a distant danger but a present and growing threat to people in both developed and developing countries.

The report of the UN Secretary-General, titled "Challenges related to sea level rise and ways and approaches to address it", said: "Rising seas are no longer a distant threat: they are happening now, faster than at any point in recorded history, and the pace is accelerating, making sea level rise one of the most profound threats to populations around the world in developed and developing States alike." It said sea level rise is already damaging urban infrastructure, water systems, transport networks, energy grids, buildings and groundwater resources, with consequences for human rights, long-term development and financial stability.

The report said the risks differ across regions. In high-income cities such as Miami and New York in the United States, and Guangzhou in China, the main impact is the financial exposure of coastal infrastructure, with assets at risk estimated at between USD 2 trillion and USD 3.5 trillion. In South Asia's low-lying deltas, the report said, the main impact is displacement. "In the low-lying deltas of South Asia, in cities such as Kolkata and Mumbai in India, and Dhaka, the defining impact is human displacement, with more than 14 million people at immediate risk of losing their homes to permanent inundation," it said.

It said this difference shows the need to strengthen and widen the indicators used to assess coastal vulnerability and exposure, so that social risks measured in human lives and displacement receive the same urgency as risks measured in financial terms. The report also said sea level rise affects public health through damage to coastal health and sanitation infrastructure, greater exposure to water-borne diseases, disrupted sanitation, higher risks of injury and death, and rising mental health stress.

The combined effects of sea level rise and land subsidence are also increasing flood risks, damaging coastal ecosystems and adding to the loss of lives, livelihoods and critical aquatic ecosystem services and habitats, it said. As the freshwater-saltwater interface moves inland, coastal aquifers face salinisation of freshwater wells and soils, while storm-driven overwash can cause long-lasting contamination of surface and groundwater. The report said this directly affects drinking water security, agricultural productivity, irrigation systems and groundwater-dependent ecosystems.

It said policy approaches linking river basins, freshwater systems, coasts and the ocean are still not adequately reflected in regulatory and land use planning frameworks. According to the report, this disproportionately affects vulnerable groups and sectors such as artisanal fisheries, small-scale tourism and port-dependent local economies.

The report said the acceleration in sea level rise is driven mainly by melting glaciers and the thermal expansion of warming oceans as a direct result of human-induced global warming. Between 2014 and 2023, global sea level rose by 4.7 mm a year. In 2024 alone, sea level rose by 5.9 mm, a new record, driven mainly by exceptional ocean warming, which in some regions was faster than at any time in the past 4,000 years. It said this rate is expected to continue increasing through 2050 because of warming already locked into the climate system.

It added that the annual rate of sea level rise was 4.75 mm during 2012-2025, with the 2025 global mean sea level remaining comparable to the record-high levels of 2024, after a rapid rise of about 5 mm during 2023-2024 due to exceptional ocean warming linked to El Nio. The report said nearly 770 million people, or about 10 per cent of the world's population, live in coastal areas less than 5 million above the high tide line, putting them at acute risk.

Across regions, sea level rise is worsening existing climate vulnerabilities, including coastal flooding, freshwater salinisation, erosion and ecosystem degradation, with consequences for safety, livelihoods, economies, cultures and the environment, the report said. It added that critical infrastructure, agricultural productivity, trade, tourism and cultural heritage are increasingly at risk, making sea level rise a core sustainable development challenge. As a threat multiplier, rising seas can damage or destroy vital infrastructure, force displacement and relocation and, in extreme cases, lead to the permanent loss of land or even the territory of a State.

"Accelerating at an unprecedented level, sea level rise driven by melting glaciers and ocean warming is redefining coastlines and posing major threats to low-lying islands, coastal cities and communities, tropical deltas and Arctic regions," the report said. It added that because sea level rise is irreversible and slow-onset, early, precautionary and long-term adaptation planning is essential. The report said this will require adequate, accessible and predictable finance, stronger data and science capacities, and robust technical, institutional and legal frameworks to help affected populations and States prepare for and manage the impacts.

In summary, the UN report said sea level rise is already reshaping coasts and daily life across the world, with financial risks in some cities and displacement risks in places such as Kolkata and Mumbai. It said the scale and pace of the threat make long-term planning, stronger systems and support for the most vulnerable essential.

With PTI Inputs

- Ends