Millions of people in Kolkata and Mumbai are at "immediate risk" of losing their homes due to rising sea levels and permanent inundation, a report by the United Nations 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," the report of the UN Secretary-General titled 'Challenges related to sea level rise and ways and approaches to address it' said.
The report, released Monday, said that sea level rise is already damaging urban infrastructure, water systems, transport networks, energy grids, buildings and groundwater resources, creating far-reaching consequences that threaten the effective enjoyment of human rights, long-term development and financial stability.
It noted that the nature of these risks varies across regions.
In high-income cities such as Miami and New York in the United States and Guangzhou in China, the primary impact is the staggering financial exposure of coastal infrastructure, with assets at risk estimated between USD 2 trillion and USD 3.5 trillion.
"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," the report said.
It added that this divergence underscores the need to strengthen and broaden the indicators used to assess coastal vulnerability and exposure, ensuring that social risks measured in human lives and displacement receive the same level of urgency as those quantified in financial terms.
It said sea level rise affects public health through damage to coastal health and sanitation infrastructure, increased exposure to water-borne diseases, disrupted sanitation, elevated risks of injury and mortality, and exposure to rising mental health stress.
The combined effects of sea level rise and land subsidence are also intensifying flooding risks, degrading coastal ecosystems and increasing the loss of lives, livelihoods and critical aquatic ecosystem services and habitats.
As the freshwater-saltwater interface migrates inland, coastal aquifers experience the salinisation of freshwater wells and soils, while storm-driven overwash can cause the long-lasting contamination of surface and groundwater, affecting public health. The result has a direct impact on drinking water security, agricultural productivity, irrigation systems and groundwater-dependent ecosystems.
The report stressed that coherent, integrated policy approaches that link river basins, freshwater systems, coasts and the ocean remain insufficiently reflected in regulatory and land use planning frameworks, disproportionately affecting vulnerable groups and sectors, such as artisanal fisheries, small-scale tourism and port-dependent local economies.
The acceleration in sea-level rise is driven primarily by melting glaciers and the thermal expansion of warming oceans as a direct consequence of human-induced global warming.
Between 2014 and 2023, global sea level rose by 4.7 mm per year. In 2024 alone, the sea level rose 5.9 mm, a new record, driven primarily by exceptional ocean warming - in some regions faster than at any time in the past 4,000 years - and this rate is expected to continue to increase through 2050 owing to warming already locked into the climate system.
The annual rate of sea level rise was 4.75 mm during the period 2012-2025, with the 2025 global mean sea level remaining comparable to the record-high levels of 2024, following a rapid, approximately 5 mm rise during 2023-2024 owing to exceptional ocean warming associated with El Nino.
Sea level rise is already reshaping how people live, work and interact with their environments. Nearly 770 million people, or approximately 10 per cent of the world's population, live in coastal areas less than 5 million above the high tide line, placing them at acute risk, it said.
Across all regions, sea level rise is intensifying existing climate vulnerabilities, including coastal flooding, freshwater salinisation, erosion and ecosystem degradation, with profound consequences for safety, livelihoods, economies, cultures and the environment. 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," it said.
The irreversible nature of sea level rise, combined with its slow-onset dynamics, makes early, precautionary and long-term adaptation planning essential.
This requires adequate, accessible and predictable finance, strengthened data and science capacities and robust technical, institutional and legal frameworks to support affected populations and States, especially those most at risk, in preparing for and managing escalating impacts, it said.
Source: PTI
– Agencies
