Rising sea levels threaten hundreds of millions worldwide, including in India

Sea-level rise is no longer a distant threat but an unfolding global crisis, with profound impacts on coastal communities, economies, and infrastructure, according to a new UN report. It underscores that the phenomenon is accelerating at an unprecedented rate in human history. In South Asia, the report highlights the growing risks faced by low-lying coastal areas, including cities such as Mumbai and Kolkata, where sea-level rise, combined with land subsidence, is intensifying the threat of flooding and displacement.

The report’s central message is clear: sea-level rise is already transforming the world and requires an urgent, coordinated, and multilateral response to protect people, economies, and ecosystems in the decades ahead.

The United Nations Secretary-General’s Special Report on ‘Challenges related to sea-level rise and ways and approaches to address it’, was presented on 31 August by UN Deputy Secretary-General during the 55th Pacific Islands Forum Leaders Meeting in Palau.

Average ocean levels are rising due to warming waters and the melting of glaciers and ice sheets, according to the report. In 2024, the annual increase reached nearly six millimetres, the highest level ever recorded.

Today, around 770 million people, equivalent to one in every ten people on Earth, live in coastal areas less than five metres above the high-tide line and are already exposed to significant risks.

Indian subcontinent faces growing coastal risks

Across the Indian subcontinent, low-lying coastal areas and delta regions are increasingly exposed to the impacts of rising seas.

The report highlights Mumbai and Kolkata in India, alongside Dhaka in Bangladesh, as cities in low-lying South Asian deltas where sea-level rise is contributing to a growing risk of displacement. More than 14 million people in these areas are at immediate risk of losing their homes to permanent inundation.

Sea-level rise can also be compounded by land subsidence, intensifying flooding and increasing the exposure of coastal communities. Saltwater intrusion can contaminate freshwater wells and soils, affecting drinking water, agriculture, irrigation and groundwater ecosystems.

The risks extend beyond homes and communities. Coastal infrastructure, essential services, livelihoods and economic activity are also increasingly exposed to rising mean and extreme sea levels.

European coastlines at risk

Even under a very low greenhouse gas emissions scenario (resulting in a 1 to 1.9 degrees Celsius end-of-century warming), the global mean sea level could rise 0.23 m by 2050, the Intergovernmental Panel on Climate Change projected in its sixth assessment report.

In Europe, extreme sea levels have already increased at many locations along coastlines.

In Germany, approximately 70 per cent of the coastline is subject to coastal retreat due to erosion.

In France, small sandy beaches on the French Riviera are vanishing, having lost roughly 50% of their surface area since the late 19th century, according to the International Union for Conservation of Nature (IUCN).

The historically 1-in-100-year coastal floods are projected to increase by a factor of 10 before the year 2050 in many locations along the Mediterranean and Atlantic coasts

In the United Kingdom, sea levels could rise by over a metre by 2100. In England, it is projected that one in four properties will be in areas at risk of flooding from rivers and the sea or surface water by mid-century.

1.2 billion people could be displaced

The impacts of sea-level rise extend far beyond environmental concerns, threatening livelihoods, food security, cultural heritage, human rights, and economic stability.

The United Nations warns that without urgent adaptation measures, up to 1.2 billion people could be displaced by 2050. Several Pacific Island communities have already begun relocation processes as a result of the gradual loss of territory.

The economic consequences are equally alarming. Damage to coastal infrastructure is currently estimated at more than $1.8 trillion, and annual global losses could reach between $1.2 trillion and $4 trillion by the end of the century if adaptation measures are not implemented. In Ireland in the city of Limerick, the cost of extreme flooding under a high-end sea level rise scenario could exceed one billion euros for a single event.

In the Caribbean, where ocean-based tourism accounts for a significant share of exports, nearly 40 per cent of beaches could disappear by 2050, jeopardising a major source of regional income.

Human rights under threat

Rising waters will also have an impact on the fundamental rights of affected populations. Access to housing, safe drinking water, sanitation, food, healthcare, and education is increasingly under threat in many parts of the world.

Indigenous Peoples and residents of small island States are identified among the most vulnerable groups, facing not only growing physical risks but also the loss of cultural heritage and historical ties to their ancestral lands.

Among the challenges identified are complex legal issues related to state sovereignty and maritime boundaries. The UN maintains that sea-level rise should not affect the continuity of States or their rights over maritime zones and ocean resources recognised under international law. The Secretary-General calls for stronger international cooperation and the adoption of a robust political declaration by Member States to ensure legal stability and the protection of affected populations.

To address the crisis, the report puts forward 18 recommendations for Member States, including accelerated reductions in greenhouse gas emissions, stronger early warning systems, increased financing for climate adaptation, improved scientific data collection, and support for at-risk communities.