Rising seas threaten not only coastlines but also the lives and livelihoods of millions who depend on coastal infrastructure and economies. A new study led by McGill University in Canada provides the most detailed assessment to date of how sea-level rise will affect buildings across developing regions in the Global South.
Published in npj Urban Sustainability, the study estimates that more than 100 million buildings could face chronic flooding if fossil fuel emissions are not curbed soon. Even under optimistic climate scenarios, millions of structures may still be swallowed by rising oceans within decades.
The First Building-by-Building Risk Assessment
This research marks the first large-scale, building-specific analysis ever conducted to map sea-level rise exposure across developing nations.
The study used satellite imagery, high-resolution topography, and machine learning algorithms to evaluate 840 million buildings throughout Africa, Southeast Asia, and Central and South America.
By simulating multiple sea-level rise scenarios — 0.5 meters, 5 meters, and 20 meters — the scientists quantified how incremental rises in ocean levels translate to widespread coastal inundation.
Lead author Maya Willard-Stepan, now an environmental scientist at the University of Victoria, explained, “Sea-level rise is a slow but unstoppable consequence of global warming that will reshape coastlines for centuries.”
Millions of Buildings at Risk Even in the Best-Case Scenario
Even under the most ambitious emission reduction pathways, which would limit sea-level rise to around 0.5 meters by 2100, about three million buildings could face regular flooding.
If oceans rise by five meters, projected within a few hundred years if emissions continue at today’s rate, that number jumps to over 100 million buildings.
In the most catastrophic case — a 20-meter rise — more than 130 million buildings could be lost permanently to the sea. “We were surprised at the vast number of buildings at risk from relatively modest increases in sea level,” said Professor Jeff Cardille, study co-author and McGill geography expert.
Coastal Development and Topography Shape Vulnerability
The study shows that not all nations will be affected equally. Exposure levels vary depending on coastal topography, building density, and local development patterns. Low-lying nations such as Bangladesh, Guyana, and Vietnam are especially vulnerable, with more than 80% of their coastal building stock at risk in the 5-meter scenario.
Coastal megacities — from Jakarta to Lagos — face immense challenges, as population growth and urban expansion push millions into flood-prone areas.
“Some coastal countries are far more exposed than others simply due to how and where their infrastructure has evolved,” said Cardille.
Economic Disruption on a Global Scale
Coastal infrastructure is central to the global economy. Ports, refineries, and shipping hubs — many situated in the Global South — are integral links in global food, fuel, and trade supply chains.
“Every one of us is affected by sea-level rise, whether or not we live near the ocean,” emphasized co-author Professor Eric Galbraith, an earth scientist at McGill.
He warned that disruptions to ports and trade routes from rising waters “could play havoc with our globally interconnected economies, threatening food and goods supply worldwide.”
A Glimpse Into the Future
The report underscores a harsh truth: even if fossil fuel use ceased immediately, sea levels would continue rising for centuries due to the ocean’s slow heat absorption and ice sheet melting.
“People often talk about sea levels rising by a few centimeters or a meter,” said Professor Natalya Gomez, Canada Research Chair in Ice Sheet–Sea Level Interactions at McGill. “But in fact, it could continue to rise by many meters if we don’t quickly stop burning fossil fuels.”
The researchers stress that while immediate and deep emission cuts cannot halt rising seas altogether, they can greatly reduce the ultimate scale of flooding. They can also significantly lessen displacement.
Mapping the Future: A Tool for Urban Planning
The McGill team has released an interactive map through Google Earth Engine that allows users to explore building-by-building exposure across vulnerable coastlines.
Urban planners and policymakers can use this data to identify high-risk zones. They can guide land-use planning and design adaptive infrastructure. This ranges from raised foundations to artificial barriers.
“This work offers actionable guidance,” said Willard-Stepan. “Communities can visualize precise risks. They can prepare adaptation strategies. Communities make informed decisions about whether to defend, redesign, or relocate critical infrastructure.”
The map highlights that entire neighborhoods and industrial districts may need preemptive adaptations. This includes essential ports and cultural heritage sites. These measures are necessary to survive anticipated floods.
The Urgent Path Toward Climate Adaptation
Global sea levels are currently rising by approximately 4.5 millimeters per year. This rate is expected to increase as glaciers and polar ice sheets melt faster due to human-driven warming.
Although the Global North dominates historical carbon emissions, the Global South bears the brunt of these environmental consequences. Those nations often face resource constraints that complicate adaptation efforts.
“There’s no escaping at least some sea-level rise,” Willard-Stepan explained. “But the sooner coastal communities start planning for it, the better their chances of continuing to flourish.”
From building seawalls to restoring mangroves and implementing flood-resilient design, experts urge immediate, equitable collaboration between industrialized and developing nations.
Planning for the Inevitable
The researchers emphasize that adaptation cannot wait for distant decades. Governments and developers must integrate long-term sea-level projections into present-day building codes, zoning laws, and insurance models.
McGill’s findings also highlight a need for comprehensive resettlement policies, particularly for rural and informal settlements located in low-elevation zones. “The worst outcomes can be avoided with strong leadership and strategic foresight,” said Galbraith. “But without planning, millions risk losing their homes — and humanity risks losing vital infrastructure that keeps global systems functioning.”
From Awareness to Action
The McGill-led study offers both a warning and a road map for future resilience. Sea-level rise is inevitable — but its devastating effects are not.
With science-backed adaptation, innovation in coastal engineering, and immediate emission reductions, nations can secure a sustainable future. This future is essential for billions depending on coastal stability. As Gomez summarized, “It’s not just about saving buildings. It’s about safeguarding the systems — ports, cities, and communities. These systems sustain our global civilization.”
