Rising Sea Levels: A Looming Threat to Coastal Communities
One of the biggest threats we face as a society is undoubtedly the rise in sea levels . This slow but inexorable process has the potential to radically alter our mental maps of geography, as coastal areas in many regions could become completely submerged. A recent study has aimed to shed light on this urgent issue, analyzing flood risk building by building in the Global South, and the results are alarming.
The Groundbreaking Study
Published in npj Urban Sustainability, this comprehensive study is the first of its kind to analyze the impact of sea level rise on such a large scale in Africa, Southeast Asia, and Central and South America. “The rise in sea level is a slow but unstoppable consequence of global warming that is already impacting coastal populations and will continue for centuries,” explains Natalya Gomez, co-author of the study.
Staggering Numbers
The study meticulously examines how various buildings will be affected by different levels of local sea level rise ( LSLR ), regardless of a specific time frame. This approach ensures that the findings remain relevant as future climate projections are updated. The data is compelling. For instance, with just 0.5 meters of sea level rise, 3 million buildings would be submerged. This scenario is almost inevitable, even with the most ambitious emissions cuts being proposed globally.
If we consider a more extreme scenario of a five-meter rise , which could happen in several hundred years if emissions are not curtailed, the number of affected buildings skyrockets to 45 million . In the most drastic case, with a 20-meter rise , this number could swell to 136 million buildings . This stark realization highlights how critical the issue is, and the urgency for action cannot be overstated.
Advanced Methodology
To achieve this level of detail, the scientific team incorporated cutting-edge technologies. They utilized the Google Open Buildings V2 database, which identifies the location and outline of billions of buildings through satellite imagery analysis. This data was cross-referenced with FABDEM , a digital global elevation model that uses machine learning to strip away the height of trees and buildings, revealing the true elevation of the “bare ground.” This meticulous process is essential for accurate flood risk assessments.
Finally, the researchers adjusted their calculations using a global tidal model to account for water levels during high tide, allowing for a more realistic assessment of flooding risks.
The Uneven Impact Across Regions
The risk is not uniform across all regions. During the early stages of sea level rise, Africa has the highest number of buildings at risk. However, as LSLR progresses, Southeast Asia quickly overtakes Africa in the number of buildings exposed to flooding.
A pivotal finding is the non-linear nature of the threat. The loss of buildings is relatively moderate below two meters of LSLR but accelerates dramatically between two and four meters . Professor Jeff Cardile, co-author of the study, states that “we were surprised by the large number of buildings at risk from relatively modest long-term sea level rise.” This suggests that the problem does not escalate gradually; instead, it may reach critical tipping points with devastating consequences, especially for densely populated areas and critical infrastructure.
Planning for the Future
Beyond raising awareness, this study aims to be a practical resource. Researchers have developed an interactive map , available through Google Earth, that allows policymakers and urban planners to visualize which regions face the greatest exposure. By using this tool, they can evaluate the risk of individual buildings, facilitating informed decisions about future developments and disaster preparedness.
Even though this study focuses on the scenarios faced by Africa and Asia, the global implications are profound. Everyone relies on food, goods, and fuel transported through ports and coastal infrastructure that are increasingly vulnerable to flooding. Disruption to these essential networks could have severe economic consequences worldwide. Therefore, employing this tool could guide climate adaptation strategies, including building protective infrastructure, adjusting land use planning, or even resettling communities. As Maya Willard-Stepan, the lead author of the study, astutely observes, “We cannot escape at least a moderate amount of sea level rise. The sooner coastal communities start planning, the more likely they are to continue to thrive.”
Images | Chris Gallagher Marc Pell