One of the biggest threats we have as a society is undoubtedly rising sea levels. A process that is slow, but that can end up changing the mental maps that we now have from world geography to finish coastal areas of some regions completely flooded. Something that a study wanted to shed light on analyzed building by building flood risk in the Global South. And the result is alarming.
The study. Published in npj Urban Sustainabilityis the first to analyze the impact on this scale in Africa, Southeast Asia, and Central and South America. “The rise in sea level is a slow but unstoppable consequence of the global warming that is already impacting coastal populations and will continue for centuries,” explains Natalya Gomez, co-author of the study.
The numbers. The study analyzes the exposure of buildings to different levels of local sea level rise (LSLR), regardless of a specific time scale. This allows the findings to remain relevant as climate projections are updated.
In this case the data is quite compelling. First of all, with just 0.5 meters of sea level rise, 3 million buildings would be submerged under the sea. Something that is inevitable right now, even if the most ambitious emissions cuts on the table are applied.
If we talk about a five-meter rise in sea level, a scenario that could occur in several hundred years if emissions do not stop, the exposure would skyrocket to 45 million buildings. And in the most extreme case, with a 20-meter rise in the LSLR, the figure would reach 136 million buildings.
How it was done. To achieve this level of detail, the scientific team combined several cutting-edge technologies. They used the database Google Open Buildings V2which identifies the location and outline of billions of buildings by analyzing satellite images.
This data was cross-referenced with FABDEM, a digital global elevation model that, thanks to machine learning, removes the height of trees and buildings themselves to obtain the true elevation of the “bare ground.” This is crucial to not underestimate the risk of flooding. Finally, they adjusted the calculations using a global tidal model to reflect the water level during high tide, thus providing a more realistic estimate of the danger.
Uneven impact. The risk is not the same in all regions, since the study reveals that in the early stages of sea level rise, Africa is the continent with the highest number of buildings affected. However, as the LSLR intensifies, Southeast Asia quickly comes to dominate the flood figures.
A key finding is the non-linear nature of the threat. Building loss is relatively high below two meters LSLR, but accelerates dramatically between 2 and 4 meters. Professor Jeff Cardile, co-author of the study, points out that “we were surprised by the large number of buildings at risk from relatively modest long-term sea level rise.”
This means that we are not facing a problem that is gradually worsening, but rather one that could reach tipping points with devastating consequences. Many of these buildings are located in low-altitude, high-density areas, affecting entire neighborhoods and critical infrastructure such as ports, refineries, and cultural heritage enclaves.
Planning. Beyond the global warning, the study seeks to be a useful tool. Researchers have created an interactive map available through Google Earth which allows policy makers and urban planners to visualize which regions face the greatest exposure. And on this map you will be able to see, building by building, the risk of ending up below sea level as a consequence of climate change.
A global problem. Although this study has focused on the effects that will occur in Africa or Asia, the reality is that it is a problem that affects us all. As the study points out, all of us depend on food, goods and fuel that pass through ports and coastal infrastructure that are exposed to this rise in sea level. Thus, disruption of this infrastructure can cause disruption with serious economic consequences globally.
That is why this tool can guide climate adaptation strategies, such as the construction of protective infrastructure, the adjustment of land use planning or, in some cases, the planned relocation of communities. As Maya Willard-Stepan, lead author of the study, concludes: “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
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