Oceans
As the oceans rise, sandy shoreline erosion happens at about 100 times the rate of sea level rise, so a few inches’ increase in the ocean level can greatly affect coasts.
And since nearly half of the world’s population lives in low-lying coastal areas, continued population growth along coasts increases vulnerability from sea-level rise, storm surge, and flooding. People who live on small islands close to sea level will be particularly vulnerable as their water supplies, homes, coral reefs, fisheries, and crops are threatened.
If both the Antarctic and Greenland ice sheets melt completely, sea levels could rise 80 meters, which would flood the area of South America seen here.
South America’s coastline if seas rise 80 meters.
If, on the other hand, sea levels rise only 6 meters, this is the inundation that would eventually result.
As sea levels rise, nearly everywhere coastlines seem likely to flood more often, particularly in cities not rich enough to build sea walls or adapt in other ways. Saltwater intrusion may spoil many freshwater aquifers that provide drinking water. In Latin America, El Salvador, Guyana, and the province of Buenos Aires would be particularly at risk from flooding and its accompanying erosion, while the drinking water of Ecuador, Costa Rica, and the Rio de la Plata estuary would be in danger of becoming contaminated by saltwater. Coastal changes could also disrupt access to fishing grounds and endanger mangroves—the nurseries of many fish—and many other coastal species.
Because of a combination of increasing population, decreasing glacial runoff, precipitation, and saltwater intrusion, the IPCC projects that 7 to 77 million people in Latin America will likely suffer from inadequate water supplies by the 2020s, increasing to 60 to 150 million by the second half of the century.
