When it comes to the impact that climate change will have on communities around the world, one of the most obvious threats is that of the rising sea. If the icy poles that currently hold the vast majority of the world’s freshwater thaw, sea levels will rise dramatically. For example, if the two glaciers that account for 12 percent of Greenland’s ice sheets thaw completely – and they’re currently melting – it's estimated that global sea levels will rise by 99 centimeters (39 inches).
Over the coming decades, this threat from the rising sea could put up to 13.1 million people living along the coast in the United States at risk, according to a new study. If sea levels rise by the National Oceanic and Atmospheric Administration’s (NOAA) upper projection estimates of 1.8 meters (6 feet) by 2100, far more people will be impacted than any current analysis suggests. And even if NOAA's lower estimate of 0.9 meters (3 feet) of global sea level rise is considered, around 4.2 million people will still be put at risk.
The number of people at risk from rising seas in each county, pictured as the lower estimate for sea level rise by 0.9 (3 feet). Hauer et al. 2016
“The impact projections are up to three times larger than current estimates, which significantly underestimate the effect of sea level rise in the United States,” explains Mathew Hauer, who led the paper published in Nature Climate Change, in a statement. “In fact, there are 31 counties where more than 100,000 residents could be affected by 6 feet [1.8 meters] of sea level rise.”
To calculate these estimates, the researchers looked at all 319 coastal counties in the continental U.S., and projected each county's expected population growth and sea level rise. They found that those living in Florida accounted for almost half of the total number of people most at risk, while more than 80 percent of those at risk live in just three counties: Monroe in the Florida Keys, and Hyde and Tyrrell in North Carolina.
The authors argue that if preventative measures are not put into place, the changes in sea level over the coming decades could displace millions of people and cause communities to migrate within the U.S. in numbers similar to those seen during the 20th century "Great Migration." This saw an estimated 1.6 million African American people move from mostly rural towns in the southern U.S. to urban and industrialized centers in the North, largely in response to racist pressures in the South and an increase in employment opportunities further North.
The cost of all the damage caused by such an event of this scale would be massive, but it's something that can be mitigated. “Adaptation strategies are costly, and these are areas of especially rapid population growth, so the longer we wait to implement adaptation measures the more expensive they become,” says Hauer. If things are acted upon now, it not only has the potential to save the economy, but also lives.