More than 3 million Americans are climate migrants – 12/21/2023 – Environment

Over the past two decades, as San Antonio and surrounding Bexar County, Texas, grew by more than 600,000 residents, about 17 percent of city blocks experienced a decrease in population.

This discrepancy is largely due to the flood risk that climate change exacerbates, according to a new report from the First Street Foundation, a data-driven nonprofit with a mission to communicate climate hazards.

Bexar, located in a stretch of Texas known as Flash Flood Alley, is part of a national trend of hyperlocal migration to escape flooding, which has been emptying city blocks, the report found.

The research is based on a model, published Monday in the journal Nature Communications, that examines population changes using detailed U.S. Census data and controls for factors beyond flooding, such as nearby job opportunities and school quality. .

In total, First Street found that 3.2 million Americans moved from areas at high risk of flooding from 2000 to 2020. However, the full extent of the migration was hidden, as most people did not move far.

“There appear to be clear winners and losers regarding the impact of flood risk on population change at the neighborhood level,” Jeremy Porter, head of climate implications research at First Street, said in a statement. “The implications of this are enormous and affect property values, neighborhood composition and commercial viability, both positively and negatively.”

The analysis also extrapolates these trends 30 years from now, predicting that vulnerable areas will continue to lose population.

In the U.S., the frequency of disasters that cause at least $1 billion in damage has increased from about three per year during the 1980s to an annual average of 17.8 over the period 2018 to 2022, according to the National Oceanic and Atmospheric Administration.

Global warming has cascading effects that especially exacerbate flooding, including rising sea levels, more ferocious hurricanes, and more frequent and prolonged rain showers.

It’s no secret that climate migration is underway, whether along the Gulf Coast, which is losing a football field every hundred minutes, or in California, where entire cities have been forced into diaspora by wildfires. However, quantifying the impact of climate change on migration down to the neighborhood level is something that has never been done on a national scale.

First Street focused exclusively on flooding, as flooding is the most common climate-related disaster.

The researchers created a model that analyzes population change down to the smallest geographic unit used by the U.S. Census, the city block. They overlaid this information with historical flood data. They then attempted to isolate the influence of flooding on migration compared to other social and economic factors commonly associated with change, such as excellent or poor schools.

They found that when between 5% and 10% of properties on a Census block are at risk of flooding, there is a tipping point, and people begin to move even if there are other attractive factors, such as a view of the coast. .

In some cases, this movement is enough to leave previously prosperous areas in decline. In many other cases, it is just enough to slow growth that would otherwise be accelerating. Taking an in-depth look at Bexar County, First Street found that neighborhoods with lower flood risk grew much faster than those with higher risk.

Of course, people’s motivations for moving can be complicated. Kristina Dahl, lead climate scientist for the climate and energy program at the nonprofit Union of Concerned Scientists, said that while she saw no flaws in the First Street model, its findings contradict most of the current scientific literature.

“I think they did the best job they could of isolating the flood signal,” she said, “but there are a lot of factors that are difficult to capture.”

When it comes to decisions about whether or not to move, “generally, the body of literature shows that environmental factors are relatively low on the list,” Dahl said. “More often, people are worried about job opportunities or being closer to family.”