As humanity copes with human-induced climate change, an important task is assessing geographic patterns of risk based on expected changes in various associated natural hazards. A recent study by ProPublica seeks to do just that, assessing anticipated risks related to excessive heat and humidity, wildfires, sea level rise, and crop yields, leading to estimates of the net effects of these changes for the GDP of each US county.
What is striking and concerning about these results is that many of the most vulnerable areas (in shades of red, above) are also areas where the US population is growing most rapidly (in shades of green, below). Why is this happening? A recent PBS video focused on this issue notes that many of the places that are most vulnerable to climate-change-related hazards are also places where the cost of living is relatively low, making them attractive places in the short term, despite the fact that most of the people moving there already know the long-term prognosis.
It turns out that the tendency of humans to move into areas for short-term gain, despite awareness of longer-term risks, is nothing new. In one study, for example, Dylan Schwindt and colleagues examined the settlement history of what is now Montezuma County, Colorado, between about 600 and 1280 AD, based on the archaeological record left by the ancestors of today’s Pueblo Indian peoples. They found that, as the regional population grew, people increasingly moved to areas where land was more available for farming, but it was also more susceptible to drought. This would have been obvious to the settlers simply based on differences in the wild plants that were growing in different areas, but people nevertheless privileged short-term gain over longer term risk. Most likely, they didn’t have a reasonable alternative. Times were good when people first moved into these areas, but when the so-called “great drought” hit in 1276 AD, about 30% of the regional population was no longer able to feed itself. The resulting social conflict led to the collapse of the entire society and the complete depopulation of the region.
Parallels between archaeological studies like these and the present-day situation suggest that when people decide where to move, their cost-benefit analyses are biased toward the recent past–a phenomenon economists call “discounting the future.” If this really is how people think, and broad demographic and social forces emerge from it, then informing the public about future climate-related risks is not likely to affect where people choose to move today. It would seem the only practical way to shape migration patterns is to implement policies that make less hazardous areas more appealing now. Moderating the social consequences of climate change may depend on it!