The human brain is sensitive to scarcity. The lack of something we consider vital, such as time or food, can powerfully shape our thinking and behavior. Take money, for example: when people play a game that makes some players abruptly wealthier or poorer, those who lose money start making decisions that result in their being better off now but worse off later.
One potential explanation for this tendency is that scarcity is mentally taxing. The sense of not having enough of what we need becomes a distraction that makes it harder for us to focus and plan.
In recent work, however, we found that people react to water scarcity very differently than they do to other shortages. In studies of people around the world, we found that those in places where water is scarce think more about the long term, and confronting people with water scarcity in a laboratory setting made them focus on the future. Worrying about water shortages prompted better planning and less wasteful behavior—not only with water but with other resources, too.
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As a species that is acutely dependent on water—without it we would die within days—we seem to be wired to plan for it. The loss of water prompts a general mindset of thrift and long-term thinking. This discovery could have important implications for humankind's response to climate change.
We explored people's thinking about water in several ways. In one experiment, we brought 211 college students to the lab and asked a portion of them to read an article we provided. Some received an article that was dire in tone. It detailed predictions of the worst “water shortage in 1,200 years.” Others read a more upbeat article that described how climate change means more rain and therefore ample water. (The latter article focused on the positives of water availability and did not discuss, for example, the threat of floods.) The rest of the students completed the study without reading an article.
We then asked the students how important it was to save resources and think about the long term. The mere idea of water scarcity was enough to kick-start them into thinking about the future. In a survey, participants who read about a serious shortage agreed more with statements such as “People should live for the future.” They also agreed more with ideas about saving, such as “There are things I resist buying today so I can save for tomorrow.”
In contrast, people who read about a future water surplus were pushed in the opposite direction. Compared with those who had answered the questions without reading about climate change at all, they were more likely to endorse living for the present and cared less about saving money and other resources.
Of course, simply reading about water scarcity might have different effects than actually experiencing it, so we looked for places where communities have experienced real water scarcity for generations. We found two geographically close cities in Iran—Shiraz and Yazd—that have similar economies and the same majority religion, language and ethnicity but sharply different amounts of water. Shiraz receives enough rainfall to support vineyards that produce its world-famous wine. Nearby Yazd is bone-dry. We gave psychological tests to 331 people in Shiraz and Yazd to measure what psychologists call “long-term orientation,” or how much individuals prioritize the future. Sure enough, people in Yazd thought that planning for the future was more important than those in Shiraz did, and people in Shiraz liked the idea of living in the moment more than those in Yazd did.
Then we went a step further. Iran is particularly vulnerable to drought, so perhaps people there are more sensitive to water scarcity than populations in other places. To get some sense of whether similar patterns exist elsewhere, we turned to the World Values Survey, a long-running global research project that gathers information about people's beliefs and values. We focused on survey data from respondents in 87 countries who were asked about the importance of thrift and saving for the future. Those who live in countries with a history of water scarcity tended to agree more with saving for the future. For example, in Europe, people in water-rich Iceland thought less about the future, whereas those in dry Spain thought more about the future.
Moreover, countries' history of water scarcity seemed related to cultural differences in a way that more obvious factors didn't. For example, income per capita did not explain differences across cultures. And although corruption might make it hard for people to think about the future, it was not a strong predictor, either. You might guess that people think about the future more in places where they tend to live longer, but astonishingly, national life expectancy was not as strong a predictor as water scarcity.
Across studies, our findings suggest that water has a meaningful place in our thinking—one that's distinct from other important resources, including wealth. In fact, humans may have evolved to be keenly sensitive to water access because it's so critical to us. Humans managed without money for many thousands of years. Our species can endure without food for weeks but without water for just days.
There is evidence of evolutionary wiring for water in our sense of smell. Humans are better at detecting the scent of fresh rainfall than sharks are at detecting blood. The fact that water is essential for human life makes it more plausible that evolution would lead to our having psychological reactions specific to the threat of water scarcity.
That sensitivity might be crucial going forward. Climate change is making droughts more common. Our work suggests that as many places dry up, global warming could reshape how people think, pushing entire communities toward more cautious, future-oriented behavior. That may offer a sliver of hope amid the threat of climate change. Water scarcity could be uniquely powerful motivation for us to prepare for and respond to a warmer world.
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