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Climate Change and Environmental Issues in Tucson

Angled late-afternoon sunlight hits the colorful buildings of Tucson's downtown.
Downtown Tucson viewed from Sentinel Peak. Photo © Bill Morrow, licensed Creative Commons Attribution.

With its delicate and finely balanced biomes and some of the most dramatic and exotic scenery on earth, Arizona has over the generations been a haven, a laboratory, and a rallying point for environmentalists and ecologists. One of the biggest threats to the state’s extremely varied ecosystems is growth; much of the desert has been paved over and crowded with homes, while the upland forests host droves of overbuilt homes just waiting for a wildfire to burn them to their foundations. There are no signs that this trend is going to let up any time soon, either.

The constant influx of people has led over the years to environmental problems far beyond the mere pavement of desert and clearing of forests. Growth and the state’s founding impetus to glean profit from the land have led to the overpumping of groundwater and the damming and taming of most of the state’s rivers. This has altered the green riverways so completely that many species of native fish are now as good as gone, and nonnative plants line the mostly dry riverbeds, crowding out native riverine flora like cottonwoods and willows.

Climate change, scientists say, is likely to increase the state’s environmental woes, and, coupled with an ongoing drought that has been more or less eating away at the state for over a decade, may lead to shortages on the Colorado River, water from which the vast majority of urban Arizonans, including Tucsonans, depend. Some scientists have recently predicted that Lake Mead may dry up by 2025, while others believe the current human culture in Arizona may, one day in the future, suffer the same collapse as did the Anasazi, the Hohokam, and other complex societies who have tried to make a go of it here, leaving behind the ruins of their rise and fall but not much else.

Is It Getting Even Hotter in Tucson?

According to at least one University of Arizona researcher, people have made it hotter in Tucson than it already was—and it was already the hottest desert in North America before we arrived en masse after World War II to begin changing the wilderness into car-centric, fossil fuel–dependent cities and suburbs.

UA professor emeritus William Sellers, in a chapter on the state’s climate in Natural Environments of Arizona, finds that the state’s “minimum temperature averaged significantly higher during the 1953–2002 period than it did prior to the early 1940s.” This is proof, Sellers writes, of the urban heat island effect, through which nighttime temperatures (which in other less-paved-over deserts tend to drop significantly, offering a cooling respite to the land while the sun is down) stay rather high because the heat is stored in buildings and asphalt.

Indeed, Sellers finds that the average minimum temperature in the Phoenix area has increased by nearly seven degrees Fahrenheit since the early 1960s, while the average maximum temperature has gone up only about two degrees Fahrenheit in that time. Apparently we love the heat so much we never want it to cool down. Additionally, Sellers writes, average nighttime temperatures in the state’s deserts were significantly lower prior to the 1940s than they are today. Temperatures as low as zero degrees Fahrenheit were recorded along washes in the Tucson area, and in 1937 Tucson’s temperatures were below normal every day for a month. “The most likely cause for most of the increase in the average temperature in Arizona since the early 1940s is the rapid expansion in the population and the industrial development that occurred in the area during and following World War II,” Sellers concludes.

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