Some Animals Win, Most Lose as Southwest Warms


Animals already deal with extreme heat and drought in the deserts and grasslands of the southwestern United States. Conditions will become ever more challenging to wildlife as the climate warms.

A team of scientists recently forecast that 4 out of 5 reptiles and 5 of 7 bird species may lose chunks of their homelands by 2099. A few species may gain territory.

Biologists and computer scientists from the U.S. Geological Survey, University of New Mexico, and Northern Arizona University created maps of how birds and reptiles may be affected as the Southwest warms. Within the next 60-90 years, climate projections suggest the Southwest may increase in average temperature by 3.5 to 4 degrees Celsius and decrease in precipitation by 5 to 20 percent.

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Between 2010 and 2099, the scientists estimated the following changes in habitat, which is the collection of environments where an animal, plant or microorganism lives.

The Winners:

Sonoran desert tortoise: Biologists recently re-classified this shelled reptile (Gopherus agassizii) as a separate species from other desert tortoises. The tortoise may manage to hold onto it homeland or experience only a 1 percent decline in the areas where the reptile lives, known as its range. However, the tortoise faces threats from expanding human developments, such as cow pastures and roads, as well as invasive species, including dogs. The International Union for the Conservation of Nature classifies the tortoise as vulnerable to extinction.

Black-throated sparrow: This small bird (Amphispiza bilinea) thrives in dry, upland areas, especially where creosote bushes grow. As these arid regions expand, the breeding range of the bird may increase by 34-47 percent. Breeding ranges are geographical areas where animals find the environments they need to reproduce.

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Gray vireo: This bird (Vireo vicinior) already lives in some of the hottest, driest parts of the Southwest. Climate change could increase the breeding range of the bird by 58-71 percent.

The Losers:

  • Sage thrasher: 78 percent decrease in breeding range
  • Pinyon jay: 25-31 percent decrease in breeding range
  • Pygmy nuthatch: 75-81 percent decrease in breeding range
  • Williamson’s sapsucker: 73-78 percent decrease in breeding range
  • Virginia’s warbler: 1.5-7 percent decrease in breeding range
  • Plateau striped whiptail lizard: 42 percent decrease in range
  • Arizona black rattlesnake: 32 and 46 percent decrease in range
  • Common lesser earless lizard: 22-49 percent decrease in range
  • Common chuckwalla: 13 and 23 percent decrease in range

Photo: Sonoran desert tortoises are expected to lose only about 1 percent of their habitat, due to global warming, but are still vulnerable to extinction. Credit: U.S. Fish and Wildlife Service, Wikimedia Commons

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