Many bird species could lose between 78 and 85 percent of their existing habitat
Birds and reptiles in the Southwest that live in fragmented habitat will be hit hardest by global warming in the decades ahead, according to a new study by scientists with the U.S. Geological Survey and the Northern Arizona University.
The researchers took a close look at about 30 different animals, including well-known species such as the Gila monster, horned lizard, chuckwalla, Sonoran desert tortoise, pinyon jay, pygmy nuthatch, sage thrasher and black-throated sparrow.
A few species could see their habitat expand as the climate warms, but many others will be hit hard by global warming. Most climate models project temperatures to increase by about 6 degrees Fahrenheit in the Southwest in the next century, while precipitation is expected to decline by between 5 and 20 percent.
The study was aimed at identifying conservation strategies to help wildlife survive those rapid changes. The findings were reached by combining data from global climate change models with new species distribution models “to estimate future losses and gains of Southwestern bird and reptile species,” said Dr. Charles van Riper III, senior research ecologist with the USGS and report co-author.
- The researchers found nuances in how different species will respond to climate change:
- One-third of the ranges are predicted to expand, while two-thirds are predicted to contract.
- Several reptile species are projected to lose between 25 and 72 percent of their range, including the Gila spotted whiptail, Arizona black rattlesnake and ornate box turtle.
- Numerous bird species are projected to lose between 78 and 85 percent of their range, including Williamson’s sapsucker, sage thrasher, red-naped sapsucker and pygmy nuthatch.
Species that currently live in warmer areas during any season may see their habitat expand, while species that currently live in wetter spring and summer locations
An important finding by the authors was bird or reptile species that currently occupy warmer locations in any season may experience range gains, whereas species that currently occupy wetter spring or summer locations may experience range contractions.
Another key finding by the authors was that the more fragmented bird and reptile ranges are under today’s conditions, the more vulnerable they appear to the future effects of climate change.
“Proactive land management actions that enhance landscape connectivity and conserve core areas might lessen the severity of range contractions projected over the coming century for birds and reptiles,” said James Hatten, lead author and research biogeographer with the USGS. “Land management actions that reduce the distance between habitat patches, increase connectivity, and enlarge core areas could be helpful for bird and reptile species across the landscape.”
The study found that, when they included data on climate change impacts to plants in their models, the projections for birds and reptiles became more dire.
When the authors modeled the assumption that reptiles will not be able to disperse fast enough to escape a shifting climate (think of animals with tiny or no legs), all their future ranges contracted. When the authors assumed reptiles can disperse as fast as the climate shifts, such as birds, over half of reptile species’ ranges expanded, but the authors think this is highly unlikely given the life histories of many reptiles. In contrast, several desert-scrub bird species (black-throated sparrow, gray vireo and sage sparrow) are projected to increase their future ranges by over 30 percent.
“Climate-related biodiversity disruption is likely to be a central theme of natural areas stewardship in the 21st century,” said Lisa Thomas, National Park Service program manager for the Southern Colorado Plateau Network. ‘By using an integrated modeling approach, the authors were able to evaluate exposure and sensitivity for a range of bird and reptile species to predicted climate change.”
The study was a partnership of the USGS, Northern Arizona University and University of New Mexico. The work was supported by the DOI Southwest Climate Science Center, which is managed by the USGS National Climate Change and Wildlife Science Center. The center is one of eight that provides scientific information to help natural resource managers respond effectively to climate change.