Climate futures for lizards and snakes
Will reptiles stay put or move as the climate changes across the West?
Scientists used climate projections to predict which parts of western North America may be habitable for 130 lizard and snake species later in the century. They found that for many, the future may be North. That could mean big changes for agencies that manage these species and their habitats.
Have you found your niche?
For us humans that usually means we’ve found a job or hobby that is perfectly suited to our interests and skills. A climate niche is similar—it’s the combination of temperature and precipitation that is perfectly suited to a species’ needs. Climate is particularly important for lizards and snakes because they are ectotherms, commonly referred to as “cold-blooded.” That means they depend on the environment for warmth since their bodies don’t generate heat on their own.
It’s no surprise then that the southwestern U.S. and Mexico are home to the most lizard and snake species in western North America. However, as the climate warms and water availability becomes more variable, the locations of species’ climate niches could change. Parts of the continent that were previously suitable for a species could become too warm, while areas farther north or higher in elevation that were previously too cold for reptiles could become “just right.”
This classic Goldilocks story was the focus of a recent study by U.S. Geological Survey and U.S. Forest Service researchers. Where will those ideal climate conditions be as climate change unfolds across the West? Answering that question could help us predict where species will live in the future, providing valuable information for those working today to sustain biodiversity tomorrow.
New reptiles coming to a backyard near you?
Scientists gathered data on the recent distributions of 130 lizard and snake species found from Mexico to western Canada.
The climate in each species’ current range defined its “climate-niche distribution” or the area where the temperature and precipitation have been suitable for survival and reproduction over the last 30 years or so.
Then, the team looked at where those same climate conditions may occur later in the century based on multiple climate change scenarios.
Overall, future climate-niche distributions are predicted to shift northward and towards higher elevations.
By the end of the century, 68% of the 130 species are predicted to have an expanded climate-niche distribution, potentially resulting in new species arriving across state and international borders if there are no barriers to dispersal.
Idaho and Colorado are the states predicted to have the most species knocking at their door. Both states border vast deserts to the south and have remarkable elevation gradients.
Dede Olson, research ecologist with the U.S. Forest Service Pacific Northwest Research Station says:
“As species migrate northward, they could cross jurisdictional boundaries, such as private lands, state lines, or even international borders. Natural resource agencies might find themselves managing species that were not previously within their regions.”
On the map to the right, areas shaded in yellow have suitable climate for a larger number of reptile species. The maximum number of species is 68 in the recent time period and 69 in the future scenario. Areas in purple are suitable for fewer species.
One of those species is the Gila monster, which is currently found in northern Mexico and parts of southern California, Nevada, Arizona, and New Mexico. By the end of the century, the climate in southern Idaho or even in pockets as far north as Washington State could be suitable for the desert species.
An early warning for climate-sensitive species
Although most species are predicted to enjoy an expanded climate niche, 8.5% of species—mostly in the southwest United States and Mexico—could lose climate-niche space as parts of their current ranges become too warm and dry for survival. The states of Chihuahua and Sonora in Mexico are predicted to lose climate-niche space for the most species.
The dunes sagebrush lizard, for example, is predicted to lose all suitable climate-niche space across the entire study area. Although parts of the U.S. to the east of the geographic scope of this study, like Texas, may still be inhabitable. The dunes sagebrush lizard was recently listed as Endangered by the U.S. Fish and Wildlife Service.
Other species predicted to have shifted or smaller climate niches in the future have not been previously identified as particularly rare or climate sensitive. Therefore, they may not currently be on local managers' radars as needing conservation attention.
Species such as the pygmy short-horned lizard, which has no protective status, is projected to lose its entire climate niche in Alberta, Canada and seven U.S. States, while retaining only a small portion of its range in Washington State and British Columbia.
A similar shift is projected for the northern rubber boa, one of only two boas native to North America. It’s current climate niche spans much of the northwestern U.S., but by the end of the century those conditions are expected to shift higher in elevation and northward into British Columbia.
Data in the hands of those who need it
The researchers behind the study released the full data set to the public and developed a data visualization tool to make it easy to explore the results and learn more about how climate change could impact local species. The data release includes downloadable data, including full-page illustrations of climate-niche predictions for each species.
Anyone from scientists and resource managers to local residents interested in the wildlife in their own backyard can use the tool. The interactive figures display the results by species, state, or elevation.
Michelle Jeffries, a biologist with the USGS Forest and Rangeland Ecosystem Science Center says:
“We created this data visualization tool so resource managers will be able to quickly identify which species may need attention as the climate changes. The tool brings the figures from the paper to life. It allows users to interact with the data, filter it, and create their own figures tailored to their specific needs or interests.”
There's always more to the climate story
Whether those reptile species can actually move towards cooler climates and survive in new habitats depends on many factors. Human-created barriers like cities or roads could block the way, or natural obstacles like rivers and canyons could halt progress.
On the map to the right, areas shaded in brown are predicted to lose climate-niche space for reptile species in the future. Areas in teal are predicted to gain species. These simulated dispersal scenarios are on opposite ends of the spectrum. Actual changes in climate-niche species richness will likely fall somewhere in between: some species will be able to disperse and others will not.
There could be other habitat suitability considerations as well, like food availability or predators. It’s also possible that some species will adapt to the changing climate of their current range and stay put. Populations with enough genetic variation could evolve tolerance to warmer temperatures over generations. In other words, a shift in climate-niche doesn’t necessarily mean a species’ distribution will shift accordingly.
David Pilliod, research ecologist with the USGS and lead author of the publication said:
“Researchers around the world are looking at links between genetics and climate adaptation, temperature and reproduction, the timing of life history events and migrations...it's a long list. Reptiles are a very diverse but understudied group, and we know they’re particularly sensitive to changes in environmental temperature. We wanted to try and focus attention on species and habitats that could be impacted by climate change relatively soon.”
This early warning that climate-niche distributions could change, and reptile species could be gained or lost, gives wildlife managers a chance to prepare. The results of this study are relevant to managers across 47 states and provinces from Mexico to western Canada with responsibilities for species conservation and habitat management.
Read the full publication on the journal's website
Access the data visualization tool
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