Researchers studying a lizard species in southeastern Arizona discovered that 70 years’ worth of climate-related extinction occurred in only seven years.
A recent study from the University of Arizona reveals that climate change is accelerating the rate of extinction. Researchers surveyed populations of the Yarrow’s spiny lizard in 18 mountain ranges across 18 mountain ranges in southeastern Arizona and analyzed the rate of climate-related extinction over time.
“The magnitude of extinction we found over the past seven years was similar to that seen in other studies that spanned almost 70 years,” said John J. Wiens, a professor in the Department of Ecology and Evolutionary Biology at UArizona, and the senior author of the study.
The Yarrow’s spiny lizard native to the southwestern U.S. and western Mexico can be spotted in oak and pine forests in 18 of Arizona’s Sky Islands mountain ranges. Wiens and his group did initial surveys of the Yarrow’s spiny lizard in these mountain ranges in 2014 and 2015. In 2021 and 2022, Wiens, along with Kim Holzmann, his former master’s student and the lead author of the study, and Ramona Walls, a part-time researcher at UArizona’s BIO5 institute, resurveyed to investigate if there had been any changes in the lizard populations since then.
During the resurveys, Wiens’ group found that about half of the lizard populations at lower elevations had disappeared. This is because temperatures are warmer at lower elevations, Wiens said, and the lizards at lower elevations were presumably not able to tolerate the increasing heat. This loss of low-elevation populations is a signature pattern of climate change, he said.
An Alarming Rate of Climate-Induced Extinction
“The rate of extinction in such a short time period was shocking,” Wiens said.
After comparing these findings to historical records from the same mountain ranges, Wiens’ group found that the average extinction rate of the lizard populations at low elevations had tripled over the past seven years, relative to the preceding 42 years.
Although previous studies have predicted that climate-related extinctions will increase with the rising pace of global warming, Wiens said he hasn’t seen any showing that this acceleration of extinction has already happened.
Also, a distinct 3-million-year-old lineage of the Yarrow’s spiny lizard from the Mule Mountains, near Bisbee, may be completely extinct by 2025, according to Wiens.
“The low-elevation populations in the Mules were fine in 2014. Now the only ones that we have found left were within about 300 feet (90 meters) of the top of the mountain in 2022, and they appear to have been losing about 170 feet per year,” he said.
Genetic Variation and Survival in a Changing Climate
However, not all low-elevation populations went extinct between the surveys, Wiens said. For example, two populations that occurred at very low elevations survived. Before they disappeared, the research group had collected genomic data from most of those populations in 2014 and 2015. They found that those populations that were less genetically variable and were exposed to greater climate change effects were the ones that tended to go extinct. This suggests that the populations with less genetic variation had less ability to adapt to climate change.
In the future, Wiens’ research group is planning to further study the extinction and survival mechanisms of the Yarrow’s spiny lizards living in these mountain ranges. They are also planning to conduct similar studies with other lizard species living in even hotter places, such as California’s Death Valley.
Wiens said it is now important to study climate change impacts on biodiversity at shorter timescales instead of only looking for changes after many decades have passed.
“We’ve shown now that there can be devastating climate change effects over very short time periods,” he said.
Reference: “Accelerating local extinction associated with very recent climate change” by Kim L. Holzmann, Ramona L. Walls and John J. Wiens, 18 September 2023, Ecology Letters.
DOI: 10.1111/ele.14303
The study was funded by the National Science Foundation.
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1 Comment
“This is because temperatures are warmer at lower elevations, Wiens said, and the lizards at lower elevations were PRESUMABLY not able to tolerate the increasing heat.”
There are two major problems with this claim and the study in general. Nowhere do they present evidence that the temperatures globally, or particularly in the study area, have increased during the 7-year study period. They have apparently assumed, that because we hear so much about global warming, that it must be occurring in their study area. Satellite data processed at the University of Alabama at Huntsville (UAH) tells a different story: “The least-squares linear-regression trend on the UAH monthly satellite global-temperature dataset for the lower troposphere shows no global warming at all from June 2014 to April 2023.” ( https://wattsupwiththat.com/2023/05/02/the-new-pause-lengthens-by-two-months-to-8-years-11-months/ ) That is, there is no evidence presented that the assumed warming took place and there is evidence to suggest that it may not have.
Beyond that, most of the warming prior to the last 9 years has been at night, in the Winter, and in cities. It is generally accepted that the Arctic has warmed 2-3X more than the global average in the recent past. What does that say about the probability that deserts are experiencing anomalous warming? The fact that Death Valley holds the record from 1913 may well be germane to this study.
It is not unusual for prey-predator populations to oscillate over short time periods because of food availability. What has the precipitation been like in the Sonoran Desert during the period of the claimed decline of the lizards? Did they research it, or just assume the problem is Global Warming?
It is the unexamined assumptions that will get you every time.