Mammal genetic diversity faces severe exposure to climate change

April 2, 2021
Global warming could affect the genetic diversity of many mammals. (AP Photo/Rob Griffith)

Global warming could affect the genetic diversity of many mammals. (AP Photo/Rob Griffith)

Around the world, genetically poor and highly diverse areas alike will be exposed to severe climate change within just a few decades, according to recent findings that researchers say call global conservation goals into question.

The study, published March 16 in Ecography, provides the first evaluation of mammal genetic diversity's global exposure to future climate and land-use change. It states that about three-quarters of the entire planet will be exposed to a mean annual temperature rise of more than 2 degrees Celsius above preindustrial levels.

The Paris Agreement, which the U.S. moved to rejoin under President Joe Biden, aims to address climate change risks by having nearly every country doing its part to limit global temperature rise to "well below" 2 degrees Celsius, with a stretch goal of 1.5 degrees.

But the first-of-its-kind evaluation puts a new dent in this plan, which, to some, appears increasingly out of reach.

"Even in the best-case scenario, the genetic diversity in many of the regions of the world will be exposed to temperatures [rising] more than 2 degrees Celsius," study researcher Spyros Theodoridis, a postdoctoral fellow at the University of Copenhagen, told The Academic Times. "Even if we stop everything now and we start caring about nature, we won't be able to reverse these effects."

The United Nations has expressed interest in the new figures and is in talks with the research team to consider including the data in upcoming target goals for global conservation. 

"It's the first time that there's a report like this. It was long missing in different environmental bodies and conservation agencies," Theodoridis said. "That's why we were approached now by the Secretariat of the Convention on Biological Diversity. They picked up on our article because we basically had no clue on how genetic diversity is distributed globally."

The study builds on past research showing that terrestrial mammal biodiversity has been increasingly exposed to major anthropogenic pressures, including climate change and land-use change, such as deforestation, and the adverse effects of such pressures. 

Reversing the projected effects is not feasible because, "Whatever we see now is probably the result of the past 20 years, and what we'll see in 20 years will be the result of what we're currently doing," Theodoridis said. "This is how climate change works."

As a follow-up to a study the team published last year, researchers considered four scenarios, all of which showed that many regions in the world will be exposed to more than 2 degrees Celsius of warming. The scenarios are based on potential pathways for future societal development as well as climate-mitigation policies.

The initial study provided part of the data used in the new research, including its maps that take into account temperature change, precipitation change and primary vegetation change, as well as human change.

Compiling the new climate scenarios with a combination of the global maps from the initial study and datasets that are being published, the second study took about a year to complete. It employed the years of 1961-90 as a baseline period and 2040-69 as the future period to arrive at global evaluations of genetic diversity.

Using thousands of mitochondrial genes for hundreds of mammal species, the team found that more than half of the genetically poorest geographic areas — primarily distributed in tundra, boreal forests and taiga and temperate bioclimatic regions — are projected to be exposed to a mean annual temperature rise that exceeds 2 degrees Celsius compared with the baseline period. The finding applies to all considered scenarios. 

At least 30% of the most genetically rich areas in tropical, subtropical and montane regions will be exposed to the same under the less optimal scenarios, the study adds.

Additionally, exposure to increased human activity will take place in regions of high genetic diversity, including East Asia and eastern North America, by the mid‐21st century, compared with low genetic-diversity regions, such as the arctic.

The findings bring more awareness to how the risk of extinction facing many terrestrial mammals has been steadily increasing, with endangered mammals in the affected regions ranging from grizzly bears and rhinoceros and moose to sloths and toucans. 

The eastern North America region was found to harbor higher genetic diversity than expected. But this region will also be exposed to severe warming and reduced precipitation sometime between 2040 and 2069, the study says. 

The team argues that the study offers the opportunity to better estimate the geography of the vulnerability of genetic diversity, the backbone of evolution, to global climate and land-use change. But the researchers do not see limiting global warming to 1.5 Celsius as being likely, even under the best possible scenario, due to the nature of climate change.

"So, apparently, we will be facing more extinctions given the genetic diversity that these regions contain," Theodoridis said. 

Although at least some of the mammal species may be able to adapt in tropical regions because they contain higher genetic diversity, other species in less genetically diverse regions are likely already living close to their thermal limits.

"Meanwhile, the post‐2020 conservation goals are overlooking genetic diversity," the study says.

This isn't the first time scientists have questioned the feasibility of worldwide climate-related targets.

A study published last year called for United Nations targets to better account for climate change to preserve ecosystems and animals over the next several decades as the body works to form new 10-year biodiversity conservation targets. 

Meanwhile, work on the Intergovernmental Panel on Climate Change's sixth report has been delayed by the COVID-19 pandemic.

The study, "Exposure of mammal genetic diversity to mid‐21st century global change," published March 16 in Ecography, was authored by Spyros Theodoridis, Carsten Rahbek and David Nogues‐Bravo, University of Copenhagen.

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