Big brains and large ranges may not save birds from climate change

Biologists have long debated why some plants and animals can adapt to a wide range of climates, while others can adapt to a wide range of climates. Understand why conservation managers and decision makers can identify which species are most vulnerable to climate change.

A new study on natural communications by researchers at the University of Texas at Austin assessed global distribution maps and other data for around 1,500 species of birds, and found surprising patterns. For example, researchers found that some species that breed in large geographical regions adapt to a rather narrow range of climates and become more vulnerable to climate change than previously thought. For example, consider the Arctic Circle, which accounts for a significant portion of the Earth’s land.

“Because the area is so large, the species that occupy it tend to have a large population and a large geographical range size. These are two traits that are often associated with lower risk of extinction,” said Carlos Botero, an associate professor of integrated biology and a senior author of the new study. “The problem here is that many of these species are adapted to a very narrow range of climates, so when climate patterns begin to change, it can be more likely to collapse at first glance.”

For example, the breeding range of Bohemian Waxwing, a bird well known to birders in North America and Europe, extends across large strips of the Arctic, while the maroon laughter is found in much smaller arcs in Asia, centered around Nepal and Bhutan. However, waxwings are much smaller than laughter and live in more extreme climatic conditions, suggesting that waxwings may be at greater risk from climate change than previously thought.

Researchers also found that species with larger brains (compared to body size) tend to adapt to narrow climate niches. A climate niche is the range of different climatic conditions (thinking about temperature, precipitation, and how much these two change over time) that a species can thrive.

“We would normally expect larger brave birds to be more adaptable, as larger brain sizes are correlated with more flexible behavior,” Botero said. “However, many big brave birds have turned out to be climate experts. This means that they have evolved to thrive in very specific climate types, so they may be more vulnerable to climate change than they expected.”

Botero conducted the study with his corresponding author and former UT postdoctoral researcher Joanne Fabricio Motor Rodriguez.

In this study, Rodriguez and Botero used bird range maps estimated from the direct observations of hundreds of thousands of citizen scientists reported through eBird. This successful partnership between birdwatchers and scientists provides a very accurate representation of where different species occur in spaces, allowing scientists to answer questions that could not be previously simply addressed.

The researchers also created a system to describe all the climate types found on the planet in terms of two factors: “temperature harshness”, values ​​increasing in “Xeric Harshness” that are lower, more variable, unpredictable temperatures (lower, more variable, more variable, increasing with unpredictable precipitation.”

We then created a 2D “climate space” map showing how much of the Earth’s surface corresponds to the possible combination of these two factors. Areas with low temperature and precipitation are closer to the center, but areas where one or both factors are severe are even further away.

Finally, for each species, we mapped the climate ranges that species tend to occupy on the climate spatial map to see where and how large the climate niche is. Birds with smaller, more extreme climate niches tend to be at higher risk of climate change.

Botero said that the study underscores why the usual methods of assessing risk for species, which usually include checklists of individual factors, miss the complexity of underlying patterns and inconsistencies.

“We need to stop looking at individual risk factors alone, but we need to assess how these complex factors combine,” Botero said. “Sometimes, the most important thing is unexpected interactions.”