A new study involving researchers at the University of Arizona suggests that changes are happening faster than trees can adapt. The discovery is a “warning to ecologists” studying climate change.

As the world warms and the climate changes, life will migrate, adapt, or become extinct. For decades, scientists have introduced certain methods to predict how things will happen. seed We will survive this era of great change. But new research suggests that method may be misleading or producing false results.

Flaws in prediction methods revealed

Researchers at the University of Arizona and team members from the U.S. Forest Service and Brown University found that this method (commonly referred to as spatiotemporal replacement) shows how a tree called the ponderosa pine, which is widespread in the western United States, grows. I discovered something that I couldn’t predict accurately. We have actually responded to global warming over the past few decades. This also means that other studies that rely on displacement in space and time may not accurately reflect how species will respond to climate change in coming decades.

The research team collected and measured growth rings of ponderosa pine trees from across the western United States, dating back to 1900, to determine how trees actually grow and how models predict how trees will respond to warming. We compared.

A view of ponderosa and Jeffrey pine forests from Verdi Mountain near Truckee, California.Credit: Daniel Perrette

“We found that substituting time for space produces incorrect predictions in terms of whether the response to warming will be positive or negative,” said study co-author Margaret Evans, an associate professor at the University of Arizona. ” he said. Tree ring laboratory. “With this method, ponderosa pines are supposed to benefit from warming, but they actually suffer from warming. This is dangerously misleading.”

Their research results were published on December 18th. Proceedings of the National Academy of Sciences. Daniel Perrette, a U.S. Forest Service ORISE fellow, is the lead author and received training in tree-ring analysis through the university’s summer field methods course at the University of Arizona Research Institute. The study was part of his doctoral dissertation at Brown University, and was conducted with Dov Sachs, professor of biogeography and biodiversity and co-author of the paper.

Inaccuracies in space and time substitutions

This is how space and time permutation works. All species occupy a range of favorable climatic conditions. Scientists believe that individuals growing at the hottest end of their range could serve as an example of what will happen to populations in cooler locations in a warmer future.

The research team found that ponderosa pine trees grow at a faster rate in warmer locations. Therefore, under the spatial and temporal displacement paradigm, this suggests that the situation should improve as the climate warms at the cold end of the distribution.

“But the tree-ring data doesn’t show that,” Evans said.

However, when the researchers used tree rings to assess how individual trees responded to changes in temperature, they found that ponderosa was consistently negatively affected by temperature fluctuations.

“If it’s a warmer-than-average year, they’re going to have smaller-than-average growth rings, so warming is actually bad for them, and that’s true everywhere,” she says.

The researchers believe this may be happening because trees are unable to adapt quickly enough to a rapidly changing climate.

An individual tree and all its growth rings are a record of that particular tree’s genetics exposed to different climatic conditions from one year to the next, Evans said. But how a species responds as a whole is the result of a slow pace of evolutionary adaptation to the average conditions in a particular location that are different from those elsewhere. Similar to evolution, the movement of trees that are better adapted to changing temperatures could save species, but climate change is happening too quickly, Evans said.

Rainfall effects and final thoughts

Beyond temperature, the researchers also looked at how trees responded to rainfall. They confirmed that, even across time and space, more water is better.

“These spatially-based predictions are really dangerous because spatial patterns reflect the end point after a long period in which species have had the opportunity to evolve, disperse, and ultimately sort themselves across the landscape. Because we do,” Evans said. “But that’s not how climate change works. Unfortunately, trees are in a situation where they are changing faster than they can adapt and are actually at risk of extinction. This is a warning to ecologists. .”

References: “Species responses to spatial climate change do not predict responses to climate change,” by Daniel L. Perrett, Margaret EK Evans, and Dov F. Sachs, December 18, 2023. Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2304404120

Funding: Brown University Department of Ecology, Evolution, and Organismal Biology, Brown Institute for the Environment and Society, American Philosophical Society Lewis and Clark Expeditionary and Field Research Fund, Department of Agriculture Forest Service Pacific Northwest Research Station, Department of Energy Oak Ridge Science Institute Education , NSF Macrosystems Biology