“Dangerously Misleading” – Scientists Using Flawed Strategy in Predicting Species Responses to Climate Change

by François Dupont
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climate change predictions

The headline can be rephrased as follows:

“Scientists Employing Flawed Strategy in Forecasting Species Reactions to Climate Change Termed ‘Misleading'”

A recent study, featuring researchers from the University of Arizona, has unveiled the limitations of the space-for-time substitution approach used to predict how species will respond to climate change. This research indicates that this method may not be a dependable means of forecasting how species will adapt to changing climates in the future.

The study, which involves University of Arizona scientists, suggests that changes are occurring more rapidly than trees can adapt. This discovery serves as a cautionary note for ecologists who are studying the effects of climate change.

As global temperatures rise and climate patterns shift, various forms of life will either migrate, adapt, or face extinction. For many years, scientists have employed a particular technique to estimate how a species will fare during this era of significant change. However, recent research suggests that this method may produce results that are misleading or incorrect.

Uncovering Flaws in Predictive Approaches

Researchers from the University of Arizona, along with colleagues from the U.S. Forest Service and Brown University, have found that the commonly used space-for-time substitution approach failed to accurately predict how the ponderosa pine, a widespread tree in the Western U.S., has responded to several decades of warming. This implies that other studies relying on this approach may not accurately reflect how species will react to climate change over the coming decades.

To reach this conclusion, the team collected and analyzed ponderosa pine tree rings from various locations in the Western U.S., dating as far back as 1900. They compared the actual growth of these trees with the model’s predictions regarding how they should respond to warming.

Margaret Evans, a coauthor of the study and an associate professor in the UArizona Laboratory of Tree-Ring Research, explained, “We found that space-for-time substitution generates predictions that are incorrect in terms of whether the response to warming is positive or negative. This method suggests that ponderosa pines should benefit from warming, but in reality, they suffer as temperatures rise. This is dangerously misleading.”

Their findings were published on December 18 in the Proceedings of the National Academy of Sciences. Daniel Perret, a U.S. Forest Service ORISE Fellow, served as the first author of the study and received training in tree ring analysis at the UArizona laboratory through the university’s summer field methods course. This research was part of his doctoral dissertation at Brown University, where he worked with Dov Sax, a professor of biogeography and biodiversity and a coauthor of the paper.

Challenges with Space-for-Time Substitution

The space-for-time substitution method operates on the premise that each species occupies its preferred range of climate conditions. Scientists have assumed that individuals thriving in the hotter end of this range can serve as an indicator of what might happen to populations in cooler locations in a warmer future.

However, the research team discovered that ponderosa pine trees actually grow at a slower rate in warmer locations. According to the space-for-time substitution paradigm, this would suggest that as the climate warms at the cooler edge of the tree’s distribution, conditions should improve. But this is not the case when examining the tree ring data.

When the team used tree rings to assess how individual trees responded to temperature changes, they found that the ponderosa pines were consistently negatively affected by temperature fluctuations. “In warmer-than-average years, they exhibit smaller-than-average growth rings, indicating that warming is detrimental to them, and this holds true across all locations,” explained Evans.

The team suspects that this occurs because the trees are unable to adapt quickly enough to keep pace with the rapidly changing climate.

Rainfall Influence and Concluding Thoughts

In addition to temperature, the researchers also explored how trees responded to changes in rainfall. Their findings confirmed that increased water supply is consistently beneficial, whether considering time or geographical location.

Evans emphasized the potential dangers of spatially based predictions, stating, “These predictions based on spatial patterns are risky because these patterns reflect the endpoint after a lengthy period during which species have had the opportunity to evolve, disperse, and ultimately adapt to their surroundings. However, this is not how climate change operates. Unfortunately, trees now find themselves in a situation where change is occurring more rapidly than they can adapt, placing them at significant risk of extinction. This serves as a word of caution for ecologists.”

Reference: “A species’ response to spatial climatic variation does not predict its response to climate change” by Daniel L. Perret, Margaret E. K. Evans, and Dov F. Sax, published on December 18, 2023, in the Proceedings of the National Academy of Sciences. DOI: 10.1073/pnas.2304404120

Funding for this research was provided by the Brown University Department of Ecology, Evolution, and Organismal Biology, Institute at Brown for Environment and Society, American Philosophical Society Lewis & Clark Fund for Exploration and Field Research, USDA Forest Service Pacific Northwest Research Station, DOE Oak Ridge Institute for Science and Education, and NSF Macrosystems Biology.

Frequently Asked Questions (FAQs) about climate change predictions

What is the space-for-time substitution method in ecological research?

The space-for-time substitution method is an approach used in ecological research to predict how species will respond to climate change. It involves studying how individuals of a species in warmer locations behave as a way to forecast how the same species will fare in cooler locations as temperatures rise.

What did the recent research discover about the space-for-time substitution method?

The recent study found that the space-for-time substitution method inaccurately predicted the response of ponderosa pine trees in the Western U.S. to several decades of warming. Contrary to predictions, these trees actually suffered from warming, highlighting a flaw in the method’s reliability.

Why is this discovery significant?

This discovery is significant because it calls into question the effectiveness of the space-for-time substitution method in predicting how various species will respond to climate change. It suggests that relying on this method may lead to misleading or incorrect conclusions about the impacts of warming on species.

How did the research team conduct their study?

The research team collected and analyzed ponderosa pine tree rings dating back to 1900 from various locations in the Western U.S. They compared the actual growth of these trees to the predictions made by the space-for-time substitution model regarding their response to warming.

What are the implications of the findings for ecological research?

The findings imply that other ecological studies using the space-for-time substitution method may also produce inaccurate results when assessing how species will respond to climate change. This has implications for the accuracy of ecological predictions and conservation efforts.

What other factors did the research consider besides temperature?

In addition to temperature, the study also investigated how trees responded to changes in rainfall. The research confirmed that increased water supply consistently had a positive effect on the trees, regardless of time or geographical location.

What is the key message for ecologists and those concerned with climate change?

The key message is a word of caution for ecologists and researchers studying the effects of climate change. The study suggests that species may not be able to adapt quickly enough to keep pace with the rapidly changing climate, posing a significant risk of extinction for some.

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