Research Offers Framework for Fast and Slow Responses to Climate Change

Life on earth has always responded to change — birds shift the timing of their migration, insect populations grow and shrink, plants evolve to deal with drought. But now, human-caused climate change is moving so quickly that only the fastest ecological responses are keeping up. Ecosystems are lagging behind in a way that makes the future of the natural world very hard to predict.

New research from an interdisciplinary team led by USU ecologists Michael Stemkovski and Peter Adler offers a new framework to anticipate impacts of climate change on ecosystems, with an eye toward conceptually integrating both fast and slow processes. They argue that a stronger focus on timescales could help predict future shifts, with many responses falling under the umbrella term “Ecological Acclimation.”

“All these processes drive ecosystems toward equilibrium with the climate, but they operate at very different timescales,” Stemkovski said. “Some will keep up with change while others lag.”

In the past, physiological plasticity (immediate changes), species turnover, evolution and phenological shifts (changes related to seasonal timing) have been viewed as entirely distinct. The new publication argues that when you account for timescales, all of them fall under the same umbrella.

“The problem is a little like forecasting weather,” Stemkovski said. “We can do it really well in the short term — predicting rain five days from now. And get it right in the long term — average temperatures in the next century. But no one knows how to accurately predict the weather 20 years from now.”

Ecological forecasting is similar, he said. Predicting what ecosystems will look like in coming decades has been a big challenge, but this is also the timeframe managers use for policy planning in much of forestry and wildlife management.

Why is forecasting at intermediate timescales so difficult?

“Think about when you start exercising,” said Adler, who is director of the USU Ecology Center. “You might feel tired and sore after the first hard workout. But if you keep it up, eventually you get stronger and have more energy. The initial effect feels negative, even though the long-term effect might be entirely different.”

The interactions in ecological timescales are similarly complex and sometimes counterintuitive, he said.

“Changes we already see in ecosystems mostly have to do with fast responses like shifts in the timing of spring flowering,” Stemkovski said. “But once slow responses like evolution start to catch up, ecosystems might look and work very differently.”

For example, in one experiment of the long-term impacts of climate change on soil, researchers determined that the warmer soil held less carbon — for a while. After 10 years of warming, carbon levels recovered to the norm and then began to increase as long-term changes shifted the plant communities from flowers to shrubs.

“Most of the data that we have from global change experiments represents fast responses, like physiological change and rapid demographic changes such as growth or deaths,” Adler said. “To make better forecasts across longer time horizons, we need a way to think about the combined effects of fast and slow ecological acclimation processes.”

In ecosystems with longer-lived organisms, like forests and coral reefs, migration and evolution can help ecosystems under stress. But these are slow processes that lag behind climate change. To save these communities, managers may have to speed up nature by assisting migration and evolution, Adler said.

Uncertainty about the timescales of ecological responses make it hard for managers to decide on actions to manage the impacts of climate change.

“Managers want to make good investments in adaptive natural resource management. It’s important that the decisions we make now don’t prove counterproductive in the long term,” Adler said.

Accurate forecasts and proactive management will require collaboration with people who understand processes on multiple levels, Adler said. The new framework outlined in the research facilitates this by creating a shared language for that response.

“No single model can include all the relevant processes needed to accurately forecast from very short to very long time horizons,” Stemkovski said. “But a focus on the timescales of ecological processes can help researchers and managers make better decisions using the models that we do have.”