How extreme weather threatens nature's essential services

These are some critical questions that a new computer simulation, co-developed by a CU Boulder ecologist, can answer. In a paper published March 5 in Nature Ecology & Evolution, researchers presented a model that aims to understand how extreme weather events, worsened by climate change, will affect ecosystems and the benefits they provide to humans.

Based on the model, a Minnesota forest could lose up to 50% of its timber revenue if a severe windstorm hits.

"With climate change, there's an urgent need to incorporate the impacts of extreme events like mega-fires and hurricanes have on the benefits nature provides," said Laura Dee, the paper's first author and associate professor in the Department of Ecology and Evolutionary Biology. "This research is an important step toward anticipating impacts to ecosystem services so that we can adapt management strategies accordingly."

Scientists use the term "ecosystem services" or "nature's contributions to people" to refer to the essential functions that nature provides to support human life and well-being. Tree roots purify water, insects pollinate crops and forests lock away carbon, helping to stabilize the climate. In addition to these tangible benefits, mountains, lakes and oceans offer recreational enjoyment for people and hold cultural significance for communities.

Previous models for predicting how ecosystems respond to climate change tend to assume that changes are steady. For example, a gradual increase in global temperatures of up to 1.5°C. But as climate change makes extreme weather events like wildfires and floods more frequent and severe, the impacts from rapid disturbances have become significant.

Dee and her team developed a new mathematical model that tracks how the probability of an extreme weather event affects certain species and the ecosystem services they provide. The model also incorporates how people value these services.

To show the model's potential, the team applied it to calculate the possible consequences of extreme windstorms in a mid-latitude forest in northern Minnesota. The model considered how winds have different effects on different tree species, each of which has distinct economic value. For example, thick white cedar trees are more resilient to windstorms than balsam fir trees, but the balsam fir can sell at a higher price.

The model suggested that a windstorm, depending on its intensity, can slash the total timber value of the forest by 23% to 50%. Recreational opportunities like hiking and camping would also take a hit.

Dee said that researchers and land management officials could use the model to evaluate the impacts of any disturbances, from drought to invasive species.

Dee's research group at CU Boulder studies how prescribed fire strategies, or deliberately burning specific areas under controlled conditions, can reduce wildfire risks in Colorado. The new model also helps to identify the areas where scientists should prioritize burning to achieve the greatest reduction in fire risk, while also considering other benefits trees provide, such as removing carbon dioxide from the atmosphere and filtering water.

"Nature's contributions to people have not typically been valued and are usually left out of key decision-making processes when developing land management policies and strategies," Dee said.

The United Nation's World Meteorological Organization announced on Tuesday that more than 150 unprecedented extreme weather events struck Earth last year. With disturbances becoming more common, future Gross Domestic Product analyses, for example, should start incorporating the impacts of climate change, Dee added.

"If we fail to consider the growing risks from extreme weather events, we could lose more than we realize," she said.