Climate risks threaten the future of the world's forests

Forests are in a delicate dance with climate change. They absorb massive amounts of carbon dioxide and host abundant biodiversity, but are increasingly threatened by disturbances associated with climate change, such as extreme weather and wildfires. 

A new study quantifies risks to forests across carbon storage, biodiversity and forest loss from disturbance, such as fire or drought. The results show that in some regions, forests are experiencing clear and consistent risks. In other regions, the risk profile is less clear.

“Large uncertainty in most regions highlights that there’s a lot more scientific study that’s urgently needed,” explained William Anderegg, inaugural director of the University of Utah’s Wilkes Center for Climate Science and Policy.

Anderegg assembled a team of researchers from the United Kingdom, Germany, Portugal and Sweden. Their task was to assess climate risks to the world’s forests that span many continents and host vastly different biodiversity.

Previous research has investigated one dimension of climate risk, either carbon storage, biodiversity, or risk of forest loss. For this new global analysis the team went after all three dimensions.

“These dimensions of risk are all important and, in many cases, complementary. They capture different aspects of forest resilience or vulnerability,” said Anderegg.  

Carbon storage: Forests absorb about a quarter of the carbon dioxide that’s emitted into the atmosphere, buffering the planet from the effects of rising atmospheric carbon dioxide. The results showed that global gains in carbon storage can be expected by the end of the century. The researchers also found higher risk of carbon loss in southern boreal (just south of the Arctic) forests and the drier regions of the Amazon and African tropics.

Biodiversity: the researchers found that the highest risk of ecosystems shifting from one “life zone” to another due to climate change could be found at boundaries of biomes – at the current transition between temperate and boreal forests. Forests of the boreal regions and western North America faced the greatest risk of biodiversity loss.

Disturbance: The risk of events like drought, fire or insect damage that could wipe out forests. Using satellite data and observations of disturbances between 2002 and 2014, the researchers projected future temperatures and precipitation to see how much more frequent these events could become. The boreal forests, again, face high risk under these conditions – as well as the tropics.  

“Forests store an immense amount of carbon and slow the pace of climate change,” said Anderegg. “They harbor the vast majority of Earth’s biodiversity. And they can be quite vulnerable to disturbances like severe fire or drought. Thus, it’s important to consider each of these aspects and dimensions when thinking about the future of Earth’s forests in a rapidly changing climate.”

Based on these results, Western North America seems to have a consistently high risk to forests. Preserving these forests will require action. 

“First we have to realize that the quicker we tackle climate change, the lower the risks in the West will be,” said Anderegg. “Second, we can start to plan for increasing risk and manage forests to reduce risk, like fires.”

The recently-launched Wilkes Center for Climate Science and Policy at the University of Utah aims to provide cutting-edge science and tools for decision-makers in the US and across the globe. For this study, the authors built a visualization tool of the results for stakeholders and decision-makers.  

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By Katherine Bucko, Earth.com Staff Writer