An international team of researchers has sought to identify those forests most at risk of fire through a global analysis of three key data.

A new study has sought to quantify the risk to forests from climate change along three dimensions: carbon storage, biodiversity, and forest loss from disturbance, such as fire or drought. The results show forests in some regions experiencing clear and consistent risks. In other regions, the risk profile is less clear, because different approaches that account for disparate aspects of climate risk yield diverging answers.

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

Anderegg assembled a team including researchers from the United Kingdom, Germany, Portugal and Sweden, and the task was formidable; to assess climate risks to the world’s forests, which span continents and climes and host tremendous biodiversity while storing an immense amount of carbon.

The researchers had previously attempted to quantify risks to forests using vegetation models, relationships between climate and forest attributes and climate effects on forest loss. Each of the previous approaches investigated one dimension of climate risk: carbon storage, biodiversity, and risk of forest loss. For their new analysis, the new team went after all three.

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

Forests absorb about a quarter of the carbon dioxide that’s emitted into the atmosphere, so they play a critically important role in buffering the planet from the effects of rising atmospheric carbon dioxide. The team leveraged output from dozens of different climate models and vegetation models simulating how different plant and tree types respond to different climates. They then compared the recent past climate (1995-2014) with the end of the 21st Century (2081-2100) in scenarios of both high and low carbon emissions.

Anderegg added: “Forests store an immense amount of carbon and slow the pace of climate change. They harbour 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.”

Anderegg also outlined his surprise that the spatial patterns of high risk didn’t overlap more across the different dimensions: “They capture different aspects of forests’ responses, so they wouldn’t likely be identical, but I did expect some similar patterns and correlations.”

Models can only be as good as the basis of scientific understanding and data on which they’re built and this study, the researchers write, exposes significant understanding and data gaps that may contribute to the inconsistent results. Global models of biodiversity, for example, don’t incorporate dynamics of growth and mortality, or include the effects of rising CO2 directly on species. And models of forest disturbance don’t include regrowth or species turnover.

“If forests are tapped to play an important role in climate mitigation,” the authors write, “an enormous scientific effort is needed to better shed light on when and where forests will be resilient to climate change in the 21st Century.”

The study is published in Science.

Image: Wildfire at Lick Creek, Umatilla National Forest, Oregon, United States. © Brendan O’Reilly/ US Forest Service