Global analysis identifies forests at risk — ScienceDaily

Forests engage in a delicate, deadly dance with climate change, sucking carbon dioxide from the air with billions of leaf blades and harboring abundant biodiversity, as long as climate change, with its droughts, wildfires and ecosystem changes, doesn’t kill them first.

In a study published in Science William Andereg, the inaugural director of the Wilkes Center for Climate Science and Policy at the University of Utah, and his colleagues quantify the risk to forests of climate change along three dimensions: carbon storage, biodiversity, and forest loss from disturbances such as fire or drought . The results show that forests in some regions are exposed to clear and persistent risks. In other regions, the risk profile is less clear, as different approaches that account for different aspects of climate risk provide different answers.

“The high uncertainty in most regions highlights that there is much more research that is urgently needed,” Andereg says.

An international team

Anderegg assembled a team including researchers from the UK, Germany, Portugal and Sweden.

“I had met some of these people before,” he says, “and had read many of their articles. In undertaking a large synthetic analysis like this, I contacted them to ask if they would be willing to participate in a global analysis and provide their expertise and data.”

Their task was enormous – to assess the climate risks to the world’s forests, which span continents and climates and contain enormous biodiversity while storing vast amounts of carbon. Researchers have previously attempted to quantify risks to forests using vegetation patterns, relationships between climate and forest characteristics, and the impact of climate on forest loss.

“These approaches have different inherent strengths and weaknesses,” the team wrote, “but a synthesis of approaches on a global scale is lacking.” Each of the previous approaches examines one dimension of climate risk: carbon storage, biodiversity, and the risk of forest loss. For their new analysis, the team pursued all three.

Three dimensions of risk

“All of these dimensions of risk are important and in many cases complementary. They capture different aspects of forest resilience or vulnerability,” Andereg says.

Carbon storage: Forests absorb about a quarter of the carbon dioxide that is released into the atmosphere, so they play an extremely important role in buffering the planet from the effects of rising atmospheric carbon dioxide. The team used results from dozens of different climate and vegetation models, simulating how different types of plants and trees respond to different climates. They then compared the climate of the recent past (1995-2014) with the late 21st centurySt century (2081-2100) in both high and low carbon scenarios.

On average, the models showed global gains in carbon storage by the end of the century, albeit with large disagreements and uncertainties across climate-vegetation models. But zooming in on regional forests and taking into account models that predict carbon loss and vegetation changes, the researchers found a higher risk of carbon loss in southern boreal (south of the Arctic) forests and the drier regions of the Amazon and African tropics.

biodiversity: Not surprisingly, the researchers found that the highest risk of ecosystems shifting from one “life zone” to another due to climate change can be found at current biome boundaries—for example, the ongoing transition between temperate and boreal forests. The models the researchers used describe changes in ecosystems as a whole, not in individual species, but the results show that forests in boreal regions and western North America face the greatest risk of biodiversity loss.

Disturbance: Finally, the authors consider the risk of “stand-replacing disturbances,” or events such as drought, fire, or insect damage that can destroy patches of forest. Using satellite data and observations of stand-replacing disturbances between 2002 and 2014, the researchers then made projections into the future using projected future temperatures and precipitation to see how much more frequent these events might become. Boreal forests again face high risk under these conditions, as do the tropics.

“Forests store a huge amount of carbon and slow down the pace of climate change,” Andereg says. “They contain the vast majority of Earth’s biodiversity. And they can be quite vulnerable to disturbances such as severe fire or drought. It is therefore important to consider each of these aspects and dimensions when thinking about the future of Earth’s forests in a rapidly changing climate. “

Future needs

Anderegg was surprised that the spatial patterns of high risk did not overlap more across dimensions. “They capture different aspects of forest responses,” he says, “so they are unlikely to be identical, but I would expect some similar patterns and correlations.”

Models can only be as good as the foundation of scientific understanding and data on which they are built, and this study, the researchers wrote, reveals significant gaps in understanding and data that may contribute to the inconsistent results. Global biodiversity models, for example, do not include growth and mortality dynamics or the effects of rising CO2 directly on species. And patterns of forest disturbance do not include regrowth or species change.

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

The key next steps, Anderegg says, are to improve forest disturbance models, study forest resilience after disturbance, and improve large-scale ecosystem models.

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

Despite uncertainty in the results, western North America appears to have consistently high forest risk. Preserving these forests, he says, requires action.

“First we need to realize that the faster we tackle climate change, the lower the risks will be in the West,” Andereg says. “Secondly, we can start to plan for increased risk and manage forests to reduce risk, such as fires.”

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