In the past 20 years, extensive forest death triggered by hot and dry climatic conditions has been documented on every continent except Antarctica, finds new review.

Already facing an onslaught of threats from logging and conversion for agriculture, forests worldwide are increasingly impacted by the effects of climate change, including drought, heightened fire risk, and disease, putting the ecological services they afford in jeopardy, warns a new paper published in the journal Nature Climate Change.

The study, authored by William Anderegg of Carnegie Institution for Science at Stanford University and Jeffrey Kane and Leander Anderegg of Northern Arizona University, reviews dozens of scientific papers dealing with the ecological impacts of climate change. They find widespread cases of forest die-off from drought and elevated temperatures, which can increase the incidence of fire and pest infestations like pine beetles. These effects have the potential to trigger transitions to other ecosystems, including scrubland and savanna. But the impacts vary from forest to forest and the authors say more research is needed to fully understand the effects of climate change on forest ecosystems.

However it is not only forests that are affected by climate change — they themselves impact climate. Forests store 45 percent of the carbon found in terrestrial ecosystems and sequester as much as 25 percent of annual carbon emissions from human activities, helping mitigate a key driver of climate change. Yet they also raise local temperate by absorbing sunlight. Clearing forests in polar regions has the paradoxical effect of increasing the reflectivity of Earth’s surface, reducing local temperatures. Yet clear-cutting of forests in the tropics accounts for 8-15 percent of anthropogenic greenhouse gas emissions.



Rainforest in Borneo. Forests in Southeast Asia, the Russian Far East, and the Amazon has been particularly affected by drought over the past 20 years. Roughly a million hectares of Amazon rainforest suffered from severe drought stress in 2010.

The authors say that the research gaps make it difficult to forecast the economic and ecological impacts of climate change on forests, which cover cover some 42 million square kilometers or 30 percent of Earth’s land surface and underpin hundreds of billions to trillions of dollars a year in economic activity.

“The varied nature of the consequences of forest mortality means that we need a multidisciplinary approach going forward, including ecologists, biogeochemists, hydrologists, economists, social scientists, and climate scientists,” said William Anderegg in a statement. “A better understanding of forest die-off in response to climate change can inform forest management, business decisions, and policy.”

Redwood forest in Marin, CA. The incidence and severity of forest fires in the Western United States has increased since 2000.

CITATION: William Anderegg, Jeffrey Kane and Leander Anderegg (2012). Consequences of widespread tree mortality triggered by drought and temperature stress. NATURE CLIMATE CHANGE 9 SEPTEMBER 2012 DOI: 10.1038/NCLIMATE1635

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