Science Says: Climate Change Stress Is Crippling Our Forests

In our ever-warming world, otherwise healthy trees will increasingly perish, further exacerbating climate change.

The future is not looking up for the world's trees. (Photo: Ella's Dad/Flickr)
The director of the Public Trust Project, Alison has written for Grist and Politics Daily, among others.

Half of the planet’s animals, birds, and insects make their homes in forests, which cover 30 percent of our blue-green planet. Forests provide jobs and livelihoods for 400 million of the world’s people. Across the globe, forests and their soils absorb a quarter of all manmade carbon emissions.

But climate change is altering all of that. Forests are increasingly susceptible to drought and heat-stress, and scientists have been recording massive tree die-offs due to the warming of the planet—a phenomenon that will only become more frequent. 

A paper published this week in Nature Climate Change provides an overview of the kinds of disturbances that climate change inflicts on forests, from radical shifts in ecosystems dynamics, to changes in the density and composition of trees, to a reduction in forest biodiversity. 

MORE: Are 'Champion Trees' a Climate Change Silver Bullet?

That might sound remote and specialized, but these impacts have serious consequences for public health, environmental safety, and the economy.

For example, the paper’s authors, Carnegie Institution for Science’s William Anderegg and Leander Anderegg, along with Jeffrey Kane, wrote that the drought-induced death of huge numbers of trembling aspen had increased the prevalence of the Sin Nombre virus in Western deer mice in the United States. Sin Nombre is a deadly virus from the same family as the hantavirus that has resurged in Yosemite, killing three visitors to the park, and infecting five more.

The widespread die-off of lodge-pole pine in the Rocky Mountains is expected to wreak havoc on public health: dying pines will increase the likelihood of forest fires that challenge respiratory health and safety.

And a study in Western Colorado, the epicenter of tree death due to ravenous pine beetles, found that for every tree killed within a hundred meters, adjacent properties declined by $648 dollars per tree. For verdant Colorado, this amounts to a real estate death sentence.   

Even worse, dying trees actually contribute to climate change, lead author William Anderegg says.

Healthy trees soak up an incredible amount of carbon dioxide from their air. “They take it up and essentially turn it into sugars in their tissues, and that’s how they grow through photosynthesis,” he said, in an interview with TakePart. “Trees can lock away carbon for long amounts of time, which not only slows climate change, but creates rich soils and rich ecosystems.”

But when trees die due to thirst or heat, not only do they stop soaking up carbon, they emit it back into the atmosphere, which in turn, accelerates climate change. “It’s a double whammy,” Anderegg says. 

Tree die-offs due to high temperatures and frequent droughts have occurred on every continent except Antarctica. 

The prevalence of thirsty, stressed trees is an emerging global trend, but the researchers make the point that the field of scientific literature on the subject is still in its infancy.

There is little analysis of the grave consequences that massive, climate-induced tree death will wreak on society, the economy, and on the Earth’s natural systems. The science will have to catch up, and quick, according to the study’s authors. 

But the average woods-enthusiast can help by documenting and bearing witness to the affects of drought and climate change on their local wilderness.

“One of the amazing and powerful messages of forest mortality is that it’s a piece of climate change that’s probably happening already in our own backyards and in our own mountains and forests,” Anderegg says. “It’s a tangible and visible early warning sign of climate change.”

Have you ever planted a tree? If not, why not? Discuss in the comments.

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