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This is where I leaf you

Tens of millions of trees across the U.S. are dying.

Climate change is a big underlying cause. And the tree loss will make climate change worse.

From Hawaii’s ohi’a to Seattle’s cottonwoods to the oldest white oak in North America, the country’s trees are in peril. In California’s Sierra Nevada Mountains alone, 66 million trees have died in the past six years, the Guardian reports.

But while the specific causes vary — from disease and insects to drought and wildfires — much of this death is driven by climate change.

This isn’t just a problem for tree-hugging hikers and homeowners distressed by brown leaves. Forests play a vital role in stabilizing the Earth’s climate. Trees act as a carbon sink by extracting nearly a quarter of human carbon dioxide emissions from the air. But when trees die, instead of sequestering carbon, they emit it.

How big could this unfolding disaster be? Richard Birdsey, a researcher with the U.S. Forest Service, told Rolling Stone last year, “if the carbon sink in forests fails, a simple speculation is that global temperatures would increase proportionally to the increase of CO2 concentration, so about 25 percent above current climate projections.”

That could mean death for a whole lot more than just trees.