More than 450 non-native insects and diseases have found their way into U.S. forests, and the millions of trees killed by these pests each year contain more than 5.53 teragrams of carbon (TgC) — equal to the emissions of 4.4 million cars, or the carbon released by one-fifth of all wildfires in the U.S. annually, according to a new study.
The study, led by researchers at the U.S. Department of Agriculture and Purdue University, looked at tree mortality from non-native pests at 92,978 field plots in the contiguous U.S. It focused on 83 pests known to have caused significant damage to U.S. forests, including the emerald ash borer, dutch elm disease, gypsy moth, and beech bark disease.
The study found that these non-native pests kill as many trees as native bark beetles, which have ravaged western forests in recent decades. The study was published this week in the Proceedings of the National Academy of Sciences.
Forests account for an estimated 76 percent of North America’s carbon sequestration. But when trees die and decay, the carbon they contain is released back into the atmosphere. The scientists warn that invasive pests could significantly decrease the amount of carbon U.S. forests are able to store, driving additional climate change.
The study also notes that most of these pests have not spread throughout their full potential range, leaving 41 percent of U.S. forests at risk of future damage.
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