1 in 6 native American tree species may become extinct

One in six tree species in the contiguous 48 states is threatened with extinction, according to the first assessment of its kind.


What you need to know

  • One in six species in the contiguous 48 states is threatened with extinction, according to the first assessment of its kind.
  • The most common threats to Native American trees are invasive insects and diseases, climate change and extreme weather, habitat changes, and use of biological resources such as logging, the analysis said.
  • According to the researchers, the Global Tree Assessment aims to assess threats to the world’s approximately 60,000 tree species, but most species in the continental U.S. were either never analyzed or the assessments were out of date.
  • The researchers concluded that 11-16% of tree species are threatened with extinction.

The most common threats to Native American trees are invasive insects and diseases, climate change and extreme weather, habitat changes, and use of biological resources such as logging, the analysis said.

The findings are published in the journal Plants People Planet.

According to the researchers, the Global Tree Assessment aims to assess threats to the world’s approximately 60,000 tree species, but the majority of species native to the continental U.S. either had never been analyzed or the assessments were out of date.

To close the information gap, researchers from Botanic Gardens Conservation International-US, The Morton Arboretum, and Natureserve conducted a five-year study to assess threats to all 881 native tree species in the lower 48 states. Scientists partnered with the US Botanic Garden and the US Department of Agriculture’s Forest Service on the project.

The researchers concluded that 11-16% of tree species are threatened with extinction. They said the discovery could help save the species from extinction.

“Trees form the foundation of many of the world’s terrestrial ecosystems,” said Natureserve President and CEO Sean T. O’Brien said in a statement. “Understand which trees are at risk and why being informed is important to protecting trees and ecosystems across the nation.”

Oaks and hawthorns dominate the American tree flora with 85 and 94 native species, respectively. They are also the most at-risk genera, with 29 oaks and 17 hawthorns identified as threatened, according to the paper.

Florida (45) and California (44) have the most threatened tree species, the researchers found. Trees that have evolved or are found only here in the United States are mainly concentrated in the southeastern part of the country, Texas and California, they noted.

Among the biggest threats to the trees are the emerald ash borer, an invasive insect whose larvae feed on living tissue beneath the tree’s bark to destroy ash populations, and a disease known as “laurel wilt” that attacks three species of evergreen trees. .

Such insects and pathogens are considered the biggest threat to tree species, but climate change, an increasing number of forest fires, could worsen the situation, the study said.

Ironically, the researchers note that “conserving and restoring trees and native forests on a nationwide (and global) scale has great potential to mitigate climate change, particularly through carbon sequestration.”

Ninety-five percent of American tree species are found in botanical gardens, arboretums or seed banks, scientists said. However, 17 species are not protected outside their natural habitat, putting them at risk of complete extinction someday.

The federal government currently recognizes only eight U.S. tree species as endangered or threatened, which carry varying levels of protection and regulation.

“This assessment advances our understanding of the threats facing America’s native trees and will help focus the conservation efforts of public gardens, federal agencies and conservation organizations,” said Susan Pell, acting executive director of the US Botanic Gardens.

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