Some of the most magnificent trees native to the United States, including the mighty redwood of California and the renowned black ash of the Northeast, are at risk of going extinct. So are some tree species that are generally unknown.
A study published by Plants People Planet estimates that between 11 percent and 16 percent of all U.S. trees are now threatened with extinction. The most common threat comes from "invasive and problematic pests and diseases." With 881 species from 269 genera (the scientific term for a group of related living things with one or more species) the first country-wide analysis of tree extinction risk estimates we're in danger of losing more tree species than ever before.
The study's authors updated the checklist of all tree species native to the contiguous U.S. and crafted over 700 new or updated assessments. "Most species native to the continental United States had either never been assessed or were outdated on the two most widely used threat assessment platforms in the United States," the study reports.
The updated information offers a more robust view of trees across the U.S., even if only eight of the tree species listed as threatened made a federally recognized list as endangered or threatened. Then there's another 17 species on the study's at-risk list that live only in the wild, leaving them prone to full extinction if they do get wiped out.
"It's easy to feel that gloom and doom because . the scope of the crisis is really, really great right now," Murphy Westwood, vice president for science and conservation at the Morton Arboretum in Illinois and a lead author of the study, tells the Washington Post. "We're losing species before they even get described."
The Botanic Gardens Conservation International coalition is working to expose "plant blindness," and to both study and celebrate the world's 58,000-plus tree species. Westwood was part of the U.S. contingent that investigated the threats to U.S. trees.
While the International Union for the Conservation of Nature Red List and NatureServe both categorize tree species, the study says lack of a coordinated mechanism for sharing data between the platforms resulted in missing and duplicated information. Plus, most of what was measured was simply outdated information, because it did not consider the latest dangers from "invasive pests and diseases, climate change, biological resource use (most commonly logging), and natural system modification (increase in fire frequency and increase in fire suppression)," the study says.
Invasive pests and diseases have upped the preservation challenges within the United States. Climate change "will likely exacerbate the threats," the authors write in the study. For example, the emerald ash borer, which first showed up in the U.S. in the 1990s, has taken out nearly half of the native Fraxinus species since, devastating everything from ash to hawthorns to apple trees. The laurel wilt, a fungal pathogen transmitted by the Redbay Ambrosia Beetle, has wreaked havoc on the laurel species within the U.S., adding three varieties to the newly assessed list as threatened. Bur oaks across the Midwest are dying from blight, manifesting as lesions and withering on leaves of trees and plants as a fungus attacks them. Researchers believe that rising temperatures are encouraging the fungal growth to unprecedented levels.
Climate change may be to blame for the deaths of some species that withstood fungus and disease as a normal part of their ecosystems for an untold number of years-before finally succumbing to disease in droves. The imbalance in the ecosystem could be due to more prominent storms, flooding or temperature changes.
The most impacted tree species include 29 hawthorns at risk and 17 oak species. Those are high percentages for two of the most plentiful trees in the U.S-84 hawthorns and 85 oak species exist in the country. Florida, Texas, and the southeastern states hold the highest concentration of tree species and endemic tree species. "Those regions," the study says, "as well as California, also hold the highest concentration of threatened tree species in the contiguous United States-the threatened hotspots-and as such are clear priorities for conservation."
The study suggests that hope for trees lies in botanical gardens and arboreta. Such settings can help conserve species and ensure they aren't fully lost if they do disappear from the wild. For example, oak seeds, which are commonly called acorns, cannot be saved by conventional seed banking methods-storing seeds for future growth-the study notes. "Growing living trees in botanical collections is a critically important conservation tool," proponents of the gardens write in the study, "in the absence of seed banking as an insurance policy against extinction."
In the meantime, you may wish to take a walk in the woods soon.