Arboretum finds 16 U.S. oak species of conservation concern
One-fourth of the United States' oak species are now considered of conservation concern, according to data compiled by researchers at the Morton Arboretum in Lisle.
The data was part of the latest update of the International Union for Conservation of Nature Red List of Threatened Species. Sixteen species of oaks, all in the southern and western U.S., now are classified as Critically Endangered, Endangered, or Vulnerable on the Red List, with another four species deemed Near Threatened.
The Red List of U.S. Oaks publication details, for the first time, the distributions, population trends and threats facing all 91 native oak species in the U.S., including updated versions of previously published assessments.
The publication serves as a baseline for current understanding of the state of the country's oak trees and an authoritative guide for future conservation action.
Known as keystone species, oaks in North America have more biomass and number of species than any other tree group; they are the backbone of many different forest communities; and provide immeasurable ecosystem services.
Yet, oak-dominated ecosystems have been in decline for the past century. The threats facing U.S. oak species include pests and diseases, habitat destruction, development and agriculture.
Notably, longevity and slow reproductive rates of oaks make them particularly susceptible to the effects of a rapidly changing climate. Until this report, it was not known exactly how many oak species in the U.S. were in danger of extinction using Red List methodology.
"In addition to being an iconic and beloved tree species in many parts of the world, oaks support many important ecosystems, such as oak savannas in the American Midwest and cloud forests in Mexico and Central America. Countless animals and other plants depend on oak-dominated habitats for survival. So, as oaks disappear, there will be a tangible, negative impact on wildlife, potentially upsetting the balance of forest habitats," said project lead Murphy Westwood, director of global tree conservation at the Morton Arboretum.
"With the IUCN Red List assessments and associated report, we now have a baseline from which to determine how to best conserve oaks and reverse the trend toward extinction for these important trees."
Adding to oaks' struggle, acorns cannot be stored in seed banks through conventional preservation methods like most tree species, so growing them in living collections in arboreta and botanical gardens is imperative for long-term survival of the species.
In partnership with the American Public Gardens Association and the U.S. Forest Service, the Morton Arboretum has a key role in a coordinated network of organizations growing and conserving threatened oaks, such as the endangered shinnery oak (Quercus havardii), propagating thousands of acorns and cuttings, and distributing plants across the network.
As the climate changes - models suggest the climate of Illinois eventually will be similar to that of today's Arkansas or even Texas - the arboretum and other public gardens may become critical refuges for even more oaks.
In 2015, the Morton Arboretum established a partnership with the IUCN Global Tree Specialist Group and Botanic Gardens Conservation International to assess all 450 of the world's oak species by 2020, contributing to the Global Tree Assessment - a global initiative to evaluate the threat level of the 60,065 species of trees in the world.
The Red List of U.S. Oaks report was funded, in part, by the U.S. Forest Service. For information about the report, visit iucnredlist.org/search.