Ash trees -- which once lined streets and parks across the suburbs -- are on the brink of extinction after years of decimation by the Emerald Ash Borer beetle, according to a report released today by the IUCN Red List of Threatened Species.
The IUCN, a global tracker of animal and plant species, says five of the six most prominent ash tree species in North America are now considered "critically endangered," which is one step away from becoming extinct. The sixth species is considered endangered.
"We predict at least 80 percent of the population of the species will disappear," said Murphy Westwood, a member of the IUCN Global Tree Specialist Group and also the director of Global Tree Conservation at the Morton Arboretum in Lisle. "It's really not looking good for the long term."
The IUCN Red List only takes into account ash trees in wild and natural habitats, like forests, and not those along suburban parkways, Westwood said. Still, the Emerald Ash Borer remains an ongoing threat to the suburbs, she said, since it can kill thousands of trees quickly and poses a serious threat to biodiversity and forests.
The ash tree went from plentiful to critically endangered in less than 20 years, Westwood noted.
The Emerald Ash Borer was first detected in Illinois in Kane County in 2006. The problem spread so quickly that, by 2015, the Emerald Ash Borer had killed nearly 200 million ash trees statewide.
Suburbs were forced to quickly cut down thousands of infected or dead ash trees in public parkways because they posed a safety hazard. Some towns spent hundreds of thousands of dollars replacing dead ash trees and treating others with insecticides, especially one called Tree-äge.
The village of Arlington Heights lost 10,000 of its 13,000 parkway ash trees to the Emerald Ash Borer, said Village Forester Dru Sabatello. But the village saved thousands of other trees thanks to a unique program where the village reimbursed homeowners 50 percent of the cost to treat a salvageable ash tree, up to $50 per tree.
The city of Naperville saved 13,000 of its 17,000 ash trees by treating them yearly with different insecticides. That came at a cost though -- Forestry Supervisor Jack Mitz estimates the city spent "hundreds of thousands of dollars" fighting the Emerald Ash Borer over the past eight years.
"The benefit of a mature tree is substantial. Every one you save, you're saving the community money," Mitz said. "There are all sorts of positive benefits, not to mention real estate values."
Both Arlington Heights and Naperville will be slowing down their Emerald Ash Borer-fighting efforts starting next year, their arborists say, believing they're almost done fighting the invasive beetle. They've since diversified their "urban forests" with a variety of tree species.
Westwood applauds the job these suburbs have done to save their trees, but sees a bigger-picture problem because the Emerald Ash Borer still exists.
It's not financially feasible to save millions of ash trees in a forest, she said. Ash tree seeds have been struggling to germinate, and a warmer climate makes it easier for the Emerald Ash Borer to thrive.
Ash trees provide a habitat for birds, squirrels, insects and pollinator species like butterflies and moths, she said.
"Will the species ever go completely extinct? No," Westwood said. "But will we lose the vast majority of these species? Yes."