The Bloomington Parks and Recreation Department received a $50,000 State Urban Forest Resilience grant from the Indiana Department of Natural Resources to evaluate and protect ash trees threatened by emerald ash borer beetles.
The emerald ash borer, an invasive beetle native to Asia, was first detected in Bloomington in 2012. The beetle burrows beneath the bark of ash trees during its larval stage and disrupts water and nutrient transportation in the tree. Most infested trees die within two-to-five years unless they are treated.
According to a city press release, the grant will allow the city’s urban forestry team to assess the health of more than 500 remaining ash trees in city parks and along city streets. Funding will support continuing treatment of healthy ash trees to protect them from infestation and removing dying ash trees to reduce safety risks associated with falling trees.
According to Sarah Mincey, managing director for the Environmental Resilience Institute at Indiana University, ash trees accounted for roughly 8 to 9 percent of the city’s street tree inventory more than a decade ago.
“The majority, I believe, were not saved and did succumb to EAB,” Mincey said. “However, I think that the strategy that the city used was to save a number of our ash trees, particularly those that were higher quality specimens and larger, older trees with bigger canopies.”
Large canopy trees provide shade, cool urban areas through evapotranspiration and help reduce stormwater runoff, she said.
“Trees really help us avoid flash flooding because they slow all of those raindrops from hitting the pavement and running off rapidly,” Mincey said.
Beyond environmental benefits, Mincey said trees also improve public health and community connection.
“Trees are incredibly helpful for our physical and mental health,” Mincey said. “When we have physical comfort from the shade, we’re more likely to go outside and be physically active.
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The emerald ash borer was officially discovered in the United States in 2002 near Detroit and is believed to have arrived in wooden shipping crates from China. Mincey said the beetle has been particularly destructive because it has no natural predators in the region.
“Nothing has evolved in this ecosystem to interact with the emerald ash borer regularly,” Mincey said. “It's a novel organism, and therefore it's able to proliferate and reproduce relatively unchecked.”
The insects can spread by flying, but Mincey said human activity has also helped move them across the country.
“There was a significant time period where we didn't have the science and understanding about emerald ash borer being in locations where people were moving firewood,” Mincey said. “For a good chunk of time, people, whether they were moving firewood to go camping with their family or maybe moving firewood to sell, they were actually transporting larva from one county where there was an invasion into several counties over where there was no invasion.”
The parks department maintains an inventory with data on every tree within city limits. According to the inventory, 698 ash trees remain in Bloomington.
In addition to evaluating ash trees, the city plans to develop a 10-year strategy to plant two native trees for each dying ash tree the department removes.
Bloomington will match the grant with an additional $67,000 in local funding. The grant period runs through June 1, 2027.
