Source: Charlie Brennan, “Boulder plots to battle emerald ash borer, preserve canopy,” Boulder News
Boulder, CO (January 1, 2018) – Boulder is developing a strategy for managing its urban forest as it faces 2018, and managing the ongoing infestation of emerald ash borer will continue to be a key component of its plan.
Within Boulder city limits, trees cover about 16 percent of the land. Of the areas that are under the urban canopy, only about 25 percent is on public turf — which includes property owned by the city, Boulder Valley School District, the University of Colorado and federal labs. The other 75 percent of the trees grow on private property.
So solutions to maintaining a healthy tree population in Boulder must involve government entities such as the urban forestry division of the city’s Parks and Recreation Department. But cooperation and buy-in from private property owners is important as well.
“It’s not easy being a tree here in Colorado,” said Kathleen Alexander, city forester for Boulder. However, she added, “I think people here are very educated when it comes to trees. We are very lucky, here along the Front Range. We have very educated people who are super-passionate, who love their trees. That’s the best of all worlds.”
That’s the good news. But the bad news is sobering, and emerald ash borer is right at the top of the list of bad news items. The emerald ash borer, an invasive wood-boring beetle that lays its eggs in the bark of ash trees where its larvae then feed, was first detected in a city ash tree near 30th and Iris streets Sept. 23, 2013 — just two weeks after another famous local disaster, the weeklong flood from which recovery across the county is still not entirely complete.
It is believed that by the time emerald ash borer was first discovered in the city, it had actually been present for several years. Since 2014, 1,353 affected ash trees have been removed from public land in Boulder through the end of October.
The city recently announced that 357 more trees are slated to be taken down across Boulder in the next four months, and that 280 of those targeted trees are ash impacted by EAB.
It is believed that about 12 percent of the trees on public space in Boulder are ash, with a similar percentage represented on private land — and that all ash trees in the area will eventually be killed by emerald ash borer unless treated with a pesticide such as emamectin benzoate.
“The Front Range is going to look very different 20 to 25 years from now,” Alexander said. “There is no real winning” the battle against emerald ash borer. “You can try to be optimistic and say if we replace a lot of these ash and replace them with a diversity of tree species, we will have a healthier and more resilient urban forest in the long term. But that involves a lot of collaboration, both public and private.”
Over the course of time that the 1,353 ash were removed, another 1,953 replacement trees have been planted, an average of about 480 per year, with a diversity of three dozen species. The next wave of tree removals — which also includes trees of other species damaged by storm, poor health or other structural issues — is to be accompanied by new plantings, either through the forestry division or via park development projects.
Ash is hardly the only species to take a hit in recent years. An extreme temperature fluctuation in November 2014, for example, cost the city some 350 Siberian elms. Climate change, and even the creeping urbanization of a once-rural region, are also factors affecting the health of various tree species.
“We were doing a pretty good job of maintaining a one-to-one ratio — until we found emerald ash borer,” Alexander said, referring to removals and new plantings.
“We do expect to see (the replacement-removal ratio) continue downward … It is going to be hard to keep up with tree planting until we see the end of how emerald ash plays out here in Boulder.”
‘Time to act is now’
The ash that is removed finds multiple pathways to repurposing, ranging from being milled for sale through Resource Central, to conversion to chips sent to the Boulder County Jail for burning in its biomass heating system, to supplying Boulder’s TreeOpp program.
There, EAB-infested wood debris is converted into crafts, furniture and other functional products for sale to the public. Sales at the Boulder Public Library of items fashioned from doomed ash have become a recent staple of the holiday shopping season for some.
With three-quarters of the urban canopy situated on private land, Alexander emphasized that there must be public participation in battling emerald ash borer. Treating unaffected trees, and acting quickly on diseased trees, she said, is critical.
“We do want residents to really determine if they do have an ash on the property, and then to make a plan that if they are not planning to treat that tree, they don’t want to wait til that tree dies, to think of that removal,” she said. “Once they die, they dry very quickly. They start to fail and they become a risk and the removal costs go up significantly.”
The city is giving added encouragement by greatly stepping up its notices to private property owners of problem trees — not all of them ash trees -— that threaten public property. From 13 such notices in 2014 to nine in 2015, the number jumped to 82 in 2015 and surged to 118 through the end of October this year.
Alexander hopes that through stepping up public outreach through a variety of strategies, the city gets the public’s help in ensuring the future health of Boulder’s urban canopy, the public portion of which is calculated as having a $5.2 million annual economic benefit.
“We’re further along in that EAB progression now than we were four years ago when we found this pest,” she said. “Now, we are seeing symptomatic dying trees all over Boulder. The time to act is really now.”
Boulder Mayor Suzanne Jones peppered those who recently briefed the council with many questions on the subject, and has faith the city’s populace will embrace its importance.
“My biggest takeaway was that we’re going to lose up to 25 percent of our tree canopy, and that’s going to be shocking to a lot of people, and a reason for us to really invest in restoring that and investing in resiliency in the face of a changing climate and other related threats, like non-native insects,” she said.
“What I want to see in our plan is, I really want to make sure we are taking into account the climate of the future, and replanting with a diversity of species that will be adaptive to warmer and more arid conditions, with an emphasis on native species.”
The mayor is encouraging public participation as the city envisions the urban forest of tomorrow.
“People are busy and paying attention to other things, but I think people care deeply about trees, and would love to know what they could do to help be a part of the solution.”