Minneapolis & St. Paul's misbegotten slaughter of the ash trees

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Kari Hoglund

Jade Patrick heard the chainsaws. She and her husband, James, had noticed a tree marked with a green “X” on a boulevard outside their East Phillips home, but didn’t think much of it.

“Oh my God,” Jade recalls thinking as she watched the ash tree die piece by piece. “There goes all of our shade in our back yard.... We were really sad.”

The tree was another victim of a killing spree taking place across the greater Twin Cities. It had yet to be infected with the emerald ash borer, the beetle ravaging ash trees across the country. But workers told them it was within a mile of one that was. That was close enough for the city of Minneapolis.

Terri Harder also found a green X this spring on the boulevard outside her home in Audubon Park. She likened it to a scarlet letter.

“Basically, I got a note saying they were removing it before it’s a problem, which is why I call it the death panel for trees. It’s always really sad to see a tree come down when it’s healthy.”

Over in the Macalester-Groveland neighborhood of St. Paul, Mary Lilly watched her entire block transform. Its ash trees were slaughtered in one fell swoop this spring. A letter from the city forester said the removal was part of a reconstruction project planned for her street next year.

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A row of trees destined for death along Summit Avenue in St. Paul City Pages

Some neighbors were on spring break vacations when the letters arrived. They came home to find a neighborhood deforested. 

“One of the explanations about why they came down was that they could not wait any longer, because they pose such a serious threat to safety, because the limbs could fly off,” Lilly says. “Well, I think every tree in the city could blow over, so maybe we should take them all down. That’s not a good reason, particularly if you’re not willing to test them and see that they’re all healthy.”

Minneapolis is about halfway through an eight-year plan to remove all 40,000 of its ash trees. St. Paul has already cut 9,000, with plans to kill 18,000 more. Yet some suburbs are taking a more proactive approach, heeding science that says Minnesota’s Great Tree Massacre needn’t be a massacre at all.

The agent instigating all this is a mere beetle. Known as the emerald ash borer, its larva feeds on ash bark, eventually killing the tree.

It’s a particularly rapacious murderer. The borer has killed hundreds of millions of North American trees since the early 2000s, prompting quarantines around the United States and Canada, where logs and wood chips can’t be shipped abroad. The attack has cost cities, homeowners, and the forest industry millions.

The beetle was first discovered in the U.S. in 2002, when it hit southeastern Michigan near Detroit, devastating the ash tree population before spreading to other parts of the country.

According to Michael Orange, a former Minneapolis city planner, an adult female beetle will lay about 20 to 30 eggs in a tree. The babies then lay more eggs and move to neighboring trees. “It cuts off the circulation for the tree, which dies out,” says Orange.

It may take three or four years, but the tree will eventually be killed from the top down. Branches become brittle and dangerous, a threat to fall.

Michigan chose an age-old military tactic to combat the menace: It would starve the beetle of its food supply. That meant wiping out its ash tree population, both healthy and sick. Other cities and states followed suit, sawing preemptively.

Ralph Sievert, director of forestry for Minneapolis’ park board, sees it as taking one’s medicine in one swift dollop, if only to hasten renewal with the planting of a mixed variety of new trees, allowing the city to better resist the next assault on its urban forest. 

“Why not just bite the bullet, get the trees down and replaced in a time frame that is manageable for us, which is eight years?” he asks.

Orange believes that view is shortsighted, a sign that cities are underestimating the value of trees. Like much of nature, their benefits are not readily apparent.

Ash trees help with stormwater management by stopping the rain before it hits the ground, allowing a portion of the water to evaporate into the air. Their roots soak up water, while their canopies absorb pollutants.

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Since it appeared in Michigan in the early 2000s, the emerald ash borer has proved a rapacious killer [Photo: Richard Sennott/Star Tribune]

Large shade trees boost property values and provide savings on electricity and natural gas. There’s even an argument to be made that they reduce crime by attracting more people to public spaces, and increase people’s shopping habits by creating a more pleasant experience as people walk from shop to shop.

According to the Tree Benefit Calculator developed by the U.S. Forest Service, most ash trees—which are around 21 inches in diameter because they were planted in the 1970s and ’80s—are worth $165 dollars in annual benefits. It may not sound like much in the grand scheme of municipal economics, but multiply that figure by 40,000, and it becomes a handsome treasure.

There’s also the matter of simple aesthetics. Drive around St. Paul, and it’s not hard to find once leafy neighborhoods that have been chain-sawed into something resembling a dusty subdivision in Oklahoma.

“To preemptively cut them down is really a waste of a prior investment and waste of resources,” Orange says.

“The benefits are well-documented and quantifiable,” says Jeffrey Hafner, Orange’s son-in-law and an arborist for Rainbow Treecare. “A tree that’s been growing in the community for 20 or 30 years is really at that peak return on investment.”

Terri Harder, a real estate agent with Keller Williams, knows well the impact on property values that comes with denuding. “People look for mature trees in a neighborhood. That’s the bummer of it, I think.”

There is a way to save the trees—at least the healthier ones. It involves injecting their trucks with emamectin benzoate, which then gets transported into a tree’s branches and leaves, where it kills beetles who ingest it. It protects healthy trees from getting infected, and slows an infected tree’s demise.

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Researchers found that killing and replacing ash trees costs four times more than treating them [Photo: John Ehlke/AP]

It’s also far cheaper than revving up the chainsaws. So say Michigan State University researchers Deborah McCullough and Rodrigo Mercader. Their study found that killing and replacing ash trees costs four times more than treating them. “Twenty percent of the ash trees could be treated for many years before treatment costs would approach removal and replacement costs,” they wrote.

Injection costs can vary. According to Hafner, Rainbow Treecare charges about $100 per treatment every two years—and less when a city operates in bulk.

Meanwhile, Minneapolis is paying between $940 and $1,835 to cut and replace each tree when costs like stump grinding and pruning are included, says Sievert. St. Paul’s price averages about $1,250, according to city forester Rachel Coyle.

But in an era where science has been kicked to the back seat, cost is only one factor.

Among liberals—including those who populate city halls—the anti-pesticide movement has taken on a religious fervor, so much so that the value of trees has become something of an afterthought.

Both Orange and Hafner assert that the insecticide carries low risk. Because it’s injected into the trunk, there’s little possibility of it seeping into soil. And because ash trees are pollinated by wind, not bees, there’s little risk to critical pollinators.

Pest control is rarely black and white, right or wrong, adds Jeff Hahn, an entomologist from the University of Minnesota, who sees a tree’s benefits outweighing the risks of insecticides. He supports a more targeted approach of treating the healthy and removing the badly infected.

Since the ash borer first hit Michigan, and even since it was discovered in St. Paul, science has advanced. “There’s a whole wide range of tools that can be used to manage the infestation, and to slow it down,” Orange says. “The real heart of the approach is to kill bugs, not trees. To save the best trees and replace the rest.”

Orange has partnered with Hafner to create management plans for cities. Through the Minnesota Shade Tree Advisory Council, they’ve also spent the last three years trying to convince state legislators to allocate $13 million annually to help cities manage the infestation. “We want cities to do the right thing, which is to use all the tools in the tool box,” Orange says.

But with a dysfunctional legislature barely capable of handling everyday duties, and a Republican majority seeing little value in Mother Nature, their push has not seen daylight. 

Not everyone is convinced that treatment is the answer. When an alarming collapse of bee colonies made national headlines, Minneapolis Councilman Cam Gordon urged the city to enact a bee-friendly resolution, which called for planting more pollinator forage and a phasing out of the city’s use of insecticides.

Gordon is among the many with a visceral suspicion of chemicals, especially when it comes to something as important as bees, insects at the foundation of life.

“It kills them,” he says. “Even if we allow more ash trees to go on living, I question the wisdom of pushing more of these systemic pesticides into the environment, where they may end up in the soil and water accumulating and entering new plants.”

Gordon believes the risks of emamectin benzoate remain unknown. “I am probably more worried about the unknown, potentially health-destroying cumulative effects to people, as well as pollinators over time, as well as the high-dose impacts.”

Gordon also accuses Orange of shilling for his clients. “Anything he provides is probably done so to further potential profits for his clients,” he says. “Use of emamectin benzoate could bring millions to the industry.”

Orange calls that nonsense. He spent 22 years as a Minneapolis city planner working on environmental issues, and now serves as a consultant to the Shade Tree Advisory Council, which isn’t exactly a shill for Big Chem. Most of his tree work is “voluntary,” he says.

Yet Gordon does have scientists in his corner. They include Karen Oberhauser, a conservation biologist at the University of Minnesota, who believes it’s time to bite the bullet. Cities have long made the mistake of planting singular species along their boulevards. Three decades ago, Dutch Elm Disease wiped out urban canopies the same way the ash borer is doing today.

“Hopefully, we’ll learn and plant a more diverse tree community to provide shade and property value,” she says.

Oberhauser contends pesticides are a short-term solution to a long-term problem. She agrees that emamectin benzoate won’t do much harm to bees. But the insecticide is toxic to other insects, such as the tiger swallowtail and giant silk moths. “The females can’t distinguish treated plants, so they are just as likely to lay their eggs on treated plants as untreated plants. This condemns their offspring to death.”

In suburbs like Burnsville, Chanhassen, St. Louis Park, and West St. Paul, the view isn’t so black and white. All have adopted more nuanced policies, classifying each public ash tree or group of trees to save the high quality (meaning larger, healthier ones that provide shade to streets and parks) and remove the low quality. St. Louis Park started its injection program last year. “We had about 1,000 trees that we rated good, so we wanted to keep those trees because of all the value that they provide, from storm water mitigation to cool air in our city, wildlife, and increased property values,” says Jim Vaughan, the city’s natural resource coordinator, who also serves as president of the state Tree Council.

Cost played a major role in St. Louis Park’s thinking. According to Vaughn, injecting two trees for 20 years would still cost less than removing one.

“Up-front costs of removing and replacing are tremendous, versus if you can delay it out and systematically inject trees, then remove some along the way, and plant some along the way,” he says. “The community would be much better off, and you’re not going to notice those big gaps in canopy that you do by just removing and replacing with tiny trees.”

Minnetonka is treating about 170 of its 500 ash trees on city land, not including forested areas. Treatment costs the city $97 every two years, as opposed to the $1,000-$1,700 for removal.

“There hasn’t been any controversy,” says city forester Hannibal Hayes, “though there’s been a lot of questions and general concern about pollinators.”

Yet science faces an uphill fight these days. After years of fiascos wrought by Big Chem, liberals have developed a native distrust of most anything it produces, regardless of what the experts might say. Conservatives, meanwhile, have built a similar resistance to anything appearing to coddle Mother Nature. All of which leaves science a lonely voice in the middle. 

U of M entomologist Jeffrey Hahn points to a call for ash tree preservation signed by etymologists, horticulturalists, and forestry experts from across the country. But that doesn’t mean anyone’s willing to listen. Even when preservation and economics share a mutual interest.

“We’ve been bolstered over the years when study after study points to not only trees being immensely beneficial to our communities, but that it costs less to preserve a tree than replace it,” says Hafner. 

Some scientists, like Michigan State entomologist Deborah McCullough, believe killing trees en masse has hastened the ash borer’s spread.

“If you’re not killing beetles, if you are just taking down uninfected trees, then the number of beetles is the same, and they just fly further to the next ash tree,” says Orange. “It was a failed approach.”

But science has always has been political. Ask Galileo. These days, whether it’s climate change, vaccinations, or GMO farming, the perception of scientific fact gets colored by worldview, emotion, and economic factors that have little to do with the truth.

Minneapolis forester Ralph Sievert admits the city’s plan is in part fashioned by politics. 

“The idea is that if we start removing and replacing before the beetle population got really big, we’d never have to think about using the treatment,” he says. “And then by not even thinking about using the treatment, we also avoid all the political ramifications of the whole perception that it’s affecting pollinators.”

He notes that if an expert came to a neighborhood meeting and was asked to guarantee pollinators wouldn’t die, the expert would balk. Nothing about nature comes with ironclad assurances. “I wouldn’t expect them to,” says Sievert, “but that’s the opinion of a lot of the pro-pollinator folks in Minneapolis.”

St. Paul has used insecticide to treat larger canopies that are healthy and in good condition. But Councilwoman Amy Brendmoen says the city has no plans to change course in cutting down the majority of its ashes.

It’s not an easy decision.

“My experience with our forestry department is that none of those foresters signed up to be foresters because they wanted to take down trees,” she says. “I have confidence that they are continuing to weigh the pros and cons....

“If science does catch up, or if there are changes in how to treat them, this is what they are living day in and day out.”

In other words, the chainsaws will continue to rev.


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