The Trees of Tree Town
What's next for our urban forest?
by James Leonard and Jeff Mortimer
As long as humans have walked Michigan's landscape, they've messed with the trees around them.
Take Ann Arbor, for example. After the glaciers receded and before European settlers arrived, what would one day be called Tree Town was part of an oak savanna, a vast grassland dotted with widely scattered trees. Though it looked natural, that landscape was actually a human creation. Native Americans set fire to the savanna every few years to encourage fresh growth that attracted the deer and buffalo they hunted. The burns cleared out most shrubs and saplings, leaving only the fire-adapted oaks.
When the settlers arrived, their first surveys showed bur oaks in the center of town, with black oak in the barrens to the west and both oak and hickory in the hills to the north. But, except for a few scattered survivors, the native oaks virtually disappeared by the mid-nineteenth century, as the land was cleared for farming.
The settlers replaced some native oaks from sprouts, but mostly they planted elms and maples with a sprinkling of locusts, sycamores, and ashes. By the mid-twentieth century, colonnades of narrow-leaved elms lined Washtenaw Avenue and Stadium Boulevard.
The elms' dominance ended in the sixties when Dutch elm disease decimated that population--and forty years later the emerald ash borer killed thousands of white and green ashes. And last year's dry winter, an early spring followed by a late freeze, and summer drought were tough on all trees. The dry winter failed to replenish the ground water, an unseasonably warm March forced premature growth that was then killed by the freeze, and the drought stressed them into shedding bark and leaves. How well they'll recover won't be known till this summer.
Beyond natural causes like drought and disease, the town's trees have been affected by the reduction of the city forestry department's staff from twenty-five to eight over the last thirty years and the cuts in its budget from $2 million to $1.5 million over the last
five. This sapped the department's resources and left jobs like pruning, planting, and regular maintenance undone or underdone, though a separate $2 million budget paid for removing dead ash and planting replacements. Since 2005, the city's planted 7,760 trees.
No one knows how many trees the city had before the epidemic of Dutch elm disease, but a recent survey estimated there are 1.45 million on public, private, and U-M property now. They create an overall leafy canopy that covers 33 percent of the city's land: 46 percent of residential areas, 24 percent in public rights-of-way, and 22 percent in recreational areas. That makes Ann Arbor just a bit above average for towns of its size.
After a rough fifty years for its trees, the city is now developing its first-ever urban forestry plan. Work began last spring, and the plan is expected to go to city council late this year or early next. Nothing in the plan is likely to transform the landscape on the scale of the settling of the savanna, in part because the government controls only about 30 percent of the city's land area (the U-M and private owners control the rest). Still, it seems like a good moment to ask a cross-section of local experts what they'd like to see for the city's urban forests: Plant colonnades of the same species or cultivate a variety of different trees? Re-create something akin to the original oak savanna, or create a configuration more compatible with the changing environment and the needs of current residents?
Everyone we talked to shares a deep love of trees, combining their awe and wonder with homely affection for the mega-flora in our midst. They all argue strongly for their points of view, agreeing there should be more trees but disagreeing about what they should be.
According to a 2009 inventory of the trees lining city streets and freestanding in its parks, broad-branched oaks like the one depicted in the city's logo constitute about 7 percent of the urban forest. Tall, sharp-leaved maples make up 37 percent, while another 7 percent are short-lived, thin-leaved honey locust, 6 percent are colorful crabapple, 5 percent are gentle linden, 4 percent each are spruce, pine, and sycamore, 3 percent are elm, and 2 percent are pear. The remaining 29 percent are scattered among sixty-nine other genera.
The oaks include a handful that are thought to predate European settlement. According to natural landscaper Mike Appel, the best-known survivors are located at 515 Detroit, at Kingsley and Division, and in Wurster Park. The trunk of the largest, in front of the Vail House Co-op at 602 Lawrence, is more than five feet in diameter.
But most of our trees are here because someone chose to plant them. And a big part of the reason Ann Arbor is still Tree Town after the devastation wrought by Dutch elm disease is the legacy of Elizabeth Dean, who bequeathed a $2 million endowment to the city in 1965 specifically for its trees.
"She was the daughter of the Dean grocery store owner," says retired educator Al Gallup, whose father, Eli, was both the city's forester and its parks superintendent from 1919 to 1961. "People were surprised she had $2 million to give." But "the city immediately cut the forestry budget by the size of the interest on the money," so Dean's bequest didn't actually result in any increase in funding for tree planting and care--until, Gallup says, "my mother and others formed the Dean Fund to make sure it would."
Paul Bairley's work was paid for in part by the Dean Fund for twenty-five years. A child of the Detroit suburbs, a graduate of the U-M School of Natural Resources, and a lifelong tree lover, Bairley says he "turned down full-time, benefit-wielding federal jobs with the forest service to work a three-dollar-an-hour part-time job in Ann Arbor, because Ann Arbor had the most progressive forestry program in the country.
"When I started [in 1980], we had probably twenty full-time personnel dedicated to tree maintenance work and eight seasonal horticultural staff [tending] 33,000 [street] trees and eighty-five parks," Bairley says. "At the high point in 2002, we had 51,000 [street] trees and about 150 parks."
For Bairley, urban forestry is "not so much about the landscaping benefits or the aesthetic appeal but the environmental benefits that trees will provide--vital, life-giving benefits. A twenty-inch-diameter tree will take in CO2, and, through the miracle of photosynthesis, give off enough oxygen in one year for a family of four to breathe. It also takes out the pollution of a car driven 11,000 miles a year and provides cooling effects equivalent to twenty room-size air-conditioners. Even a dog knows it's cooler in the shade."
Though he retired from the city in 2006, Bairley remains involved in urban forestry, first in Detroit and now back in Ann Arbor working part time for the U-M, and he applauds the city's first forestry plan--and hopes it leads to planting more trees.
"A 40 percent [tree] canopy will greatly reduce the urban heating effect," he says. Getting to 40 percent is "the big challenge, because the city only controls parkland, some non-parkland like the water treatment plant, and the public street rights-of-way. That's not a whole lot of land. But what's very cool is that the university has a canopy goal of 40 percent." And since it purchased the former Pfizer property, the university now controls 18 percent of the town.
"Paul is absolutely right that maintaining a forest canopy in the city has multiple benefits," agrees Bob Grese, director of the university's Nichols Arboretum and Matthaei Botanical Gardens. "Making sure they have good conditions is key. Studies across the country suggested the average lifetime of an urban tree is seven to nine years because of construction, salt, soil compaction, and all the other things that cause stress."
Like everyone else we interviewed, Grese loves trees. "I've been fascinated with trees from fifth or sixth grade on. For me and for many other people, there's a reverence for something that lives through many generations. The other aspect is the role of what's called 'nearby nature' in people's lives in reducing stress, creating a sense of balance, and just overall contributing to the enjoyment in people's lives. Watching the leaves sway in the breeze and the birds that use the trees and the seasonal changes, it all helps us maintain our mental and emotional stability. That's incredibly important in urban environments, to have a wonder about life outside of ourselves."
It's important, Grese says, "to think of the urban forest as part of a larger healthy ecosystem. There's been a lot of discussion lately by people interested in broader urban ecological issues about the species of trees that are selected as part of maintaining broader ecological integrity. What insects use those trees? What birds feed on those insects? Some of the trees we've introduced have no value to wildlife. They may be attractive, but they aren't part of an ecological system in the city."
That's why Grese hopes that future plantings will hark back to the pre-settlement landscape. "Could the Diag or many of our city parks or streets include some of the trees and other species from the oak savanna as part of the overall framework in the city? It isn't something that, in an urban setting, you would replicate exactly, but it does provide a guide in terms of the overall mix of trees."
Including the former Pfizer property--now the North Campus Research Complex--the university counts 17,000 trees in its campus landscapes, plus 198 acres of forest on North Campus between Huron River Drive and Green Road. This yields an overall canopy of 30 percent. Marvin Pettway, head of the university's forestry group, confirms in an email that the goal is to get to 40 percent tree cover in 2025. They'll do it, he says, "by expanding and improving the quality of our woodlots on North Campus while continuing to maintain and replace as necessary trees in our ornamental landscapes."
"It's ambitious, yes," Pettway acknowledges by phone. "But if the areas are left alone, and we can maintain where we are with our ornamental [trees], we can accomplish it."
For most of the city's history, most trees have been ornamental: people planted them because they liked the way they looked. "People really love identical, symmetrical alleys of trees, like classical European gardens," says Tony Reznicek, assistant director and curator at the University Herbarium, who maintains michiganflora.net, a website listing every plant known to grow in the state.
"Personally, I think that's terrible," adds Reznicek, who learned to love trees from his European-born mother. "We should celebrate some more uniquely American horticulture ideals. And not planting all the same kind of trees is an absolute minimum because you open yourself up to all sorts of problems if you do that; not just something that will come through and kill everything, but diseases and pests that can build up when they have lots to eat."
After the devastating effects disease and invasion had on single species, Reznicek says, "We seem to have hopefully learned our lesson a little bit. I do notice a lot greater diversity of trees planted now, though." Not that all diversity is good, he adds: "I see lots of people that, whenever a tree comes up in their yard, they're reluctant to cut it down. That means their yards are full of weedy, invasive trees. [Non-native] buckthorn are fast spreaders because they're bird dispersed, and at first glance they don't look too bad or too dangerous. But they're really quite nasty things."
Guerin Wilkinson, owner of Green Street Tree Care and another School of Natural Resources alumnus, agrees with the need for variety--but also sees the virtues of symmetry. "There's this argument that we did so badly with elms and ashes because we overused them and didn't diversify," he says. "You don't want 50 percent of your trees to be all one species. But to take one bald cypress from the Southern swamps, put it next to some untested ornamental tree from Asia and a disease-resistant American elm, and it's this hodgepodge of stripes and plaids with no fashion sense. Why not have a street of hackberries? It's so much nicer when you've got that view, like France with alleys of sycamores or lindens, and they make these spectacular shows."
"Our main goal is to preserve, protect, maintain, and expand Ann Arbor's tree canopy and urban forest," says Kerry Gray, the city urban forestry and natural resources planner who's overseeing the new plan. A key change, she writes in a later email, is "to develop a proactive tree maintenance program [for] publicly managed trees emphasizing routine pruning, removals and care. A routine pruning program is more efficient, cost effective and improves the quality, condition and value of the urban forest."
Gray doesn't expect the plan to dictate what home owners plant. But "if the city approves a site plan for commercial development, it should have a list of species that can't be planted. Another approach is developing partnerships with nurseries to encourage plants that are part of the heritage of the region. In Michigan, the Nature Conservancy has partnered with Meijer to remove plants that are invasive from their nursery operations. That's been a big help in reducing plants that are most problematic."
While the city does control what trees are planted along streets and in parks, it has limited resources. By the terms of Elizabeth Dean's bequest, the principal of the Dean Fund must be invested in U.S. Treasury notes. So at the same time that the forestry department's staff and budget have shrunk, interest from the fund has plummeted. Bairley says the fund brought in about $200,000 a year during the high-interest Reagan years. Thanks to the Great Recession and Federal Reserve chair Ben Bernanke's commitment to keeping interest rates low, this fiscal year's income is just $50,000.
"With cutbacks, there are others trying to fill in what the city can't afford to do," Al Gallup notes. "The Rotary spends $80,000 a year on trees and parks, and they've done it for at least five years."
But Gallup fears that "the forest service in Ann Arbor is slowly disappearing, and the city is not concerned. My father was superintendent of parks, city forester, and manager of the airport, and he had direct contact with city council. Now there are a couple of layers between them, and they're not knowledgeable."
Whether they're knowledgeable or not, so far the current council hasn't been overly curious about the coming plan. "I have not received a high volume of questions from council members about this topic or draft recommendations," writes Gray in an email.
Paul Bairley has a different fear: "I just hope we get the support we used to have to make sure at least the major goals of the plan can be realized over time. My big worry is they'll say: 'Nice plan, but we can't afford it.'"
They might: a majority of the current council typically oppose spending city money on much beyond public safety. Or they might not: two-thirds of the city's voters just passed a parks millage renewal. Of course, how they'll vote ultimately depends on the plan that emerges, and right now the plan has only prioritized recommendations, not price tags. Aspiring to a thicker urban forest is one thing; paying for it is another.
[Originally published in April, 2013.]