Superhero trees could reduce heat deaths
DES MOINES, IOWA >> The trees were supposed to stay.
It did not matter that the owners of the squat building alongside were planning to redevelop the property. The four eastern red cedars stood on city land, where they had grown for the better part of a century.
“There’s no way these trees are coming down,” Shane McQuillan, who manages the city’s trees, recalled thinking. “The default position for us is, you don’t take out big trees to put in small trees.”
Here is why: At a time when climate change is making heat waves more frequent and more severe, trees are stationary superheroes. Research shows that heat already kills more people in the United States than hurricanes, tornadoes and other weather-events, perhaps contributing to 12,000 deaths per year. Extreme heat this week in the Pacific Northwest and Canada has killed hundreds.
Trees can lower air temperature in city neighborhoods 10 lifesaving degrees, scientists have found. They also reduce electricity demand for air conditioning, not only sparing money and emissions, but helping avoid potentially catastrophic power failures during heat waves.
“Trees are, quite simply, the most effective strategy, technology, we have to guard against heat in cities,” said Brian Stone Jr., a professor of environmental planning at the Georgia Institute of Technology.
So, in Des Moines, McQuillan worked with the property owners and city planners to find a way to redevelop while keeping the trees.
But one day several months later, he got word that a crew was taking them down.
McQuillan raced to the site, just a couple blocks from his office. One tree had already been cut to a stump, and another was almost down. McQuillan halted the work and fought to stay calm. At first he assumed someone had taken matters into their own hands. But after investigating, he came to believe it was simply a mistake; the property had been leased for a restaurant and the tenants seemed sincerely unaware of the agreement.
“There’s a defeated feeling,” McQuillan said.
They were two losses in an enormous struggle. Versions of this story are playing out in cities across the country, including Boston; Atlanta; Cleveland; Chicago; Houston; Spokane, Washington; and Los Angeles, according to the U.S. Forest Service.
Despite long-standing and ongoing efforts across the country to plant trees, communities in the United States are not adding to their total number or even maintaining it. Research shows that American cities and towns lose the canopy of 36 million trees every year.
‘A challenge ... To thrive in the city’
Considering the cast of characters in Des Moines, its urban forest should be thriving. The longtime mayor is an environmentalist. The director of public works hails trees as “the only infrastructure that add value over time.” A nonprofit group plants and tends the next generation of trees while giving green jobs and training to local teenagers.
In recent years, though, the larvae of an iridescent green beetle that arrived from across the ocean, the emerald ash borer, have claimed 6,000 of the city’s 8,000 public ash trees. A storm last year took out about 500 more of all kinds. Another big factor is the everyday losses: The tree felled to repair a water line underneath. The homeowner who removed a tree to build an extension or get more sun on the lawn. Countless new developments where trees were in the way. These are often mature trees whose canopy will take decades to replace.
Then, there are the bare-branched victims whose cause of death can only be guessed at: Not enough water? The extracold winter combined with all that street salt?
“It’s a challenge to get trees to thrive in the city,” said Phillip Rodbell, who leads a Forest Service team studying the social, economic and ecological impact of urban trees.
At the same time, American cities are facing a heat crisis: The largest are warming at twice the rate of the planet as a whole.
Thinkin of trees as infrastructure
On an afternoon that felt too sweltering for June, a 14-year-old named Kiara Wright bent over a young honey locust along a busy road in Des Moines, carefully splashing water from two 5-gallon buckets into the dry soil. The city was in drought, and abundant water is critical to trees for at least two years after the shock of transplanting.
Earlier in the spring Kiara had helped plant that season’s 500 trees, becoming fond enough of them to name a few: Sparkles, Linden, Jose. Now she was watering, mulching and pulling weeds for $10 an hour. Over the course of the summer, her small team would also learn about financial literacy and shadow people in various green jobs.
“We grow the trees and we grow the teens,” said Kacie Ballard, who coordinates the program for Trees Forever, a nonprofit group that is now planting almost all of the city’s street trees. “It’s cheesy but it’s true.”
Along with the environmental benefits of trees come economic opportunities.
“This is a field where the employers are begging,” said Jad Daley, president and chief executive of American Forests, a nonprofit group. “There is definitely a job waiting.”
Planting in Des Moines will resume in the fall, focusing on formerly redlined communities most in need of trees. Around the country, racist policies have left these neighborhoods especially bare and hot.
Leslie Berckes, director of programs at Trees Forever, hopes to get 1,000 trees in the ground by the end of the year, surpassing an agreement with the city. But the number still feels bittersweet. Four times that many are needed, on public and private land, to reach a state goal of increasing canopy 3% by 2050. Instead, she fears their efforts are not enough to stay even.
“We could be keeping pace if we wanted to,” Berckes said. “We need more money. I know it’s so boring to say.”
By all accounts the mayor, Frank Cownie, is trying. Des Moines has increased its $200,000 tree planting budget to $300,000 next year and $450,000 the following, with a goal of reaching $1 million. Its forestry department, with a budget of $2 million, employs a team of 13 arborists, up from 11 a couple years ago, who prune the city’s trees, extending their lives.
But it’s a tricky balancing act.
“You’ll hear, ‘Why are you doing this, you should be creating homes for the houseless,’” Cownie said. “Which we are.”
The crux of the problem, according to scientists and environmental planners, is that Americans, from everyday citizens to government officials, are often not fully aware of the benefits that trees provide.
In addition to reducing heat, trees filter out air pollution, suck up storm water, store carbon, nurture wildlife and even improve people’s mental and physical health.
“It’s hard for us to think of trees as actual infrastructure rather than an amenity, and because of that, we don’t allocate sufficient funds,” said Stone of the Georgia Institute of Technology. “If we think about it as actual infrastructure on par with investing in roads and sewers and everything else, those costs will become more acceptable to us.”
‘Trading one risk for another’
A tree’s shade, that sweet relief from solar radiation, is only part of its cooling power. Trees also evaporate water, pulling it from the ground and releasing it into the air through their leaves. That’s why walking through a forest, or just sitting in a playground surrounded by several large trees, feels more refreshing than the shade of a lone tree.
Carefully positioned trees can reduce a home’s energy costs by 25%, according to the Department of Energy. Nationwide, urban trees offer an estimated $18.3 billion in air pollution removal, carbon sequestration, lowered energy use in buildings and reduced emissions from power plants.
Still, across the country many people see trees as a nuisance or liability. They drop nuts, seeds and leaves. They buckle sidewalks. They are accused of destroying pipes wrongly, according to scientists, who say that pipes crack from age, which only then leads nearby trees to send roots toward the leaking water. Some towns and cities avoid the perceived hassle altogether by not planting on the strip of lawn between the sidewalk and the street.
Occasionally, their limbs break or they blow over, posing real danger. With climate change increasing the intensity of storms, David Nowak, a senior scientist with the Forest Service who studies urban trees, acknowledges the risk. Trees close to houses need to be especially well monitored for weakness. But he points out that trees also block wind, reducing the force of storms.
“You’re trading one risk for another,” Nowak said. “Branches falling, and having to clean up branches, versus having to clean up broken rooftops.”
One major challenge is persuading property owners, who own a large share of the land in cities and towns, to plant and maintain trees in their yards. It is important to choose the species carefully. Large shade trees offer more cooling and carbon storage than small ornamentals. For wildlife, oaks are usually the best bet, according to Doug Tallamy, a professor of entomology at the University of Delaware. They feed more than 900 species of caterpillars, which, in turn, feed birds, whose populations have plummeted.
Incentives can help, but tight budgets often keep them modest. In Louisville, Kentucky, which threw itself into planting more trees after it was found to be the fastestwarming large city in the country, residents can get a $30 “treebate,” up to three per household, for planting certain shade trees.
The director of public works in Des Moines, Jonathan Gano, came up with an idea to give away “tiny trees,” seedlings that look like mere sticks with roots. Once a year, residents can pick up five each.
“They’re tiny, yes,” Gano said. “They’re also practically free,” costing the city $1 per seedling.
“You could have 99% mortality and still be in the money 20 years from now on canopy,” Gano said. “I planted a bunch on my property and about 50% of them have survived. One of them’s 11 feet tall now.”