LAKEWOOD — This suburb west of Denver boasts 625,000 mature trees for its approximately 160,000 residents.
But along the sun-splashed and parched Front Range, where increased urbanization threatens to boost temperatures faster than they are already rising, it may not be enough for Colorado’s fifth-largest city.
An in-depth tree canopy survey of the nearly 45-square-mile city, released this month, shows that trees cover 16% of Lakewood’s land mass. The city’s 2015 sustainability plan calls for a 30% tree canopy across Lakewood by 2025.
To reach that goal over the next three years, according to Lakewood forester Luke Killoran, would require the planting of half a million trees.
“It’s just unrealistic,” he said.
But that doesn’t mean Lakewood won’t work on continuing to gradually widen its canopy — coverage increased by 2% from 2011 to 2019, according to the study — but it should do so in ways that make the most sense for its residents and work within the confines of the natural habitat, Killoran said.
The canopy study estimated that Lakewood’s trees create environmental, economic and social benefits for the city amounting to $1.8 million annually. Aside from providing shade and a noise buffer, trees help clean the air, regulate temperature and help absorb the planet-warming gases humans release daily.
“As a community, we’d like a larger canopy,” Killoran said. “And there are opportunities for plantings.”
One of those locations is Coyote Gulch Park in the Rooney Valley neighborhood, at the western edge of Lakewood. The city plans to plant trees there next year in an effort to provide more shade in a space that today is mostly ballfields and sun-blasted open space.
But the site is feasible for tree planting largely because Coyote Gulch is water-ready. Many other areas of Lakewood — like the largely treeless Green Mountain Park and Bear Creek Lake Park — are not nearly as tree-friendly due to their almost desert-like conditions.
“This is an irrigated bluegrass park,” Killoran said of Coyote Gulch.
Austin Troy, a professor at the University of Colorado at Denver’s department of urban and regional planning, said the western United States’ drier and harsher climate makes it tougher to grow a forest than back east.
“Trees are not natural here, except in the river corridors,” Troy said of the Front Range’s ecology. “Planting trees is not enough — maintenance is really important.”
That’s because without sufficient water, trees won’t survive. And that’s a real challenge in a “semi-arid Western city” like Lakewood, Troy said. In December, Denver along with parts of Adams, Arapahoe, Boulder, Broomfield, Jefferson and Weld counties, were considered to be in an extreme drought, according to the National Drought Mitigation Center.
And metro Denver saw its first snow-free April in 20 years in 2022.
“How many trees can we afford to irrigate?” Troy said. “It’s more important to have trees in strategic locations where they are really needed.”
And where trees are needed, according to many urban planners and ecologists, is in poor and racially diverse neighborhoods that have long been neglected. A scientific study released last year determined that “inequality in tree cover between low- and high-income blocks was widespread in the U.S., occurring in 92% of the urbanized areas we studied.”
The researchers found that on average, there was 15.2% more tree cover in richer parts of a city than in less affluent ones. And with fewer trees, there was higher heat — a phenomenon known as the “urban island heat effect,” where dense concentrations of pavement, buildings and other surfaces absorb and retain heat.
Denver has emerged as one of the nation’s most “impervious,” or paved-over, cities. Roughly 8% of Denver’s 155 square miles has been designated as parkland, compared with 21% in New York, 23% in San Diego, 15% in Minneapolis and 13% in Los Angeles, data from the Trust for Public Land showed in 2019.
That’s why Denver has been planting around 3,000 trees a year over the last few years, said Ben Rickenbacker, the city’s forestry operations supervisor. He estimates Denver has an 11% to 13% tree canopy.
“It’s going to take a while,” Rickenbacker said.
Ean Thomas Tafoya, Colorado program director for GreenLatinos, an environmental justice organization based in Boulder, and a candidate for Denver mayor, said Lakewood should use the data it collected from the canopy study “to reduce inequity — and that means targeting things where the health benefits will be seen.”
That might mean planting more trees along major transportation corridors in the city — like Wadsworth Boulevard, Kipling Street, Sheridan Boulevard, Colfax Avenue and Interstate 70 — places lower-income families often call home, Tafoya said.
According to the Tree Equity Score from American Forests, a Washington, D.C.-based environmental advocacy group, Lakewood does fairly well on its index. For example, one neighborhood fronting Sheridan Boulevard with a 72% poverty rate scored higher on the tree equity index than a neighborhood on the west side of town near Green Mountain, where the poverty rate is just 8%.
But Killoran, Lakewood’s city forester, said having sufficient trees in a neighborhood is one thing — maintaining them so that they don’t weaken and pose a danger to people living below is another. And in that regard, the city faces challenges — from drought to insects to disease.
“We’re seeing a lot of stressed trees that weren’t stressed before,” he said.
Honey locusts are getting hit particularly hard with gummosis and thyronectria canker, Killoran said. And the city’s ash trees, which account for two to three of every 10 trees in Lakewood, are under threat from the emerald ash borer, a beetle that first arrived in Colorado nearly 10 years ago.
Its spread in Colorado has been slow. Largely confined to Boulder County for the first seven years it was in the state, the ash borer was found in Arvada two years ago. Last month, Thornton announced it too had discovered the ash-devouring beetle.
“It’s coming,” Killoran said. “How do we replace the ash trees with a more appropriate tree for our area?”
The good news for Lakewood is that the canopy survey concluded that there are 22 trees per acre in the city and four trees for every city resident. It also determined that 41% of the city’s land mass is considered a “possible planting area” for new trees, which serves as a vital offset to the 38% of the city that is considered impervious — or paved over.
“As a community, we’re doing pretty well,” Killoran said.
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