Thanks a lot, Westword!
Residents of Lower Downtown are experts in mapping a summer walk to maximize shade. We already knew it’s been damn hot outside.
Westword nonetheless took it upon itself to drill down into recently published data identifying the country’s hottest urban heat islands, comparing the neighborhoods within Denver’s central city heat island. With temperatures on average 10.95 degrees hotter than temperatures just outside the city, LoDo took the dubious trophy! We are the hottest neighborhood in Denver.
This comes as no surprise because LoDo is also the city’s most walkable neighborhood, which is precisely why many of us choose to live here
High walkability and high heat scores, both primed by urban density, represent the best and worst of inner-city life. At the same time, dense urban neighborhoods are among the most effective ways to address climate change. We center-city residents can easily walk to meet most daily needs and partake of energy-efficient mass transit systems.
Urban density is also the antidote to urban sprawl, which creates far more pavement to radiate heat. At the same time, sprawl reduces vegetated open spaces, destroying their cooling and carbon storage characteristics. Moreover, it generates countless more vehicular miles driven.
The conundrum makes urban street trees a key to our collective salvation, helping more of us to live comfortably in neighborhoods like LoDo. We need more, bigger, trees, arguably as urgently as any Denver neighborhood. Fortunately for us, Denver established a goal of increasing the “urban forest” starting in the early 2000s, refining plans for how to do so since, culminating with the city’s Urban Forest Strategic Plan, published in June. The Plan’s ambitious goal is to increase the city’s tree canopy coverage from 15 percent in 2020 – up from 13 percent in 2014, but still among the lowest in the country among comparable cities – to 20 percent by the year 2050.
For downtown, the goal is to increase the tree canopy from today’s four percent to ten percent.
Still, don’t you wonder when you stroll the neighborhood, especially during one of our increasingly frequent heat waves, why there are so many sickly trees and empty tree beds?
To learn more about the state of LoDo’s urban forest, I asked Amanda Miller, the Manager of Sustainability Initiatives with the Downtown Denver Partnership (DDP), if she had time to give me a brief tutorial on the subject.
We started with the best news any urban forest plan could have: the recently planted trees – with many more to come – on the 16th Street Mall. Here, Miller explained, the DDP seized the rare opportunity to give over 200 new urban trees – ten species – an optimal environment to grow large and live long. As we know all-too-well, the 16th Street Mall Project, already over two years in and still only half done, has been a huge disruption. But thanks to its ambitious scope, replacing every bit of the mall’s infrastructure both above and below ground, the project had the opportunity to incorporate trees as a piece of “living infrastructure,” as the Urban Forest Strategic Plan describes them.
“One of the most important things trees need to thrive is enough soil volume,” Miller explained, as we admired the thriving trees on the block of 16th Street between Larimer and Lawrence. “These trees have as much soil as they would likely utilize in a natural environment.”
The reason, she explained, is that each block of the mall’s underground infrastructure includes two soil vaults, one on either side of the bus transit lane, each of which runs for the entire length of that block. That adds up to thousands of cubic feet of soil available for root growth per block.
The original construction of the 16th St. Mall was undertaken as Denver’s first Streetscape Improvement Project in the 1980s. As such, there is an agreement between the City and the Downtown Denver Business Improvement District (BID), which is managed by the DDP, for the DDP to maintain 16th Street.
Despite all their advantages – not least being planted and cared for by a quasi-governmental agency that had the vision and ability to create infrastructure for them – I couldn’t help noting that some of the new 16thStreet trees do not look healthy on some blocks.
“Most will recover from the stress of being transplanted,” Miller explained. “Those that are struggling are being closely monitored by arborists, and any that don’t recover will be replaced.”
By themselves, the 16th Street urban forest will surely inch downtown’s tree canopy above the current four percent closer to the ten percent target. These trees could serve for generations to come as a demonstration of what is possible in an urban environment at the heart of a heat island. While we can hope that these trees inspire similar efforts on other critical downtown arteries, it is impossible to predict whether or when the city might undertake another downtown Streetscape Project that could provide an opportunity to include trees in a complete upgrade of infrastructure.
This leaves Miller to navigate a welter of regulatory, right-of-way, and existing-condition obstacles in nurturing the urban forest elsewhere downtown. Outside Streetscape Project streets – 16th Street, 14thStreet, and a few blocks of Lawrence, California, and Curtis streets, where the DDP is responsible for the public right-of-way – Miller’s office administers the Urban Forest Initiative, which works with building owners interested in helping grow the urban forest to develop a site plan for the street trees that they are responsible for planting and maintaining.
We stopped to discuss some tree beds on 16th Street below Market Street where trees had died. “There were problems with the irrigation from the adjacent property owners here,” Miller explained. “A tree can fail to thrive for a lot of reasons. We have to figure out what that is first, and fix that before we replace the tree. We have limited resources to do all this, so it can take some time to get to it. But we are scheduled to plant trees here next year.”
As new tree beds are created, not only the forest but the workload grows, because the DDP also administers a maintenance program for all of the trees in the district. Trees are fertilized, given an organic soil treatment, and the soil is remediated for salt infiltration annually. Trees are pruned on a five-year cycle.
We strolled north on Blake St. where new tree beds were recently completed between 17th and 18th streets in partnership with the adjacent building owner. For a striking before-and-after comparison, Miller pointed out the difference between older tree vaults on the sidewalk in front of the neighboring building and the new ones.
The new tree beds are protected by a concrete curb to prevent street salts from contaminating the soil, which is protected by mulch, allowing for moisture and nutrient retention, aeration, and the planting of annuals. (Unfortunately, this also attracts dogs, whose urine has to be remediated.) Miller also pointed out the compromises that were necessary at this location to accommodate existing conditions: a requirement to leave space for motorists to step up from the street to the curb after parking and to leave enough room for pedestrian egress on the sidewalk. Still, these trees, new to their home, have a great chance to thrive, especially in comparison to their neighbors just to the south.
Given the complexity of nurturing an urban forest, it’s impressive that the DDP has completed 107 tree beds since 2020, not counting 16th St., with fifty more in the planning stages.
The next few days as I walked downtown, I paid much closer attention to the signs of an urban forest slowly taking root. The generous tree beds on California St. date back at least to 2011, when that Streetscapes Project was completed, and the tree canopies there are impressive. There are many more newer tree beds all over downtown, where trees have not yet had time to deeply root and fully branch out. And there are locations where new trees are struggling.
Perhaps the biggest challenge is that there are many property owners who installed street trees in compliance with their development approvals but have not kept up with their obligation to maintain them. Downtown residents can report missing or struggling trees by reporting the violation to 311. For more information, click here and choose the link “Get Help With a Notice or Citation.”
After being impressed by how much progress has been made, I unchivalrously texted Miller a photograph of a dead tree on 14th St.
“We will be replacing at least four trees on 14th St this season, likely more, but we do operate under a limited budget and need to prioritize,” she texted back. “The block where you took the picture has several empty or dead trees because there is an issue with dog owners in this area. It requires a different solution than simply replacing the trees if we want them to survive.”
Such, I have learned, is the nature of the beast. Outside of new or expanded parks – here’s looking at you, Cherry Creek and Speer Blvd Vision and Reconfiguration Study – and rare opportunities for a dramatic improvement, like 16th St. – our downtown forest can only be nurtured tree by tree. Those trees cannot grow an expansive canopy any quicker than it takes for trees to grow, a process measured in decades.
To view what’s been done to date, you can take an Urban Forest Walking Tour of Downtown Denver’s new and improved tree infrastructure improvements, developed by the DDP’s Urban Forest Initiative.
