By Roxanne Ready, Theresa Diffendal, Bryan Gallion and Sean Mussenden
University of Maryland
Editor’s note: This is the third story in a four-part series on Code Red heat in Baltimore by the University of Maryland’s Capital News Service and the Howard Center for Investigative Journalism. A longer version is available to read on the Code Red project website.
BALTIMORE, Maryland — Kwamel Couther stands on the front lines of a campaign to bring thousands of cooling shade trees to some of the hottest streets in Baltimore.
City trees are especially vulnerable in the first two years of life, requiring about 20 gallons of water per week to stay alive. Couther, who supervises a tree maintenance team for a Baltimore tree nonprofit, intervenes in case the clouds fail to provide.
He needs a lot of water, too, as he works in the summer heat on one of the city’s hottest–and poorest–blocks.
In a city marked by startling inequity, leaf cover is just one more thing that has been historically distributed in unequal measure. The city’s poorest areas tend to have less tree canopy than wealthier areas, a pattern that is especially pronounced on the concrete-dense east side, in neighborhoods like Broadway East.
“The trees that we planted so far aren’t providing that much shade,” Couther said of the new arrivals on this street. “Yet.”
The question of whether these trees–and thousands of other recent arrivals–will ever provide enough shade is critical to the health of people in Baltimore’s hottest neighborhoods, as they face a future of increasingly intense summers driven by the climate crisis.
The urban heat island effect makes Baltimore hotter than surrounding suburbs. A major reason: many of the materials that define Baltimore’s urban landscape–brick rowhouses, concrete sidewalks, black tar roofs, asphalt streets–are very effective at trapping, storing and then radiating heat.
To cool neighborhoods, you could remove those materials or replace them with heat-repellent versions. Or you could prevent some of the sun’s heat energy from reaching those materials in the first place. Trees–especially dense clusters of large trees with expansive canopies, like those common in Baltimore’s wealthier northern neighborhoods–offer the best hope for doing that.
This helps partly explain why in Baltimore, the coolest neighborhood has 10 times more tree canopy than the hottest neighborhood. In temperature readings taken by researchers at Portland State University in Oregon and the Science Museum of Virginia on one particularly hot day in August 2018, there was an 8-degree Fahrenheit difference between the coolest and hottest neighborhoods in the city.
“If you live in a… city that is seeing more extreme heat days, but you don’t have tree cover to cool down your neighborhood, that can literally be a life or death issue,” said Jad Daley, president and CEO of American Forests, a nonprofit working to expand urban tree canopy in an equitable way across the U.S. “Bringing tree cover into neighborhoods can cool what we call ‘urban heat islands’ dramatically.”
U.S. cities are losing 29 million trees every year, and many cities are struggling to reverse their dwindling canopies, according to an investigation by NPR and the University of Maryland’s Howard Center for Investigative Journalism. Between 2009 and 2014, 44 states lost tree cover in urban areas, according to the U.S. Forest Service, though Baltimore bucked the trend with a small increase between 2007 and 2015.
The city’s forestry division, nonprofits like the Baltimore Tree Trust, neighborhood associations and others have spent the last decade aggressively working to expand the city’s tree canopy.
They’ve collectively spent millions of dollars and thousands of professional and volunteer hours to increase planting across the city, targeting some of the poorest neighborhoods. Just as critically, they’ve spent millions more doing vital maintenance work to keep new and old trees healthy, nurturing them through young adulthood and caring for them as they age.
“Trees are not just scenery. They’re critical infrastructure for the health and wealth and well-being of communities,” Daley said. “[Distributing] the cooling shade of trees more equitably across our cities is an absolutely essential strategy. We like to say hashtag tree equity equals hashtag health equity.”
Trees are an effective cooling solution, but are not a quick fix. They start small, and take years–in some cases, decades–to provide enough shade to significantly move the temperature needle. That’s a big reason canopy growth has been relatively measured despite recent planting efforts.
Between 2007 and 2015, tree canopy in Broadway East grew from 9 percent to 10.6 percent. Roland Park, a wealthy northern Baltimore neighborhood already covered with trees, grew by 2.1 percentage points to 64.5 percent.
The city’s tree canopy is fluid like this. It grows when new trees are planted and existing trees grow larger. It shrinks when trees are trimmed back, or even removed, to accommodate city life, when limbs fall during storms, or if trees die from disease or other causes.
“Baltimore is one of those few places where the growth and the planting has outpaced the loss,” Grove said, pointing to an increase in the city’s tree canopy from 27 percent in 2007 to 28 percent in 2015.
Those gains and losses were not distributed equitably. About 40 percent of city neighborhoods had net losses. The rest had net gains, but the increases in Baltimore’s hottest neighborhoods didn’t come close to correcting the inequity.
For Daley, of American Forests, a city’s overall level of canopy cover is less important than the numbers in each neighborhood–and the differences between them.
“A simple percentage for the whole city… can mask those inequities,” he said. “Whatever the right level of tree canopy is for a given city, given its climate and its setting, we should hit that same mark in every single neighborhood. And we have a lot of work to do to bring, particularly, low-income neighborhoods and communities of color up to that citywide standard.”
Jake Gluck and Jane Gerard of the University of Maryland and Meg Anderson and Nora Eckert of NPR contributed to this story.
One aspect of the great effort underway by a number of organizations in Baltimore to increase our tree canopy that, as far as I can tell, is almost completely overlooked is fertilizer. Almost all trees planted in street tree pits are planted is extremely poor soil. Many newly planted trees die the first year or two from lack of water and never or seldom being watered during dry periods. Another reason they often don’t get enough water is they are planted too high above the surrounding sidewalks and the dry packed dirt slopes down at the edges, repelling rain water flowing downhill from sidewalks sloping downwards towards the tree pits as well as funneling excess water from heavier rains away from the tree and losing it into the gutters. If the outer edges of the dirt in the tree pits were an inch or inch and a half below the sidewalk surface, especially on the uphill side, much of the rainwater could be saved and used by the young trees. And even light amounts of rainfall could add enough water to the dry soil to make a difference by funneling the rains from the uphill sidewalk into the tree pit.
But in my extensive experience caring for years for new trees in the Federal Hill/South Baltimore area, applications of a meaningful amount of appropriate fertilizer in the spring and fall can make a huge, and often quite surprising difference and contribution to the survival and growth of the trees. This is especially evident with trees planted in particularly bad soils. I’ve done simple control experiments where I applied fertilizer to one tree and not to another nearby of the same species. The difference has often been almost shocking. Fertilized trees can grow at sometimes triple or more the rate of their unfertilized neighbors. And being much healthier they are far stronger and better able to withstand prolonged periods of drought.
I use liquid fertilizers to minimize runoff into the storm drains and ultimately the Harbor and Bay. Miracle Gro or Peters or the generic store brands with similar formulations are easy to use and dissolve quickly in water and are relatively inexpensive per tree when purchased in bulk. I add a liquid root growth booster on newly planted trees the first year to help them develop the larger root structure that helps them survive our frequent extended dry periods.
If the various organizations planting the thousands of new trees around Baltimore would put just a small part of their limited budgets into adapting a few vehicles with water tanks and filled them with a fertilizer/water solution and applied that to new trees a couple times a year for the first two or three years we could achieve the common goal of greening Baltimore far more quickly and inexpensively than by just planting the trees. And the additional expense would be offset by the elimination of the current need to replace the hundreds or thousands of newly planted trees that die the first few years because survival rates would increase dramatically. Or possibly the fertilizer solutions could be applied by volunteers. However done the cost of the fertilizer per tree would be negligible.
And the fertilized young trees, growing at rates many times faster than they currently grow especially if they were planted slightly differently as I described above, would spread their cooling, pollution purifying green canopies over the city far faster than the current system of just planting and putting a water bag around it, usually never to be refilled again. And after all, that is the common desired goal of all involved.