After 10am, it’s too hot for Hajar Logan to work upstairs, so she moves her home office to the basement. By 11am, she can’t leave her house until the sun sets. The heat is too “suffocating”, she says, in her mostly tree-less neighborhood of Dorchester in Boston.
Logan is diabetic, so she’s prone to dehydration. The heat makes it harder for her body to cool off, retain water and manage insulin. She doesn’t have air conditioning because it would be too expensive to cool her entire home. She uses fans instead.
“When it gets hot through July and August, there are weeks where I can’t do anything, I can’t think,” she said. “The only way to survive is to stay in the basement.”
During the day, her kids are shut in too. Dorchester – a majority-black area where roughly half of the population makes under $50,000 a year – lacks shaded green spaces within walking distance for them to play.
Logan, who is a climate and transit development director at the Boston environmental justice non-profit Alternatives for Community and Environment, is also concerned for her friends whose health conditions are worsening as the summers get hotter in the face of the global climate crisis. One recently had a third stroke, and another was diagnosed with heart failure.
“Especially the elderly,” she said. “Their bodies can’t handle it.”
But there is one simple thing that might help. As American cities cope with rising temperatures and the public health burdens they impose, some are starting to invest millions of dollars to plant and maintain trees to keep communities cooler as the world warms.
In fact, increasing tree coverage is one of the best solutions cities have for fighting the “urban heat island effect” in neighborhoods that are often blanketed with pavement and lack greenery. Those heat islands can experience temperatures that are up to 10C hotter than more canopied spaces.
For example, Washington DC plans to cover 40% of the city with trees by 2032. Seattle’s goal, which it has already almost achieved, is 30% coverage by 2037.
But experts warn that unless city blueprints emphasize racial equity in their plans for more trees, they may benefit wealthy neighborhoods rather than the poorer ones that need them the most.
“Tree equity is about more than just planting more trees. You can plant more trees and not achieve equity,” said Eric Candela, senior manager of the Community ReLeaf program at the not-for-profit American Forests. “The question is, what are municipalities willing and prepared to do about it now that they’ve identified the problem?”
Discriminatory practices like redlining – when banks refused or limited loans and mortgages within inner-city neighborhoods – are among the biggest predicting factors for heat inequities, Candela said. In a study of 108 US urban areas, formerly redlined neighborhoods were hotter than their non-redlined neighbors 94% of the time.
Research shows low-income areas are particularly tree-less. An NPR analysis of 97 of the most populous US cities found that in three-quarters of cities the hotter areas tend to be poorer. The heat makes it more expensive for people who are already on stretched budgets to cool their homes too, especially in the midst of coronavirus stay-at-home orders.
Extreme heat already kills more Americans than all other extreme weather events combined, and projections show that by 2100 deaths from heat may surpass the current rate of deaths from all infectious diseases combined.
As that death toll rises, it is likely to be highest among people of color who are disproportionately affected by heat-related illnesses like worsened asthma and pregnancy difficulties, and who are more likely to live in hotter neighborhoods.
In Baltimore, the tree inequity is starkly apparent. The high-income neighborhood of Roland Park is two-thirds covered with canopy, while the lower-income Broadway East has about 10% tree coverage, according to an analysis by the Howard Center for Investigative Journalism.
In San Diego, the neighborhoods most affected by redlining are the hottest. Paradise Hills, which has 91% minority homeowners, experiences temperatures 3.4C above the city average. The majority white Heritage Park neighborhood is 3C below the city average.
A review of tree coverage in Tampa, Florida, also found fewer trees in majority-black neighborhoods.
Cities with tree coverage goals are racing against a warming climate simply for the sheer length of time it takes trees to grow. After planting, it can take 20 to 30 years for trees to mature enough to temper heat. Meanwhile, the heat is getting worse. Climate projections show the world is on track to be 3C hotter than before industrialization by the end of the century, with heatwaves that are longer and stronger.
The Green Seattle Partnership, a city-non-profit collaboration, has recruited volunteers who spent more than 1m hours planting 306,779 trees since 2005. Seattle also uses a policy checklist, the Racial Equity Toolkit, to prioritize communities with lower canopy coverage, engage citizens in planning discussions and mitigate environmental injustice.
Sandra Pinto de Bader, Seattle’s urban forest policy adviser, said in an email that “the city’s urban forestry team conducted outreach and engagement efforts to intentionally engage people of color, immigrant, refugee, Native Americans and low-income populations to participate in the process, provide input, help shape policies, strategies and actions in support of the urban forest.”
Houston sent 75 community scientists out to track and map heat islands across a 300 sq mile radius, which the city will then overlay with tree canopy records to inform their planting goal of 4.6m trees by 2030. Houston is then sharing its censors and gear with Austin and El Paso for their own heat projects.
Even with their best efforts, cities face a number of setbacks. Trees can have a high mortality rate with experts citing figures from 15% to 40% or even as high as 50%.
In many cities, the greatest potential for correcting inequities is by planting trees on private property. That’s because the public property between roads and sidewalks often has obstacles, like underground pipes that constrict roots.
Washington DC is nearly at capacity for street trees, meaning there is a tree next to the street in every place possible, said Jessica Sanders, director of science and policy at Casey Trees in DC. The local department of transportation is finding new places for street trees – even by eliminating parking spaces where possible.
Tree non-profits have turned to encouraging residents to increase tree canopy in their own yards, but they are meeting resistance.
“The hardest part is getting trees on private land,” Jessica Sanders, Casey Tree’s director of science and policy, said. “Especially for renters, landlords aren’t willing to put trees on their property. Their response usually is, ‘Who’s going to take care of that tree when you move out?’”
As some cities wrestle with those challenges, many more have not even begun to seriously consider how to increase tree coverage to prepare for rising heat.
Logan, the Boston climate justice advocate, said time is against the efforts.
“It can take years for a tree to be effective, and no politician is around long enough to make sure those trees grow,” Logan said. “There’s not enough political incentive.”