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As our planet grapples with the consequences of man-made climate change and the excessive summer heat it is causing, a lesser-known repercussion is coming to light: its correlation with the uptick in gun-related incidents in America’s cities. But how exactly are rising temperatures and gun violence intertwined, and could addressing the effects of climate change in cities hold the key to curbing this alarming trend?

Near the end of July 2022, the city was in a heat wave. On Tuesday, July 19, a series of oppressively hot 90-degree days began with the humidity hovering above 70% in some places. The air was thick and heavy, the kind of heat that sent streams of sweat down your spine in minutes and made clothes cling to skin like a damp blanket. On some days, the air barely felt like it was moving. 

In Central Park that Wednesday, it was 95 degrees. In Tremont and Brownsville, it was about 100 and felt like 105 degrees. In that week and before the following Tuesday was done, shots rang out in 47 different places in the city, leaving six people dead.

A man uses a wet towel to cool off, Tuesday, July 28, 2020 in New York. The city has opened more than 300 fire hydrants with sprinkler caps to help residents cool off during a heat wave. (AP Photo/Mark Lennihan)

According to a recent study by researchers at the University of Washington and Boston University looking at heat and shootings in 100 U.S. cities from 2015 to 2020, nearly 7% of gun violence incidents could be directly attributed to above-average seasonal temperatures. In New York City, that percentage doubles to around 15%.

That means that in New York in 2020, a pandemic year with the highest number of shooting incidents in the city’s recent history, an estimated 286 shooting incidents wouldn’t have occurred if it wasn’t exceptionally hot outside, according to the researchers. That’s one of the highest of the 100 cities studied, said Jonathan Jay, a Boston University researcher and a co-author of the paper.

“In general, the Northeast and the Midwest had shown the most dramatic heat effects,” Jay said.

Aiming to better understand how day-to-day fluctuations in temperatures affect the number of gun violence incidents, the researchers analyzed U.S. shooting data from the Gun Violence Archive from 2015 to 2020. To more accurately demonstrate the impact of daily temperature changes, they made sure to factor in specific tendencies that take place in different seasons like holidays, more kids being out of school – what scientists call “seasonality” –  in their analyses. 

“On a day-to-day basis, we don’t have any control over the weather,” Jay said. “But it’s unlikely that daily heat is just kind of off to the side in terms of contributors to gun violence.”

But how does the weather impact an individual’s decision to resort to violence? What happens between someone experiencing exceptionally hot temperatures and the drawing of a firearm isn’t really well understood, though theories about how heat impacts gun violence have surfaced in academic research. One theory suggests that heat raises stress levels, increasing the likelihood of aggression. Another posits that warmer days increase the number of interpersonal interactions, creating more opportunities for conflict. It’s possible, Jay said, that it’s a combination of both. 

What we do know is that summers are getting hotter: we’re experiencing record-breaking heat in summer that’s worse than years before. 2023 has already broken records for the most excessive heat warnings and July was the hottest month ever recorded on Earth. These more frequent days of moderate to extreme heat aren’t the main cause for gun violence, but having more hot days at higher temperatures contributes to its rise. 

How inequity creates heat islands and adds to gun violence

This is not just about understanding the weather: it’s about how heat exacerbates existing social and environmental disparities. Jay said that daily heat puts further stress on Black and brown communities that are disproportionately impacted by climate change and gun violence. Many of these communities reside in urban heat islands—cities and neighborhoods that trap heat because buildings and dark asphalt roads are reflecting heat and have too little foliage and green space to absorb it. 

“The motivation [of the study] was… to understand heat exposure as one of the factors in the physical environment that influence the social environment in ways that produce these huge inequities and gun violence exposure,” he added. 

But there are ways to combat this rise. Climate mitigation strategies that lower temperatures in cities can potentially help reduce shootings, the study states. A growing number of researchers and advocates are championing community revitalization efforts, often referred to as “cleaning and greening,” as a way to reduce violence and heat, all the while reinvesting in Black and brown neighborhoods, enhancing green spaces and overall quality of life.

“There’s a whole range of things that cities are doing and thinking about to reduce heat,” said Daniel Webster, Director of the Johns Hopkins University Center for Gun Violence Solutions in Baltimore. Webster adds that cities may not know that their heat reduction efforts may also be supporting the reduction of gun violence, but there is data that “certainly support[s] that [their efforts do],” he said.

The City of Brotherly Love: Fighting violence with greening

In Philadelphia, the Urban Health Lab at the University of Pennsylvania is spearheading the “cleaning and greening” approach. Their Deeply Rooted project, a collaborative between researchers, the Pennsylvania Horticultural Society, and mostly-Black and brown communities in west and southwest Philly, cleans and transforms vacant lots into lush green spaces.

A few years ago, Urban Health Lab researchers randomly sampled and selected 541 vacant lots across the city to monitor for three years and assigned a service to them: no treatment, cleaning, or cleaning and greening treatment. They also randomly selected 445 people in the community to survey about the changes experienced over 38 months. 

The results were striking: areas around vacant lots receiving the full “cleaning and greening” treatment witnessed up to a 29% reduction in gun violence and a 28% decrease in nuisance calls. Beyond the numbers, community members surveyed reported feeling safer and more connected in their transformed neighborhoods.

“Those around the green spaces really felt that they could go out and enjoy their porch, their stoops, their neighbors, in a different way,” said Nicole Thomas, the director of the Urban Health Lab.

What’s more, the violence didn’t seem to shift to other areas. 

“We’ve had a sort of a nice decline [of gun violence] since the 80s, but [we] really are seeing an increase in recent years,” Michelle Kondo, a research scientist for the U.S. Forest Service and co-author on the study, said of the city. “So to see this evidence that [not only] crime overall, but gun violence in particular, reduced around and nearby the landcare, the cleaned and greened lots relative to what was happening at the controls, was a real significant finding.”

Kondo says that they also observed that vacant lots had more narcotics trade and stashed guns in their vicinity. Ethnographers involved in the study noted that cars carrying these guns or drugs were intentionally parked in front of vacant lots. 

So cleaning and greening these lots “disrupts those things,” she said. 

Another benefit for cities and taxpayers that Kondo saw coming out of this work was the return on investment: in the first year after remediation, there was a $333 return for every dollar spent on preventing firearm assaults by greening a vacant lot.

Series of before-and-after photos from a cleaned and greened site in Philadelphia (Source: PNAS study 2018)

This initiative didn’t record any reduction of heat, but Veronica Pear, social epidemiologist and assistant professor at the UC Davis Violence Prevention Research Program, says it’s a green solution that does contribute to the reduction of violence. 

“Cleaning and greening initiatives address some features of the built environment (like vacant and neglected lots) that can give rise to violence and they play a legitimate role in prevention,” Pear told the Amsterdam News.

Thomas said that making sure community leaders and members are involved in the decision-making, research, and implementation stages was crucial to their approach. A lifelong Philadelphia resident herself, she said that she understands the skepticism towards greening efforts in neighborhoods like hers. 

She recalls about 15 years ago when her mother and neighbors cut down trees in their neighborhood that were causing damage to their residential property. She later learned the trees planted were ill-fitted for the area and said that going out and talking to community members should be a crucial part of their approach.

The Urban Health Lab earmarked funds to maintain the vacant lots for a few more years and Thomas said that this year, they received two $3 million grants from Penn Medicine and the Children’s Hospital of Philadelphia. The group also has set their eyes on increasing tree canopy across west and southwest Philly.

“We have the goal of planting trees, greening vacant lives, supporting community projects, micro grants, and creating mini parks,” Thomas said.

They’ve had a track record of success, but the work of maintaining the vacant lots to reduce violence and increase safety have yet to be taken up by city agencies. Thomas hopes that more places around the country embrace this approach. 

“The science shows that having trees, cleaning and greening and stabilizing vacant lots and all sorts of community-building activities really go a long way to improve health,” she adds. “So we’re hoping that this will be a model that other health systems could use.”

In the meantime they are working on bolstering community participation in the maintenance and care of the spaces and trees.

“All of those pieces of green infrastructure are not amenities, they’re pieces of the basic infrastructure of any neighborhood,” Thomas said. “If anyone’s developing neighborhood plans or community plans… green spaces [should be] included in those plans.”

Cooling temps – and heads – in New York 

New York has a number of community programs aimed at mitigating the effects of climate change or gun violence, but rarely both. That said, some organizations are taking the approach of using green methods to get at some important community needs: youth training and economic opportunity.

NYC CoolRoofs, a program launched in 2009 through a collaboration between the NYC Department of Small Business Services, The HOPE Program, and the Mayor’s Office of Climate and Environmental Justice, is one of the enduring examples of these programs. Their approach addresses heat by painting rooftops with special white paint to reduce temperatures of buildings in the Bronx. This strategy of painting roofs with light colors allows them to reflect solar energy, rather than absorb it, creating a cooling effect for buildings and reducing energy bills. 

The average number of days per year above 90 degrees Fahrenheit (°F) could be as high as 69 days per year by the 2050s, approximately four times the average from 1981 to 2010. (Source: PlaNYC Report)

For young participants of the CoolRoofs program, most of whom are under 30 years old, it’s a paid opportunity to learn about the environment and get some foundational training that could open the door for work, including green jobs, said Ana Chapman, chief program officer for The HOPE Program, a nonprofit providing work training. Their green programs include NYC CoolRoofs, Sustainable South Bronx, and Intervine, a horticulture program that trains and pays participants to do green infrastructure and maintenance work around the city. Chapman envisions these programs as opportunities for young participants to be active contributors to transformative environmental changes within their communities.

“You go out on jobs, you’re doing the hands-on [work], you’re learning [about] the ‘why’ behind this work,” she says.

CoolRoofs trainees, who are recruited twice a year, will be out on rooftops in the Bronx painting until mid-October, when they complete the program and begin job searching. In 2021, The HOPE Program received funding for youth gun violence prevention work to support their job readiness programs. The organization has gone where it has been welcomed but hasn’t measured the temperature reduction impact of the roofs they’ve painted. 

“When you’re in the program, you’re not out on the street,” Chapman said. “And so on a hot Tuesday afternoon, perhaps you might have been hanging out and now because you’re in the program, maybe you’re removed from an incident that may happen.” 

In Brooklyn, gun violence prevention groups like Kings Against Violence Initiative (KAVI) in East Flatbush, have incorporated some cleaning up community spaces as part of their approach. “We recognize that [the] environment plays a huge role,” in preventing gun violence said Ramik Williams, co-executive director at KAVI. 

The youth development organization has recently cleaned a park and community garden in central Brooklyn, and Williams said that some of the teens have shared how the state of their neighborhoods make them feel.

Community garden clean-up at Marge Matthews Garden in Ocean Hill, Brooklyn. Courtesy of Kings Against Violence Initiative (KAVI).
NYC CoolRoofs participants painting a roof in the south Bronx. (Courtesy of The HOPE Program)
Intervine participants gardening in Soundview, Bronx. (Courtesy of The HOPE Program)

An Uphill Battle to Create Lasting Change

While these endeavors hold promise, there’s a significant obstacle in the way: funding. Those spearheading these organizations say that their work is possible primarily through grant funding. To ensure the enduring impact of “cleaning and greening” approaches, more public dollars need to be allocated to support these initiatives.

“Long-term funding for effective preventive efforts is key to their enduring impact,” Pear said.

Last year, New York City Council resolved to make June “Gun Violence Awareness Month,” as part of a slew of actions recommended by NYC Public Advocate’s Office. 

But gun violence prevention funding has to catch up to the staggering upward trend in gun-related deaths: Between 2019 and 2020, it has become the leading cause of death among children and teens, surpassing car accidents. Black Americans also experienced the largest increase in fatal homicides of any race or ethnicity. 

“There’s not as much research on gun violence in the health literature as there ought to be,” Jay  said. “Gun violence is one of the most under-studied under-resourced topics, for political reasons.”

Gun violence legislation in place since 1996 effectively prevented the Centers for Disease Control and Prevention (CDC) from funding research into gun violence prevention and gun control in the United States for more than two decades. The Dickey Amendment was a provision lobbied for by the National Rifle Association, and while there are federal efforts to fund gun violence prevention programs in states, the field of gun violence prevention research is far behind other causes of death and injury.

Jay hopes their study would help leapfrog research in this lane. “There’s no way we’ll be able to understand violence exclusively in terms of heat,” Jay said. “But I think that it’s unlikely that we’re going to find that heat is just this one factor that’s totally independent of all the rest.” 

What researchers and community organizations understand is that our environment and climate plays a role in exacerbating an already difficult problem, and that any important solution will have to take this into account. 

“Firearm violence is a complex, multifaceted problem that can only be addressed by complex, multifaceted solutions,” Pear said.

Funding towards these programs are a drop in the bucket compared to funds earmarked for other climate change mitigation or gun violence prevention initiatives, and cleaning and greening and planting trees “doesn’t address the root causes of climate change and violence,” Kondo said. “These are systemic, worldwide, nationwide structural issues that are contributing to these things.” 

But Kondo says that not doing this work – cleaning and greening vacant lots and planting trees and the like – have a downstream impact on real estate values, sanitation, safety, and criminal activity. “It’s a negative spiral,” she said. 

Producing a physically and mentally healthy and safe environment with green measures is also about bringing communities together and helping people feel connected and in control of their neighborhoods. According to Kondo, “It’s a building block and can contribute to civic engagement and, ultimately, democracy.”