What Your Neighborhood is Missing: More Trees

Everyone wants to have it made in the shade, and new research suggests that shade can actually save lives. Normally, planting more trees is done with clean air in mind — trees transform atmospheric carbon dioxide into oxygen, a two-front attack on polluted air. But in a recent study published in the Lancet, a team of researchers concluded that efforts to plant more trees, specifically in urban centers, could save lives by offering vital reprieve from unbearable heat.

The research team from Barcelona's Institute for Global Health was specifically concerned with identifying the negative effects of urban heat islands and the role that trees can play in mitigating their harm.

According to the U.S. Environmental Protection Agency, urban heat islands appear "when cities replace natural land cover with dense concentrations of pavement, buildings, and other surfaces that absorb and retain heat. This effect increases energy costs (e.g., for air conditioning), air pollution levels, and heat-related illness and mortality.”

The research team found that planting more trees in the densely-packed urban centers where urban heat islands most often occur would result in tree canopies that could provide refuge from relentless summer heat.

"Our results showed the deleterious effects of [urban heat islands] on mortality,” the study reads, "and highlighted the health benefits of increasing tree coverage to cool urban environments, which would also result in more sustainable and climate-resilient cities.”

Urban green infrastructure offers twofold benefits

Okay, so shade from tree canopies can help to mitigate intense heatwaves. But even further, the research team found that expanding tree coverage to 30 percent could reduce urban temperatures altogether, cooling cities by an average of .40 degrees Celsius. That may seem slight, but it is important to remember that even slight spikes in intense heat can be just enough to reach the tipping point into heat-induced mortality.

"Overall, 6700 premature deaths could be attributable to the effects of [urban heat islands],” the research team found. "We also estimated that 2,644 premature deaths could be prevented by increasing city tree coverage to 30 percent, … corresponding to 84 percent of all summer deaths.”

Tree-planting is just the start to mitigate urban heat islands

Increasing tree coverage is not a panacea that addresses every adverse effect of climate change, and urban planners will have to take further action to ensure their cities don’t become archipelagos of urban heat islands. What’s more, the success of a movement to plant more trees in urban centers will vary from city to city, as some existing city centers have not been planned or developed in a way conducive to increasing green coverage.

So, planting more trees may not be a one-size-fits-all solution, but it is a great place to start. Given the European Environmental Agency declaration last year that climate change was the main threat to human life in the 21st century, any action that even slightly combats the disastrous effects of climate change is a valuable action.

"Reducing the health impacts of heat requires implementing a wide range of solutions, including effective heat health action plans, urban greening, appropriate building design and construction, and adjusting working times and conditions,” the EEA stated in a 2022 report.

The data shows that urban heat islands have been killing thousands of people each year. In the past, policymakers may have shrugged off tiny rises in summer heat as ineffectual. Maybe heat-induced deaths in urban centers didn’t register on government radars before, but it looks like legislators have finally begun to sweat the small stuff.

Image credits: Josh Wilburne and Nelson Ndongala via Unsplash