How Trees Can Assist in Cooling Our Warm Planet
With soaring temperatures impacting the East Coast, Midwest, and Southeast, the reliance on air-conditioning powered by a strained grid is a critical issue affecting millions of lives. The deadly consequences of recent heat-related blackouts in India serve as a stark reminder of the risks posed by climate change to American cities, which depend even more heavily on A/C than their Indian counterparts.
The problem is straightforward: extreme heat, like the current “heat bomb” affecting much of the US, forces people indoors, where air conditioning becomes essential for survival. The surge in electricity consumption that follows puts the grid at its greatest risk of failure.
Last year, the US power grid narrowly avoided a catastrophic collapse, managing to “quietly survive” one of its toughest summers. Scientists are warning that future summers may not be as forgiving, with projections showing that a heat-related blackout in Phoenix could result in half of the city requiring emergency room treatment and 13,000 fatalities. Leading experts had urged federal agencies to make emergency plans before a heat-induced power outage claims millions of American lives.
To prevent such a grim scenario, addressing the urban heat island effect (UHIE) is crucial. This deadly multiplier effect of climate change can be mitigated using technologies that are not solely reliant on the grid.
The UHIE intensifies summer temperatures, leading to deadly outcomes. New research underscores the significant impact of the UHIE and emphasizes the importance of reducing extreme heat risks.
The key lies in understanding why certain blocks within cities are more susceptible to heat-related deaths due to the UHIE. This helped shed light on the mystery of why fatalities during a heatwave in Portland were concentrated in specific neighborhoods as opposed to being evenly distributed.
Studies led by Portland State University Professor Vivek Shandas revealed significant temperature variations across neighborhoods in cities, with differences as high as 15°F. The distribution of heat-related fatalities clearly showed the life-saving impact of addressing these disparities.
Surprisingly, the main factor distinguishing the coolest from the hottest neighborhoods was the presence of trees and vegetation rather than the typical scapegoat of construction materials like concrete.
Urban tree canopies and green spaces serve as powerful tools in combating the UHIE and climate change. Unlike air conditioning, which can fail during peak usage times, vegetation’s cooling effects increase as temperatures rise. Trees and shrubs not only provide shade but also cool the environment through evapotranspiration.
Even small trees have a cooling impact equivalent to multiple air conditioners running for hours. Within a few years, this effect doubles, highlighting the value of planting trees and creating green spaces in urban areas.
By leveraging data from initiatives like CAPA, strategic interventions such as green walls, rooftop gardens, and increased tree plantations can significantly reduce heat-related risks in communities.
These solutions can be implemented promptly. As we face another scorching summer, the lessons learned should guide efforts to redesign our habitats, protect vulnerable residents, and demand action from local leaders.
Nadina Galle, PhD, an ecological engineer and 2024 National Geographic Explorer, is the author of “The Nature of Our Cities: Harnessing the Power of the Natural World to Survive a Changing Planet,” available on June 18, 2024.
