A Data-Driven Approach to Cooling a City
City governments face critical challenges as more and more people move into urban areas, including rising housing costs, traffic congestion and waste generation. For fast-growing cities, particularly those in warmer climates, there is growing awareness of another environmental issue that impacts public health: heat islands.
In large cities, the urban heat island effect results in annual average temperatures that can range from 1.8 to 5.4 degrees higher than the surrounding areas; at night, cities can be up to 22 degrees hotter. This happens because cities are landscapes of asphalt and have buildings of concrete and steel that stretch into the skies. These materials absorb heat, hold it during the day and release it when the sun goes down. Urban traffic congestion aggravates this problem as carbon dioxide emissions from vehicles trap heat.
Hotter temperatures have serious implications for public health. According to the Environmental Protection Agency, exposure to extreme heat can lead not only to heatstroke and dehydration but also to cardiovascular, respiratory and cerebrovascular disease. Prolonged periods of extreme heat now kill more people in the United States every year than all other weather-related events combined, according to the Centers for Disease Control and Prevention.
Growing rapidly in the Sun Belt, Dallas is warming faster than all but two large U.S. cities, Louisville and Phoenix, according to one study. Knowing they had to act to stave off a public health crisis, Dallas officials and environmental groups partnered with the Trust for Public Land (TPL), the Texas Tree Foundation (TTF) and several other organizations to develop Smart Growth for Dallas, an initiative to improve the city’s social, economic and environmental resilience.
Smart Growth for Dallas is intensely data-driven. In 2017, a report from TTF found that “greening strategies” to preserve and expand the tree canopy can provide as much as 15 degrees of cooling on hot summer days. TTF also found that tree planting and preservation are three and a half times as effective in lowering temperatures as “cool materials strategies” such as the use of paving and roofing materials that reflect light.
Data provided by TTF and TPL helped craft the five pillars of Dallas’ smart growth strategy.
