The City of Chicago is harnessing the potential of trees to reduce the impact of heatwaves by developing and implementing a strategic management plan for its ‘urban forest’.
In the early 1990s the City of Chicago commissioned a study to explore the effects of the city’s trees on its environment. Published in 1994, the Chicago Urban Forest Climate Project (CUFCP) report found that the city’s 4.1 million trees were delivering a wide range of quantifiable benefits, such as providing pollution removal valued at $1 million (1994 value), storing 855,000 tons of carbon, reducing surface rain-water run-off and reducing the need for air-conditioning by intercepting up to 90 per cent of solar energy. It found that the larger the tree, the greater the effect to reduce city temperatures.
In light of these findings, the city authorities decided to take a strategic approach to managing trees and maximise the functional role that trees can play in moderating the environment. A heatwave in 1995 had caused around 600 heat-related deaths, so finding ways in which trees could mitigate extreme temperatures was one of the city’s priorities.
An in-depth analysis of existing tree coverage showed that the areas with the lowest coverage suffered most during heatwaves. This enabled the city authorities to develop an evidence-based tree management system which treats the urban forest as a vital part of Chicago’s infrastructure. Rather than considering trees individually and only in terms of their aesthetic impact, the new system views trees as part of a city-wide system that can provide a range of functional and cost-effective environmental benefits.