Leslie Kaufman in the New York Times has a good article, A City Prepares for a Warm Long-Term Forecast, that reviews Chicago’s efforts to improve its ecological infrastructure. The article describes the city’s approach to climate change adaptation:
As a first step, the city wanted to model how global warming might play out locally. … the scientists said, Chicago would have summers like the Deep South, with as many as 72 days over 90 degrees before the end of the century. For most of the 20th century, the city averaged fewer than 15. By 2070, Chicago could expect 35 percent more precipitation in winter and spring, but 20 percent less in summer and fall. By then, the conditions would have changed enough to make the area’s plant hardiness zone akin to Birmingham, Ala. But what would that mean in real-life consequences?
A private risk assessment firm was hired, and the resulting report read like an urban disaster film minus Godzilla. The city could see heat-related deaths reaching 1,200 a year. The increasing occurrences of freezes and thaws (the root of potholes) would cause billions of dollars’ worth of deterioration to building facades, bridges and roads. Termites, never previously able to withstand Chicago’s winters, would start gorging on wooden frames. Armed with the forecasts, the city prioritized which adaptations would save the most money and would be the most feasible in the light of tight budgets and public skepticism.
… Much of Chicago’s adaptation work is about transforming paved spaces. “Cities are hard spaces that trap water and heat,” said Janet L. Attarian, a director of streetscapes at the city’s Department of Transportation. “Alleys and streets account for 25 percent of groundcover, and closer to 40 percent when parking lots are included.” The city’s 13,000 concrete alleyways were originally built without drainage and are a nightmare every time it rains. Storm water pours off the hard surfaces and routinely floods basements and renders low-lying roads and underpasses unusable.
To make matters worse, many of the pipes that handle storm overflow also handle raw sewage. After a very heavy rain, if overflow pipes become congested, sewage backs up into basements or is released with the rainwater into the Chicago River — … As the region warms, Chicago is expecting more frequent and extreme storms. In the last three years, the city has had two intense storms classified as 100-year events.
So the work planned for a six-point intersection on the South Side with flooding and other issues is a prototype. The sidewalk in front of the high school on Cermak Road has been widened to include planting areas that are lower than the street surface. This not only encourages more pedestrian traffic, but also provides shade and landscaping. These will be filled with drought-resistant plants like butterfly weed and spartina grasses that sponge up excess water and help filter pollutants like de-icing salts. In some places, unabsorbed water will seep into storage tanks beneath the streets so it can be used later for watering plants or in new decorative fountains in front of the high school. The bike lanes and parking spaces being added along the street are covered with permeable pavers, a weave of pavement that allows 80 percent of rainwater to filter through it to the ground below. Already 150 alleyways have been remade in this way.
… Awareness of climate change has filled Chicago city planners with deep concern for the trees. Not only are they beautiful, said Ms. Malec-McKenna, herself trained as a horticulturalist, but their shade also provides immediate relief to urban heat islands. Trees improve air quality by absorbing carbon dioxide, and their leaves can keep 20 percent of an average rain from hitting the pavement. Chicago spends over $10 million a year planting roughly 2,200 trees. From 1991 to 2008, the city added so many that officials estimate tree cover increased to 17.6 percent from 11 percent. The goal is to exceed 23 percent this decade.
The problem is that for trees to reach their expected lifespan — up to 90 years — they have to be able to endure hotter conditions. Chicago has already changed from one growing zone to another in the last 30 years, and it expects to change several times again by 2070. Knowing this, planners asked experts at the city’s botanical garden and Morton Arboretum to evaluate their planting list. They were told to remove six of the most common tree species. Off came the ash trees that account for 17 percent of Chicago tree cover, or more than any other tree. … So Chicago is turning to swamp white oaks and bald cypress. It is like the rest of adaptation strategy, Ms. Malec-McKenna explains: “A constant ongoing process to make sure we are as resilient as we can be in facing the future.”