We all know that trees can make streets look prettier. But in her new book, Urban Forests, Jill Jonnes explains how they make them safer as well. During heavy storms, trees are able to absorb a great deal of rainwater, decreasing the burden on sewer systems and preventing flooding. They also function as “natural air conditioners,” she writes, dispersing air moisture that keeps cities cooler during heat waves–and saving millions of dollars in energy costs. Studies show that more trees can even deter crime; they make neighborhoods feel more pleasant, which in turns makes residents (read: witnesses) more likely to spend time outdoors. It’s no wonder, then, that cities like New York, Denver and Sacramento have already invested heavily in urban planting. Now Jonnes argues that others should follow their lead. It’s time, she writes, “to get serious about creating the lushest tree canopies we can nurture.”
This appears in the October 03, 2016 issue of TIME.