MUCH OF Detroit is in ruins. The city spreads over 139 square miles, but about 20 square miles of that—an area just under the size of Manhattan—is vacant. Home in 1950 to more than 1.8 million people, today Detroit has less than half that many residents. There are tens of thousands of abandoned homes and buildings that are crumbling and decaying in the metropolis, and the city is demolishing these structures because they can be, among other things, good hideaways for people with drug addiction and places to dump the bodies of murder victims. Since 2014, teams have razed more than 18,000 buildings, with thousands of demolitions still to come.
But, as the buildings and their concomitant problems begin to fade away, a different menace is filling the lots left behind. Plants and weeds grow with abandon in the newly exposed soils, and, during their growing seasons, those plants release their pollen loads into the air and into Detroiters’ airways. This newly sprouted “urban prairie” can spark human health effects that range from mild irritation to severe asthma attacks.
“What’s happening is, for better or for worse, a lot of Detroit is becoming reforested,” says Daniel Katz, a plant ecologist at ?the University of Michigan School of Public Health. “And so, we have these vacant lots, and first there’s ragweed in them, but then other grasses come in and we get this kind of grassland habitat.”