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There are practical challenges to running a controlled experiment to test the effects of plants on local air pollution levels. Barbara Maher, an environmental researcher at the University of Lancaster in the UK, should know—for a study she’s running at four primary schools set along busy streets in nearby Manchester, for example, she and her colleagues had to rent expensive air quality monitoring equipment. They also had to get administrators at the four schools on board, which meant waiting until school let out for summer to install the plants, even though the timing was far from ideal for collecting data. At the same time the plants went in the ground last year, the volume of traffic dropped precipitously due to the summer holiday, she says.
For Maher, though, these challenges were worth taking on because she sees the plant installations—which she calls tredges, a combination of ...
