Trees and other plants often do a better—and cheaper—job of scrubbing pollution from the air than technological solutions, according to a study led by an Ohio State University engineer.
The researchers collected county-by-county data on vegetation and air pollution across the 48 contiguous states. They then estimated how plants impact the levels of several common pollutants: coarse and fine particulates, sulfur dioxide, and nitrogen dioxide.
They found that restoring trees, shrubs, grasses, and other vegetation across an entire county to the average greenery level of nearby counties could reduce pollution by an average of 27% through capturing the particulates and absorbing the gases.
For 75% of the counties they analyzed, they calculated that mitigating pollution by planting vegetation was cheaper than keeping it out of the air in the first place by installing such technological solutions as smokestack scrubbers.
They explained their findings in a study published last week in the journal Environmental Science & Technology.
"The fact is that traditionally, especially as engineers, we don't think about nature; we just focus on putting technology into everything," said Bhavik Bakshi, who led the research.
"And so, one key finding is that we need to start looking at nature and learning from it and respecting it. There are win-win opportunities if we do—opportunities that are potentially cheaper and better environmentally."
Bakshi is a professor of chemical and biomolecular engineering at Ohio State. He was quoted in a university news release.
Plants aren't always the best solution, and sometimes aren't even a feasible solution. Densely populated areas don't provide much opportunity for restorative planting, for example.
The study acknowledges the limitations of scrubbing by shrubbery. It treats nature and technology as complementary approaches rather than either/or solutions. "This suggests that even though vegetation cannot fully negate the impact of emissions at all times," says the abstract, "policies encouraging ecosystems as control measures in addition to technological solutions may promote large investments in ecological restoration and provide several societal benefits."
Bakshi said nature should always be part of the planning process in devising ways to fight air pollution.
"The thing that we are interested in is basically making sure that engineering contributes positively to sustainable development," he said. "And one big reason why engineering has not done that is because engineering has kept nature outside of its system boundary."