Researchers Discover How Exhaust Turns Tree Friends Into Clean Air Enemies

It's hard to imagine ever shaking the idea of trees being a signifier for clean, clear air. We all know that trees act together as a big air purifier, creating free oxygen from carbon dioxide, lowering air temperatures, scrubbing out particulate matter (soot, dust, assorted bad things), and absorbing pollutants like carbon monoxide, sulfur dioxide, and nitrogen dioxide. Fuck yeah, trees.

Of course, it's not as easy as that. Trees (and all plants) don't just "disappear" carbon--eventually, trees die and decompose or they're burned, releasing that carbon back into the atmosphere. Trees just play a role in a larger cycle, one the reader might remember from middle school biology. Anthropocentrism wires us to think of trees as doing the bidding of humans, as if they're highly convienient life-support machines and not life doing its own thing that happens to help along other life. Like us.

That anthropocentrism is part of what makes things like a new study in the Proceedings of the National Academy of Sciences interesting, just for frustrating the idea of stuff in nature serving us out of some sort of cosmic altruism. The main finding of the paper, which comes courtesy of a team at the University of North Carolina, is that trees are a partner in smog production. Yep. Good ol' trees working for the dark side. But the dark side in nature is usually just life acting in its own interests.

The idea of trees-as-air pollution conspirators first came up in 2004, when it was revealed that isoprene, a molecule trees use as a leaf protectant, contributes to particulate matter in the air. That particulate matter does all kinds of bad things, not only for the environment at large, but for human health, contributing to problems like lung cancer and asthma.

The UNC paper outlines the mechanism by which the isoprene is reborn as particulates and--well, well--it traces back to human activity. Isoprene is mostly benign in its intended form, but, once out in the world of people, it reacts with man-made nitrogen oxide, a byproduct of the fossil fuels we all know and love.

“The work presents a dramatic new wrinkle in the arguments for reducing man-made pollutants worldwide,” says study author Jason Surratt. “Isoprene evolved to protect trees and plants, but because of the presence of nitrogen oxides, it is involved in producing this negative effect on health and the environment. We observe nature’s quirks, but we must always consider that our actions do have repercussions.”

One imagines that there exists somewhere in the United States House of Representatives a legislator or two happy to suggest cutting down trees as a solution. In fact, it'd barely be a notable break from the records of at least a few right-wing members of that chamber's so-called Committee on Science. But, no, the actual answer remains the same: cutting back on all of the man-made stuff reacting with isoprene and letting our tree friends get back to doing their damn job.

Reach this writer at michaelb@motherboard.tv.