Can Oak Trees Help Improve Air Quality?

Sunday - October 8 2023, 13:43 UTC - 1 year ago

Michigan State University has published a research article in the scientific journal Proceedings of the National Academy of Sciences that reveals that on a warming planet, plants like oaks and poplars will emit more of a compound called isoprene that exacerbates poor air quality. The team led by University Distinguished Professor Tom Sharkey is now working to better understand the biomolecular processes plants use to make isoprene and how these processes are affected by the environment, especially in the face of climate change. The main goal is to understand how the increasing carbon dioxide and temperatures counteract isoprene production.

It’s a simple question that sounds a little like a modest proposal. "Should we cut down all the oak trees?" asked Tom Sharkey, a University Distinguished Professor in the Plant Resilience Institute at Michigan State University. Sharkey also works at the MSU Department of Energy Plant Research Laboratory and in the Department of Biochemistry and Molecular Biology. To be clear, Sharkey wasn’t sincerely suggesting that we should cut down all the oaks. Still, his question was an earnest one, prompted by his team’s latest research, which was recently published in the scientific journal Proceedings of the National Academy of Sciences.

The team discovered that, on a warming planet, plants like oaks and poplars will emit more of a compound that exacerbates poor air quality, contributing to problematic particulate matter and low-atmosphere ozone. The rub is that the same compound, called isoprene, can also improve the quality of clean air while making plants more resistant to stressors including insects and high temperatures. "Do we want plants to make more isoprene so they’re more resilient, or do we want them making less so it’s not making air pollution worse? What’s the right balance?" Sharkey asked. "Those are really the fundamental questions driving this work. The more we understand, the more effectively we can answer them." .

Sharkey has been studying isoprene and how plants produce it since the 1970s when he was a doctoral student at Michigan State. Isoprene from plants is the second-highest emitted hydrocarbon on Earth, only behind methane emissions from human activity. Yet most people have never heard of it, Sharkey said. "It’s been behind the scenes for a long time, but it’s incredibly important," Sharkey said.

It gained a little notoriety in the 1980s when then-president Ronald Reagan falsely claimed trees were producing more air pollution than automobiles. Yet there was a kernel of truth in that assertion. Isoprene interacts with nitrogen oxide compounds found in air pollution produced by coal-fired power plants and internal combustion engines in vehicles. These reactions create ozone, aerosols, and other byproducts that are unhealthy for both humans and plants. "There’s this interesting phenomenon where you have air moving across a city landscape, picking up nitrogen oxides, then moving over a forest to give you this toxic brew," Sharkey said. "The air quality downwind of a city is often worse than the air quality in the city itself." .

Now, with support from the National Science Foundation, Sharkey and his team are working to better understand the biomolecular processes plants use to make isoprene. The researchers are particularly interested in how those processes are affected by the environment, especially in the face of climate change. Prior to the team’s new publication, researchers understood that certain plants produce isoprene as they carry out photosynthesis. They also knew the changes that the planet was facing were having competing effects on isoprene production. That is, increasing carbon dioxide in the atmosphere drives the rate down while increasing temperatures accelerate the rate. One of the team’s main goals was to gain a better understanding of how these opposing forces interact.