In a Hotter Climate, These Trees Could Make Air Pollution Worse

Poplars in southern New Zealand.

Poplars in southern New Zealand. Bernard Spragg via Flickr

As temperatures rise, warmer weather will spur some trees to release a chemical known to worsen air quality, a new study finds.

In hot weather, trees such as oaks and poplars produce isoprene, a compound that helps plants cope with heat stress. In cities, isoprene reacts with car exhaust to form ozone, a pollutant that, at ground level, can cause lung damage.

Until now, it was unclear if climate change would cause trees to generate more isoprene or less. In warmer weather, isoprene production speeds up, but at higher levels of CO2, it slows down. To gauge the potential impact of climate change, scientists at Michigan State University exposed young poplars to both high heat and high levels of CO2.

Heat was the clear winner. At 95 degrees F (35 degrees C), CO2 does almost nothing to dampen isoprene production, scientists found. At that temperature, “isoprene is pouring out like crazy,” lead author Abira Sahux said in a statement. “With that, we can say the temperature effect trumps the CO2 effect.”

The findings, published in the Proceedings of the National Academy of Sciences, will help scientists predict how much isoprene trees could produce in the future and the potential impact on air pollution.


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