Answer to speedy tree growth lies in air pollution, Auburn University study shows

As the scientific community worries about greenhouse gas emissions contributing to global warming, a new Auburn University study suggests the Southeastern U.S. absorbs more carbon than it produces. And, at least in the short term, air pollution may actually be helping to speed the growth of young, carbon-absorbing forests in the region.

“Our study actually showed that Southeast carbon uptake is much faster than other regions,” said Hanqin Tian, a professor at Auburn’s School of Forestry and Wildlife Sciences, and lead author of the study published in the journal Ecosystems. “This area has trees that are very young and the growth is very fast. So, they uptake more carbon from the atmosphere.”

While earlier studies have examined the effect of individual factors on carbon storage and climate change, Tian developed a computer model that takes into account multiple natural and manmade variables – such as land use, climate and pollution – over the past century.

The model suggests that moderate amounts of air pollution, in the form of carbon and nitrogen, had a fertilization effect on young forests. Many of these new trees appeared on abandoned agricultural land during the mid-20th century.

“In the short term, it could increase the carbon uptake,” Tian said. “But that’s not guaranteed for long.”

The Auburn study suggests the Southeast is approaching a “tipping point.” The region’s urban areas are growing. And, despite the temporary fertilization effects of atmospheric carbon and nitrogen, Tian said increasing levels of other pollutants, such as ground level ozone, threaten to do more harm than good to the environment in the long-term.

“The take-home message is we really need to do urban/land use planning and also air pollution control to help the Southern U.S. forests to become maybe a sustainable carbon sink,” Tian said.