Most trees in NYC could worsen air quality, Columbia researchers say

We are barking up the wrong trees.

A new study finds that most of New York City’s 7 million trees are emitting “volatile compounds” that do more harm than good to our air quality — especially during scorching heat.

“We are all for planting more trees. They bring so many good things,” said study co-author Róisín Commane, an atmospheric chemist at Columbia University’s Lamont-Doherty Earth Observatory. “But if we are not careful, we can worsen the air quality.”

The trees in question include oaks and gum trees which produce high volumes of a chemical called isoprene – and they are rooted in the Big Apple more than any other species.

“There’s no reason to think that trees don’t play a role in what’s in the air,” said lead author Dandan Wei, of Columbia’s School of Climate Change. “We just didn’t have the tools before this to understand this particular aspect.”

When this compound interacts with nitrogen oxide pollution, which is emitted from cars and building exhausts, the result is a major driver of respiratory disease.

Asthma and chronic bronchitis were ranked as the most vulnerable conditions, according to the new report in Environmental Science & Technology.

And, if NYC continues its usual planting of such trees, Manhattan’s isoprene levels will rise about 140% with a 30% increase in ozone.

In the more leafy Queens neighborhood, both isoprene and ozone are expected to quadruple, the researchers note.

Oak trees, which already emit 800 times more isoprene than maples, emit in particularly high volume when the city reaches boiling temperatures even in the high 90s. They make up 37% of the city’s trees while gum trees make up 17%.

After analyzing satellite images combined with Parks Department data, the research team found that local trees played a role in creating ozone during hot days.

But they say it’s not empirically the trees to blame – but rather what their organic emissions are mixing into.

“If we were to sit down [nitrogen oxides] Significantly, the trees would not be a problem,” Wei said. “We don’t want to convey the idea that trees pollute the air. It’s the cars.”

Although the researchers note that the city is making some progress in reducing nitrogen oxides from emissions and man-made pollutants, it would take up to 80 years to see a real improvement.

“No quick fix appears imminent,” the news release said.