第 1 段S1In line with longstanding initiatives to expand its green spaces, New York City is planting tens of thousands of trees each year.S2They provide shade, lower surface temperatures, absorb a surprising amount of airborne carbon, remove tiny pollutants, and provide wildlife habitat along with just plain beauty.
第 2 段S3Something could go wrong, though, according to a new study.S4Oaks and sweetgums, which currently account for a majority of the city's trees, produce huge amounts of a chemical substance called isoprene.S5Harmless by itself, isoprene interacts rapidly with polluting nitrogen oxides released by vehicles, buildings and industry to form ground-level ozone—a major factor in many breathing problems.
第 3 段S6The research, carried out by scientists at the Columbia Climate School and other institutions, found that if the city maintains past species patterns in new plantings, isoprene production in Manhattan in coming decades will go up by about 140%, and resulting summer ozone levels as much as 30%.S7“We're all for planting more trees. They bring so many good things,” said study coauthor Roisin Commane.S8“But if we're not careful, we could make air quality worse.”
第 4 段S9The Parks Department is not oblivious to the issue.S10A study carried out by some of its researchers several years ago concluded that city trees did release isoprene.S11“We didn't make a big deal of that,” said Novem Auyeung, a Parks Department senior scientist.S12She said trees should not be viewed as the enemy.S13“We could plant any trees we want to, if we just rethink our car-centric lifestyle,” she said.
第 5 段S14“We're not going to go cutting down any big old oaks,” and neither will the department completely stop planting new ones, said Auyeung.S15“You have to think about what you would lose if you do that.”S16Oaks are keystone species, she pointed out, providing food and habitat for native insects, birds and other animals.
Although trees provide shade and absorb carbon, some species release isoprene, which reacts with nitrogen oxides to form ozone. A study predicts that keeping past planting patterns could raise summer ozone levels. Therefore, the city should diversify its tree species and reduce vehicle emissions instead of simply stopping planting or cutting old oaks.
注意：文章没明说“多样化树种（diversify its tree species）”，这是我们根据文意做的推断，只代表一种合理的想法。你写出别的合理建议，同样可以。