Flying across the eastern half of the country, mostly what you see looking down is ... trees.
Yeah but .. we didn't used to have much of an air quailty issue - when the wind stopped blowing - like we have now; nowadays, all the outlying suburbs around Dallas are populated, with man-planted, deciduous, fast-gowing trees like Maples et al; net result, if this article is true, additional emmissions into the atmosphere ...
The 'trees' that uses to inhabit the plains here in Tejas were much more protective of the water the would allow to 'evolve' from their leaves, not so with most of the varieties that are planted now ... the natural trees growing in this area have to be darned near desert varieties, given some of the droughts I've seen ...