these are careless overall impressions more than systematic observations. i think the region where i live (let's say mid-atlantic) is considerably lusher than it was, say, thirty years ago. the vegetation is thicker, with vines and suckers all over everything. it's greener, and of course the east coast has overall reforested in the last half century, and existing forest has matured, even though logging continues in relatively small doses.
the greening may well have something to do with warming, and the vibe is going from temperate to semi-tropical. but also, the way they farm out here is having perhaps underappreciated environmental effects. so the way operate around here is that they come early in the spring and spray round-up on everything with large combines, killing the spring green immediately. then a week or two later they seed soybeans or corn in rows and spray the fields with fertilizer. the seed must be round-up resistant. they return late in the fall and harvest, and that's the sum total of the interaction of farmer and field: it's all done with very big machines extremely quickly. i'm betting it's ten minutes or less per acre for the whole season.
i'm quite surrounded by intense ag at my little scholhouse is adams country, pa. i'm below many fields, and i think the runoff partly accounts for the incredible green fecundity all around me (also, this is a very wet area; every town named for a spring: york springs, boiling springs, mt holly springs, etc). but i also think that a number of species of plants around me have become herbicide resistant. it's been amazing trying to get rid of the poison ivy, which grows around here in a way that entirely covers whole barns or hundred-foot trees, or where you realize that what you thought were branches of that maple are gigantic ivy/oak vine/branches.
you can soak this viciously toxic vegetation pretty thoroughly in the stuff that home depot bills as 'poison ivy and brush killer,' and give it barely a pause. the crap is insanely hard to handle. i feel i have to kill it with herbicide before iattack it or else i'd need a head-to-toe hazmat suit. as it is, i've worked with coveralls and a mask at times. anyway, even to have a crack at it, i need to mix a triple-strength solution.
i think the same is true of the english ivy and the honeysuckle around here. i've never seen anything like the honeysuckle: there's an acre of just thick bowers of vines around my house. the whole county smells like honey. here's a pic.
at any rate, i think we are in an experiment with this manner of farming to see what happens when you drench whole counties in herbicide every year. and then what happens to ag and everything else if a hundred resistant weeds emerge.
on the other hand, i wouldn't say that all this stuff seems to be making this area any less alive, per se: my heavens it's a blooming buzzing confusion of birds bugs animals and no doubt everything else.