I tend to be a bit of an environmentalist (conservationist, really), but I have my limits. For instance, I’m not ready to conclude that global warming is a) a unique phenomenon separate from cyclical climate changes, and b) if it is, that human activity is mostly to blame for it. I have an open mind about global warming, and a big reason is my scientific education. I can’t look at the data (especially since it’s way out of my field of expertise) and confidently state points a and b. Mankind simply hasn’t been keeping climate records long enough for us to be certain that we’re ruining the planet. I should point out, though, that it’s better to be safe than sorry. There’s nothing wrong with being responsible stewards. Also, based on the evidence, I cannot conclusively dismiss not-a or not-b.
Now, having made my position clear (I hope), check this article out. Apparently, unbeknownst to scientists until recently, plants emit methane. In fact, they seem to emit quite a bit; current estimates range from 10 to 30 percent of the yearly global methane budget (between 62 and 236 Teragrams). For a breakdown of the budget (that doesn’t include the new findings, of course), go here. If I’ve calculated correctly, humans account for about 120 Tg CH4 per year. IOW, plants might be just as bad as humanity. Worse yet, planting trees to absorb nasty gases might be backfiring if trees and other plants are putting out that much methane. It’ll be very interesting to see if these results stand up to scrutiny, and if they do, how rabid "Hug a tree" lefties and "Earth first; we’ll stripmine the other planets later" righties will spin them.