Looking for answers...must be in all the wrong places

OK. I am by no great stretch of the imagination...a tree hugger. Whitetail has been giving me reasons to contemplate this whole global warming phenomenon. I keep reading lots of different information on the subject and I grow more and more confused all the time.
I would basically be described as a pragmatist. I like to find the solution that best fits a problem or solves it most expediently. Taking into account the solutions impact on the surroundings. Basically...I like to think things through. I'm and ENTP for Pete's sake.
So explain to me this...according to wikipedia, "On Earth, the major natural greenhouse gases are water vapor, which causes about 36–70% of the greenhouse effect (not including clouds); carbon dioxide (CO2), which causes 9–26%; methane (CH4), which causes 4–9%; and ozone, which causes 3–7%.[13][14]"
Wouldn't lowering the water vapor level in the atmosphere have the biggest bang? Sure seems like summers in Minnesota are much more humid now than they have ever been.
Next. I understand that the level of CO2 in the atmosphere has been raising steadily due to BOTH fossil fuel combustion AND deforestation. Why is it that, for the most part, tree huggers love the idea that we need to really cut the cars from buring gas. Why is the other side of the equation igored? In this problem, the number trees and forest land is shrinking...why don't we plant more trees? I see plenty of push to stop burning things...but why don't we plant more trees? Seems like it would be cheaper and easier to plant tons of new trees. Not to mention, they also help to absorb huge quantities of water vapor. And their cooling effect on civilization can not be denied. Plus, if you believe in chaos theory, this might even have a positive change on the weather.
Oh...and lastly...kill all the cows...looks like their toots also a problem....mmmmm fresh meat....aaaaarrrrrrgggggggggg.....