I am the only one who worries about stuff like this. I found a site where if you drive a yuppy SUV you can calculate how much more carbon dioxide green house gas you are producing compared to economy car--and then for a small price you can pay to have someone else plant enough trees to absorb that carbon dioxide. Its a carbon credit exchange. Therefore you get a bumper sticker saying : "I drive neutral !" Meaning no more green house gas than the average car. I figure about 600 gallons of gas a year for a pickup, this gas weighs about 3600 pounds, which when combined with oxygen produces about 8000 pounds of carbon dioxide. So...how much grass does it take, in square feet to absorb 8000 pounds of CO2. And how much does it take to absorb the just the difference between a pickup and a sedan which burns maybe 500 gallons of gas. How much grass to absorb the products of burning 100 gallons of gasoline? Maybe we can get paid to plant more grass.