No, the harms are environmental. Spraying weed killers (ie glyphosate) uses much less carbon than the mechanical methods. Tractors pulling something through the soil need a lot of fuel. A sprayer running over the same field spraying a gallon of glyphosate uses much less fuel. If you have any concern about global warming you should demand that only GMO crops be grown.

Note that I work for John Deere. We sell to farmers who are both for and against GMO so I'm not supposed to have a bias, but I still need to make this connection clear.