Example: some GMO crops are more tolerant of compacted soil and weed competition, reducing the need to till the soil. Tilling the soil requires enormous amounts of diesel fuel, with obvious bad environmental implications. By reducing the use of diesel, the GMO crops help the environment.

Oh, you don't even have to accept global warming to see how using diesel to till the soil can cause harm. Particulate matter in the air is really harmful. (both the diesel exhaust and the soil getting churned up into the air) Disturbed soil runs off into streams, leading to dead zones. Competition for crude oil seems to support war, which has lots of bad effects on the environment.

So... eat GMO to save the environment.