of the GMO divide seem to agree that crops that create their
own insecticide (e.g., Bt corn) have lowered insecticide use. It
would have been shocking if they did not. That said, the use of
any insecticide, whether it is sprayed by the farmer or created
by a GM plant, leads to pest resistance, making the pesticide
less effective. Lately, the corn rootworm has become resistant
to the insecticide produced by Bt corn, such that farmers are
now having to spray insecticides again. If this continues, then
the reductions in insecticide use may be reversed.
But what about the pesticides in the plant itself? If the EPA
considers the Bt corn to be an insecticide (it does), it should
certainly take into account the Bt insecticide produced by the
plant in calculating total pesticide use. At the time of this writ-
ing it is unclear how total insecticide use trends would change
if the plant's own insecticide is accounted for. Although some
sources claim the Bt toxin is thousands of times more concen-
trated in GM plants than pesticides containing Bt (like Foray
48B) this is something EPA would take into account when
determining whether Bt crops are safe, so it is doubtful that Bt
products lead to increased exposure to pesticides.
There is a disagreement regarding GMO's effect on herbi-
cides. One line of research shows total herbicide use decreas-
ing because of GM crops, while another measures an increase.
So, do GM crops like Roundup Ready cotton lower total her-
bicide use? It is unclear. One thing known is that the toxicity
of Roundup is very low relative to the herbicides it replaced,
so even if herbicide use has risen, the total amount of harmful
substances applied to cropland—expressed in units called the
Environmental Impact Quotient (EIQ)—has probably fallen,
benefiting the environment and consumer safety.
Are GMOs Good for the Environment?
How can GMOs benefit the environment in ways other than
pesticide use? If GM crops are more productive, then farm-
ers can produce the same amount of food with fewer inputs,