Will genetically engineered crops help or harm the environment?
It depends on whom you ask.
Two of the most commonly used GE crops are corn engineered to resist
pests (Bt corn) and soybeans engineered to tolerate (Roundup ReadyTM soybeans). Proponents
of the crops say they allow farmers to apply significantly fewer
chemicals to control for weeds and pests. Fewer chemical applications
are certainly a beneficial environmental impact. More controversial
are the potentially negative impacts from these crops, usually grouped
into three main categories.
- Unintended Effects on the Food Chain.
Monarch butterflies made big news when a study showed that consuming
pollen from corn killed the Monarch caterpillar (the larval stage of the butterfly).
Bt corn is genetically engineered to produce a toxin that kills
the European corn borer. The pollen from the Bt corn drifts onto
nearby milkweed plants, a main food source for Monarch caterpillars,
and may kill the caterpillers. Other beneficial insects like the
green lacewing, a natural predator to the corn borer, may also
be affected by the genetically engineered pollen. Bird populations
might be affected by Bt too because fewer insects means less food
for the birds.
- Genetic Drift
Often referred to as pollution, genetic drift occurs when pollen from a genetically
engineered crop blows into fields where other related crops grow.
This could result in cross-pollination, which is of special concern
for organic farmers whose bottom line depends on being GE free.
(A GE variety of corn might cross-pollinate with a non-GE species.)
Farmers using GE seed are supposed to follow regulations that
include planting a buffer zone to prevent this pollen drift. But
some farmers don't provide a buffer zone. And pollen can drift
for miles on windy days.
- Resistant Insects
resistance is another concern with widespread
use of Bt crops. Insects may eventually become resistant to Bt*,
making the GE crops ineffective. And because Bt is also used by
organic farmers, Bt resistant insects would certainly become a
very challenging problem for the organic farmer. Farmers who use
GE crops are encouraged to plant 20% of their crop as non-Bt corn,
in order to prevent or slow the development of resistant insects.
*Bt can be applied directly to a field -- it does not have to be
geneticaly engineered into a plant to be effective.