As a responsible shopper, I started wondering about the effects of genetically modified crops on the environment and whether GMO crops are sold in bird food, such as suet. Starting this year, some genetically modified food items sold for human consumption must be labeled as such, but not those marketed and sold for wildlife consumption.
“Roundup Ready” crops don’t manufacture their own glyphosate, but they’re genetically modified to withstand heavy applications of it. Like most pesticides, this weed killer has important uses, as land managers trying to eradicate invasive exotic weeds know. Rachel Carson didn’t argue that pesticides should never be used; she simply warned that it’s wisest to use them as a last resort, both because of potential toxicity issues for humans and wildlife and because pests (weeds, insects, etc.) build up resistance to pesticides far more quickly than other plants and animals, resulting in spiraling pesticide applications.
A McGill University study published in March in the journal Nature Ecology & Evolution found that heavy use of Roundup can trigger loss of biodiversity. Since the 1990s, when the farming industry adopted Roundup Ready crop seeds, use of the herbicide has boomed, and researchers found that glyphosate has leached into surrounding areas, including rivers and streams. Some plankton and algae adapt, but others don’t, reducing biodiversity at the base of the food chain for aquatic life. Aquatic insects such as dragonflies and mayflies are essential food for Purple Martins and swallows, nighthawks, whip-poor-wills, and other insectivorous birds. The distressing loss of 3 billion birds over recent decades coincides both with plummeting numbers of insects and spiders and with increasing pesticide use. Glyphosate also has been implicated in cancers in animals and humans.
Glyphosate kills insects indirectly by killing the plants they need. Another pesticide, Bacillus thuringiensis, or “Bt,” kills larval insects outright. The form called BtK appears to be safe for birds and mammals but kills caterpillars of all moths and butterflies, not just gypsy moths and other pests.
“Bt corn” has been genetically modified to produce the insecticidal proteins that occur naturally in Bt. Few beneficial insects feed on corn, but pollen from Bt-corn may be carried by wind onto milkweed, where it is known to kill monarch caterpillars. This issue is complicated, though. Bt is produced and stays within genetically modified plant tissues, so the vast majority of the pesticide stays in the cornfield, and farmers using Bt corn seldom need to apply more harmful insecticides to their crops. That’s a good thing.
Over 90 percent of all corn and soy grown in the United States is genetically modified, and Roundup Ready corn is virtually always exposed to heavy applications of glyphosate. Even if I weren’t concerned about that, corn is also susceptible to fungi that produce extremely dangerous aflatoxins. Corn sold for human, pet, and livestock consumption must be certified aflatoxin-free, but not that sold for wildlife consumption. And GMO labeling laws simply do not extend to wild bird food. I don’t know how to make an informed decision about most ingredients in suet cakes, but when it comes to corn, I just say no.