The Earth Journal feature in the U-B on March 14 says a cause of declining monarch butterfly populations wintering in Mexico is the use of glyphosate on genetically modified corn and soybeans in the U.S. to kill milkweed, the monarchs’ essential food.
This is a hugely misleading statement. Milkweed is called a “weed” for good reason.
Milkweed is so competitive that if it is left uncontrolled, then corn and soybeans cannot be grown at all. In the days before glyphosate herbicide and glyphosate-tolerant corn and soybean varieties, the methods available for controlling milkweed — namely, non-biodegradeable chemicals and excessive tillage of erodible soil — were environmentally harsh and left water and air polluted.
Growing food for humans requires war against milkweed.
You can wage the war by dirty methods, or by clean methods. Either way, there’s less food for the butterflies. Thus, the cause of declining monarch populations is not glyphosate and genetically modified plants, as the Earth Journal seems to imply. The cause of declining monarch populations is expanding human populations.
The federal mandate to use corn for ethanol and soybeans for biodiesel has encouraged farmers to plant more acres of those crops, well beyond what is absolutely necessary for human food production, causing, in turn, an increase in the area where milkweed is considered undesirable.
Thus, ironically, the national desire to “reduce the carbon footprint” is resulting in the death of butterflies.
By the way, since milkweed is toxic to livestock, there are some areas of the country where you would be subject to legal prosecution if you were to deliberately spread milkweed seeds, as Earth Journal is encouraging you to do.