The number of monarch butterflies wintering in Mexico has plummeted in the last two years. Many factors are involved, but widespread use of glyphosate (an herbicide) is one cause that’s under human control.
The development of genetically modified plants that resist glyphosate is often sited as one of the causes of monarch butterfly decline. Because agricultural fields can now be liberally covered with the chemical, the little patches of milkweed that once thrived on on the edges of farm fields throughout the Midwest are now gone, taking the monarch caterpillar’s food source with them.
The Los Angeles Times reports that the Natural Resources Defense Council has filed a petition with the US Environmental Protection Agency asking that glyphosate not be spread on highway margins and utility rights of way to allow milkweed to grow there, as long as human safety isn’t compromised. It also asked that farmers establish glyphosate-free zones in their fields.
Read the entire article in The Los Angeles Times, here.
Photo: Monarch butterfly, Mark Musselman, USFWS
Depending on where you live, you may have noticed it in autumn. There were very few monarch butterflies around. It wasn’t unexpected. Numbers were low last winter in Mexico, and the weather over the summer didn’t favor the hatching of new monarchs.
World Wildlife Fund, Mexico’s Environment Department and the Natural Protected Areas Commission just announced that the numbers of monarch butterflies overwintering among the Transvolcanic mountains of central Mexico are the lowest since they started keeping records back in 1993. They measure the butterflies in the number of hectares that they cover in the park. This winter they covered 0.67 hectares. At their recorded high, in the winter of ’95-’96 they covered over 20 hectares.
Why, oh, why, do you ask? At one time the forest where the monarchs roost over the winter was being cut down, but that problem seems to have been solved. Climate change is in the mix. But the big problem, according to MonarchWatch, at the University of Kansas, is that herbicide tolerant (HT) crops have removed milkweed from a part of the country vital to the monarchs’ migration: the Midwest.
Read the report from MonarchWatch, here. It includes all the details on the HT crops theory.
Read the Associated Press news story in SF Gate, here.
Photo: by Mark Musselman, courtesy US Fish and Wildlife Service
The Washington Post reports that the monarch butterfly population wintering in Mexico has shown a drop in six of the last seven years. “…There are now only one-fifteenth as many butterflies as there were in 1997,” the article says.
Journey North reports that this year’s population is lowest since record-keeping began.
Drought and herbicides that have killed off milkweed, which the monarchs require as host plants — particularly in the Midwest, are thought to be the main contributors to the decline. While populations have rebounded after drops, the overall trend is down, down, down.
Read the Washington Post article here.
Read an Associated Press article here.
The Journey North Facebook page is here.
Photo: Monarch butterfly by Mark Musselman, used courtesy of the US Fish and Wildlife Department.