Random Thoughts From Marybeth

Blame Game

Anyone who has even a passing interest in butterflies probably knows that monarchs migrate from their summer homes in the U.S. and Canada to winter in Mexico. In previous years, problems with illegal logging in Mexico have affected the butterflies by reducing the area in which they can nest. Now Mexico is blaming the U.S. and Canada for a reduction in their winter visitors.

Mexico's Environment Department said on Wednesday that 75 percent fewer monarch butterflies have appeared in 2004 compared with previous years.

It blamed cold weather and intensive farming -- including genetically modified crops -- in areas of the United States and Canada, where the butterflies spend the summer and reproduce.

Monarchs lay their eggs on milkweed. This is what the caterpillers eat. Adults drink nectar from a variety of plants, including many common garden flowers (coneflower, snapdragon, zinnia, azaleas, lilacs, and butterfly bush). The reason genetically modified crops are getting part of the blame is because a study done in 1999 indicated that the pollen from transgenic corn could blow onto milkweed and kill the monarch caterpillers. More extensive follow up studies showed that the risk to the butterflies from the corn pollen was negligible. (More here.)

I don't remember last summer being unusually cool so I searched for information to support/refute Mexico's claim that this was one of the causes of the reduction in monarchs. I found that the summer of 2004 was cooler than average for much of the northern hemisphere but not enough to set any records. (There have been much cooler summers over the last 20 to 30 years.) It also wasn't outside the range of survivability for the monarchs.

Mexico says the forests in which the butterflies winter are "healthy or in full recovery". Logging of the Oyamel firs may have been stopped, trees may have been replanted, but that doesn't mean the conditions are ideal. The trees need to be mature to provide a canopy to protect the butterflies from cold and wet weather. Just providing a place for them to roost isn't enough.

Changes in the monarch population aren't unusual (there was an 80% decline in the winter of 1999) and Mexico's statement seems to be a case of "shift the blame". I do hope they elaborate on who they think is responsible for making last summer cooler than normal. Whoever it is must be asleep at the controls...lately we've had temperatures in the 70s and below freezing in the same week. I want to lodge a complaint.