Saturday, February 1, 2014

Monarch Decline

Male Monarch- Patrick Coin
Many of the volunteers at the Bill Roston Native Butterfly House have been noticing decreasing numbers of monarch butterflies moving through our area each year.  We now have solid statistics to back that impression, as reported by the News-Leader.

Monarchs migrating to Mexico are impossible to count as they clump together for warmth in the forests outside Mexico City.  They are measured in their dense collections by the number of acres they pack into.  This year the butterflies cover only 1.65 acres (0.67 hectares) in the pine and fir forests west of Mexico City, compared to 2.93 acres (1.19 hectares) last year. and 44.5 acres at their recorded peak in 1995.  Let me repeat: 44.5 acres down to 1.65 acres!

Monarch Migration in Mexico- Wikimedia
The factors which threaten the monarch migration are well known.  In the words of  Lincoln Brower,  leading entomologist at Sweet Briar College in Virginia, "The main culprit is now GMO herbicide-resistant corn and soybean crops and herbicides” in the U.S., which “leads to the wholesale killing of the monarch’s principal food plant, common milkweed.”  Add to this the expanding farm land acreage with the rising demand for corn related to ethanol and the ability to use practically every inch of farmland and you have the perfect storm destroying the milkweed plants (notice the "weed") they require to reproduce.

Monarch Butterfly Migration-
We recently took a road trip through Iowa, Minnesota, Wisconsin and Illinois.  The most striking impression was the ability to see for miles without obstructing growth in ditches, drainages and fence lines.  What the herbicides didn't kill along the edges, the DOT mowing finished off.  Not a standing weed left for miles on end.

There is certainly more to the story.  There has been logging the forest refuges they use in Mexico, reducing their winter opportunities.  Severe weather and drought in the US has also been a factor.

The monarch isn't headed toward extinction as they can survive in southern climes.  However, there is a strong likelyhood that the dramatic migration that we celebrate is likely to end.  The miraculous multi-generational trip where the great grandchildren find their way back from the northern US to the same area in Mexico, never having been there, is one of the greatest unexplained mysteries of nature.

We continue to urge people to plant milkweed to expand their migratory food resources, even if we eventually fail to save their centuries of instinctive migration.  If nothing else, it helps remind more people of what we can lose if we don't take better care of the planet.

There is a lot more detail in the Washington Post Interview.

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