The orange and black throng of monarch butterflies flocking to their winter home in central Mexico was drastically reduced this year, the country’s National Commission of Natural Protected Areas announced on Wednesday. The reasons are two things we’ve heard too much about: extreme weather and farmlands planted with crops genetically modified to resist insecticides.
The area of forest the butterflies occupy fell to its lowest level in 20 years in 2012, according to an annual census conducted in December, to 2.94 acres from a high of 50 acres. The exact number of butterflies themselves cannot be counted, so the combined size of their colonies is used to determine their numbers. Any way you look at it, the numbers of monarchs have been dwindling: in 2011, 7.14 acres were measured.
All told, the wintering monarch population in Mexico has dropped by 59 percent, with last year’s decline the sixth in seven years.
One factor was the record-breaking heat and drought that plagued North America where the monarchs migrate to in late spring, as Chip Taylor, director of the conservation group Monarch Watch at the University of Kansas, tells the New York Times. The monarchs’ breeding cycle was disrupted by the hot weather, which dried up their eggs and affected their source of food, milkweed, by drying up its nectar. Weakened, the butterflies laid fewer eggs.
As it is, the use of soybeans and corn genetically modified to resist pesticides has wiped out the milkweed that once grew on millions of acres, between the rows of crops. Milkweed also once grew plentifully on U.S. grasslands, but these have also disappeared with 25 million new acres devoted to farmland since 2007.
So many fewer monarchs spells trouble for the food chain, for the birds who eat insects and for the predators who pray on birds. Parts of Mexico also count on tourists who flock to see the marvel of crowds of monarchs and the Mexican government has halted what had been widespread illegal logging in the monarchs’ winter home.
At a news conference in Zitácuaro, Mexico, Omar Vidal, head of the World Wildlife Fund’s Mexican operations, called on the U.S. and Canadian governments to also do more. Specifically, he called on the U.S. “to do much more,” by taking measures to replenish milkweed.
Scientists including monarch expert of Lincoln Brower of Sweet Briar College in Virginia say that Mexico can still increase its efforts, too. As he says to the Guardian, he saw small-scale logging going on in the monarchs’ winter home in February. Even small-scale reductions in the forests can affect the butterflies, as these mean lower temperatures and changes in humidity and direct sunlight. Tourism itself is a problem, as it is insufficiently controlled.
Certainly the drastic decline in the population of monarchs is a call for cross-border collaboration. As Brower emphasizes, “the numbers are getting so slow now that the migratory phenomenon of the monarch is becoming endangered.” Nothing less than the “glorious migration phenomenon” is at stake. We can do something — better regulating and safeguarding their forest habitat and putting controls on the use of genetically modified crops — and we need to, to keep the monarchs from disappearing altogether.
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Photo credit: farflungphotos