Butterfly Immigration Reform? Make Way for Migrating Monarchs Between the U.S. and Mexico

This last year, tens of thousands of children across the Midwest watched IMAX film Flight of the Butterflies on the  miraculous migration of monarch butterflies from Canada and the U.S. to their winter habitat in the mountains of central Mexico. This migration typically gives cause for celebration among millions of schoolchildren and citizen scientists alike. But this week’s news from the butterfly’s overwintering grounds in Michoacan is being met with sorrow not just in St. Louis,  all across North America.

Mexican conservationists are reporting the total area occupied by monarch colonies overwintering in Mexico this January is only .67 hectares, roughly a tenth of the average roosting area recorded from 1994 to 2014. This strongly suggests that the number of monarchs arriving in Mexico from the U.S. and Canada may be lowest in the butterfly’s refuges since reliable counts began to be taken in the early 1990s.

Have destructive and ultimately counter-productive weed management practices in America’s croplands arrested one of the greatest natural migrations on the face of this planet?

That’s what over one hundred thousand Americans may ask this week as the sad news from Michoacan hits them. At least a quarter of a million schoolchildren, college students, adult naturalists and elderly volunteers are annually engaged in counting monarch caterpillars on milkweeds, and tagging adult butterflies as they move southward. Record low numbers of monarchs cannot be blamed on a lack of dedicated observers.

At least for the last decade, the low numbers appear to be correlated with the increasing use of deadly pesticides and herbicides. Specifically, scientists are most concerned about the excessive and untargeted use of glyphosate weed-killers.

In corn and soy fields throughout America’s heartland, such herbicides are sprayed in ways that eliminate milkweeds that would otherwise serve as host plants for monarchs, other butterflies and many additional beneficial insects. The best scientific estimates suggest a 58% decline in milkweeds and an 81 % decline in monarchs from 1999 to 2010 in farmscapes across Midwestern states.  Since then, a number of factors have combined to lower numbers even further. However, the bulk of milkweed habitat lost on farms may be due to the excessive spraying associated with the adoption of herbicide-tolerant crops on more than 100 million acres of croplands.

And yet, the losses of monarch populations and scarcity of some native milkweeds are not the only collateral damage done by the poorly targeted and under-regulated spraying of herbicides. The excessive use of glyphosate herbicides has led to the emergence and spread of at least a dozen superweeds in croplands. The virulence of these superweeds—none of them milkweeds– now costs as much as five to seven times per acre to control as they did a decade ago.

Farmers are losing their battle with these superweeds, despite increasing out-of-pocket costs and time expended in the field trying to control them.  And so, tragic damage is not merely being done to pollinators and their nectar plants, but to the livelihoods of farmers themselves.

Rather than wishing to assign blame for this impending disaster, I wish to see solutions. I am hopeful that farmers and roadside maintenance workers, wildlife habitat restorationists and and weed scientists will collaborate on solutions-based strategies to avert any further damage to wildlife and to farm viability.

According to the Farm Bureau, half of all American farmers are already voluntarily engaged in efforts to protect or restore wildlife habitat on their properties. Why not extend their efforts to establish herbicide-free refuges for much-needed pollinators such as butterflies and bees in wild uncultivated margins of the 400 million acres of privately-owned, food-producing farmscapes in the U.S.?

We need to support farmer-to-farmer training in integrated weed management strategies effective in controlling superweeds while retaining milkweeds for monarchs. Farmers should not be accused of being at the root of this problem, for many have both the knowledge and will to help forge lasting solutions.

Why not also ramp up the funding of public-private partnerships to protect and restore populations of the many kinds of milkweeds found on the 10 million acres of highway roadsides in the U.S.?

We need a collective effort to keep migratory monarch butterflies from the brink of extinction. In recent national surveys, Americans have claimed their willingness to voluntarily pay for safeguarding milkweed corridors so that the flight of these pollinators may continue among Canada, the U.S. and Mexico.

It’s time to put our money where our mouths and hearts are. Got milkweed? Then keep them safe enough to assure that our grandchildren may one day see millions of overwintering monarchs, and revel at this wonder of creation.


Gary Paul Nabhan is an orchardkeeper, a pollinator habitat restorationist, and an Ecumenical Franciscan brother. For further information, see www.makewayformonarchs.org.

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