Threats to the Migratory Monarch

The garden of my home used to be covered in these glorious critters. They were drawn, year-round, to the temperate climate and flowering nectar plants meticulously cared for by my neighbor. And I lazily benefitted. It was not so uncommon to start my mornings with the sublime: sipping morning coffee amidst a mosaic of orange and black.

For all our collective fear and disgust of insects, the near-universal appeal of butterflies is curious. Around the world, butterflies are hailed as symbols of rebirth, change, and hope – taking on a spiritual dimension in a staggering number of cultures. Moving away from this beautiful garden marked a sudden shift to dreary and butterfly-less mornings. Guilt over my ungratefulness soon compounded. I was shocked to learn that, over the last 25 years, Monarch populations have fallen dramatically. Current estimates put the decline at 80% in eastern North America and 99.4% in western North America. If these trends continue, it won’t be long until we lose the Monarch for good.

At first their decline puzzled scientists, since it didn’t appear that human intervention could be the culprit. Strangely gregarious insects, Monarchs are not sensitive to noise or the presence of people like many other butterflies. In fact, as many city-dwellers can attest, they are perfectly able to thrive in urban environments.

Predation also seemed to be out. Monarchs are generally immune to being prey given their special relationship with a plant called milkweed. Breeding and feeding on the plant in the early stages of life allows the Monarch to store toxic sap in their outer tissues, rendering them quite poisonous. And also brightly-colored.

Nevertheless, our role in their dwindling numbers was soon made clear. “Summering” in central Mexico (like the sophisticate befitting their name) they are the only insect known to travel thousands of miles to overwinter in warmer climates. Along this remarkable migration, Monarchs depend on what are called “working lands,” the areas including cropland and pasture that make up more than 75% of the United States. But this once-vast prairie landscape has been transformed to make way for human agriculture. Instead of wildflowers and milkweed, more and more Monarchs are discovering corn and wheat.

While current trends suggest a serious risk for extinction, the rate of decline in western populations is particularly concerning. There are a whole suite of theories, but one that I think is quite compelling has to due with climate change. Researchers at the University of California, Davis speculated that Monarchs, and the plants they rely on, have responded differently to changing environmental signals. Rising temperatures have cued Monarchs to begin their migration prematurely, departing before what available milkweed has a chance to germinate. Without milkweed, Monarchs lose their clever protection strategy and the only plant on which they will breed.

Thanks to lobbying efforts by the Environmental Defense Fund and other conservation groups – a variety of organizations have signed on to help stop this decline. The pitch? Planting habitat for Monarchs and other wildlife species within some of the most sophisticated landscape operations (e.g. farming, hunting, golfing) produces commercial as well as environmental benefits – whether that’s flood mitigation or natural water purification. Target areas for this intervention focus along Monarchs’ existing migratory routes: along the I-35 corridor in America’s Midwest and California’s Central Valley.
And even small changes can make a big difference. On whatever piece of land you have access to (whether it’s a small pot on your porch or a plot in your backyard) plant milkweed and the nectaring plants that Monarchs need.

To the extent you can, try to keep chemicals out of your garden. And become a citizen scientist! There are many opportunities to become involved. Monarchs migrate in tight geographies and are easiest to count in these periods. The population numbers are then extrapolated to give scientists as accurate figures as possible. So participate in the citizen counts in the fall (around Thanksgiving), especially if you live on the west coast. You’ll be contributing to applied research all while witnessing one of nature’s most remarkable sights. Visit the Xerces Society for more fantastic information on Monarch conservation and how to become involved. This work, in tandem with small changes in commercial landscaping, is a key stopgap to saving these magnificent creatures.