Scientist, Author, Educator, Tree Canopy Biologist

Monarch butterflies in peril

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When we try to pick out anything by itself, we find it hitched to everything else in the Universe. — John Muir

Nature's Secrets by CanopyMegYou don’t have to be a scientist to know and love the monarch butterfly. That iconic, fluttering orange-and-black creature represents a harbinger of summer, of happiness, and of beauty.

Not only does it grace our gardens and roadsides, but it may also be the only butterfly whose identification is learned, remembered, and beloved by almost every American school child. Many of us can fondly recall watching a monarch caterpillar consume milkweed leaves in a school classroom, and magically transform from chrysalis to adult butterfly. Even the busiest venture capitalist can probably recognize a monarch butterfly if it flutters by a high-rise office window upon occasion.

Over the last two decades, the monarch population has declined by more than 90 percent, from 1 billion in the 1990s to less than 35 million last year. For the first time ever, the U.S. Fish and Wildlife Service will conduct a one-year status review on the monarch, as a preliminary step to placing it on the endangered species list.

How can such an icon of American nature be decimated in only two decades?

The monarch’s downfall seems inextricably linked to American agricultural practices in the Midwest, where herbicide use associated with genetically engineered crops has destroyed milkweed, the host food plant for butterfly caterpillars.

With an enormous increase in the use of the herbicide Roundup (part of the “recipe” for successfully growing genetically modified corn and soybeans), approximately 165 million acres of habitat for milkweeds have been destroyed, including the edges of fields and adjacent meadows.

In addition to this chemical genocide, threats of global climate change, drought, heat waves, urban sprawl and logging in their Mexican wintering grounds have sent monarch populations plummeting.

One of nature’s most incredible miracles is the migration of monarch butterflies approximately 3,500 miles from the forests of Canada and the United States to central Mexico. How can their fragile wings combat winds, thunderstorms, cold and drought to winter in the subtropics?

An extraordinary multigenerational migration from Canada and the northern United States to central Mexico brings these delicate fliers into forests to roost during the winter months. One of the most breath-taking experiences of my lifetime was observing millions of mariposas (Spanish for butterflies) roosting in their Mexican forest canopies.

As we rode donkeys into the towering stands of oyamel trees, tiny specks of orange appeared overhead. Further up the track, butterflies swarmed closer, until we reached a clearing where literally millions clung to low branches. With their wings folded, the monarchs camouflaged in the evergreen canopies, resembling brown foliage. But when they fluttered, brilliant orange hues revealed the magic of this special place. The sensation was overwhelming.

As a biologist, I will never forget the privilege of observing these mariposas, and still ponder the miracle of their epic journey from Canada all the way to the tree canopies of Mexico.

No one truly understands the complex miracle of monarch butterfly life cycles, or the factors which determine annual population fluctuations. In August, as daylight hours diminish in the temperate zones, the butterflies stop reproducing and fly south to one evergreen forest region in central Mexico. During March, they fly north, lay their eggs on milkweed plants, and die. Not every monarch migrates as far as Michoac√°n, Mexico, but different populations move gradually north, with every third or fourth generation culminating in the Mexican migration.

If the monarch is put on the endangered species list, it becomes subject to legal oversight; it is likely that schoolchildren will no longer be allowed to rear a monarch caterpillar in captivity and watch the wonder of its emergence from a chrysalis to a gorgeous butterfly.

And if the monarch butterfly achieves endangered species status, it is a true admission that our American “technology” is no longer a good steward of our environment.

Like butterflies, humans require a healthy environment in which to live. Maybe the monarch is a canary in the coal mine for all of us, as we contemplate a world of herbicides killing milkweeds and in turn destroying monarchs, and ultimately impacting a complex web of life that links directly to humans.

Do we choose a world where our children can’t watch a monarch caterpillar turn into a butterfly in a jar in their school classroom?

Meg Lowman, a longtime Sarasota-based scientist and educator, is chief of science and sustainability at the California Academy of Sciences.

Originally posted in the Sarasota Herald-Tribune.

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