Saturday, May 18, 2019

What Happened to the Monarchs?

Monarch butterflies are in crisis.

Flying over the Midwest, it is easy to see the impact of humans. The land is neatly tiled into monoculture farms, with hardly a wild spot in sight. Unseen is the chemical crusade that has happened over the same time period, making insects and weeds sparse on this land as well. All this has contributed to a phenomenally productive agriculture, making our food with almost factory-like consistency using a variety of high-tech machinery, chemicals, and plenty of CO2 emissions. But each of these assaults on nature has also multiplied the plight of (among many others) the Monarch butterfly, which eats weeds, is an insect, and migrates over astonishing distances in a multigenerational trek to communal wintering sites. While Eastern populations of Monarchs are in decline and in peril, the condition of the separate Western population, which circulates up the Sierra and back down the Pacific coast, is dire, headed towards extinction.
"... the Midwest lost more than 860 million milkweeds between 1999 and 2014, mostly in agricultural fields" -Entomology Today
Monarch butterflies have a curious method of migration. While birds live several years, and thus may commute several times over their lifespan, (for instance from Northern breeding grounds to Carribean or South American wintering sites), Monarch butterflies live only roughly a month. But they also migrate over long distances, either from Mexico up through the Eastern US and Midwest, or from Coastal California across Central California, to the Sierras, then North to Oregon and Washington, then back down in fall. Like birds, the Monarchs use these routes to move through optimal habitats as the Northern Hemisphere goes through its seasons. But the migration must encoded in their genes, not learned from experience or from others, since it takes several generations to make the trek, somewhat like the colonization space ships of science fiction, which would go through many generations to get to, say, Alpha Centauri.

Now a rare sight.

It also means that Monarchs rely on suitable environments (which is to say, the milkweed) every step of the way. And our technologies of weed, insect and physical habitat extermination are making enormous swathes of their routes uninhabitable, not to say lethal. The Western population is down from millions in the 1980's to 30,000 today. This is not sustainable, and likely to drop to zero unless big changes happen to render the landscape less lethal. Thankfully, there are many milkweed species, many of which can grow widely in the region, if allowed to.

But this is just a small example of the harm humans are doing to the natural world. We are a plague, and have initiated a new age in biology- the Anthropocene, complete with our own mass extinction event. While the process is well underway here in California, it is only beginning in regions like the Amazon and Africa, whose human populations are growing steadily and whose natural environments are being decimated and whose wildlife is declining, including being directly killed and eaten. Climate heating will kill off far more species, until we end up in a world of mega-cities separated by monoculture croplands and nature reserves that will be faint shadows of a vanished, and richer, world.