After creating a protocol that included netting a monarch and attaching a small sticker with an identification number and with the help of hundreds of volunteers, what the Urquharts discovered after four decades of research was mind-blowing, and rocked the world of natural history.
Monarch migration made headlines
The announcement was showcased in National Geographic magazine in August 1976. Urquhart himself wrote the article, which detailed how every year between August and early November monarch butterflies in the east migrate to the Sierra Madre Mountains of Mexico. The world read in disbelief. I still have that issue with Mexican naturalist Catalina Aguado on the cover surrounded by thousands of orange and black monarchs, dalliances no more.
It’s an astonishing story often taught in elementary schools today. You can ask a group of kids, “Does anyone know where monarchs go in winter?” And one or more will answer “To Mexico!” The epic odyssey of a half-gram butterfly (they weigh less than a postage stamp) has been retold often on PBS. Most grandly, it’s the subject of a 2012 documentary titled Flight of the Butterflies. The 3D IMAX film presents their long migration in all of its breathtaking glory, including scenes of thousands of monarchs clinging to the Mexican trees in winter.
Because of their panache, monarchs have perhaps been studied more than any other insect. There are two populations in North America. Our eastern population migrates from as far as southern Canada to Mexico every year. West of the Rockies, the population migrates to Southern California. Monarchs produce four generations a year, the ones that migrate south for the winter are the great-grand offspring of the monarchs that spent their winters there the year before.
Monarch data is still being collected. Locally, Great Smoky Mountains Institute at Tremont nets and tags monarchs annually in a program of shared community science that originated in 1998 with naturalist Wanda DeWaard.
This feel-good story has curdled over a remarkably short period of time. How do you conduct a census of an insect population? Quickly. Go outside and count all the swamp cicadas you can find. Impossible. Fortunately, because all living North American monarchs overwinter in only two locations, it is possible to get a rough estimate. And those numbers have been declining at more alarming rates with each passing year.
The Xerces Society tallies the western population in the forested groves of California, including Santa Cruz, Fremont, Pismon Beach and several places in Monterey, Riverside and Los Angeles counties.
In 1997 their estimate was 1.26 million monarchs. By 2008, that number had dropped to roughly 150,000. And by 2019, only 29,418 wintering monarchs were recorded, representing a drop of 98 percent in just 22 years. A similar decline in the eastern population has also been reported, with an overall decline of more than 80 percent.
Why such a dramatic decline?
A 2021 study by Michigan State University on the declines cited the same lethal cocktail we have been hearing about since the 1970s: habitat loss, climate change, pesticide and herbicide use. The steepest decline between 1994 and 2003 coincides with the widespread increase of herbicides that kill the plants the monarchs depend on, such as milkweed.
Widespread pesticide use kills insects and the orange and black dalliances are most certainly insects. While from 2004 to 2018, the breeding-season weather was nearly seven times more impactful than the other causes of decline. Has anyone noticed our fluctuating weather? With climate change the delicate butterfly is a lot like us. They like it hot but not too hot, dry but not too dry and wet but not too wet.
Why should we care? Monarchs are glamorous environmental indicators. They are also pollinators. If this can happen to a beloved species that has been carefully watched, what about the other 17,500 butterfly species on the planet? It is estimated that 90 percent of flowering plants will disappear with the loss of butterflies and other insects that pollinate them.
We simply do not have to ask, “For whom the bell tolls?” It tolls for we.