Monarch Butterfly Migration
03 Feb

A Monarch Butterfly’s Journey Through Climate Change

As children, butterflies represented the magic of fairies and long summer day adventures. Little one's dreamed of what colors wings they would have or flapped their arms and pretended to fly. The monarch butterfly established its reign over all the butterflies with its brilliant golden orange patterned wing. Also going by the name of common tiger, black veined brown, and wanderer, this majestic winged insect struggles to survive in a changing climate.

While the monarch butterfly may appear to have cousins in the butterfly family, these other similarly patterned butterflies are only lookalikes. Most people think the viceroy butterfly and the queen butterfly are monarchs, but on closer inspection, a few differences appear. An almost straight black line across the bottom segment of the viceroy’s wing separates these two butterflies from each other. Meanwhile, the queen butterfly has a bunch of standalone white spots in the wing pattern without the monarch’s characteristic black lines framing the white.

One unique aspect of monarchs is their ability to travel across a large geographic range and home in milkweed and Oyamel Fir Trees. With short lifespans but high reproductive rates, monarchs have the ability to adapt quickly as a species. And yet, the rapid climate change may be too quick.

Every fall, monarch butterflies travel 3,000 miles from the northern United States and Canada to their winter habitats in California and Mexico. However, in 2018, the Western Monarch Thanksgiving Count revealed an 86-percent drop in monarch butterflies wintering in California. Mexico also experienced a decline in their numbers as well. This does not bode well for the beautifully winged insects.

The reasons behind the steep decline in the number of monarch butterflies result from multiple problems stemming specifically from how humans are using the earth’s resources. Climate change alters the monarch butterfly’s weather dependent trigger for determining the best time to start the 3,000-mile migration, and the change in climate affects the monarch’s main food source of milkweed as well.

In the spring, monarch butterflies lay their eggs in milkweed plants to ensure that their larvae will have food upon hatching. In the summer, the migration begins. This 3,000-mile, 5-month long migration is grueling, and several generations of monarchs will pass before the trip is complete. And by fall, a “super generation” is born with the ability to survive nearly eight months rather than the more common lifespan of 5-7 weeks.

Without clear seasonal cues, the concern is that monarchs will continue to travel south and not return north to their regular habitat. The change in winter also means that old habitats will become inhospitable for monarchs. Warmer temperatures coupled with an increase of carbon dioxide prompt the milkweed to increase its natural production of cardenolide, a poisonous chemical. Although monarchs have a tolerance to this poison, high concentrations can still be fatal.

Meanwhile, in Mexico, the Oyamel Fir Trees, the main habitat for monarch butterflies, is disappearing due to deforestation. This means that there is less opportunity for the butterflies to safely winter in Mexico.

The climate change may also be causing a small, but consistent change in the butterfly species. Micah Freedman, a University of California Ph.D. student, conducted a study and measured the size of the thousands of monarch butterflies. The wingspan of monarch butterflies’ average sizes from 3.5 to 4.8 inches. But Freedman’s numbers included butterflies from the 1870s until 2017, and his data showed a 4.9 percent increase in wing size of the butterfly over the past century and a half. Freedman suspects that climate change and a longer migration route is giving larger monarchs an advantage over smaller winged monarchs.

While the monarchs may be genetically altering to adapt to the changing world, they cannot change size fast enough to wing their way to certain survival. As a society, we can help the monarchs by becoming involved with habitat protection and learning about the needs of monarchs in our area as well.

At Golden Arrow, we strive to protect the environment by using renewable resources for our products and having a production process that adds no waste to the environment. We believe in the future, and so we’re making decisions today to benefit the earth tomorrow.