Stories

The great monarch migration

A unique phenomenon under threat

Date: March 16, 2021
Author: Liz Watt

The annual migration of the Eastern monarch butterfly is one of the most impressive there is. Flying up to 2,500 miles from the US and Canada where they breed, all the way down to the forests in central Mexico where they hibernate, the monarch’s migratory pattern is the most highly evolved of any known species of their kind.

A monarch lands on a cluster of milkweed in the Northern Great Plains

But this grand migration is under threat. Climate change in both their winter hibernation grounds in Mexico and their summer breeding grounds in the US is having a considerable impact on the monarch migration. Deforestation in Mexican forests coupled with the conversion of grassland to farmland, the use of herbicides and pesticides, and a reduction of milkweed—the only plant in which the monarchs lay their eggs—across the butterfly’s flyways in the US, all come together to create the perfect storm of sorts for these tiny creatures.

Every year for the last 17 years, WWF-Mexico, in coordination with local communities and partners, assesses the population of monarchs in the Monarch Butterfly Biosphere Reserve (MBBR) in central Mexico. Since it would be impossible to count every individual butterfly to determine the population, the team instead measures the amount of forest area that is occupied by the monarchs, providing a scientifically robust indicator of their population status. The more forest occupied, the healthier the monarch population. But when that number continues to decrease year after year, that is cause for concern.

While we have seen the monarch populations rise and fall slightly year over year, the Eastern population of the North American monarch butterfly has been in a steady decline, on average, over the last two decades. Nearly 45 acres of forest in the monarch region in Mexico were covered with monarchs in the winter of 1995-96 and from that time, their populations fluctuated annually until 2003-04 when scientists recorded 27.5 acres of forest coverage. Since then, surveys have documented a continued downward average trend. According to the latest survey, the monarch’s forest presence in the winter season of 2020 occupied just over 5 acres—a 26% decrease from the previous year.

Meanwhile, a second report by WWF and partners reveals that the area of degraded forests in the core zone of the MBBR increased by four times the amount of the previous year: from 12.35 acres degraded in March 2019, to 50.06 acres degraded in 2020. According to the analysis, illegal logging was the main driver, accounting for 33.03 acres of deforestation.

With their breeding grounds in the US threatened by expansive land-use change, grassland plow-up, and climate change, and their hibernation grounds in Mexico threatened by deforestation and climate change, these monarchs need our help more than ever to save this unique migration phenomenon.

What is WWF doing?

We are working to turn this around. In collaboration with the Mexican government, local scientists, and with the support of donors and the participation of local communities, WWF works to promote good forest management and the wellbeing of local communities. This includes financing and providing technical assistance for sustainable projects such as tree nurseries, and mushroom production, education on the monarch butterfly migration, and tourism management.

WWF also works with many leading food companies in the US to not only reduce the impact that their crop production has on our environment, but to increase the biodiversity on their lands. And in an effort to reverse some of the damage that has been done to the Northern Great Plains over the years due to plow-up, WWF and Air Wick have partnered up to reseed 1 billion square feet of previously disturbed grasslands and wildflower habitats.

How can you help?

1 billion square feet is a huge amount of land and participating in this effort may seem daunting at first, but you can help, and all it takes is 1 square foot. One square foot of space in your backyard, on your front patio, or even on a patio or window box is all the room you need to offer pollinators like monarchs a helping hand. By joining the WWF and Air Wick partnership and planting native wildflowers in your own space, you are helping to rebuild habitat for not only monarchs, but other pollinators like bumble bees and hummingbirds in your area.

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