Experts: Climate Change Threatens Monarch Butterfly Migration

The Monarch Butterfly and Pollinator Festival, which began Thursday at the Instituto Cultural de México, continued through Friday evening with a symposium on the relationship between the Monarch Butterfly migration and climate change. The festival will conclude Saturday at the Pearl with a parade, a butterfly release, and more.

Katharine Hayhoe, director of the Climate Science Center at Texas Tech University in Lubbock, joined Michoacán-based forester and researcher Cuauhtémoc Sáenz Romero, citizen scientist and conservation specialist Cathy Downs, and Texas Butterfly Ranch founder Monika Maeckle onstage for the discussion. Maeckle also is founder of the Monarch Butterfly and Pollinator Festival. The panel was moderated by Dan Goodgame, Vice-President for Executive Communications at Rackspace. 

Monarchs are under threat due to many different factors, primarily those created by humans. Pesticides like neonicotinoids, which are suspected as largely responsible for honeybee die-offs are also responsible for killing other insects like butterflies. Glyphosate, a compound found in Roundup, is a potent herbicide that can seriously hurt milkweed and other plants that Monarchs rely on as a food and breeding ground.

Beyond chemical threats, humans are destroying important habitats that Monarchs rely on during their long migration. As cities expand and many forests are reduced, locations for milkweed and other important plants decline as well.

Climate change is a “threat multiplier” for these risks, according to Hayhoe. It adds additional stresses that make each other problem more threatening for the butterflies.

Monarch Butterflies have an unusual and incredible life cycle of migration where they spend winter in the high altitude mountains of Michoacán, Mexico and then migrate through the “Texas Funnel” to reach all the way to southern Canada. No single butterfly makes the entire trip, so the migration is spread over five full generations. This indicates something particularly spectacular about the butterflies – their navigation is somehow genetic, rather than learned.

Monarch Butterfly tagging programs, primarily from “citizen scientists,” provide enough data to estimate the total amount of Monarchs that migrate each year. This year, while the butterflies have been slower to return than normal, their numbers are estimated at around 200 million, well below the 30 year average of 300 million, but well up from the all-time recorded low of 34 million.

The entire migratory population spends the winter in a single area, making them particularly sensitive to changes in that location.

The trees themselves are vulnerable, especially the Oyamel fir. According to Sáenz, climate change will make the trees much more susceptible to problems like parasitic insects such as pine beetles because of stress from higher temperatures. Based on Sáenz’s research, every part of the Monarch Butterfly Biosphere Reserve will become dangerous for the trees by the year 2090. Higher temperature also will affect the butterflies themselves.

“Where they overwinter, it’s not too cold nor warm,” Sáenz said. “They almost do not eat in Mexico. They almost hibernate, living off of their fat reserves. If it’s too warm, however, they will burn their lipids (fats) faster and not survive.”

Rising temperatures and increasing drought also affects ecosystems throughout North America that the Monarchs rely on as they migrate. Critical species like the milkweed plant, which they rely on as a breeding ground, and nectar-heavy wildflowers are going to undergo substantial population reductions as climate change sets in.

Those changes are all gradual, but climate change also increases the propensity of extreme weather events. An enormous storm in the usually dry winter season in the roosting site in Michoachán could decimate the butterflies all at once. Climate change, which causes more unseasonal storms and freezes, dramatically increases the risk.

Sáenz has proposed a somewhat radical solution to the dangers posed to the roosting forests of Michoachán. He wants to “move the forest.”

Planting new Oyamel seedlings in higher altitudes, which are likely to stay cooler for longer, may create a more resilient forest that the Monarchs can choose to roost in as the warmer forests die off. No one knows, however, if the genetic expertise that the Monarchs use to navigate back to their Mexican home after never visting before will allow them the flexibility to return to a new location.

“Can this system be changed? Who knows, but we must try to do what we can to ensure that there are healthy trees that the monarchs can return to, if they can,” Sáenz said.

San Antonio has been named the country’s first Monarch Butterfly Champion City for pledging all 24 of the National Wildlife Federation‘s recommendations for Monarch conservation, including things like adding milkweed to city properties and banning the use of neonicotinoid pesticides on city lands. However, all of those actions are based on local land-use practices, not on climate change.

San Antonio has been conspicuously silent on a unified Climate Action Plan so far. As other cities like Austin, Denver, and Boston have made commitments to both adapt to expected changes and also change their greenhouse gas emissions, San Antonio’s sustainability strategies have left the relationship between the city and the global atmosphere absent.

That could all change at the Nov. 1 Sustainability Summit, where the public has been invited to make suggestions to push the city towards the development of a full Climate Action Plan. Doug Melnick, the City’s Director of the Office of Sustainability, has said that a Climate Action Plan is either coming “this year or next year.”

Councilman Roberto Treviño (D1), who was in attendance at the symposium, told the Rivard Report that “scientists tell us that the built environment’s heat island effect can change migration patterns.

“We can design a better city for not just our quality of life, but also for our natural environment,” he added. “We can, for example, eliminate the amount of heat we absorb just by changing the color of our roofs.” Treviño’s proposed Under1Roof program would do just that.

For those who want to help the Monarchs on an individual level, planting useful varieties like milkweed in gardens can provide a food and breeding ground for the butterflies. It’s important, however, to ensure that seedlings purchased from nurseries don’t have pesticides or herbicides that are toxic to the Monarchs. For a list of vetted nurseries in San Antonio, Austin, and Dallas, gardeners can check the Monarch Watch website.

Monarchs are not in danger of extinction, since non-migratory parts of the species are based in California and parts of Mexico, but the climate change and environmental problems may threaten their migration route.

“What is the consequence of doing nothing?” someone in the audience asked Maeckle, during the question and answer session. Maeckle responded with humble passion.

“The species may survive, but besides the loss of pollinators in the ecosystem, we may lose a real marvel that we can witness every year,” she said. “I want my grandchildren to be able to experience this. Is it a vanity to want to see something this majestic and beautiful? I don’t know. But I think it’s important.”

Hayhoe put it in different terms. “If we continue on the path of our current fossil fuel use, we will see 30% of all species on the planet gone by the end of the century.

“Without a doubt, the butterflies can adapt if they have the time,” Hayhoe added. “The question is if they can change within the time that they have to because of climate change. Some ask, ‘Are we trying to interfere in nature?’ The answer is yes, but we are already interfering. Taking action to help may be the only way that the Monarch migration survives in the time they have been given.”