Can Conservation and Assisted Migration Save Biodiversity?
The migration route of monarch butterflies spans southern Canada to Mexico, a distance of about 2,500 miles. In their journey across the North American continent, the monarchs must cross the broad waters of Lake Superior. In the middle of this arduous leg of the journey, the monarchs make a mysterious hard turn to the east before continuing south. We’re not sure why the monarchs do this. One theory suggests that thousands of years ago there may have been a mountain blocking their way.
The monarchs have weathered obstacles before, but any change in the habitat of this stalwart traveler is likely to have devastating effects. And now the monarch butterfly is officially listed on the IUCN Red List as endangered.
Ensuring the survival of threatened species has never seemed more urgent, but there is debate about how to proceed among some ecologists and conservationists. Some say efforts should be directed to reversing climate change so threatened species can naturally restore their diminished populations. Others think it’s time to intervene, to make sure species will survive.
An intervention may involve physically moving plants and animal species to an area where they are more likely to thrive, a process known as assisted migration. Insects and plants are particularly sensitive to the effects of climate change and may require some human assistance to adapt quickly. For example, since 2007, the San Mateo County Parks Foundation in California has been making a concerted effort to restore populations of the San Francisco Bay checkerspot butterfly. The butterflies and their larva are moved into the conservation area and monitored by trained volunteers.
For the monarchs, human intervention was needed to restore their unique winter habitat in northern Mexico.
Oyamel fir forests, which grow in mountainous terrain, have dense canopies that can retain heat from the ground and keep Monarchs warm. The trees also protect the butterflies from rain, wind and snow.
Mexico has created sanctuaries, such as the Monarch Butterfly Biosphere Reserve. In 2015, a devastating, illegal logging event destroyed part of the forest, and oyamel fir seedlings have been planted again to restore the monarch habitat.
Critics of assisted migration techniques cite past disasters, such as the invasive cane toad. The cane toad was brought to Queensland, Australia, as a control for agricultural pests, but with no natural predators on the island, it became a notorious ecological disaster. Critics argue that when a threatened species is moved to an area outside its original habitat, it becomes, in effect, an invasive species. But with the climate warming, many species may find themselves outside of their historical range.
Saving the Three-toothed Cinquefoil
Some scientists think moving plants from one location to another will increase genetic diversity among populations that may help them weather climate change.
One experiment taking place in Acadia National Park, Maine, involves a rose family plant called three-toothed cinquefoil (Sibbaldiopsis tridentata).
Modeling has shown that this low-growing plant with small white flowers may be particularly susceptible to temperature changes and may lose much of its original range as the climate warms. In particular, it may disappear from Mount Cadillac, one of the park’s treasures, and leave the summit susceptible to erosion.
Climate change biologist Chris Nadeau is studying the plant as part of the Sustainable Summits Project, a research program in association with Acadia’s scientific research partner, the Schoodic Institute.
Nadeau is measuring the performance of three-toothed cinquefoil taken from the summits of southern mountains in Massachusetts and New Hampshire and replanted in a controlled garden setting in Maine. Nadeau wants to see if plants from warmer climates have genes that will help their northern counterparts weather the warming conditions in Maine. The experiment is one of the largest and most rigorous of its kind, and it could provide valuable information about how increasing genetic diversity can help a species endure.
The process of relocating a species to create genetic diversity is called assisted gene flow. "What we’re doing is moving genotypes within the distribution of species," said Nadeau, "So we’re not extending the range of three-toothed cinquefoil, we’re just moving individuals from one location to another distribution."
Searching for the Best Response to Climate Change
Nadeau’s experiment is controlled to prevent potential disease and invasion from plants from other states, but one of the reasons Nadeau chose three-toothed cinquefoil was because it was already being used to restore vegetation on Cadillac’s summit. Therefore, Nadeau’s research poses a very practical question: can current restoration efforts continue to provide a benefit in a warming climate? "This is phase one of trying to understand how we can restore vegetation on the degraded mountain summits throughout New England and ensure that those restorations persist into the future," said Nadeau.
Nadeau’s project fits into a new framework that has been adopted by the National Park Service as a response to climate change.
The Resist-Accept-Direct (RAD) framework is a departure from an earlier directive, outlined by the park’s famous Leopold Report, written by Aldo Starker Leopold in 1963, that recommended that National Parks be restored to "vignettes of primitive America."
When faced with climate change-related challenges within the park, RAD is used to calculate a response. "Resisting" might involve the removal of a new invasive species, and "accepting" would mean no intervention. The Sustainable Summits Project would fall under the heading of "direct," where conservation efforts are calculated with a warming future in mind. But Nadeau believes that his project has implications beyond the parks: "We are expecting to learn a ton, not just about sustaining mountain summits, but climate change adaptation throughout the world."
For the monarchs, the effort to restore their destroyed habitat in Mexico seems to be a success, but the future of the trees, like the monarchs, is not secure. As warming progresses, oyamel firs, like the three-toothed cinquefoil, may be unable to weather the heat in a place where they were once common.
What conservationists and others do today—working together collectively, like the Monarchs’ migration—may help sensitive species find a more secure future.
*Mal Cole is a freelance science and nature writer based in Massachusetts.
Sources: Nadeau, Chris, interview by author, July 29, 2022.