North America’s rapidly declining population of monarch butterflies could have an important habitat in the Mountain West, according to experts. This comes as federal officials consider listing the recognizable insects under the Endangered Species Act.
Every spring, the orange-and black-winged butterflies flutter north from Mexico. The Rocky Mountains serve as a natural barrier between their two main migration routes.
Monarchs typically don’t frequent these high-elevation mountainous areas, but Denver Metropolitan State University biology professor Robert Hancock said that could change as the climate warms.
“A lot of animals are going to have [more] opportunities at higher altitudes than they used to,” Hancock said. “Maybe the monarch butterfly has a great opportunity waiting in the foothills on the Rocky Mountains.”
He said the monarch's main food and sole breeding grounds — the milkweed plant — would have to lead the way and expand in that habitat.
Milkweed is currently in decline, in part due to development and pesticide use, since it’s commonly found in prairies, fields and roadsides. Researchers believe that milkweed decline — and factors such as parasites — are causing monarch numbers to dwindle.
The U.S. Fish and Wildlife Service estimates the eastern migratory population has declined by about 80%, and the western one has decreased by more than 95% since the 1980s.
When populations like this decline, University of Wyoming zoologist Lusha Tronstad said research shows they “contract to the edge of their range.”
“So Wyoming might be really important to these butterflies,” she said. “One reason, we're at the edge of both the eastern and western [migration routes]. Another reason, we don't have the parasites here.”
Tronstad’s Phd student Nina Crawford said species often seek these “edge” areas to become more genetically diverse.
“Some of these groups can chunk off from the main population,” Crawford said. “And then they develop their own genetic diversity through multiple generations and just can become hardier than a population that's right in the smack-dab center that isn't experiencing harsher environments that they need to adapt with.”
According to the U.S. Fish and Wildlife Service’s most recent Species Status Assessment, the western population has a 99% chance of extension by 2080, and the eastern one has a 56 to 74% chance by then. So, the agency recently proposed listing them as “threatened” under the Endangered Species Act.
The proposal has received almost 70,000 comments. That’s about 15,000 more than has been received about protections for another recognizable species — grizzly bears.
”If you ever wanted a poster child, the monarch could be the poster child,” Hancock said.
Many environmental groups support the proposal, saying the listing is long overdue. But critics, such as the Wyoming Department of Agriculture and the Colorado Sugarbeet Growers Association, worry regulations could hurt the agriculture industry, restricting use of treatments for invasive plant species.
In order to give everyone a chance to weigh in, the Service recently extended the public comment until May 19.
This story was produced by the Mountain West News Bureau, a collaboration between Wyoming Public Media, Nevada Public Radio (KNPR) in Las Vegas, Boise State Public Radio in Idaho, KUNR in Nevada, KUNC in Colorado and KANW in New Mexico, with support from affiliate stations across the region. Funding for the Mountain West News Bureau is provided in part by the Corporation for Public Broadcasting.
