Some of the butterflies most at risk of disappearing do better when their habitats are actively managed by people, a recent study shows.
A team led by researchers Cheryl Schultz and Collin Edwards of Washington State University analyzed data from 114 populations of 31 butterfly species in 10 US states. Scientists have long warned that insect populations worldwide are declining rapidly due to the combined effects of climate change, habitat loss and pesticides. Overall, the research team found that these at-risk butterflies are particularly vulnerable, with populations estimated to decline by 8% per year, translating into a decline of about 50% over a decade.
The research results, reported in the Journal of Applied Ecologyoffer hope that habitat management can slow or even reverse this sharp decline.
“The strongest signal we found is that in places where people are actively working on ways to manage the habitat, butterflies do best. That’s super exciting to me because it means that habitat management can make a difference, even in the face of stressors like climate change,” said Cheryl Schultz, WSU professor of conservation biology and co-lead author of the study.
Warmer temperatures due to climate change have caused many butterflies to shift the timing of their seasonal activities, often becoming active earlier in the year. It is an open question in ecology when shifts in timing are good, bad, or relatively neutral for a species.
“We found that for these butterflies, large shifts in timing were generally bad. Populations with larger shifts were more likely to decline,” said Edwards, a recent WSU postdoctoral fellow and co-lead author of the study. “However, we were excited to find that habitat management appeared to dampen the effect of climate change on butterfly timing. Populations that were managed more frequently had smaller shifts in their timing.”
Despite the overall negative population trends identified for these species, the links the research team found between population trends, shifts in timing and management provide a path forward for butterfly conservation.
“This may not solve the impact of climate change, but we can mediate some of its effects,” said co-author Elizabeth Crone, a professor at the University of California, Davis. “It is within our power at the local level to do something positive for these populations.”
The study included species such as the Oregon silverspot, Taylor’s checkerspot, Karner blue and frosted elfin. It also included Fender’s blue, which has become the poster child for restoration efforts after being developed with the help of researchers like Schultz and public land managers and private landowners, including many vineyards in the Willamette Valley.
In this study, researchers found that the type of habitat intervention selected by managers was appropriate, with activities such as prescribed burns, mowing, weeding and actively planting nectar or “host plants” for butterfly caterpillars, selected based on the needs of each area.
Volunteers can help actively manage local natural areas by helping with new plantings and eradicating invasive plants, Schultz said. People can also support butterflies in their own backyards.
“We really encourage people to plant an abundance of wildflowers and plants that are both hosts for caterpillars and provide nectar for butterflies,” says Schultz. “These must be ‘clean plantings,’ meaning they are free of pesticides. The more we can reduce pesticides in our environment, the better it will be for butterflies and insects.”
This research was funded by the U.S. Strategic Environmental Research and Development Program, the U.S. Fish and Wildlife Service, and the U.S. Geological Survey.
