Threatened butterflies have a better chance of surviving thanks to human help

Some of the most endangered butterflies are doing better when their habitats are actively managed by humans, a recent study finds.

A team led by Washington State University researchers Cheryl Schultz and Collin Edwards analyzed data from 114 populations of 31 butterfly species across 10 U.S. 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 endangered butterflies are particularly vulnerable, with populations declining by an estimated 8 percent per year, which translates to a decline of about 50 percent over a decade.

The results of the study, reported in the Journal of Applied Ecologyprovide hope that habitat management can slow, or potentially reverse, these drastic declines.

“The strongest signal we found is that in places where people are actively engaged in habitat management, butterflies are doing best. To me, that’s very exciting because it means that habitat management can make a difference, even in the face of stressors like climate change,” said Cheryl Schultz, a WSU professor of conservation biology and co-senior author of the study.

With increasing temperatures caused by climate change, many butterflies have had to shift the timing of their seasonal activities, often by becoming active earlier in the year. In ecology, the question of when these timing shifts are good, bad, or relatively neutral for a species remains open.

“We found that for these butterflies, large shifts in timing were generally detrimental. Populations that had the largest shifts were more likely to decline,” said Edwards, a recent WSU postdoctoral fellow and co-senior author of the study. “However, we were excited to find that habitat management appeared to mitigate the effect of climate change on butterfly timing. Populations that received more frequent management had smaller shifts in timing.”

Despite the overall negative population trends identified for these species, the links the research team found between population trends, timing and management changes provide opportunities for butterfly conservation.

“This may not solve the consequences of climate change, but we can mitigate some of the effects,” said Elizabeth Crone, a co-author of the study and a professor at the University of California, Davis. “We have the power, at the local level, to do something positive for these people.”

The study looked at species such as the Oregon spotted butterfly, Taylor’s checkerspot butterfly, Karner blue butterfly and frosted checkerspot butterfly. It also looked at the Fender’s blue butterfly, which has become a poster child for recovery efforts, having rebounded from a few thousand butterflies in the 1990s to more than 30,000 today with the help of researchers like Schultz as well as public land managers and private landowners, including many Willamette Valley wineries.

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 active planting of 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 removing invasive species, Schultz said. People can also support butterflies in their own gardens.

“We really encourage people to plant an abundance of wildflowers and plants that are both hosts for caterpillars and provide nectar for butterflies,” Schultz said. “These plantings need to be ‘clean,’ meaning free of pesticides. The more we can reduce pesticides in our environment, the better it will be for butterflies and insects.”