For much of the 20th century, the tiny Fender’s blue butterfly was thought to have followed the path of the carrier pigeon and the dodo, driven to extinction by people.
Today, as many as 30,000 of the delicate butterflies flit through meadows in Oregon’s Willamette Valley. What once appeared to be a cautionary tale about the inexorable devastation of the natural world has instead become a story about the possibility of bringing endangered insects back from the brink through concerted human effort.
While the Fender’s blue is an unusually uplifting example, it turns out it’s not alone. As rare butterfly populations around the country dwindle, pressed by habitat loss, pesticides and a warming climate, intensive efforts by people can counteract that trend, helping some groups of the insects hold steady or even increase, according to research published this week in the Journal of Applied Ecology.
“In places where people are actively engaged with ways to manage the habitat, the butterflies are doing the best,” said Cheryl Schultz, a conservation biologist at Washington State University who helped lead the new work. “That to me is super exciting because that means that habitat management can make a difference, even in the face of stressors like climate change.”
At some level, it makes sense that a species fare better when people devote more time and money to it. But in the case of rare butterflies, that idea hadn’t been put to the test by more comprehensive research. It also wasn’t clear whether work to conserve or improve habitat was enough to counteract the effects of climate change, such as the earlier onset of spring or hotter summers.
Schultz and fellow scientists from the U.S. West and Midwest delved into decades of records tracking the ups and downs of 31 species of rare butterflies in 10 U.S. states. Much of the data came from citizen scientists, who conducted regular surveys of butterflies, including population counts and the timing for when the insects were taking flight.
Overall, the results were disheartening. On average, butterfly numbers declined by 8% per year during the surveys, the researchers found. That adds up to a halving in a population’s size over a decade.
But a closer look revealed that not everything was gloom and doom. Among the 114 populations of butterflies (some species were tracked in more than one place), 21 were growing, and in another 44 there was no clear trend.
When the scientists looked for factors that could help explain the differing fates, one thing stood out: Improving butterfly numbers were strongly correlated with more intensive management efforts aimed at helping the insects.
The data offered clues about some of the ways in which these efforts might be countering effects from global warming. One concern about climate change is that animals’ annual life patterns – when they hatch, mate, eat, migrate or hibernate – can get thrown out of whack as seasonal markers change, such as flowers blooming earlier.
The butterfly populations that did better had the least year-to-year fluctuation in one key life event – when they emerged from their larval stage and took flight. On the whole, butterfly groups with bigger shifts in that timing were more likely to experience declines in their numbers.
One possible explanation is that conservation efforts, such as burning, grazing or weed control, helped create more habitat variety on the landscape. That, in turn, could give butterflies a better chance of finding places to which they were better suited and able to maintain their life rhythms in a changing climate.
“The fact that we might be able to – not solve climate change – but we might be able to buffer some of the effects with things we do locally at the site, it’s exciting. It’s empowering. Because it means we can help at the local level,” said Schultz.
In the case of the Fender’s blue, the revival has been driven by efforts to create more of the rare habitat on which the insect relies. The butterfly’s life revolves around Kincaid’s lupine, a plant whose flowers once spread a purple blanket across Willamette Valley prairies. The butterfly lays single eggs on the lupine’s leaves in the spring, and the caterpillars feed on the plant. But less than 1% of the prairie remains today, the rest plowed under and turned into farms growing grass-seed, fruit orchards and grape vines. The lupine, as well as the butterfly, are listed as “threatened” under the federal Endangered Species Act.
After the butterfly’s rediscovery in the late 1980s, half a century after it was thought to have gone extinct, a coalition of conservation groups, landowners, government officials and scientists began working to find ways to restore the insect and its habitat. Strategies including protecting interconnected islands of habitat, controlling weeds that choked remnants of prairies and using fire to burn vegetation and spark new growth.
Among the people working on these projects starting in the 1993 was a 24-year-old graduate student, looking for a way to help conserve species: Cheryl Schultz.
Edwards, et. al. “Phenological constancy and management interventions predict population trends in at-risk butterflies in the United States.” Journal of Applied Ecology. Sept. 4, 2024.
Image: U.S. Army Corps of Engineers
