Western US butterfly declines linked to warmer autumns

March 9, 2021

According to a study published in Science, butterflies are decreasing about 1.6% annually, and these decreases could be linked to warmer autumns. The authors, which included SNRE?s Katy Prudic, analyzed butterfly observations collected by citizen scientists through platforms such as iNaturalist and the North American Butterfly Association (NABA).
The team analyzed a number of factors, including life history traits, land use metrics, and climate characteristics, and found that their observations were best explained by indices of climate change, particularly changes in the maximum fall temperature. Warmer autumns may cause declines by disrupting life stages, inducing stress, reducing the health of the host plant, or increasing predation. Their study design allows the unique capacity to parse out declines due to land use versus climate change and provides the startling conclusion that even species considered ?safe? from land use changes, including those commonly found in cities as well as those found in relatively remote, undisturbed landscapes, are facing steep declines.

?The monarch population that winters along the West Coast plummeted from several hundred thousand just a few years ago to fewer than 2,000 this past year?Essentially, the western monarch is on the brink of extinction, but what?s most unsettling is they are situated in the middle of the pack, so to speak, in our list of declining butterfly species.? ~Dr. Katy Prudic

A decline in butterflies, in addition to other insects, is particularly concerning because much of our food supply relies on these pollinators. Without insects to pollinate our crops, these plants will be unable to reproduce, leaving nothing to feed ourselves and our livestock. There is still much work to be done, and there are likely many interacting factors contributing to insect declines worldwide. Shifting conservation efforts toward targeting entire suites of species and minimizing further anthropogenic climate change are imperative for mitigating further losses.
Citizen science platforms are a powerful collaborative tool that allows the global community to join scientists in making new discoveries that could help minimize adverse effects of human development and climate change. These platforms also allow researchers to answer questions on large regional or even global scales, often with a vast library of data impossible for a single team of researchers to collect alone.

"Even if you just took the professors that were on this paper, all of us, we couldn't cover that geographic area," said Katy Prudic, an entomologist at the University of Arizona who helps run one of the online butterfly databases. "There's just not enough of us. So this work, the comparison across the entire West, could not be done without citizen science." ~ Dr. Prudic

In addition to leading research addressing insect declines, Dr. Prudic co-directs a citizen science platform, eButterfly, which hosts observations of over a thousand species of butterflies from across the globe. Taking advantage of citizen science platforms to address conservation questions across large scales, she uses her findings to inform conservation decisions and help insects adapt with a changing world.
View University of Arizona?s full coverage of this story here.
Slideshow Photo by Erin Minuskin on Unsplash