Govind Tekale
America’s butterfly populations have plummeted by 22% in just two decades, according to a landmark study published in Science. This significant decline means that for every five butterflies present in 2000, only four remained by 2020.
“This is a wake-up call. People should be seeing this number and being very, very concerned, not just about butterflies, but about the state of insects in general,” says Eliza Grames, a conservation biologist at Binghamton University and co-author of the study.
The research represents the most comprehensive analysis of butterfly populations in the United States to date. Scientists compiled data from 76,957 surveys across 35 monitoring programs, counting 12.6 million butterflies from 554 species at 2,478 locations nationwide.
Widespread Decline Affects Most Species
The decline affects butterflies across most regions and species. Researchers found that 114 species showed significant declines while only nine increased in population. More than 100 species experienced drops greater than 50% over the twenty-year period, with 22 species declining by more than 90%.
Among the hardest hit are the Hermes copper, tailed orange, West Virginia white, California patch, and sandhill skipper. The Florida white butterfly has essentially vanished from survey records during this period.
“It’s such a short timespan to lose this many butterflies, it’s very sobering,” Grames noted.
Regional Variations
The Southwest region of the United States has experienced the steepest butterfly losses, with populations dropping by more than half since 2000. This area, which includes Arizona, New Mexico, Texas, and Oklahoma, is particularly vulnerable due to its arid climate.
“It looks like the butterflies that are in dry and warm areas are doing particularly poorly,” said Collin Edwards, the study’s lead author and an ecologist at the Washington Department of Fish and Wildlife.
The Pacific Northwest showed the least decline among all regions, partly due to some resilient species in that area.
What’s Causing the Decline?
Scientists point to three main factors behind the butterfly population crash:
- Habitat loss from urbanization and agricultural expansion
- Climate change creating harsher conditions, particularly drought in the Southwest
- Pesticide use, especially in agricultural regions
Nick Haddad, an entomologist at Michigan State University and study co-author, believes insecticides play a particularly significant role. “It makes sense because insecticide use has changed in dramatic ways in the time since our study started,” Haddad explained.
Even common and adaptable species haven’t escaped the decline. The invasive white cabbage butterfly, described by Haddad as “a species that is well adapted to invade the world,” has seen its numbers fall by 50%.
The red admiral butterfly, known for calmly landing on people, has decreased by 44%, while the American lady butterfly with its distinctive eyespots has declined by 58%.
Why Butterfly Declines Matter
Butterflies serve as both pollinators and indicators of broader ecosystem health. Their decline mirrors a larger crisis affecting global insect populations, estimated to be dropping at a rate of 1-2% annually.
“The loss of butterflies, parrots and porpoises is undoubtedly a bad sign for us, the ecosystems we need and the nature we enjoy,” said Cornell University butterfly expert Anurag Agrawal. “Butterflies are an ambassador for nature’s beauty, fragility and the interdependence of species. They have something to teach us.”
Beyond their ecological importance, butterflies contribute economically to agriculture. They are significant pollinators for crops such as cotton in Texas.
University of Connecticut entomologist David Wagner, who wasn’t part of the study, called the findings “catastrophic and saddening” when compounded over time. “In just 30 or 40 years we are talking about losing half the butterflies over a continent,” Wagner warned.
Conservation Efforts and Hope
Despite the troubling trend, conservation efforts might still reverse the decline. Butterflies have relatively short generations, meaning habitat improvements can show quick results.
“If you’re improving habitat for elephants, let’s say, you’re going to be waiting decades before you see results of that,” explained Grames. “If you improve habitats for butterflies that can have one to three generations per year, you’re going to see a pretty immediate increase in population.”
Simple actions like creating butterfly-friendly gardens with native plants can help. Recent efforts to protect monarch butterflies demonstrate the potential for population rebounds when habitats are restored.
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“You can make changes in your backyard and in your neighborhood and in your state,” Haddad said. “That could really improve the situation for a lot of species.”
The U.S. Fish and Wildlife Service is currently considering listing monarch butterflies as a threatened species under the Endangered Species Act, and several states are working to expand pollinator-friendly habitats along butterfly migration routes.
Researchers emphasize that addressing larger issues like climate change and pesticide use remains crucial for butterfly conservation, while highlighting that individual actions can still make a difference.
FAQ
How much have butterfly populations declined in the US?
According to the most comprehensive study to date, published in Science, butterfly populations in the United States have declined by 22% between 2000 and 2020. This means that for every five butterflies present in 2000, only four remained by 2020.
What’s causing butterfly populations to decline?
Three main factors are driving butterfly declines:
1. Habitat loss due to urbanization and agricultural expansion
2. Climate change creating harsher conditions, particularly drought in the Southwest
3. Pesticide use, especially agricultural insecticides
Of these, research suggests that insecticide use may be playing the most significant role in many regions.
Why should we care about declining butterfly populations?
Butterflies are important for several reasons:
– They are pollinators for many plants, including crops like cotton
– They serve as indicators of overall ecosystem health
– Their decline reflects a broader crisis affecting global insect populations
– They play a role in food webs as prey for birds and other animals
As Cornell University butterfly expert Anurag Agrawal noted, “The loss of butterflies is undoubtedly a bad sign for us, the ecosystems we need and the nature we enjoy.”
Which butterfly species are most affected by the decline?
While the decline affects most butterfly species, some have been hit particularly hard. More than 100 species have experienced drops greater than 50% over the twenty-year period studied, with 22 species declining by more than 90%.
The most severely affected species include:
– Hermes copper
– Tailed orange
– West Virginia white
– California patch
– Sandhill skipper
The Florida white butterfly has virtually disappeared from survey records during this period.
Which regions in the US are seeing the worst butterfly declines?
The Southwest region of the United States has experienced the steepest butterfly losses, with populations dropping by more than half since 2000. This area includes Arizona, New Mexico, Texas, and Oklahoma.
The Pacific Northwest showed the least decline among all regions. Research indicates that butterflies in drier, warmer areas are generally faring worse than those in cooler regions.
What can individuals do to help butterfly populations?
There are several practical steps individuals can take to support butterfly conservation:
– Plant native flowering plants in gardens to provide nectar sources
– Include host plants that butterflies need for laying eggs (like milkweed for monarchs)
– Avoid using pesticides in gardens
– Participate in butterfly monitoring programs like the North American Butterfly Association’s Fourth of July counts
– Support conservation organizations working to protect butterfly habitats
Because butterflies have short life cycles with multiple generations per year, habitat improvements can show relatively quick results compared to conservation efforts for longer-lived species.
