Scientists have warned for several years that Monarch butterflies were endangered because the number of winter colonies was diminishing.
Several research projects over the past 20 years have found that population numbers were down up to 95%. The causes for this issue are variable, but most scientists suggested that changes to the long-term climate were responsible. []
Monarch butterflies can travel up to 100 miles per day, but extreme weather events are known to make them vulnerable. That issue increases when the roost or cluster migrates.
Habitat loss, deforestation, and herbicide overuse are also thought to be contributing factors to the butterfly’s population challenges.
New research suggests those concerns could be unfounded.
Monarch Butterfly Populations Have Remained Stable for 25 Years
“There’s this perception out there that Monarch populations are in dire trouble, but we found that’s not the case,” said Andy Davis, who serves as an assistant research scientist in the Odum School of Ecology at the University of Georgia.
“It goes against what everyone things, but we found that they’re doing quite well. In fact, Monarchs are one of the most widespread butterflies in North America.”
Davis’s study on Monarch butterfly populations was published in Global Change Biology. It suggests that although population losses occur due to changing environmental factors, winter weather, and migration issues, gains during the summer compensate for these changes. []
William Snyder helped with the study, and he works as a professor in the College of Agricultural and Environmental Sciences at the University of Georgia. “There are some once widespread butterfly species that now are in trouble,” he said. “So much attention is being paid to Monarchs instead, and they seem to be in pretty good shape overall.”
“It seems like a missed opportunity,” Snyder continued. “We don’t want to give the idea that insect conversation isn’t important, because it is. It’s just maybe this one particular insect isn’t in nearly as much trouble as we thought.” []
The study looked at more than 135,000 Monarch observations made by the North American Butterfly Association between 1993 and 2018. That data allowed researchers to see population patterns and change drivers, including herbicides and precipitation changes.
Data Comes from Citizen Scientists in the Field
The North American Butterfly Association documents butterfly species and total counts during a two-day stretch each summer. Observation groups of “citizen scientists” are assigned to patrol an area that spans 15 miles in diameter.
Their job during this time is to count every butterfly they see, including Monarchs.
Davis found that when they carefully examined all the information from the 25 years of data, the annual increase in Monarch abundance was over 1.3%. That suggests the population is not declining as suggested.
Although direct observations in Mexico have found that the number of butterflies migrating for the winter months has decreased, the summer breeding in the United States and Canada is making up for those losses.
Davis believes the migration could be changing how the butterflies manage their environment. “A single female can lay 500 eggs, so they’re capable of rebounding tremendously, given the right resources,” he said. “The winter colony declines are almost like a red herring. They’re not really representative of the entire species’ population.”
Researchers found that the habitat for Monarchs is similar to what people prefer. “If you think about it… Monarchs are good at utilizing the landscapes we’ve created for ourselves,” said Davis. “Backyard gardens, pastures, roadsides, ditches, old fields – all of that is Monarch habitat.”
Plant a Different Milkweed Species to Encourage Monarchs
With over 100 different milkweed species to consider, it isn’t easy to decide which ones to plant to attract more Monarchs to a garden.
The one that is the easiest to obtain for most home gardens is called Asclepias curassavica. It’s a tropical option that is invasive, but isn’t well-suited because it isn’t native to the northern reaches of North America during the summer breeding time.
It is also essential to reduce or eliminate the use of fungicides, insecticides, and pesticides in the garden whenever possible. These products can store in milkweed, eventually becoming part of the food chain for the butterflies.
The study was funded by USDA National Institute of Food and Agriculture grants.
[] What’s causing the decline in monarch butterfly populations? (inhabitat.com); [] Opposing global change drivers counterbalance trends in breeding North American monarch butterflies - Crossley - - Global Change Biology - Wiley Online Library; [] Good news: Monarch butterfly populations are thriving in North America - ScienceBlog.com; [] 5 Spring Plants That Could Save Monarch Butterflies (monarchbutterflygarden.net)