What it takes to get a monarch listed as endangered – and how citizen scientists helped

The Science Near Me blog is a partnership between Discover magazine and ScienceNearMe.org.


If you live in North America, chances are good that you’ve seen a monarch butterfly—if you didn’t quite like their stops in your area. The black and orange beauties are a sure sign of the changing seasons, whether their arrival heralds spring, summer or fall where you live. Flying, flying, swimming they glide over our gardens looking for a sip of nectar or a leaf of milkweed to lay their eggs.

But these special sightings are becoming rarer as butterfly populations decline. The larger, eastern population of the butterfly declined 84 percent from 1996 to 2014. reports the International Union for Conservation of Nature (IUCN).while the smaller western population has declined by nearly 99.9 percent since the 1980s.

Experts from the IUCN, which supports IUCN Red List of Threatened Species, officially listed the species as endangered this July. This means they face a very high risk of extinction in the wild.


Join us on Tuesday, August 30, 2022 for a special SciStarter LIVE event: Observing Monarch butterflies, for science! Learn more and register for the free event.


Monarchs have a special migration pattern – it takes them several generations to travel across the continent. In summer, they live in the US and southern Canada, extract nectar from flowers and lay eggs exclusively on milkweed plants. In winter, they congregate in only a few places in California and Mexico. It is in these places that the decline is most pronounced and qualifies the insects as endangered – in the winter of 2020-2021 they were found in only about five acres of forest. Only 1,914 butterflies were counted in California.

The biggest threat to monarchs is logging and habitat loss in their winter range. If the specific forests where these butterflies winter disappear, so do the monarchs. Add to that the widespread removal of milkweed—which monarchs need to reproduce—throughout their breeding range, especially thanks to improvements in the herbicides farmers use to keep farmland weed-free. On top of everything with climate change leading to extreme temperatures, drought and changes in when flowers bloom, it’s no surprise that butterflies are in such trouble.

Monarchs spend the night. (Credit: Mike Budd/USFWS)

The IUCN Red List is separate from list of endangered species maintained by the US Fish and Wildlife Service, which offers legal protection to the species under the Endangered Species Act. Although the Red List has no legal backing, it is considered the gold standard for assessing the status of species worldwide.

The new list is important, entomologist Anna Walker explains, because it provides a frame of reference for how threatened a species is with extinction. “I think it’s really important to put the conservation status of an iconic species like the monarch into a global context,” says Walker. “It gives people a way to contextualize, how worried should we be?”

Walker, a species survival officer at the New Mexico Biopark Society, led the assessment of the monarch. She is a member of the IUCN Species Survival Butterfly and Moth Specialist Group.

How a species gets listed as endangered

To get a new species added to the IUCN Red List, conservation biologists like Walker put together a comprehensive report on how much and how fast the species’ numbers have declined, how much of their habitat has been destroyed, what threats remain, what conservation efforts are underway, and etc.

“Most of the insect species I’ve looked at just don’t have information, and that’s really frustrating,” she says. “We did a project where we assessed all 132 species of fireflies in North America, and more than half of them were data deficient, which simply means we don’t know enough about the species to determine if it’s endangered or not. That’s really common.”


Learn more from The Citizen Science Podcast: Palouse pollinator! Learn about scientists’ efforts to monitor important pollinators like bumblebees, monarch butterflies, and hummingbirds, and how you can help, including citizen science projects Bumble Bee Watch, Journey North, and the Monarch Larva Monitoring Project.


Fortunately for the Monarchs, Walker had plenty of information to compile the report. “There was a lot of data to sort through because not only is there academic research on this, but it’s a species that has benefited from community science as well,” she says.

Walker says the most important data for the assessment is population counts from monarch wintering grounds. “Because this butterfly congregates in a small area during the winter, it’s relatively easy to tell how many there are,” she explains. “Also, the wintering population is the smallest – that’s when there are the fewest individuals and therefore that’s when it’s most vulnerable.”

A monarch butterfly sips nectar from a New England aster. (Credit: Greg Thompson/USFWS)

How citizen scientists drive conservation

Walker says her conservation work would be easier if more people contributed to citizen science projects. “We just don’t have enough researchers, we don’t have enough resources just for scientists to go out and collect all this data,” she says. “There are millions of insects, and we understand so little about most of them.”

Monarch butterflies are somewhat of an exception due to their popularity. They are easy to spot and recognize, they are aesthetically pleasing, they are even easy to grow in classrooms or at home to release into the wild. As for insects, they are incredibly well studied and their decline is well documented.

“It’s really, really important and people can make a big difference,” she says. “And I think the monarch is a good example of that.”


Get involved: Find citizen science projects that help monarchs near you ScienceNearMe.org!


For example, monarch tagging programs like the Southwest Monarch Study have led many researchers to find out where specific populations overwinter—like those in Arizona. “We certainly have community scientists to thank for much of our understanding of migration,” Walker says.

Observations of milkweed, which can be submitted through citizen science apps like iNaturalist, can guide recovery efforts (where is the milkweed missing?) and tell conservation biologists where important milkweed habitats are.

Even just general butterfly observations are also helpful. For example, the North American Butterfly Association conducts an annual butterfly census, and this data is also useful for monarch conservation. “Even if you’re not specifically looking for monarchs, but just looking at butterflies in general, you can contribute to monarch research,” Walker says.

A future for monarchs

Walker came across some good news while working on the IUCN report. Although the number of monarchs is still too low, their decline at least seems to have slowed down a bit. Their summer breeding populations have been more stable recently. Walker suspects a big part of that is milkweed planting efforts. “People are planting milkweed in their yards and parks, and it seems like it can make a big difference,” she says.

Do you want to participate? Learn more about citizen science projects and other opportunities to help monarchs at Science Near Me. Science Near Me is a free resource that helps you find opportunities to get involved in all kinds of science events, projects and programs near you, in person and online. Her citizen science projects come from partner SciStarter.org, which hosts thousands of citizen science projects from around the web! Find ways to report monarch sightings, participate in tagging campaigns, raise caterpillars, attend monarch events and more at ScienceNearMe.org.


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