Monarch butterflies can thrive after years of decline. Is this a return? | California

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On a recent November morning, more than 20,000 western monarch butterflies gathered in a eucalyptus grove, covering the swaying trees like orange lace. Each year, up to 30% of the butterfly population congregates here in Pismo Beach, California, as the insects migrate thousands of miles west for the winter.

Just a year ago, this vibrant spectacle had all but disappeared. The monarch population has plummeted in recent years as dynamic invertebrates struggled to adapt to habitat loss, the climate crisis, and the use of harmful pesticides across their western range.

Last year, fewer than 200 arrived at this site in 2020 – the lowest number on record – and fewer than 2,000 were counted on the California coast.

But before the official annual tally that takes place around Thanksgiving, the first tally shows that monarchs could once again thrive across California. The increase has brought joy and relief, but researchers, state park officials and advocates say that doesn’t mean the species is safe.

Up to 30% of the western monarch butterfly population converge on Pismo Beach each winter. Photograph: Gabrielle Canon / The Guardian

Even with the exponential increase, the population is still far from the once normal numbers. It is still unclear whether butterflies are making a dramatic comeback or will continue to decline.

“The takeaway is that the migration is not over, which some people really feared last year,” says Emma Pelton, senior conservation biologist for the Xerces Society, an organization dedicated to protecting pollinators and other invertebrates. Between 4 and 10 million butterflies once graced California’s coastlines before dropping to just over one million in the late 1990s. In the decades that followed, the population peaked at around 200,000.

Then, in 2017, the numbers collapsed to less than 30,000 butterflies at the annual count. Monarchs are resilient and adaptive, but they continue to face challenges. This year’s increase is small if you put it in perspective with past population levels, but “the good news is, it’s not too late,” Pelton adds.

A remarkable migration

There is still quite a bit of mystery surrounding Western monarchs and their incredible annual migration. Each year they follow a celestial compass and head west from the Rocky Mountains to the coast. Remarkably, each generation of butterflies often returns the same groves along the coast each year, sometimes even a particular tree, never having been there before.

Typically, they arrive in California around November and disembark in the spring, heading east when the weather warms. A distinct population of monarchs overwinters in Mexico, originating from Canada and the eastern United States.

Stephanie Little, a California State Park scientist, uses binoculars to look in trees and count butterflies at Pismo Beach.
Stephanie Little, a California State Park scientist, counts the butterflies at Pismo Beach. Photograph: Gabrielle Canon / The Guardian

Their dedication to routine makes them easier to count each year. But the process isn’t entirely straightforward, especially when the numbers are low and they’re harder to spot. In the grove of Pismo Beach, which usually hosts the largest gathering, three state park officials are tasked with counting them before the Thanksgiving count which relies on the help of volunteers.

Armed with binoculars, butterfly counters estimate numbers based on the clusters visible in the branches, about 15 meters above the ground. California State Parks have partnered with advocacy organizations to create a welcoming environment for them. This means planting more non-native eucalyptus trees, which butterflies love to roost in.

The reasons for this sharp increase remain a mystery. Monarchs that live in the west tend to have three or four generations each year, each with a different role to play in the migration that can stretch for thousands of miles, and there are opportunities at every step for big changes.

Monarch butterflies congregate in the branches of a eucalyptus tree, about 50 feet above the ground.
Monarch butterflies congregate in the branches of a eucalyptus tree, about 50 feet above the ground. Photograph: Gabrielle Canon / The Guardian

But what is behind their precipitous decline is clear. Their historic habitats in grassland ecosystems across the United States are being destroyed. Commercial agriculture is eating away at their range which is increasingly laden with deadly pesticides. And, sensitive to both fluctuations and temperature extremes, monarchs are vulnerable to climate change. This is in part why they are considered a so-called “indicator species” revealing the devastating toll suffered by other insects and ecosystems.

“Butterflies are just very adaptable and strong,” said David James, an entomologist at Washington State University who has spent decades studying the species. “But they also give us a warning – and we have to heed that,” he adds. “Their decline will affect other organisms.”

“There is still time to act”

The butterflies have also felt the impact of extreme heat, fires and drought, as well as severe winter storms on the California coast where they overwinter. “Some of those storms tore up trees and threw butterflies on the ground,” says James.

But he also believes that last year’s extremely low numbers may be the result of dispersal, not necessarily death.

“When we only had 2,000 overwinterers at traditional sites, at one time there were many reports inland in San Francisco and the LA area of ​​monarch butterflies breeding in backyards. and people’s parks and gardens throughout the winter, ”he says, noting that this spread makes them hard to count.

But even though last year’s low numbers can be attributed to changes in behavior, it’s still a sign that the climate crisis is causing problems. “They tell us things are bad,” said James.

Visitors search for butterflies at Pismo Beach Butterfly Grove.
Visitors search for butterflies at Pismo Beach Butterfly Grove. Photograph: Gabrielle Canon / The Guardian

People can make a difference by planting native nectar-bearing plants, including milkweed on which monarchs lay their eggs and limiting the use of pesticides. Members of the public can also volunteered to watch monarchs across the west. And, according to Emma Pelton of Xerces, the promising numbers show that small changes can have a big impact.

“The main message for me is that there is hope,” she said, noting how the monarchs have inspired the public to reimagine the way they see insects and the role each can play in them. conservation. “The story of the insect apocalypse and the very real biodiversity crises we face can seem very dark,” she says. “But the question is not insoluble and we can make a difference. There is still time to act.

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