From our community:
Monarch butterflies are hanging on but their population numbers continue to decline. Saving them requires an intricate choreography of data collection, ecosystem enhancements, legal regulations, agricultural modifications, citizen science, and parameters still unknown. Each year new threats arise, but also new records are set that increase our knowledge.
As always, nature’s role is unpredictable because climate and weather are changing. Longer summers, warmer winters, unusually cold wet winters, increased intensity and frequency of hurricanes and wildfires — all are known to play a role in monarch survival. Agencies and non-profit groups develop projects to protect and enhance monarch habitats concurrent with agricultural plans to increase use of pesticides that degrade habitats. In Mexico, economic troubles increase illegal logging and unseasonal storms affect the overwintering forests protected as a UNESCO Biosphere Reserve. In California, diseases, drought, and wildfire damage overwintering sites. Some are protected by the state and USFWS, but natural disasters cannot be banned from nature reserves.
Both the California and Mexico monarch overwintering population data have been reported now and the numbers are lower than we hoped. Monarch butterfly populations are censused during winter when the animals are less mobile. In California, monarchs are counted by volunteers organized through The Xerces Society. In Mexico, counts are overseen by World Wildlife Federation and partners who evaluate the amount of area used by clustering monarchs to extrapolate the number of individuals.
In California this year, the same as last year, more overwintering sites were surveyed by more volunteers, but fewer monarchs were counted. Over 150 volunteers looked for clusters of monarchs and counted samples to extrapolate number of individuals. Solo monarchs flying around are not counted as their movement makes accuracy impossible. Twenty years of data is available for the Western Population Thanksgiving Count. In 2016, a second census was added around the New Year, so we have two years of this data set. For the Thanksgiving Count, 192,629 monarchs were counted at 262 sites. this is the second lowest number since 2012 and the sixth lowest since the census began in 1997. In late February 2018, California monarchs started moving out of this overwintering habitat, mating, and beginning their northward migration.
In Mexico, 6.13 acres (2.48 hectares) were documented with an estimated 93 million monarchs. This sounds encouraging, but the total size is 15% lower than last year. Mexican population data is available from 1994-95 onward. In the mid-1990s the monarch population was nearly 10 times greater. The 93 million estimated this winter is less than half the size believed required for a stable population. (A large table that toggles among acres, hectares, and number of butterflies is available from Annenberg Learner.)
Migration is underway from Mexico as monarchs are seen mating and flying north. Two sightings were reported north of the sanctuaries on March 3rd.
While some people suspect both the California and Mexico population declines this year are weather related, there is no solid evidence. Certainly, unseasonably warm weather, wildfires, and smoke all were present in Oregon during migration and in California this winter, but teasing out relative impacts from these situations is difficult as other factors also affect the butterflies.
The Xerces Society received numerous reports of late season breeding, and fewer clusters this fall, suggesting that some monarchs may have arrived at overwintering sites later and stayed active longer. The low estimate of monarchs this year may be attributable, in part, to later than average clustering.
One of the big unknowns about the western monarchs is their migration routes. The general belief has been that monarchs summering west of the Rockies migrate to California and the eastern population migrates to Mexico. But the eastern migration routes are much better mapped (except for the weirdness of Florida’s winter migrants).
Tagged monarchs from Washington and Oregon often are found in California, but despite 2,594 monarchs tagged in Idaho through the program run by Washington State University associate professor David James, none has been found in California. However the reverse isn’t true — one monarch “tagged in May in northern California was recovered 35 days later and 707 km ENE in Twin Falls, Idaho.”
Thus, the March 2nd discovery (and rescue) of an Idaho-tagged monarch near Santa Barbara was this season’s Oh Wow story. Monet was born and raised in Treasure Valley near Boise and set two records this year.
She flew 662 miles to southern California to the greater Santa Barbara area where she had a near-death experience by falling into a swimming pool. Fortunately Monet was spotted and rescued by homeowner Mike McBirney who saved her from an uncertain fate. He then released Monet back into the wild….
“Monet is the first Idaho monarch in my study to be recovered in California, and at six months of age she is the longest-lived monarch documented in this Washington State University tagging effort,” says James. “Monet will go down in Idaho monarch history, that’s for sure.”
Last year, Miracle, a monarch tagged by a different project in Boise, was their first tagged monarch to be found in California. She also set another record.
On a cold, windy, late October day B-3930 was released into the air of a wildlife refuge near Boise Idaho. This was a late start in bad weather for a monarch butterfly who needed to travel southwest to California’s overwintering habitat. But B-3930 made it and was found in Santa Cruz after flying 537 miles in 32 days. Now called Miracle, she set a record for the latest known departure date for monarchs who successfully migrated from a latitude similar to Boise. That monarchs are still setting records in California is startling considering they were first seen here by foreign explorers exactly 200 years ago.
This fall unusually warm weather in the eastern monarch populations summer range (especially in Canada) seemed to stall monarchs from beginning their migration south. A particularly busy hurricane season across their migration corridor from the Atlantic states to Texas may have influenced how many monarchs were able to reach Mexico. But specific consequences of these impacts are unknown.
Humans can’t control impacts from hurricanes and wildfires, but we are taking steps to protect and enhance habitat in California.
The U.S. Fish and Wildlife Service, Xerces Society for Invertebrate Conservation, Groundswell Coastal Ecology and California Department of Parks and Recreation have developed a western monarch butterfly overwintering site management plan that also serves as a template for land managers at other overwintering sites.
Environmental Defense Fund and partners have developed a plan to enhance monarch summer range habitat across North America.
A multi-stakeholder effort is now underway to build a Monarch Butterfly Habitat Exchange, which would enable efficient and effective restoration and conservation of vital milkweed habitat, which monarchs need for breeding and feeding. Developing this program will require strong partnerships across the country, so EDF experts are partnering with key groups including Monarch Joint Venture and the Iowa Monarch Conservation Consortium. [...]
By applying an advanced habitat quantification tool, the Monarch Butterfly Habitat Exchange can accurately determine the value of habitat on any given property and enable incentive payments to be directed to priority habitat restoration and conservation sites, ensuring maximum bang for the buck, and for the butterfly.
The Tribal Alliance for Pollinators is a new organization working with Indian tribes to restore grassland habitat to protect pollinators and native plants “that serve as the foundation for Indigenous cultural, medicinal and culinary traditions.”
...a coalition of seven tribal partners — Chickasaw, Seminole, Citizen Potawatomi, Muscogee Creek, Osage, Eastern Shawnee and Miami Nations — who are restoring monarch habitat on their lands with the assistance of Monarch Watch and the Euchee Butterfly Farm. The TEAM coalition has restored over 32,000 milkweeds to date and is in the process of restoring 28,000 native wildflowers on 350 acres of habitat.
These and other efforts attempt to offset losses due to habitat disintegration and agricultural damages. The Natural Resources Defense Council is suing the EPA for failing to address monarch impacts from Enlist Duo, a newly approved pesticide combination of glyphosate (Roundup) and 2,4 D. Both these herbicides kill milkweeds (monarch larval host plant) and nectar plants.
Earlier this month, the Center for Biological Diversity released a report showing that Dicamba, an herbicide designed for genetically modified soybean and corn that harms nectar plants and milkweed, will be used on over 60 million acres of monarch migratory habitat by 2019. The Center has an interactive map showing when and where Dicamba now can be used relative to monarch migration. Dicamba already is the subject of lawsuits for damages due to how easily it drifts from the target areas.
Other key findings include:
- Accelerating harm: In addition to 61 million acres of monarch habitat being directly sprayed with dicamba, an additional 9 million acres could be harmed by drift of the pesticide.
- Deadly timing: The timing and geographical distribution of dicamba use coincides precisely with the presence of monarch eggs and larva on milkweed.
- Double trouble: Dicamba degrades monarch habitat both by harming flowering of plants that provide nectar for adults as they travel south for the winter and by harming milkweed that provides an essential resource for reproduction.
- Greater menace to milkweed: Research has shown that just 1 percent of the minimum dicamba application rate is sufficient to reduce the size of milkweed by 50 percent, indicating it may have a greater impact on milkweed growth than the already widely used pesticide glyphosate.
Despite the dire pesticide news and declining population data, scientists still believe that monarchs can be saved. We know what is needed — cooperative programs uniting conservation, industry, and the public will benefit monarchs, other pollinators, humans, and agriculture.
A program out of Iowa State University called STRIPS has demonstrated that converting 10% of a given agricultural field into strategically placed native prairie strips can bring overall benefits not only ecologically (including increasing pollinator abundance 3.5 fold), but to the farmer as well in the form of reduced nutrient and water runoff and enhanced soil quality with minimal impact to production.
Saving monarchs will cost millions of dollars in restoration, protection, and educational programs. But even people who are squeamish about bugs marvel at the sight of monarch butterflies. Despite the population declines in Mexico, millions of monarchs are a spectacle worth hiking an hour or more upslope at >10,000 feet in elevation. But to keep this spectacle, monarch’s entire range of habitats across North America requires our finely choreographed attention.