Endangered Eastern Monarch Butterflies Need Not Die Off in 20 Years

Summary: Endangered eastern monarch butterflies will survive the next 20 years if they get Endangered Species Act protection and 225 million milkweed-filled gardens.

A black spot on each hindwing identifies resting and sunning eastern monarch butterfly (Danaus plexippus) as male at overwintering site in Piedra Herrada Monarch Butterfly Sanctuary near Vale De Bravo; photo by USGS senior scientist and biologist Steve Hilburger: Public Domain, via US Geological Survey

Endangered eastern monarch butterflies are risking quasi-extinction within 20 years unless North Americans reverse climate change and habitat loss, according to a study published online March 21, 2016, in Scientific Reports.

One researcher each in California, Iowa, Kansas, Minnesota and Wisconsin and two each in Arizona and Colorado base their findings upon Bayesian multi-variate auto-repressive state-space modeling. The model can be used to calculate, at 11 to 57 percent, the quasi-extinction risk, the point where decline cannot be reversed or a population rehabilitated. It also describes, at five times the numbers overwintering in Mexico during winter 2014/2015, the target population size that will decrease quasi-extinction risks by 50 percent.

Study co-researchers Jay Diffendorfer, Laura López-Hoffman, Karen Oberhauser, John Pleasants, Brice Semmens, Darius Semmens, Orley Taylor, Wayne Thogmartin and Ruscena Wiederholt emphasize environmental and predatory impacts.

The nine co-researchers and co-writers of the study find overwintering populations of endangered eastern monarch butterflies declining by 84 percent from winter 1996/1997 to winter 2014/2015.

Recordkeeping since 1994 gives maximum areas covered with overwintering monarchs at 13.90 hectares (34.35 acres) in 1996/1997 and minimums of 2.20 hectares (5.44 acres) in 2014/2015. Population levels and surface areas sustained by monarch colonies head upward in winter 2015/2016 and then downward after winter storms, according to World Wildlife Fund Mexico. The nine co-researchers and co-writers indicate that “The number of individuals present in overwintering colony areas is strongly dependent upon the density of monarchs per hectare.”

An estimated per-hectare (per-acre) density of 6.9 million overwintering monarchs, at the low end of the range, joins an estimated 60.9 million at the high end.

Scientists know that what happens to overwintering colonies of endangered eastern monarch butterflies does not stay behind in Mexico when returning populations head northward in spring.

Clustering into colonies, whose minimum size is one viable colony per occupied tree on 0.01 hectares (0.03 acres), lets individual overwintering monarchs regulate their body temperatures. Surviving extreme temperatures and severe weathers never means that spring’s northbound migrants have only to enjoy sailing, slow, strong flight patterns all the way back home. Migrants overwintering in Mexico and returning to Canada and the United States need to elude predatory crab spiders, dragonflies, frogs, lizards, robberflies, toads and web weavers.

Mating and nectaring occur after leaving Mexico so that “Diminished colony size can therefore result in higher winter mortality rates and lower fecundity in the spring.”

Cash cropping, climate change, disease incidence, habitat loss, invasive species, natural enemies, neonicotinoid insecticides and weather extremes provide threats alongside northern Mexico’s and southern Canada’s borders.

The researchers quantify agro-industrial impacts upon endangered eastern monarch butterflies through declining availability of milkweed hostplants and increased cultivation of genetically modified, herbicide-tolerant corn and soybeans. They reveal that “The documented decline in available breeding habitat is likely a major driver of the monarch population decline” among homeward-bound populations and overwintering colonies. North America-wide “efforts to recover the population towards the [White House’s] 2020 goal [of 225 million monarchs] should focus on the creation and restoration of habitat.”

It only takes Endangered Species Act protection, under review since 2014, and 225 million citizen scientists cultivating 225 million milkweed-filled gardens to sustain 225 million monarchs.

Research published March 21, 2016, in Scientific Reports by Scripps Institution of Oceanography at UC San Diego and U.S. Geological Survey reveals a concerning decline of 84 percent in the Eastern migratory monarch population from the winter of 1996-1997 to the winter of 2014-2015: USGS Wildlife Health @USGSWILDLIFE, via Twitter March 21, 2016

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

A black spot on each hindwing identifies resting and sunning eastern monarch butterfly (Danaus plexippus) as male at overwintering site in Piedra Herrada Monarch Butterfly Sanctuary near Vale De Bravo; photo by USGS senior scientist and biologist Steve Hilburger: Public Domain, via US Geological Survey @ https://www.usgs.gov/news/eastern-monarch-butterflies-risk-extinction-unless-numbers-increase; (specific image URL @ https://www.usgs.gov/media/images/monarch-male-close)

Research published March 21, 2016, in Scientific Reports by Scripps Institution of Oceanography at UC San Diego and U.S. Geological Survey reveals a concerning decline of 84 percent in the Eastern migratory monarch population from the winter of 1996-1997 to the winter of 2014-2015: USGS Wildlife Health @USGSWILDLIFE, via Twitter March 21, 2016, @ https://twitter.com/USGSWILDLIFE/status/711986242724823040

For further information:

The Center for Biological Diversity; The Center for Food Safety; The Xerces Society; and Dr. Lincoln Brower. 26 August 2014. Before the Secretary of the Interior: Petition to Protect the Monarch Butterfly (Danaus plexippus plexippus) under the Endangered Species Act. Monarch ESA Petition 1 - 159.
Available @ http://www.biologicaldiversity.org/species/invertebrates/pdfx/Monarch_ESA_Petition.pdf

Derla, Katherine. 22 March 2016. “Eastern Monarch Butterflies at Risk of Extinction.” Tech Times > Science > Environment.
Available @ http://www.techtimes.com/articles/143133/20160322/eastern-monarch-butterflies-at-risk-of-extinction.htm

Marriner, Derdriu. 5 March 2016. “250 Million Monarch Butterfly Gardens for 250 Million Monarchs in 2020.” Earth and Space News. Saturday.
Available @ https://earth-and-space-news.blogspot.com/2016/03/250-million-monarch-butterfly-gardens.html/

Puckett, Catherine; and Mario Aguilera. 21 March 2016. "Eastern Monarch Butterflies at Risk of Extinction Unless Numbers Increase." U.S. Geological Survey > News.
Available @ https://www.usgs.gov/news/eastern-monarch-butterflies-risk-extinction-unless-numbers-increase

Semmens, Brice X.; Darius J. Semmens; Wayne E. Thogmartin; Ruscena Wiederholt; Laura López-Hoffman; Jay E. Diffendorfer; John M. Pleasants; Karen S. Oberhauser; and Orley R. Taylor. 21 March 2016. “Quasi-Extinction Risk and Population Targets for the Eastern, Migratory Population of Monarch Butterflies (Danaus plexippus).” Scientific Reports 6 (23265). DOI: 10.1038/srep23265
Available @ http://www.nature.com/articles/srep23265

USGS. 21 March 2016. "Piedra Herrada Monarch Butterfly Sanctuary." YouTube.
Available @ https://www.youtube.com/watch?v=uDMA5f7mXE8

USGS Wildlife Health @USGSWILDLIFE. 21 March 2016. "Per #USGS report: eastern #monarch #butterfly at risk of extinction unless numbers increase." Twitter.
Available @ https://twitter.com/USGSWILDLIFE/status/711986242724823040

Vilsack, Tom; and Gina McCarthy. 19 May 2015. National Strategy to Promote the Health of Honey Bees and Other Pollinators. Pollinator Health Task Force 1–58.
Available @ http://www.whitehouse.gov/sites/default/files/microsites/ostp/Pollinator%20Health%20Strategy%202015.pdf