Insect Apocalypse: Count Finds Critically Low Number of Monarch Butterflies for Second Straight Year

Liz Kimbrough February 29, 2020

Monarchs Cluster on Monterey Pine in California.

Edi­tor’s Note: This arti­cle was orig­i­nal­ly pub­lished by Mongabay news and is repub­lished here under a cre­ative com­mons license.

Monarch but­ter­fly pop­u­la­tions are at a crit­i­cal low, accord­ing to the annu­al West­ern Monarch Count in California.

In the fall and win­ter, west­ern mon­archs (Danaus plex­ip­pus plex­ip­pus) stop to roost along the Pacif­ic coast in Cal­i­for­nia. Here, under the direc­tion of the Xerces Soci­ety, near­ly 200 trained vol­un­teers find and count mon­archs for the annu­al West­ern Thanks­giv­ing and New Year’s counts, now in its 23rd year.

And for the sec­ond year in a row, the counts have gen­er­at­ed trou­bling num­bers. Few­er than 30,000 indi­vid­u­als were found — the num­ber, researchers say, may be the tip­ping point for the population.

For an ani­mal that ranges across the entire West and has his­tor­i­cal­ly been in the mil­lions, we just don’t know how low it can go,” Emma Pel­ton, the west­ern monarch lead at the Xerces Soci­ety, told Mongabay. So, 30,000 is a best guess. The past two years have been real­ly test­ing that guess. If they do col­lapse it would look like a down­ward spi­ral of the pop­u­la­tion … it would nev­er real­ly recover.”

This year, vol­un­teers count­ed 29,418 mon­archs. And although this is 2,200 more indi­vid­u­als than last year, the increase, accord­ing to the Xerces Soci­ety, rep­re­sents no mean­ing­ful dif­fer­ence in the pop­u­la­tion. Instead, it attrib­ut­es the num­ber to greater sur­vey­ing effort by more volunteers.

We had real­ly hoped last year was an all-time low and that we would have a bounce back,” Pel­ton said. We didn’t see that. On the flip side, it didn’t get small­er. We didn’t see a total collapse.”

Key Take­aways:

  • The lat­est annu­al count of west­ern monarch but­ter­fly num­bers at their over­win­ter­ing sites on California’s Pacif­ic coast has revealed a sec­ond con­sec­u­tive tal­ly of less than the crit­i­cal thresh­old of 30,000.
  • The group behind the count says that fig­ure may be the tip­ping point for the species, below which the pop­u­la­tion decline would accel­er­ate into a down­ward spiral.
  • A major threat to the but­ter­flies is the loss of suit­able habi­tat; 20 of their over­win­ter­ing sites have been dam­aged by human activ­i­ty in the past five years, and the vast major­i­ty of the remain­ing 400 sites lack protection.
  • Sci­en­tists are call­ing on farm­ers to min­i­mize pes­ti­cide use and plant cli­mate-adapt­ed hedgerows; land man­agers to restore habi­tat by grow­ing monarch-suit­ed veg­e­ta­tion; and ordi­nary cit­i­zens to make their own small yet mean­ing­ful contributions.

West­ern monarch but­ter­flies mate in Neva­da. Pho­to cour­tesy of Stephanie McK­night / Xerces Society.

The annu­al West­ern Monarch Count is a mas­sive com­mu­ni­ty sci­ence project start­ed in 1997 by three sci­en­tists: Mia Mon­roe, who is still active­ly involved, and Den­nis Fray and David Mar­riot, who both passed away in 2019. This group, accord­ing to Pel­ton, had the fore­sight to get peo­ple to band togeth­er to count the but­ter­flies at these sites because they were con­cerned about a notice­able drop in numbers.

I grew up in the SF Bay Area and monarch but­ter­flies were abun­dant, added beau­ty, won­der and a chance to enjoy the cycles of nature,” Mon­roe told Mongabay. Vis­its to over­win­ter­ing sites were a high­light of each year … the decline I’ve wit­nessed through the for­mal Thanks­giv­ing Count has been very disturbing.”

The world is fac­ing an insect apoc­a­lypse, and monarch but­ter­flies are no excep­tion. Monarch pop­u­la­tions have been declin­ing for decades, threat­ened by insec­ti­cides, cli­mate change, par­a­sites and dis­eases spread by agri­cul­ture, and habi­tat loss.

And for mon­archs, habi­tat is key. Mon­archs are the only known but­ter­fly to make a two-way migra­tion, sim­i­lar to birds, though their migra­tion hap­pens over the course of sev­er­al gen­er­a­tions. Along this migra­to­ry route, they choose very spe­cif­ic sites to over­win­ter, some­times return­ing to the same tree or even the same branch gen­er­a­tion after gen­er­a­tion. These areas rep­re­sent spe­cif­ic micro­cli­mates, best suit­ed for the rest of the winged travelers.

Monarch but­ter­flies clus­ter on a tree branch. Pho­to cour­tesy of Can­dace Fal­lon / Xerces Society.

Mon­archs are divid­ed into two main pop­u­la­tions: west­ern mon­archs, which over­win­ter in Cal­i­for­nia, and east­ern mon­archs, which over­win­ter in the Sier­ra Madre moun­tains of Mex­i­co. The east­ern pop­u­la­tion is fac­ing a sim­i­lar cri­sis to its Cal­i­for­nia kin; pop­u­la­tions of east­ern mon­archs have declined 80% over the past 20 years.

Mex­i­can over­win­ter­ing sites face threats from defor­esta­tion and min­ing. And the recent mur­ders of Home­ro Gómez González, a long­time but­ter­fly defend­er who man­aged the El Rosario but­ter­fly sanc­tu­ary with­in the much larg­er Monarch But­ter­fly Bios­phere, and Raúl Hernán­dez Romero, a but­ter­fly tourist guide, have under­scored the seri­ous­ness of the threats to these plots of land and those who defend them.

Home­ro Gómez González man­ag­er of the El Rosario but­ter­fly sanc­tu­ary was found dead in Jan­u­ary 2020. Image tak­en from his Face­book page.

The U.S. Fish and Wildlife Ser­vice is expect­ed to decide in Decem­ber 2020 whether or not the monarch but­ter­fly war­rants inclu­sion in the Endan­gered Species Act, which would offer sig­nif­i­cant legal pro­tec­tion for the species in the U.S.

In Cal­i­for­nia, there is no com­pre­hen­sive legal pro­tec­tion for monarch over­win­ter­ing sites. In the past five years, 20 such sites active­ly used by mon­archs were dam­aged or destroyed by human activities.

In lieu of legal pro­tec­tion, the Xerces Soci­ety has been part­ner­ing with state parks in Cal­i­for­nia, which are the sin­gle largest landown­ers of over­win­ter­ing sites. It is now work­ing with six state parks to cre­ate pro­tec­tion and restora­tion plans.

But this,” Pel­ton said, can feel like a drop in the buck­et. There are 400 sites that need pro­tec­tion and the vast major­i­ty are not pro­tect­ed. There is a huge gap with not enough resources or atten­tion paid.”

As depress­ing as these num­bers are,” she added, let them real­ly be a wake­up call to moti­vate peo­ple, even if it’s just for the swal­low­tail in your yard.”

The Xerces Soci­ety is also edu­cat­ing and urg­ing farm­ers to min­i­mize pes­ti­cide use and plant cli­mate-adapt­ed hedgerows, and encour­ag­ing land man­agers to restore habi­tat by grow­ing ear­ly-sea­son milk­weed and oth­er flow­er­ing plants.

A west­ern monarch nec­tars on rab­bit­brush in Neva­da. Pho­to cour­tesy of Stephanie McK­night / Xerces Society

The Xerces Soci­ety has edu­ca­tion­al resources for cit­i­zens who want to help the west­ern mon­archs. But, if you live in a place where mon­archs aren’t native, Pel­ton says, focus on your local bees and but­ter­flies; reduce pes­ti­cide use in your home and gar­den; buy native veg­e­ta­tion; grow flow­er­ing plants; advo­cate for changes around pes­ti­cide use at a local or region­al scale; and just remem­ber that every­one can con­tribute.”

I believe in the resilien­cy and adapt­abil­i­ty of life,” Mon­roe said. I’ve cel­e­brat­ed the rebound of pel­i­cans and whales; con­dors and otters, so I hope that mon­archs will respond to the enthu­si­as­tic work many are under­tak­ing now.”

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