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Butterfly on Flower Titled: HBW
Credit: Rachel Kramer (rkramer62 on flickr) / Licensed under Creative Commons Attribution 2.0 Generic

This week, I read a fascinating article by Emily DeMarco in AAAS (American Association for the Advancement of Science) called Monarch butterfly studies tell a perplexing tale. The key point is that seven studies have yet to flesh out what is behind the monarch butterfly's drastic decline at their wintering site in central Mexico's highland forests.

National Geographic's Eve Conant reported the following in her October 11th, 2014 article titled As Dwindling Monarch Butterflies Make Their Migration, Feds Try to Save Them:

IMG_1180Edward Rooks (edwardrooks on flickr) CC-by-2.0In the last twenty years, the North American monarch population has suffered a "catastrophic 90 percent drop."

The only food plant that the monarch caterpillar consumes is milkweed. This plant is crucial for protecting the monarch right through metamorphosis and even as a butterfly. Their larval stage milkweed diet renders the monarch butterfly bitter-tasting and toxic to predators.

Milkweed loss has been blamed on the use of glyphosate-based herbicides for genetically modified crops. But loss of a food source doesn't explain it all; summer monarchs are laying fewer eggs. Since 2006, the number of monarch eggs found on milkweed plants has decreased. University of Minnesota's Karen Oberhauser, the biologist who co-authored the study remarked:

 "It’s pretty scary, it probably means there aren’t enough monarchs out there to find the remaining patches."

In the northern reaches of the monarch's migratory path (Ontario, Canada and Michigan), their decline doesn't appear nearly as dramatic as further south. And there appears to be a lack of data collected in the Texas region, about midway to Mexico.

Monarch Butterfly Tagging 2012
Credit: Katja Schulz (treegrow on flickr) / Licensed under Creative Commons Attribution 2.0 Generic

Knowledge Gaps and Theories

Monarch Butterfly Tagging 2012 (a tagged butterfly)Katja Schulz (treegrow on flickr) CC-by-2.0As for the use of herbicides that kill milkweed, few studies have provided definitive conclusions.
 
It's quite likely, according to Georgetown University's Leslie Ries, author of one of the seven studies, that those collecting the data (volunteers and researchers) may have "under-sampled agricultural areas" impacted by herbicide use.
 
Instead, butterfly-watchers may have focused their attention on protected regions and parks.
 
I wondered about why monarchs are laying fewer eggs. An obvious reason is they are unable to find mates, due to habitat fragmentation and their declining numbers. So I looked up the University of Minnesota's Monarch Lab and discovered the following:
 
It takes about a month for summer monarchs to reach adulthood and those that do only live another two to six weeks. This is in stark contrast to monarchs that migrate – they live throughout the winter (between six and nine months).
 
But here's another factor: "Monarchs remain in the egg stage of their life-cycle for 3-8 days, depending on the temperature." Hence, why climate change may be driving the monarch butterfly's population down, especially in the south.
 
And I'm guessing that caterpillars that emerge from the egg on day three are substantially less well-developed than those who remain in the egg for eight days. Yet, according to Learn About Nature, "it takes about four days for the eggs to hatch."
 
Be-Jeweled Monarch (Butterfly) ChrysalisPROLinda Tanner (goingslo on flickr) CC-by-2.0And the new caterpillar (larva) eats only milkweed (for a span of about two weeks), until fully-grown.
 
Then it attaches itself with silk to a stem or something strong enough to support its weight while it transforms into a chrysalis. 
 
This process raised a few questions for me such as:
 
A) Is the "four days to hatch" adequate? Would monarch butterflies be stronger if they remained in their egg for five to eight days?
 
B) Since monarch larvae only consume milkweed, is there something lacking in the milkweed itself (nutrients or quality) or is it solely the herbicide on the plant that causes problems. Is milkweed so scarce that the monarch's habitat has become too fragmented?
Monarch Butterfly, El Rosario Sanctuary en Michoacàn-Mèxico.
Credit: Luna sin estrellas on flickr / Licensed under Creative Commons Attribution 2.0 Generic

Why Do Monarch Butterflies Head to Mexico?

Biologist Lincoln Brower, a professor at Sweet Briar College in Virginia, explained in Eve Conant's National Geographic piece that the monarch butterfly does not head south to keep warm. They fly to that specific region to remain protected from the elements by Mexico's forest canopy.

Brower mentioned:

"It's very interesting [that] everybody thinks monarchs go south to be warm during the winter. But they're going up into these high-elevation forests to keep cold so that they can get through winter with their fat reserves."

And those facts caused me to wonder if:

A) The "high-elevation" forests are no longer able to provide the ideal temperature due to global warming.

B) Are we losing the trees in these forests due to logging or human encroachment? 

Turns out that illegal logging was blamed for part of the problem. Fortunately, for over 10 years, Mexican businesses and philanthropists have funded programs to police this practice, plant trees, and promote ecotourism.

In a November 24th, 2014 Sci Dev Net post titled Hope for monarch butterfly after Mexican logging halted, large-scale logging has been stopped. Even the locals have ceased logging for firewood and timber. The director of WWF in Mexico, Omar Vidal (who also co-authored a 10-year study), concluded:

"Our decade-long research shows that actions to stop illegal logging in the monarch overwintering grounds are working thanks to efforts from local communities, authorities, civil society organizations, and the private sector."

Yellow Lantana Lunch
Credit: tdlucas5000 on flickr (taken June 20, 2015) / Licensed under Creative Commons Attribution 2.0 Generic

What is Needed for Monarch Butterflies to Recover

As Emily DeMarco's article pointed out, it appears crucial to restore, plant and conserve the regions where milkweed grows – the monarch butterly's breeding habitat. Curtailing or eliminating the use of certain herbicides, especially in the Midwest, would also help.

More data about what happens to monarch butterflies during migration might offer more clues. And the question is how much can we do to protect their migratory paths?

Climate change and global warming are probably huge factors beyond our control. But I wonder if various types of pollution in the air (or even if radioactive fallout from the 2011 Fukushima Daiichi's nuclear disaster) might be playing havoc with the monarch's reproductive health or the quality of the milkweed – or both.

When I viewed the distribution map of Cesium-137 in an August 20th, 2013 ENENews post titled Study shows Fukushima nuclear pollution becoming more concentrated as it approaches U.S. West Coast, the concentrated region appears to head straight for Mexico's northern border.

It's clear that monarchs need a multifaceted approach to restoring their numbers because with the decline of other insect pollinators such as bees, our entire food supply is at risk. In fact, the White House issued a memorandum on June 20th, 2014 which pointed out the following:

  • Pollinators contribute substantially to the economy of the United States and are vital to keeping fruits, nuts, and vegetables in our diets. 
  • The problem is serious and requires immediate attention to ensure the sustainability of our food production systems, avoid additional economic impact on the agricultural sector, and protect the health of the environment.
  • There is hereby established the Pollinator Health Task Force (Task Force), to be co-chaired by the Secretary of Agriculture and the Administrator of the Environmental Protection Agency.

Given the fact that in the US the "honey bee pollination alone adds more than $15 billion in value to agricultural crops each year", it's imperative for all of us to save monarch butterflies (and all pollinators).

It's truly incredible how dependent we are on these butterflies. And according to a January 5th, 2015 Scientific American article by John R. Platt, monarch butterflies could gain endangered species protection. I certainly hope so. 

Up next is a 1:07 minute report from Newsy Science's Sebastian Martinez about the U.S. Fish and Wildlife Service's pledge to save monarch butterflies.

U.S. Gov't Pledges $3.2M To Protect Monarch Butterflies

Published on February 10th, 2015

Monarch Butterfly
Credit: Paul VanDerWerf (pavdw on flickr) / Licensed under Creative Commons Attribution 2.0 Generic

Want to Help Monarch Butterflies? Create a Rest Stop

Published on August 19th, 2014 by National Geographic

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