Monarch butterflies often winter south to Mexico
Editor's note: Butterfly enthusiast John Weber reports in the second of a three-part series on the international Monarch conference held this summer in Minneapolis.
In the previous column on the June international Monarch butterfly conference I attended, I mentioned some aspects pertaining to the U.S.
Now I turn to Mexico, where the bulk of the eastern migratory Monarch population - that includes the Minnesota-raised butterflies - over-winter.
Until as recently as 1975, North Americans in the U.S. and Canada had no idea where Monarchs flying south in the fall ended up. Where they ended up was in trans-volcanic highlands west of Mexico City.
The over-wintering areas are small and have a patchwork-quilt of land ownership. They straddle two Mexican states -Michoacan and the State of Mexico. Ten municipalities have ownership as well as 100 agrarian properties.
A number of speakers and poster presenters were from Mexico. They valiantly spoke in their non-native English. They and their research associates from the U.S. painted this picture:
The main forest components of the over-wintering areas are oyamel fir, cedar and pine. Ideal conditions for the Monarchs would include an intact forest. However, that is no longer possible due to logging, storms and climate change.
Already early stages of climate change have occurred. Projections for the future suggest that the forest needs to be raised 300 to 400 feet. As one speaker said, "Trees can't move as fast as Monarchs fly." So seeds are being collected at lower elevations to be planted at higher elevations. The firs need to avoid the warmest months.
As a speaker via Skype from Mexico said about the Monarch Biosphere Reserve, aquifer recharge is an important aspect for the over-wintering Monarchs. As several other speakers echoed, the reserve is an important zone for rainwater capture - both for the forest and the surrounding indigenous communities.
As I listened, I was struck by "what a small world it is!" That is, here in northern Minnesota there are serious concerns about sustainable forests and long-term water resources.
Until recently, tourism attracted to the Monarch sanctuaries centered on the winter months when the Monarchs were present. However, during the last five years the focus was expanded to the rest of the year by developing other recreational activities such as hiking, mountain biking, camping and flora and fauna photography.
Again I was struck by the broad similarities facing the tourist-based economy around here.
Keynote speaker Dr. Lincoln Brower tied the U.S. and Mexican situation together in his somber talk entitled "Deluge and Drought: Conservation Concerns Based on Research Fieldwork in Texas and Mexico."
Based on his 58-year journey with Monarchs, he can certainly be called "Mr. Monarch." Chances are excellent that you've seen him on televised programs on Monarchs or quoted in newspaper and magazine articles.
Unlike many keynote speakers who jet in ... and immediately jet out after the speech, Brower was present throughout the entire conference, while carefully listening and talking to any and all persons who approached him.
The "deluge" in Brower's talk happened in Mexico in January-February 2010. Winter is the dry season at the over-wintering forests.
As Ernest Williams (Hamilton College, N.Y.) reported in his talk, "dry" Monarchs are an important over-wintering condition. "Wet" Monarchs succumb to hypothermia, disease, etc. and die.
Brower said the 2010 deluge totaled 14 inches Feb. 1-4 recorded at the Chincua station. The storm washed out hundreds of trees.
Subsequently, Brower returned to the storm site some months later. He feels these conservation lessons were learned from the Mexican deluge:
n Agencies must communicate more effectively with one another.
n On-the-ground enforcement of forest protection continues to be inadequate.
The "drought" in Brower's keynote happened last fall. On Oct. 31, 2011 the North American Drought Monitor showed much of Oklahoma and Texas in the D4 "exceptional" category. Drought also stretched well to the south deep into Mexico.
He wondered what effect the 2011 drought would have on the "lipid" (i.e. fat) stores of migrating and over-wintering Monarchs. In November, he found the Monarchs at the over-wintering sites had normal lipid levels. Initially he found this quite surprising after witnessing the Texas drought in person.
He discounted the "easy answer" that starving Monarchs simply did not make it to Mexico. Rather, he feels it highly likely that substantial unidentified and crucial nectar sources exist in Mexico north of the over-wintering sites.
Because he feels Texas nectar sources away from floodplains and oxbows are fallible, he deems nectar sources in northeastern Mexico as "crucial."
In 1994, Mexican researchers began making precise area measurements of the overwintering colonies. Last winter, Monarchs occupied less than 7.25 acres; only two winters were any lower.
Overall, the over-wintering population in Mexico declined 65 percent during the decade 1999-2010.
I am ending part two as a "cliff hanger," of sorts, for the future of Monarchs.
Next: Monarch Joint Venture.