The Monarch

[Paul Cherubini]

Stan Gorodenski wrote:
> 
> I just got back from the Pacific slope meeting of the Lep Soc. Ron
> Leuschner gave a short summary of the meeting in South Carolina.
> Apparently, it is now fact beyond dispute that 75% of the Monarchs died
> in the freeze that had occurred in Mexico. This was caused by a rain
> that preceeded the freeze. The rain got all the Monarchs wet and as a
> result the normal congregating behaviour to prevent a freeze did not
> work.

Conservation society articles say forest thinning (selective logging) 
is to blame for the reason the butterflies get wet and freeze:
http://www.saber.net/~monarch/wwf.jpg

But here is a scientific article 
http://www.saber.net/~monarch/Picture122.JPG that concludes
"it is clear from this study that  forest cover is not sufficient to protect
 all butterflies within a colony from occassional winter storms..."

The article further speculates that a closed forest canopy
- where the tips of the tree branches touch one-another - probably
favors butterfly survival by helping to prevent butterflies from becoming
saturated.

But this begs the question - is the present day closed canopy forest 
in some monarch overwintering areas of Mexico a natural situation or
the result of decades of fire suppression and cutting older trees?

Indeed most of the fir and pine trees in the monarch reserves in Mexico
around only around 40 years old, grow very densely and the trunks are 
about as thin as telephone poles (not exactly old growth forests).
http://www.saber.net/~monarch/chincuadense.JPG

On the ecology-l listserve some forestry authorities pointed out that
one reason the half million acre Show Low fire in northern Arizona  
burned so fiercely in recent weeks was because the forest is dominated
by young pine trees (40-80 years old) growing more closely together than 
than they used to when old growth forests existed in the area.  
They attribute this situation to decades of fire suppression and
selective logging of old trees, thus creating dense stands of young 
trees with a more closed canopy than is natural. 

By analogy with the forest situation in northern Arizona, it appears
possible that the present day closed canopy forest in Mexico,  which 
some monarch scientists believe is important to prevent wetting of the 
butterflies, is actually an artificial, man made forest situation due to
decades of fire suppression and selective logging !

In other words,  when old growth forests used to exist in the monarch 
overwintering area, the forest canopy may have provided less protection
against butterfly wetting because the canopies were more open than
they are today.

Ironic to say the least !

Paul Cherubini

 
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