FW: Mexico expands monarch butterfly habitat

[Paul Cherubini]

Cris Guppy  wrote:

> The only problem is, there is a considerable difference between winters in
> southern California and the mountains of northeastern Mexico. The two types
> of hibernation sites are simply not comparable. It is COLD in the mountains,
> and the air temperature in small stands is significantly colder than in a
> large continuous tract of forest.

During the past 23 years there have been many snow storms and freezes
in the mountains of Mexico and many opportunities for scientists to
find out whether monarch mortality was greater in thinner vs. thicker
forests. In not one case have scientists find a correlation between forest
density or stand size and the amount of mortality during frigid or snowy 
weather - despite the fact there is a 2- 7 fold difference in forest density
from one colony to another.

All time historical record low temperatures along the California coast and at the
overwintering sites in Mexico are in the 20-25 degrees F range. Monarchs
have a certain degree of freeze resistance and most survive temperatures
this low (unless they are soaking wet in which case they freeze at slightly 
higher temps). 

> Also, although the area has been set aside as a reserve, it is obvious that
> disturbances (natural and human) will continue within that area. If a
> disturbance affects a small reserve, the Monarchs lose their winter habitat.
> If a disturbance affects a large reserve, the Monarchs just move to another
> part of it.

62 square miles of forest (=39,680 acres =16,000 hectares) in Mexico was 
set aside for monarchs back in 1986. This is a huge amount of forest 
considering the butterflies occupy only a miniscule fraction of it. Even the
smallest exisitng reserve is huge from this perspective. There have been 
no cases of disturbance to date (natural or man made) anywhere in central
Mexico sufficient to leave the mountain tops bare of forest - hence no cases of
monarchs losing their habitat.  So the bottom line as I see it is there is no 
scientific basis for tripling the size of the reserves from their already
substantial size (62 square miles =39,680 acres =16,000 hectares) 
to 216 square miles = 138,240 acres = 56,000 hectares.

> In California, if a disturbance (storm, fire) knocks out the remant stands,
> what is going to replace them? Trees take many decades to grow.

Seven monarch overwintering sites burned during the devastating
Malibu coast fires in California in Oct 1993. All recovered by 1998. 
Monarch overwintering sites have been created from scratch on bare ground
in just 7-15 years - pines, eucalyptus and firs grow fast. Trees need to be 
only 20-30 feet tall to make suitable overwintering sites. 

In Mexico, devastating crown fires such as those which are common in
British Columbia in summer are almost unknown in the monarch 
overwintering area because the forest is moist year round (ir rains almost
every afternoon in summer).

Paul Cherubini, Placerville, Calif.

 
 ------------------------------------------------------------ 

   For subscription and related information about LEPS-L visit:

   http://www.peabody.yale.edu/other/lepsl