Interesting ...

[Paul Cherubini]

Ron wrote:

> My Milkweed/Monarch question is different.  I have  wondered if 
> there is any study that estimates the range and density of 
> various Milkweeds before the advent of Europeans on this continent.  

Ron, there are several biological issues all monarch experts agree on:

1. 92% of the overwintering monarchs in Mexico fed on Asclepias
    syriaca as larvae.  

2. Asclepias syriaca grows only in the central and northern USA
    and southern Canada.

3. Asclepias syriaca is abundant on disturbed ground,  but
    is absent in undisturbed prairie soil.  Therefore Asclepias syriaca
    is thought to have been a comparatively rare plant 400 years ago.

4. Deforestation of the Great Lakes region and New England
    by the Europeans the past 200 years (to grow crops) has greatly 
    increased the abundance of Asclepias syriaca.

Prior to the arrival of Europeans, certain milkweed species that
are rare today were probably alot more abundant because they
grow well on undisturbed ground.

The bottom line is that 400 years ago Asclepias syriaca could not
have been the milkweed species that supported 92% of the migratory
monarchs like it does today. From a conservation standpoint, this
history demonstrates how monarchs can do well even after humans 
have radically altered their SUMMER breeding habitats.

In the western USA the amount of milkweed available to monarchs
dramatically increased after the arrival of European man. Humans
irrigated and cultivated the river valleys of the near milkweedless Great
Basin desert which made it possible for disturbed ground milkweeds like 
Asclepias speciosa to thrive and spread.
http://www.saber.net/~monarch/yerington.JPG
http://www.saber.net/~monarch/nevada.JPG

On the California coast, the europeans planted groves of Australian 
eucalyptus trees on the formerly treeless coastal grassland prairies. 
Monarchs largely abandoned the native conifers, willows and sycamores
they had been using and moved into the eucalyptus.
http://www.saber.net/~monarch/oceano.JPG
http://www.saber.net/~monarch/oceano2.JPG From a conservation standpoint, 
this history demonstrates how monarchs can do well even after humans 
have radically alter their WINTER breeding habitats.

Now despite all this evidence that both the summer breeding
and overwintering habitats of monarchs can be radially altered
without causing a problem for the butterflies, the American monarch
scientific establishment refuses to be intellectually open to the 
possibliity that the same could be true of the overwintering habitats 
in Mexico.  Instead, they went in and told the 60,000 local 
indigenous people that selective logging in vast tracts of their 
forests like this one http://www.saber.net/~monarch/chincuadis.JPG 
can no longer be allowed, even though such limited logging has been 
practiced for centuries without harm to the butterflies.

But there is alot of evidence that demonstrates monarchs will exploit 
openings in the Mexican forests to their advantage just like they
exploit other kinds of human landscape disturbances.  Like this past
January after the big freeze the Chincua colony moved out of
the dense forest where 30% got killed and into this forest clearing to
get some sun
http://www.saber.net/~monarch/chincuapropertyline.jpg
The Mexicans cut this clearing decades ago to mark a property line
division.  They also cut a few such clearings to create fire breaks. Nowadays 
this kind of logging would not be allowed even though the monarchs 
obviously enjoy visiting the clearings to get some sun and warmth.

Another kind of landscape disturbance the American scientists object 
to is farming the slopes below the monarch colonies. For example, last
year in the News of the Leps Society Kurt Johnson & Robert de Candito  
had this to say:
http://www.saber.net/~monarch/kurt1.JPG. The casual reader
might think this farming has devasted the monarch overwintering area.  
But to the contrary, monarchs come down by the millions to these very
same farm fields and find an abundance of drinking water and flower 
nectar. 
http://www.saber.net/~monarch/kurt2.JPG 

In other words, logging in the forests below the monarch overwintering 
sites inadvertently creates water and flower nectar resources for 
the butterflies.  Apparently some kind of cultural conditioning issue 
prevents American scientists & conservationists from being happy 
about this win - win situation for both the local indigenous people
and the monarch butterflies. Possibly the same cultural reason they are
not happy to see California monarchs overwintering well in Australian 
eucalyptus trees. 
http://www.saber.net/~monarch/oceano.JPG
http://www.saber.net/~monarch/oceano2.JPG 

Paul Cherubini
Placerville, Calif.

 
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