Trees used by Monarch butterflies in California

[James J. Kruse]

On Wed, 23 Sep 1998, Paul Cherubini wrote:

> Another fact of monarch behavior that fustrates the "natural is always
> best" folks is that the numbers of monarchs overwintering in a grove of
> eucalyptus trees can sometimes greatly increase if one cuts out a large
> house sized hole in the grove.  When a home or industrial building is
> constructed inside a dense eucalytpus grove, the numbers of butterflies
> coming to the grove can rise dramatically.  This fact of monarch
> behavior is another issue that puts anti-development activists between a
> rock and a hard place.  The concept that residential or industrial
> development inside a eucalyptus grove could enhance the butterfly
> habitat seems to be sickening to them.

Say what you mean, just say 'Ecofreaks' :-)  You sound bitter, tell us
why?

Hmmm. Actually, you might as well put a house or industrial building
inside a dense eucalyptus grove because nothing else can grow there.
Literally _everything_ benefits when you cut a hole in a eucalyptus grove.
Sort of like cutting a hole in a plastic tarp that has been on the ground
for a couple of years. 

I have no doubt that planting eucalyptus will help monarchs, though to say
that eucalyptus groves are monarch 'habitat' is a little misleading. In
most places, the monarchs are around for about 3 months before they leave
the eucalyptus groves to find non-eucalyptus areas (since nothing
else grows there) with milkweed. In fairness, you did say 'roosting
habitat' when discussing enhancement by development.

I like monarchs, but there are other life forms on this planet. If you
have seen a mature grove of eucalyptus in California you can acknowledge
that nothing else grows where they grow. Between the shade and the oils,
there is nary a blade of grass. When eucalyptus groves are cut down, often
severe erosion results because of the lack of _any_ ground cover (Angel
Island for example).

There are plenty of examples where organisms have flourished when in
keeping with this kind of 'eucalyptus subdivisions' idea. European corn
borer has done quite well in the large monoculture corn plantations. Bark
beetles really like monoculture forest stands, which forest managers have
realized, and now have started mixing species of trees in a stand. Balance
is good. Too much of anything is bad (ice cream excepted).

I have met prairie 'activists' who insist prairie should be burned every
other year in order to grow nice lupine for the Karner Blues at the
expense of late-successional prairie species. The dune area at Antioch, CA
has turned into a virtual weed lot due to planting of wild buckwheat for
Lang's Metalmark. It has really helped them. They are everywhere. Notice
these last two examples were efforts for _endangered_ species, which
monarchs are not. We can definately help out one species where we want to,
but at what cost? I vote for balanced management, which in this case
means the monarchs can find another site (which they can, at least in
California). I don't feel caught between a rock and a hard place at all.

> This all seems to me to be a matter of our western society cultural
> conditioning. We are taught that we OUGHT to be sickened by such
> phenomena as a native butterfly prefering an exotic groves of roosting
> trees and OUGHT to think it is totally impossible for development to
> enhance a roosting habitat. 

oh...       Well, my posting drought is over anyhow.

Poised in fire retardants,
Jim Kruse
University of California at Berkeley
Dept. of Environ Sci, Policy and Mgmt.
Div. of Insect Biology
Sperling Lab
201 Wellman Hall
Berkeley, California, 94720-3112
(510) 642-7410/5114
http://www.CNR.Berkeley.EDU/sperlinglab/sperlinglab.html