Dr. Sears, Monarchs, Bt corn

Chip Taylor chip at ukans.edu
Tue Oct 10 21:13:57 EDT 2000

Hmmm. You missed on the last shot - so now you are diverting the 
discussion. Good ploy but I really don't have time to explain basic 
ecology, forest dynamics, the needs of the local people in Mexico, 
long term economic forces, global warming, or our current 
understanding of the impact, or lack thereof, of Bt corn etc.- Dr 
Sears notwithstanding. These issues are far more complex than you 
have assumed in your black and white scenarios.

For information on deforestation readers can consult the 12 September 
NYTimes. Papers will be published on this soon.

Loss of habitat includes loss of milkweeds and any change in 
agriculture that results in a reduction of milkweeds, such as Roundup 
Ready corn and soybeans, will have a negative impact on monarchs.

The jury is still out on the Bt corn issue in spite of the vigorous 
assertions of Dr Sears and the recent statements by the EPA. Polemics 
are involved here - not data.

Monarchs are identified in a recent study as being one of the species 
likely to be strongly impacted by global warming. Plants don't expand 
their ranges very rapidly, not as rapidly as will be needed in this 
case. Further, beyond the current northern range of milkweeds the 
soils and the plant/animal communities are thought to be less 
suitable for milkweeds.

>Item #1: Dr. Taylor fails to disclose that there are approx.
>33,000 acres of oyamel fir forest in the monarch overwintering
>area in Mexico and the monarchs' occupy a miniscule 20 acres of this
>acreage. Even if we assume the butterflies really need
>something like 500 acres to comfortably
>thrive,  it could be centuries before the butterflies
>are THREATENED due to deforestation (because of the huge
>amount of forested area available to them).  Moreover, it is
>downright silly to think that maintaining 500 hundred acres of
>forest cover (roughly 1 square mile) for the butterflies
represents a major technological hurdle.

>Item #2:  There are around 7,000,000 square miles of land in
>the USA. Somewhere between 600-900 square miles of this land
>each year is replaced with concrete and asphalt due to urban sprawl.
>At this rate we would be looking at 400+ years before even 5% 
>of the current open land area is lost to urban sprawl.To claim the
>monarch migration phenomenon is "threatened" by
>"habitat loss in the summer breeding range" is a serious
>Item#3: Over $100,000 of studies to date indicates Bt corn
>poses no THREAT to the monarch. Dr. Sears pointed
>out that even the most toxic form of Bt corn, that represents just
>1% of the Bt corn crop acreage may not be lethal to monarch
>larvae in real world field situations. Last year Dr. Taylor
>told reporters Bt corn "could raise hell with monarchs".
>Item #4: Global warming a threat to the monarch migration?
>How? If anything, global warming means milkweed plants
>can thrive further north into Canada, hence expanding the
>monarchs' summer breeding habitat. In my opinion, it is
>unprofessional behaviour for a university professor to cavalierly
>(without data or a model) tell a public crowd in New York
>that the  continuation of the monarch migration phenomenon is
>THREATENED by global warming.
>Dr. Taylor's may try to say what I just wrote above is itself
>somehow a misrepresentation or an example of "Cherubini's
>conspiracy theories"  In order to present Dr. Taylor's views
>as accurately as possible, below I have copied and pasted
>statements he currently has posted on his own website:
>Dr. Taylor wrote: (capitols my emphasis)
>"Given the great numbers of Monarchs (up to 100 million)
>that gather to migrate each fall, it is hard to imagine them
>facing any threat of EXTINCTION. In reality, however,
>Monarchs and their amazing annual migration are
>SERIOUSLY THREATENED by human activities, in both
>their summer and overwintering sites. Many of
>these threatening activities hinge on the destruction of
>good Monarch habitats.
>In the north (the United States and Canada), Monarchs face
>direct habitat destruction caused by humans. New roads, housing
>developments, and agricultural expansion - all transform a natural
>landscape in ways that make it impossible for Monarchs to live
>there. Monarchs in the north also face more subtle habitat
>destruction in the loss of their host plants. Milkweed, the plant
>larvae feed on exclusively, is considered a noxious weed by
>some people, which means it is often destroyed. In some areas
>across North America, milkweed plants are also being severely
>damaged by ozone. Both milkweed and adult nectaring plants
>are also vulnerable to the herbicides used by many landscapers,
>farmers, gardeners, and others. And Monarchs themselves can
>be killed outright by many pesticides.
>Eastern Monarchs migrate only to the Transvolcanic Mountains
>in Mexico where there are only eleven to fourteen known sites
>each year. Each site is a few hectares in size and contains
>millions of Monarch butterflies. This combination -a high
>concentration of individuals in a only few small sites - makes the
>possibility of habitat destruction in Mexico VERY SERIOUS."


Monarch Watch
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