Monarch Migration Predicted to be Extinct within 16 years

Stanley A. Gorodenski stan_gorodenski at
Tue Oct 7 12:51:27 EDT 2003

Patrick already made some of the points I would have made had he not 
beat me to the post. I just want to add to it by stating that I think 
you are misrepresenting Brower's statement. He said, as you showed in 
the link to your web site, "...will probably be destroyed within 10 to 
20 years". I do not read this to be a forecast that it _will_ become 
extinct in 2000. Further, as Patrick pointed out, did he blunder or 
warn? I do not think his statement, which was couched in such uncertain 
terms (using the word "probably" and giving a 10 year range of when the 
event _might_ occur), to be of such a nature that it can be called a 
"blunder". Even if his statement could be held up as a blunder you 
cannot call it that now because we still have seven(?) years to go yet. 
He did give a range of years. Further, I recall reading about 
conservation efforts and conflicts with Mexican loggers. It seems to me 
that Brower's warnings, as Patrick indicated, may have resulted in the 
Monarch doing better than expected.

As an aside, I can see some potential problems with the current method 
to determine the size of overwintering populations. How well are the 
hectare area results corrected for such things as thinning, new growth, 
dead growth, etc. so that we know within a certain range of statistical 
confidence that one hectare of overwintering Monarchs equals to X number 
of adults? It may be that Brower is overestimating the population size 
of overwintering Monarchs when he said it is above average.

I do not recall you giving long range forecasts of  the Manarch. What 
are your predictions? A graph like what Brower had would be good.

Patrick Foley wrote:

> Paul,
> Is it possible that without Brower's constant harping, the Monarch's 
> wintering habitat in Mexico would be more threatened than it is today?
> Did Brower blunder? Or did he warn? Is the habitat in Mexico secure 
> now? Brower gets ten more years on his "blunder", based on the quote 
> you link. And note, Brower is not claiming that Monarchs will be 
> extinct in ten years, he is claiming that the Eastern migratory 
> phenomenon is likely to be extinguished. I think Brower may be wrong, 
> partly because he was right to push for the protection of the 
> overwintering sites. But I also think that the migratory phenomenon is 
> more fragile than you do. At some point of overwintering mortality in 
> Mexico, the Eastern monarch population is going to be under strong 
> selection to avoid it.
> If you are so concerned with getting the research right, why not do 
> some research into that? You certainly have a right to your own 
> constant harping (as does Brower), but are you helping clear up the 
> ecology and evolution of this organism, or are you just pissing people 
> off?
> Obviously you know a lot about the Monarch, and your posts do provide 
> some interesting insights. However you will get more respect if you 
> treat others with more respect, and if you are scrupulous to avoid 
> biasing your insights.
> It is not the business of scientists to be infallible. We leave that 
> to others. At the end of the day, Brower will surely be wrong about 
> some things and right about others. And we will know a lot more baout 
> the Monarch. And maybe the Eastern migratory phenomenon will be more 
> secure. If his conservation organization also is rolling in money 
> (which I greatly doubt), this is the least of our worries.
> Enjoy the historical recall vote today!
> Patrick Foley
> patfoley at
> Paul Cherubini wrote:
>> Stan wrote:
>>> I have to question what Dr. Brower meant by "...normal..."  If his
>>> "normal" is a 10 year moving average,  and if (as an example) the
>>> average 11 years ago was three times what it was last year, saying 
>>> it is
>>> "slightly above normal" could cause one to misinterpret this to mean 
>>> the
>>> Monarch is doing very well.
>> The total size of the monarch overwintering population in Mexico
>> is determined by measuring the total forested area occupied by the 
>> butterflies.  Over the years, the total forested area occupied has 
>> been found
>> to range from 2 - 18 hectares and the average has been about 8 
>> hectares (= 20 acres).
>> During the 2001-2002 overwintering season, the total area occupied
>> by the monarchs was found to be 9.6 hectares, so that is why Dr. Brower
>> said the size of monarch overwintering population was "slightly above 
>> normal".  
>> Back in 1988-1991, however, Dr. Brower was predicting the extinction 
>> of the monarch migratory phenomenon
>> as early as the year 2000.  For example, here is what Dr. Brower
>> wrote in the journal "American Zoologist" in 1991:
>> In spite of this blunder, Dr. Brower continues to predict the 
>> extinction of the monarch migration, but has moved the date of
>> final demise up to the year 2019.  
>> Paul Cherubini
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