[leps-talk] Why aren't Mexico's overwintering monarchs in the news yet this winter?

[Paul Cherubini]

I originally wrote:

> the monarch overwintering population in Mexico this
> winter was 35% above normal and 3.34 times as large as
> last winter.

Dr. Kurt Johnson responded:

> it still doesn't add up-- 35% increase in the Monarch's 
>returning to Mexico from a bumper year of good breeding 
>weather up north, still does not solve the problem of a 
>circa 50% loss of available forest land for overwintering
>in Mexico 

Cherubini follow up: 

Dr. Johnson, I did not say there was a 35% increase in the 
numbers of monarchs returning to Mexico this winter as 
compared to last winter. I said there were 3.34 times as many. 
Specifically, 93.35 million monarchs in Mexico this winter
vs. 28 million last winter = 333% increase.

>still does not solve the problem of a circa 50% loss of 
>available forest land for overwintering in Mexico 

I don't understand your point. My point is that the census
data indicates the size of the monarch overwintering 
in Mexico has been stable from 1985-2001

Here is the raw census data:

        Number of butterflies overwintering in Mexico

1985   80  million
1987   46  million
1988   40  million
1989   92  million
1990 120 million
1994   78 million
1995 125 million
1996 179 million
1997   32 million
1998   53 million
1999   60 million
2000   28 million
2001   93 million  (my graph said 100 million, but 93.35 
                              is the official census number
                              that just came in today)

Average: 76.7 million

Thus we see the numbers overwintering in Mexico 
this winter are above average and 333% larger than
last winter. We also see there is no upward or 
downward trend in the census figures.

Therefore is there any scientific evidence here that forestry
practices in Mexico or agricultural practices in
the USA have been harmful to monarchs in recent
decades? No.

So I don't understand your comment:

>still does not solve the problem of a circa 50% loss of 
>available forest land for overwintering in Mexico.

Can you elaborate on this?

Thanks,

Paul Cherubini

 
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