SC - Columbus' chilies

[Jeff Gedney]

> What evidence do we have that the Sahara was still a grassland in Classical
> times? Or by "Antiquity" do you mean further back than say 100 AD?
this goes back to something I remember from school (we were 
discussing climatology...)

Lybia and the North of Africa were called " the Breadbasket of Rome", 
where where the gigantic "Grain ships" of the Romans loaded up.
I remember reading that at its peak North Africa supplied some 80% 
of the Empires total cereal grain supply. 

What apparently happened is that the Roman farming practices were 
not efficient, and they never heard of crop rotation or letting a field go 
fallow to replenish the soil. as the soil grew more impoverished, and 
yeilds decreased, the Romans simply expanded the fields to makeup 
the difference.
They effectively Agriculturally "stripmined" much of Noth Africa.
a very similar cause and effect to the Dust Bowl catastrophe of 
Midwestern America 70 - 80 years ago.

The problem with this is that what they were farming on was actually 
a thin layer of glacially deposited soil over what had been a HUGE 
prehistoric desert.  As the impoverished soil dried up and blew away,
it began to expose very large areas of the prehistoric desert.

Now the process of desertification occurs at the margins, and the 
desert expands because the area of sand affects the atmosphere
over the deserted area, and as the moisture is sucked out of the 
periphery, the dunes blow over and cover the soil, and the desert 
grows until it is limited by a barrier, either climatological, such as the 
monsoon rains of equatorial Africa, or physical, such as the 
mountain ranges of the American Southwest, or the Mediterranean.

If you want to see this desertification in miniature, check out the 
"Desert of Maine", which was a prehistoric Desert, and which
was "liberated" by sand quarrying in the 40's and 50's.

Brandu