>> Most obvious was the fact that where animals were
>> present, plants
>> were green and growing. In areas without animals
>> they were gray and
 in most

that is called synchronisation  or reversing the cause and effect
relationship ,it remind me the sentence of Masanobu Fukuoka when he is
talking about the rain : <the rain doesn't come down from the sky, it comes
from the leaves. >
the leaves need the rain to survive so they call for the clouds. the animals
need the plants so they call for their optimum growth. the predatory animals
need their prey so they care for their herds
IN fact i suspect the human species have been the only one to depart from
fulfilling  this essential function "caring " for their food source .
I say often to my vegetarians environmentalists friends that the best way to
care for the animals is to eat them

>> cases today, it's livestock that stimulate the wild
>> herd behavior -
>> are the only realistic tool that can halt the
>> advance of deserts over
>> billions of acres of rough country.

I am agreeing but question the ability of humans to simulate ( i understood
that it was this word intended to be written instead of stimulate)the wild
herd behavior with their livestock.
I have seen in India the effect of overgrazing the mountains of Kerala on
desertification
Thoses mountains , 50 years ago were still  a lush forest inhabited by
tribes of mostly hunter gatherers
It was a land that supported BIg mammals like elephants . The Indians from
the plains started to colonise the aera with their plow and their grazing
herds of sheep goat and cattles. The result in 50 years is dramatic streams
are running out.
I walk  one of this dried out river bed from the watershed to the running
river . In the 15 minutes that we sat at the top of this watershed we saw 3
childrens with 3 differents herds going by (sheep,  goat and cattles).
we saw too how the fencing off of thoses herds ,of an other water shed could
do in 10 years time (the forest was back, the stream running year round
again).
it is just a question of balance,  yes plants needs the animals as much as
the animals need them, they care for each over. and will naturally balance
each over 's population.
the herds of big mammals will trampled at time an aera and will leave it to
rest for a long while before visiting it again. Hard to mimmic this pattern
when you are limited by ownership of the land.
It is certainly true that the barbed wire had a desastrous effect on the
health and productivity  of North america's grass  lands . It gave the
illusion to the ranchers that they could keep easely more cattles than the
land was abble to support sustainably. The proof is that the need for grain
suplementation became a kind of necessity..
I have seen recently an old  picture ( at the begining of the century)of a
hay field in this island where the grass was taller than the mens, Now in
those same pastures the grass is half size on  average ( and the white mens
came only 100 years ago here)
With the famous salt spring island sheeps the grass can't get taller than
the knee.
we have a lot to learn for fullfiling the role that have been imparted to us
in the bible (Taking care of all the animals and plants)
jean-claude