[tt] NS: How cowboys choked the American West

[Premise Checker]

How cowboys choked the American West
http://www.newscientist.com/article.ns?id=mg19826502.200&print=true
8.4.5
Fred Pearce

Dust is as much a part of the Wild West as guns, whiskey and cowboys.
Churned up by the hoofs of millions of longhorn cattle and filling the
streets of flyblown towns, it is the backdrop for many a shoot-out.
Until recently, most assumed that the American West was a natural dust
bowl where every cowboy breathed true grit. Now it seems that the dust
was mostly man-made and came with the cows. Head 'em up, move 'em out -
and choke on the dust. Before the cows and the cattle trails
immortalised in TV series such as Rawhide, there was no dust. Even
today, with Rawhide replaced by Brokeback Mountain in cultural
iconography, the dust continues to permeate. It could even explain some
of the changes in the region now blamed on global warming.

EVER since settlers moved west across the US there has been dust -
clouds of it everywhere. It was part of the landscape, or so it seemed.
But there were no records of the landscape of the West until the
settlers arrived. Now evidence is starting to emerge which suggests
that before the settlers there was very little dust.

The evidence comes from the San Juan mountains of south-west Colorado,
downwind of the badlands of Arizona and New Mexico. There Jason Neff, a
geochemist from the University of Colorado, Boulder, has been analysing
sediments laid down over the past 5000 years in alpine lakes.
Atmospheric dust was minimal throughout those five millennia until the
mid-19th century, he says. "Then bang. It was like flipping a switch.