Philip;
I attended Grad school at New Mexico State University in Las Cruces and majored in Desert Ecology. This area of southern New Mexico historically was grassland. There are reports from early settlers of grass high enough to "tickle a horse's belly".
The early European settlers had no idea how fragile this landscape was and treated it just like grassland everywhere. The grass was mainly gone after the extensive droughts of the late 1800's. With the loss of grass went most of the topsoil. It's amazing to look at photos and see such differences even in the past 130 years! In California the same thing happened with our native bunch grasses and by the turn of last century they were replaced by invasive Spanish grasses.
I too have the second volume of the Changing Mile and just haven't found time to read it yet. Its interesting o read the first edition as the authors are trying to walk a political tightrope between singling out cattle as the culprit or some other factor.
Its too bad we missed each other by one day last summer at the WW&F (I was hiking Katahdin the day you were there).
Maybe next time...