Thanks, Rick - that helps me understand better.

Any thoughts on the long-term effects? It would seem that, without the forests or even the grasses, the ground would be more susceptible to erosion (long-term impairment of soil, faster runoff for flooding and, more importantly, an impaired ability to hold the snowpack that's essential for water supply management, etc.) It would also seem that air quality would be impacted long-term (fewer trees = less carbon stored.) All of this - especially flooding - would seem to make human habitation in these areas more precarious.