Summary: Archer, S. 2010. Rangeland conservation and shrub encroachment: new perspectives
on an old problem. In: Rangelands or Wildlands? Livestock and Wildlife in
Semi-Arid Ecosystems (Johan du Toit, R. Kock, J. Deutsch, eds.). Blackwell
Publishing Ltd. In Press.
Rangelands support the majority of the world's livestock production and provide
important wildlife habitat. Their airsheds and watersheds influence the health and well
being of the 30% of the world's human population that live in them. Woody plant
proliferation has emerged as a major issue in managing many of the world's rangelands.
This phenomenon is a stark contrast to deforestation, which has received considerably
more attention. Traditional concerns about this change in land cover were narrowly
focused on impact related to livestock production and management of wildlife valued for
sport hunting. We have only recently begun to explore the implications of this
widespread change in land cover on ecosystem goods and services that arise from the
changes in biogeochemical cycles and land surface-atmosphere interactions that
accompany the conversion of grasslands to shrublands or woodlands.
In arid and semi-arid regions, woody plant encroachment represents desertification and
is accompanied by accelerated rates of water and wind erosion. The latter has known
impacts on ocean productivity and snow pack persistence. Pollen and dust production
triggered by encroaching trees and shrubs can contribute to human health problems