1. Introduction
1.1. Agricultural land use in arid ecosystems
Increasing demands and needs from a growing human population
have resulted in the widespread use and rapid conversion of
most natural land-cover types to agriculture. This conversion trend
only slowed down in recent decades because of the intensification
of agricultural practices resulting in increased crop yields from
fertilizer and pesticide use (Tilman et al., 2002). However, other
limiting factors (water, sunlight or temperature) for each particular
agricultural region also affect productivity (Rabbinge, 1993).