The 2008 Joint Meeting of the Society for Range Management and the America Forage and Grassland Council.

Thursday, January 31, 2008 - 11:20 AM

Man as A Super-Engineer in Semiarid Ecosystems: Past Evidence and Future Role

Eugene David Ungar and Avi Perevolotsky. Agronomy and Natural Resources, ARO - The Volcani Center, Institute of Plant Sciences, POB 6, Bet Dagan, 50250, Israel

The natural vegetation of the semiarid Northern Negev region of Israel has been considerably impacted by grazing, cultivation and shrub cutting. Herding of small livestock and grain farming have been practiced for millennia. Till the 1950's, humans controlled shrub cover by harvesting it for energy for households and small industry. Recent comparisons have indicated that there is a qualitative difference between the Old and New Worlds in their resilience to grazing. According to this view, systems with millennia of grazing history are more robust when subjected to traditional patterns of heavy pastoralism. These ideas are discussed in the light of 20 years of research conducted at the Lehavim LTER site in the Northern Negev. Since its establishment, a slow increase in shrub cover (primarily Sarcopoterium spinosum) has been observed at this site. Grazing exclosures tended to exhibit enhanced shrub cover, supporting the claim that grazing is not the cause of "shrub desertification" but is a means of controlling it. The herbaceous productivity varied primarily in response to habitat and climate; no long-term trends in productivity have been detected. It seems that the herbaceous vegetation is well adapted to unpredictable rainfall and high grazing intensity. The diversity of annual plants is determined by the interaction between grazing and small-scale spatial and temporal variation in primary productivity. Shrubs act as a refuge for herbaceous species that are grazing sensitive. Scientific attitudes towards shrub vegetation and grazing animals have become less negative over recent decades. In the most progressive viewpoint, both types of organism are viewed as ecosystem engineers that can promote landscape heterogeneity and the preservation of resources at the hillside scale. Man's challenge is to understand this complex system and play the role of the super-engineer that manages the natural engineers to promote the long-term sustainability of the rangeland resource.

See more of Livestock Management in Shrub-Dominated Semi-Arid Rangelands: A Comparison of Landscape Histories and Pattern Use in the Mediterranean and Southwestern North America
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