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Human action and natural processes have modified the ecosystems of the earth in many ways, but one of the most pervasive effects of these processes on the environment is dissection of natural systems into spatially isolated parts, a process of fragmentation. Fragmentation has restricted the movements of people, livestock, and wildlife across landscapes, thereby limiting their access to resources that vary over space and time. This restriction impairs the ability of people and animals to compensate for temporal heterogeneity in vegetation and water by exploiting its spatial heterogeneity, and in so doing has interrupted ecological processes that sustain natural and human economies. Our thesis contrasts sharply with the mainstream view that exclusivity of use promotes human welfare and sustains natural processes. We propose that the sum of the productivities of land fragments may be less than the productivity of the unfragmented landscape.

The concept of fragmentation is explored in this book as it applies to arid, pastoral systems throughout the world. Global significance of the world's vast rangelands is large. Arid and semiarid rangelands make up almost 25% of the earth's landscapes and support more than 20 million people whose livelihoods depend on these lands. It is the home of the planet's last remaining megafauna and many other important species. The case is developed that fragmentation arises from different natural, social and economic conditions worldwide but creates similar outcomes for human and natural systems. With information from nine sites around the world the authors examine how fragmentation occurs, the patterns that result, and the consequences of fragmentation for ecosystems and the people who depend on them for their livelihoods.