The arrival of Anglo settlers in the 1870s marked the beginning of major vegetation changes in southeastern Arizona, including an increase in woody plants in rangelands, the degradation of riparian wetlands, and the spread of non-native plants. While many of these changes have already been linked to human land-use through comparative photographs and historic descriptions, it has long been presumed that changes in the region's climate have also contributed to vegetation change. Geographer Conrad Bahre now challenges the view that these vegetation changes are due to climatic change. Correlating his own field research with archival records and photographs, Bahre demonstrates that most of the changes follow some type of human disturbance, such as cattle grazing, fuelwood cutting, wildfire suppression, agriculture, and road construction. Indeed, all available evidence suggests that Anglo settlement brought unprecedented changes to the land. Vegetation change in the American West has long been an issue of concern. This careful scrutiny of one corner of that region—one of the most ecologically diverse areas of the United States—shows how poorly understood is the relationship between human activities and vegetation. More important, it introduces new techniques for differentiating between natural and anthropogenic factors effecting vegetation change that can be used to help ecologists understand vegetation dynamics worldwide.

contributors - biologists, ecologists, geomorphologists, historians, hydrologists, lawyers, and political scientists - weave together threads from their diverse perspectives to reveal the processes that shape the past, present, and future of the San Pedro's riparian and aquatic ecosystems. They review the biological communities of the San Pedro and the stream hydrology and geomorphology that affects its riparian biota. They then look at conservation and management challenges along three sections of the San Pedro, from its headwaters in Mexico in its confluence with the Gila River, describing legal and policy issues and their interface with science; activities related to mitigation, conservation, and restoration; and a prognosis of the potential for sustaining the basin's riparian system." "Complemented by a foreword written by James Shuttleworth, these chapters demonstrate the complexity of the San Pedro's ecological and hydrological conditions, showing that there are no easy --