One of the last undammed perennial rivers in the desert Southwest, the San Pedro River in southeastern Arizona illustrates important processes common to many desert riparian ecosystems. Although historic land uses and climatic extremes have led to aquifer depletion, river entrenchment, and other changes, the river still sustains a rich and varied selection of life. Resilient to many factors, portions of the San Pedro have become increasingly threatened by groundwater pumping and other impacts of population growth.

This book provides an extensive knowledge base on all aspects of the San Pedro, from flora and fauna to hydrology and human use to preservation. It describes the ecological patterns and processes of this aridland river and explores both the ongoing science-driven efforts by nonprofit groups and government agencies to sustain and restore its riparian ecosystems and the science that supports these management decisions.

An interdisciplinary team of fifty-seven contributors—biologists, ecologists, geomorphologists, historians, hydrologists, lawyers, 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 affect its riparian biota. They then look at conservation and management challenges along three sections of the San Pedro, from its headwaters in Mexico to 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.

These chapters demonstrate the complexity of the San Pedro’s ecological and hydrological conditions, showing that there are no easy answers to the problems—and that existing laws are inadequate to fully address them. Collectively, they offer students, professionals, and environmental advocates a better grasp of the San Pedro’s status as well as important lessons for restoring physical processes and biotic communities to rivers in arid and semiarid regions.

All over the planet, organisms of many species are appearing outside of their natural habitats—often carried by that particularly peripatetic species Homo sapiens. This book marks the first comprehensive attempt to address problems posed by expanding populations of exotic plant and animal species in the Sonoran Desert and adjacent grasslands and riparian areas. It describes the arrival and spread of non-native species as diverse as rats and saltcedar, covering both their impacts and the management of those impacts. It is estimated that as much as 60 percent of the vegetative cover of the Sonoita Creek-Patagonia Reserve, the first Nature Conservancy area designated in Arizona, is dominated by exotic plants, and that introduced fish pose a recurrent threat to the native fish of that area. Meanwhile at the Grand Canyon, invasives such as tamarisk, red brome, carp, and catfish are pervasive either in the Colorado River or in the patches of desert scrub along its shores. Throughout the Sonoran Desert and adjacent areas, from islands in the Sea of Cortés to desert grasslands, some six hundred species of non-native plants and animals have become established, with bullfrogs and Mediterranean grasses now common where they once never existed.

The book brings together contributors from academia, government, and nonprofit organizations, including such experts as Gary Paul Nabhan, Richard Mack, and Alberto Búrquez-Montijo. They review historic and even prehistoric origins of non-native species—not only exotic plants, amphibians, and mammals but also insects, fish, and birds. They then examine significant problems in each major subregion and ecosystem and discuss control efforts. The volume contains the first compiled list of more than 500 naturalized exotic species in the Sonoran region. Invasive species issues are rapidly emerging as major environmental concerns both locally and worldwide. This book assists professionals—ecologists, conservation biologists, and policy makers—involved in invasive species control in the Southwest and will be a rich resource for all concerned with protecting native species and their habitats.