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Riparian habitats historically constituted 1% of the land mass in western North America. Within the past 100 years, an estimated 95% of this habitat has been altered, degraded or destroyed due to a wide variety of land use practices such as river channelization, clearing for agriculture, livestock grazing, water impoundments and urbanization. Many authors now concur that the single most important land management practice impacting western riparian ecosystems has been unmanaged domestic livestock grazing. Over 70% of the western United States is currently being grazed by livestock in habitats ranging from sea level to alpine meadows. Unwise grazing practices have been shown to negatively affect Southwestern riparian vegetative composition, ecosystem function, and ecosystem structure. This has resulted in negative impacts on native wildlife populations including insects, fish, reptiles, amphibians, birds, and mammals. Negative impacts due largely from over a century of heavy domestic livestock utilization in riparian ecosystems has resulted in the decline of many wildlife populations. Studies have shown that up to 70% of avian species in the desert Southwest depend upon riparian habitats for survival at some stage of  life. Over torty percent of Arizona’s state-listed bird species are considered to be riparian obligate species. Ninety percent of Arizona’s native fish species are now extinct, extirpated, or Federally or state listed. Many other vertebrate species have declined in recent years due to alteration of riparian habitats, and may soon be considered for Federal listing. To prevent future listings and to reverse population declines of sensitive wildlife species, land management agencies need to implement appropriate practices within riparian ecosystems. (source abstract)