A watershed at a watershed: the potential for environmentally sensitive area protection in the upper San Pedro Drainage Basin (Mexico and USA)

Spatial variability in dissolved organic matter and inorganic nitrogen concentrations in a semiarid stream, San Pedro River, Arizona

“…Nutrient and solute concentrations in stream ecosystems generally are related to the characteristics of the surrounding watershed [ Aiken and Cotsaris , 1995; Allan and Johnson , 1997; Aryal et al , 2003; Boyer et al , 2000; Findlay et al , 2001; Heiny and Tate , 1997] and changes in land cover and land use often are reflected in stream and river chemistry. Semiarid regions throughout the world are experiencing substantial population growth and consequently urban expansion, which ultimately alters the characteristics of the watershed [ Butturini and Sabater , 2000, 2002; Parks and Baker , 1997; Steiner et al , 2000; Stromberg et al , 1996; Westerhoff and Anning , 2000], but how and if this land use change affects stream biogeochemical cycling remains an open question. The conversion of the natural landscape to agricultural or residential land uses can cause an increase in sedimentation and nutrient, particularly nitrogen, concentrations, especially when combined with the encroachment of nitrogen‐fixing species such as mesquite [ Allan and Johnson , 1997; Findlay et al , 2001].…”

From knowledge to action: lessons and planning strategies from studies of the upper San Pedro basin

“…However, due, in part, to the absence of a conceptual framework to assist local, state, federal and bi-national protection objectives, this work is not comprehensive. Content analysis of government documents on the upper San Pedro basin revealed the patchy nature of concerns for environmentally sensitive areas, owing in part to the fact that state and local government can employ different techniques to protect these lands depending on the nature of the statutory support (Steiner, 2000;Steiner et al, 2000a). As a result, a more thorough and rigorous framework is warranted.…”

“…The land uses and landscapes of the upper San Pedro basin exemplify these concerns Steiner et al, 2000a;Varady et al, 2000;Meredith, 2001). The fragmentation of individual land parcels is related to landscape fragmentation (see Lesson 2 in Section 4.2).…”

“…The historical, economic and political history of the basin has led to different systems of land tenure that further complicate the environmental consequences of land use. As populations and demands on land and water increase, another scenario of the tragedy of the commons might take place in upper San Pedro basin (Steiner et al, 2000a;Steinitz et al, 2003). On the U.S. side of the border, land tenure is divided between private, public land and preservation areas managed by governmental (federal, state, local, Indian) or nongovernmental bodies.…”

“…Ejidos occupy a major portion of the watershed. Historical change in land ownership in México has been influential on the future of watershed (Corcuera et al, 2000;Steiner et al, 2000a). The decision to convert land from one state to another-whether from natural to agriculture or agriculture to urban-is often a private one.…”