Natural Landscapes and Optimal Resource Use at the Rio Grande Drainage Basin, Oaxaca, Mexico | Evaluación de la aptitud natural de los paisajes físico-geográficos en la cuenca del río Grande, Oaxaca, México

anglais. Environmental conservation depends largely on the appropriate management and rational use of natural resources. The assessment of natural landscapes and their suitability for human occupation is key to ensure optimal resource use. The criteria for establishing land-use potentials vary according to the type of activity concerned. For example, in determining the most suitable areas for growing grapes in Cuyo, Argentina, Valpreda (2005) focused on topography, soil quality and water availability, whereas in their study on the oil-producing region of northern Chiapas, Mexico, Bollo et al. (2010) applied markedly different criteria. Soil components and their variability were key to the multi-purpose study of Ovalles and Núñez (1994), while morphometric criteria have been used by Bocco et al. (2010) on farming; for cattle raising, Travieso-Bello et al. (2013) added soil quality and moisture, similar to Rodríguez-Gallego, et al. (2012). In the state of Oaxaca, scientific studies on the feasibility of human activity in different natural landscapes are yet to be undertaken. This study assesses the natural landscapes and resources of the Río Grande drainage basin aimed at establishing optimal locations for agriculture, livestock farming, forestry, wildlife conservation and their combinations. Following the FAO studies (1976, 1993), geomorphological and morphoclimatic systems have been considered as landscape units for analysis. The methodology was adapted from the following studies: The Revised Universal Soil Loss Equation (Ouyang, 2002); an estimate of soil pH based on Landsat imagery (López-Granados et al., 2005); a calculation of potential livestock carrying capacity (LCC) (Semarnat, 2003; Vergara and Ortiz-Espinoza, 2010); and a land use and vegetation cover analysis for forestry  suitability and the potential distribution of two cat species (Lynx rufus and Panthera onca) (Chávez y Ceballos, 2006; Medellín-Legorreta and Bárcenas, 2009; Semarnat 2010; Semarnat-Conanp, 2010). Our analysis shows that 15.6% of the total area (152 km²) has optimal conditions for agriculture; 12.5% (122 km²) for livestock farming; 6.5% (64 km²) for conservational agricultural activities; 11% (108 km²) for conservational livestock production; 11.7% (114 km²) for conservational forestry activities; and 167 km² (17.1%) for conservation alone. Finally, 25.6% of the territory (250 km²) is suitable (but not optimal) for agriculture, conservational livestock activities and conservation. This methodology based on physicalgeographical landscapes allows to identify vocational land-use patterns across the Río Grande drainage basin as a means to optimize the management of the various economic activities. The identification and evaluation of productive and conservation potentials in the various geomorphologic and morphoclimatic systems of the river basin were governed by two basic geographic principles: spatial analysis of physical and geographic constraints with a holistic approach, and the mapping of natural resources as inputs for territorial analysis and the development of optimal management strategies. Both principles allowed the establishment of sectorial planning under the magnifying glass of natural aptitude and optimum land use. The same exercise may be carried out to benefit other Oaxacan regions, as well as other regional and national projects.

espagnol; castillan. El objetivo central de la evaluación de los paisajes físico-geográficos para optimizar su uso demanda el análisis de su aptitud natural o vocación con vistas a proponer patrones de ocupación adecuados a sus condiciones intrínsecas. Esta evaluación constituye una herramienta metodológica clave a partir de la cual es posible seleccionar formas óptimas de uso para cada unidad de paisaje, como unidad de análisis espacial. En el estado de Oaxaca son escasos los estudios científicos integrales, sobre todo aquellos enfocados a la evaluación de la vocación natural de sus unidades de síntesis natural −los paisajes físico-geográficos−. En este sentido se aborda la aptitud natural en la cuenca del río Grande, mediante la evaluación de los atributos naturales de sus paisajes, tomando algunos criterios de la metodología de la evaluación de tierras (FAO, 1976, 1993), enfocados a los requerimientos para las actividades agrícola, pecuaria, forestal, de conservación y sus combinaciones. El área con las mejores condiciones para la práctica de actividades agropecuarias equivale al 15.6% de la cuenca (152 km²); para la actividad pecuaria se identificó un 12.5 % (122 km²); la aptitud óptima para la conservación con actividades agropecuarias ocupa 6.5% (64 km²); la actividad mixta de conservación-pecuaria abarca 11% (108 km²); la actividad de conservación-forestal posee 11.7% (114 km²) y la actividad de conservación alcanza 17.1% (167 km²). Finalmente, 25.6% de la cuenca (250 km²) posee condiciones para el desarrollo agropecuario, de conservación-pecuario y de conservación, pero no clasifican con una aptitud óptima.