Evaluación de la aptitud natural de los paisajes físico-geográficos en la cuenca del río Grande, Oaxaca, México

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 physical-geographical 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.