Introduction

Soil is the surface layer of unconsolidated mineral material that covers terrestrial areas which, besides supporting many organisms, maintains complex dynamic interactions with the atmosphere and underlying strata, allowing the maintenance of environmental services of ecosystems and influencing climate and the hydrological cycle (SSSA, 2009). Thus, soil is, along with climate, one of the key factors that determine the distribution of ecosystems and natural resources in a region. In Mexico, as a result of its complex geological history and climatic diversity, there are 26 of the 30 soil groups recognized by the World Reference Base for Soil Resources (IUSS, 2007), the dominant being Leptosols (28.3% of the territory), Regosols (13.7%), Phaeozems (11.7%), Calcisols (10.4%), Luvisols (9%) and Vertisols (8.6%) than jointly account for 81.7% of the country’s surface area (INEGI, 2007).

Modern human societies have conceived soils as simple mechanical supports for plants or sites for the establishment of human settlements, ignoring their biological, ecological, physico-chemical, socioeconomic and cultural importance  (Cotler et al., 2007 y 2011). This conception has contributed, along with other factors, to the destruction and degradation processes that affect soil resources. Soil degradation essentially refers to the processes related to human activities that reduce the soil’s current and future capacity to support natural or managed ecosystems and deliver their intrinsic environmental services (Oldeman, 1998). Soil degradation processes include water and wind erosion, characterized by the removal of soil particles; and physical, chemical and biological degradation, mainly related to the impairment of soil quality. Soil degradation occurs in many countries, including Mexico, especially in those characterized by growth patterns based on the unsustainable use of natural resources (UNCCD, 2012). Soil degradation leads to negative environmental and socioeconomic effects due to its relationship with biodiversity loss, poverty, migration and food security (Oldeman, 1990; Cotler et al., 2007; UNCCD, 2012).

The causes of soil degradation are multiple. It results from multiple environmental and socioeconomic factors such as production systems, deforestation, overgrazing, geology, hydrology, precipitation intensity and duration, soil type, population density, and land tenure systems, among others (Cotler et al., 2007). Globally, the main driving force of degradation is overgrazing, deforestation inappropriate agricultural practices, firewood extraction and industry and urbanization (Nachtergaele, et al., 2011). In Mexico, the extent of edaphic issues is aggravated by the scarcity of expertise on this resource (particularly with regard to soil suitability and vulnerability), as well as by flaws in the regulations on soil use and management (Cotler, 2007).

Under such circumstances, several programs aimed at addressing, protecting and preserving soils, have been launched in the country by different government agencies, at national, regional and state levels. Approaches to soil conservation have changed markedly worldwide in recent decades, and Mexico has adopted these new trends. Efforts used to focus initially on mechanical protection measures, such as building levees and terraces, largely to reduce runoff; currently, efforts are being redirected to biological methods aimed to integrate water conservation and soil protection by managing soil-plant-water interactions, and by reducing soil disturbance through tillage (Conafor, Semarnat, 2009).

To adequately describe the pressures imposed on soil and the conditions and responses implemented for its conservation and management, it is necessary to differentiate them according to their use. On one side, there are soils that support natural ecosystems with varying degrees of conservation which still maintain their original function; on the other hand, there are soils where the original vegetation cover has been completely removed to be used for some economic activity such as agriculture. In the first case, restoration could be attempted; in the second, objectives should focus on maintaining the soil productivity.

References

Conafor, Semarnat. Restauración de ecosistemas forestales. Guía básica para comunicadores. Conafor, Semarnat. 2009.

Cotler, H., E. Sotelo. J. Domínguez, M. Zorrilla, S. Cortina y L. Quiñones. La conservación de suelos: un asunto de interés público. Gaceta Ecológica  83: 5-71. 2007.

Cotler, H., C. A. López y S. Martínez-Trinidad, ¿Cuánto nos cuesta la erosión de suelos? Aproximación a una valoración económica de la pérdida de suelos agrícolas en México. Investigación Ambiental 3: 31-43. 2011.

INEGI. Conjunto de datos vectorial edafológico, escala 1: 250,00 Serie II (Continuo Nacional). México. 2007.

IUSS, Grupo de Trabajo WRB. Base Referencial Mundial del Recurso Suelo. Primera actualización 2007. Informes sobre Recursos Mundiales de Suelos No. 103. FAO. Roma. 2007.

Nachtergaele, F., R. Biancalani y M. Petri. Land degradation. SALOW Background Thematic Report 3. FAO. Roma. 2011.

Oldeman, L.R., R.T.A. Hakkeling, y W.G. Sombroek. World map of the status of human-induced soil degradation. ISRIC. Wageningen. 1990. Disponible en: www.isric.org/projects/global-assessment-human-induced-soil-degradation-glasod. Fecha de consulta: octubre de 2013.

Oldeman, L.R. Guidelines for general assessment of the status of human-induced soil degradation. Working paper 88/4. ISRIC. Wageninen. 1998.

SSSA. Glossary of soil science terms. 2009. Disponible en: www.soils.org/publications/soils-glossary. Fecha de consulta: octubre de 2013.

UNCCD. Zero net land degradation. A sustainable development goal to Rio+20. UNCCD Secretariat. Bonn, Germany. 2012.