Changes in livestock footprint and tree layer coverage in Mediterranean dehesas: a six-decade study based on remote sensing

摘要

The decade of the fifties of the twentieth century triggered huge changes in land use and management in ecosystems worldwide, including the iconic Mediterranean ecosystems known as dehesas. In this study, we have quantified the changes in dehesa landscape status within a geographic area of 200,000km(2) covering mainly the Spanish dehesa range over the last 60years. We focused on changes of two important dehesa elements: tree density and live stocking rates. Tree density and tree cover change were measured via remote sensing in 29 sample plots (16km(2) each) and selected from the plot-monitoring network of Spanish Rural Landscapes (SISPARES). Live stocking (cattle, sheep, and pig) rates data were obtained from the National Statistical Institute of Spain and were used to assess the entire study area. During the 1950-80s, tree density and cover declined significantly (by 18% and 13%, respectively). By the 1960s, sheep was predominant over cattle in all provinces; pigs had higher stocking rates than in the following decades. However, during the 1970-80s, sheep and pig stocking rate declined drastically (by 90% and 70%, respectively) in just 20years. In contrast, cattle stocking rate increased progressively since the 1960s, reaching a 60% increment by the 2000s. At the municipality level, we observed similar trends. Our multi-scaled analysis explains the impact of social, political, and economic factors on the conservation status of the main dehesa territory within Spain. We conclude that it is necessary to ensure the effectiveness of these systems through sustainable activities to avoid negative consequences of poor management practices which threaten dehesa perpetuation.