Los agroecosistemas mediterráneos de zonas semiáridasvaloración y demanda de servicios ecosistémicos

Abstract

Determining the provision of and social demand for the ecosystem services (ES) and counter-services (EDS) provided, given the influence they have on human well-being, is one of the current challenges in the study of agroecosystems. ES are the benefits that society obtains from a given ecosystem, while EDS are the negative social impacts caused by an ecosystem. ES are usually grouped to be studied in four broad categories: provisioning, regulating, cultural and supporting. One of the main ecosystems located in the semi-arid areas of the Mediterranean basin is the agricultural systems, or agroecosystems. Agroecosystems are characterised on the one hand by the variety of services they provide, given their highly multifunctional nature, and on the other by their high vulnerability to the effects of climate change, land use changes, etc. Thus, analysing the provision and relationships of ES/EDS of agroecosystems, and determining their valuation, is key to achieve an effective design of agricultural policies that would lead to the socially demanded model of agriculture. Currently, there is a gap in research literature on ES/EDS of Mediterranean semi-arid agroecosystems, not in terms of production technology aspects, but in terms of service provision levels and social demand, especially in certain areas such as peri-urban spaces or extreme aridity areas. The aim of this thesis is to generate new knowledge on the ES/EDS provided by Mediterranean agroecosystems in semi-arid areas, focusing on the design and application of approaches for the analysis of their provision and social demand. The case study, the Region of Murcia (Southeast Spain), is particularly appropriate for this purpose, given the existence of a dual character of its agriculture, combining rainfed agriculture, not very productive, highly technified irrigation systems, with a clear commercial orientation and, traditional irrigation systems in the fertile riversides with cultural components coexist. In order to achieve this aim, methodologies for the identification and quantification of ES/EDS are developed and adapted, applying both spatial techniques, using Geographic Information Systems tools, and socio-economic valuation methods through the stated preferences approach, using contingent valuation, ranking contingent and choice experiments. Given the most relevant ES/EDS in semi-arid Mediterranean agroecosystems identified in the literature, this thesis identifies and constructs a set of variables and indicators for them. Thus, a regional quantification and mapping of the provision of food supply, water consumption, waste treatment and water purification, climate regulation, genetic diversity and recreational opportunities is carried out, which offers a novel global vision of both the level and the territorial distribution of ES/EDS. Regarding the climate regulation ES, a more detailed spatial analysis of its provision is carried out, leading to the proposal of a method for its quantification in perennial crops agroecosystems. Likewise, and given the influence that the aesthetic quality of the landscape has on the provision of other cultural services such as recreation, this ES is specifically quantified by considering the objective and subjective perspective of the landscape together. Regarding the study of social demand, two cases are studied: the social preferences of agroecosystems in drylands with high cultural values (Badlands); and the social welfare generated by the implementation of allotment gardens in degraded peri-urban ecosystems. The results obtained provide new criteria to be considered in the formulation of agri-environmental and land-use policies that allow managers to better understand the relationships between agricultural ES/EDS, in order to make decisions that maximise social welfare.