Agricultural land covers approximately 40% of Earth’s land surface and affects hydromorphological, biogeochemical and ecological characteristics of fluvial networks. In the northern temperate region, agriculture also strongly affects the amount and molecular composition of dissolved organic matter (DOM), which constitutes the main vector of carbon transport from soils to fluvial networks and to the sea and is involved in a large variety of biogeochemical processes. Here, we provide first evidence about the wider occurrence of agricultural impacts on the concentration and composition of fluvial DOM across climate zones of the northern and southern hemispheres. Both extensive and intensive farming altered fluvial DOM towards a more microbial and less plant-derived composition. Moreover, intensive farming significantly increased dissolved organic nitrogen (DON) concentrations. The DOM composition change and DON concentration increase differed among climate zones and could be related to the intensity of current and historical nitrogen fertilizer use. As a result of agriculture intensification, increased DON concentrations and a more microbial-like DOM composition likely will enhance the reactivity of catchment DOM emissions, thereby fuelling the biogeochemical processing in fluvial networks and resulting in higher ecosystem productivity and CO₂ outgassing.

The flow of goods and services occurring in catchment areas allows the production of a series of ecosystem services. These have a direct impact on the inhabitants of the territory, who in turn recognise and value ecosystems (social value) as a function of the benefits which they generate. This has a direct impact on public policies that contribute to the development of local economies. The present study therefore sought to identify and recognize the social value of the various ecosystem services provided by a mixed-use catchment area in which different productive activities are concentrated. This study examined the social value of ecosystem services and offers qualitative or quantitative, non-monetary estimates of the relative importance of different benefits for human society derived from the functioning of ecosystems (Laterra et al, Valoración de Servicios Ecosistémicos, Conceptos, herramientas y aplicaciones para el ordenamiento territorial, 2011). The methodology involved the participation of leading actors in the territory, and a panel of experts who defined criteria and weighting which were applied to a multicriteria spatial model. They assigned ordinal scale to the territory representing levels of appreciation based on the various ecosystem services in the ecological, productive, landscape and cultural dimensions. The results showed that the inhabitants of the territory recognise the ecosystem benefit of areas covered by native forest, in particular the species Nothofagus dombeyi (Mirb.) Oerst., in contrast to areas used for farm production. The functioning of the ecosystem is recognised, and particularly its contribution to regulating water flows and to water production and quality. The study results showed that areas covered with secondary forest of N. dombeyi provide a variety of ecosystem functions which support the creation of ecosystem services to the population, especially in riparian areas throughout the basin where they are important for water production and quality. ES ponderations for provision, regulation and cultural showed that the native forest and riparian units (HEU 1 and HEU 6) as a very important group in relation to the ES because there are recognized by the local society (P < 0.05). The leading actors assigned a low social value to other land-uses, like mixed use and farmland, because of the high degree of anthropisation of these ecosystems; this viewpoint has generated conflicts in the territory. Neither foresters nor farmers recognise or accept the impacts of their activities on the various ecosystem services provided by the territories where they operate, even though they are leading actors for the development of local economies. The participation of the leading actors of a territory, represented spatially in a multicriteria analysis model, highlighted the social value of the ecosystems present in a hydrographic catchment area which supports different productive and conservation activities. The model contributed to understanding of the functional processes which generate goods and services present in the physical medium. The study used a hybrid method which included definition of homogeneous environmental units and multicriteria and multivariate statistical analysis. This allowed the information provided by the actors in the territory to be analysed with different spatial scales, levels of perception and elements of territorial planning which contribute to the generation of public policies and the sustainable management and conservation of natural ecosystems.

Background: Forest ecosystems provide services that are important for human use; one of the most critical ecosystem services is the provision and regulation of water. Basins with high forest improves hydrological functionality by promoting reduction in surface runoff, increase infiltration and aquifer recharge, and ensures base flow regulation amongst others. On the other hand, the conversion towards highly anthropized productive systems is usually accompanied by precarious environmental management that alters the hydrological cycle and reduction in water quality in basins. Aim: The goal of this study was to analyze land use changes and their effect on water efficiency index (WEI) in three sub-basins. Methodology: The methodology included a multi-temporal analysis of satellite images to identify land uses, also the use of SWAT (Soil and Water Assessment Tool) model for hydrological analysis in each sub-basin, information needed for calculating the WEI. Results: The results revealed the existence of no significant difference in terms of WEI between the sub-basins with predominant tree cover of native or artificial, being higher (0.89) than the WEI values reported by the sub-basin with agricultural land use (0.65). It is concluded that hydrological functions are more efficient in basins with forest cover, made up of native or exotic species, than agricultural land use with annual crop rotations. The results contribute to decision making on public policies associated to the rural productive activities. Concluded: Finally, we conclude the necessity of the promotion of forest plantation management techniques that avoid clear-cutting and multiple rotations in basin headwaters and riparian areas.