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 Cautin river is located in the Araucania region, Chile (38°S), and is characterized by alterations through human interference in its surrounding basin, by the presence of introduced salmonids, and by its mixed regime, which originates from melting snow in summer and rains in winter. The fauna of this river includes an invertebrate fauna composed of both endemic and widespread species, which has, however, been only poorly studied until now. The aim of the present study was to make a review of the ecological role of the benthic inland water crustaceans of the River Cautin, in order to understand their importance in the ecosystem of the river. The literature revealed the presence of abundant populations of amphipods and freshwater crabs as well as of aquatic insects along the river’s course. Many of these crustaceans are prey for both introduced salmonids and native fishes. Similar results have been reported for other southern Argentinean and Chilean Patagonian rivers.

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In recent years, social and environmental conflicts concerning the aquaculture sector have increased. These conflicts arise from the different perception that individuals, collectives, private companies and the State have about the potential impacts of aquaculture on the environment and quality of life. The Environmental Impact Assessment (EIA) of aquaculture projects in Chile is the main administrative tool for decision-making, allowing identify, predict, and propose preventive measures to mitigate negative consequences of this growing sector. This article analyzes the performance of the EIA in Chile concerning aquaculture projects between 1994 and 2019. Of the 5323 projects entering the Chilean EIA during this period, the EIA system-performance analysis selected the 71 most representative. For a reliable comparative analysis, the selected projects were first classified in accordance with the active regulation within the period. Subsequently, 14 performance indicators were selected and similarities—by means of a principal coordinate analysis—were explored. Significant differences between the third (SD40) and the first two (SD30 and SD95) regulations were observed. Based on these results and considering demands of local communities and social leaders (who request continuous articulations among technical areas, administrative tools, and policies to increase the sustainability standards of aquaculture), four opportunities for improving the EIA in aquaculture projects are proposed: incorporation of synergistic and cumulative effects, adaptation to climate change, development of a general methodology, and incorporation of early citizen participation (in projects having environmental charge) increasing the performance and confidence of the EIA. The introduced methodology enables comparisons of the EIA process in different regulatory periods using indicators, serving as guidance to evaluate the performance of the EIA in aquaculture. This methodology can also be used by other aquaculture producing countries around the world.

Background: Urbanisation is a dominant geographical trend and an important component of global change, with unprecedented implications for socioeconomic , cultural and environmental characteristics. However, green areas, including original fragments, can help to conserve native diversity, improving the functioning of these artificial systems in the long term. Urban areas can still provide habitats usable by wild birds, however the structural characteristics of the habitat formed by different types of green area differ, and therefore dissimilar bird diversities are to be expected. The object of this study was to characterise the α and β diversities of birds in different green areas and to analyse how diversity relates to ten variables that characterise the habitat. Methods: We studied the green areas in the city of Temuco, southern Chile (Park, Square and Median strips of main streets), evaluating the variables: (a) surface area, (b) vegetation, (c) estimated human impact as the proportions of vegetation and bare soil by area, and the vehicle traffic. The bird assemblage structures were characterised by α (intraenvironment) diversity and β diversity (between environments) and the statistical analysis identified the environmental variables related with the presence and abundance of birds. A statistical model was constructed to describe the contribution of the variables to bird diversity. Results: We found significant differences between the diversity of bird species in the three types of green area. The β showed medium to high similarity between the different study units. There was a negative correlation with bare soil areas; the correlations with vehicle flow, plant structure and tree and shrub cover were not significant, meaning that these variables did not explain the variation in the richness of bird species between the green areas. However the surface area did explain this variation presenting a positive potential relation. There was also a high correlation with the origin (native) of shrub species. Conclusions: The bird diversity varied significantly according to the type of urban green area. The environmental variables presenting significant correlations with bird diversity were: surface area, native species of shrub stratum, shrub cover, and bare soil area. The best multiple regression model showed that the three most important variables for bird diversity are the surface area of the green area, the cover of the shrub stratum and the presence of native shrub species.