Local extinction and colonisation in native and exotic fish in relation to changes in land use

Distribution patterns of many native and exotic fish species are well documented, yet little is known about the temporal dynamics of native and exotic diversity in relation to changes in land use. We hypothesised that colonisation rates would be higher for exotic fish species and that extinction rates would be higher for native species in large stream systems. We also predicted that cold-water species would be more impacted than thermally tolerant species. To test these hypotheses, we used generalised linear mixed models to compare changes in native and exotic fish species richness over 10 years in a French drainage basin subjected to landscape alterations. Exotic fish were more susceptible to local extinction than the native ones. Extinction was greater among cold-tolerant species and at higher elevations. Colonisation by exotic species was higher at lower elevations. Although a decade of expanding urbanisation affected fish colonisation, agricultural lands experienced higher extinction rates. In the context of global changes in land use and population pressure, our study suggests that the temporal dynamics of fish diversity are driven by landscape alterations as well as by the thermal tolerance of species

Spreading of Antarctic Bottom Water in the Atlantic Ocean

This paper describes the transport of bottom water from its source region in the Weddell Sea through the abyssal channels of the Atlantic Ocean. The research brings together the recent observations and historical data. A strong flow of Antarctic Bottom Water through the Vema Channel is analyzed. The mean speed of the flow is 30 cm/s. A temperature increase was found in the deep Vema Channel, which has been observed for 30 years already. The flow of bottom water in the northern part of the Brazil Basin splits. Part of the water flows through the Romanche and Chain fracture zones. The other part flows to the North American Basin. Part of the latter flow propagates through the Vema Fracture Zone into the Northeast Atlantic. The properties of bottom water in the Kane Gap and Discovery Gap are also analyzed

Effects of a large irrigation reservoir on aquatic and riparian plants: a history of survival and loss

Dammed rivers have unnatural stream flows, disrupted sediment dynamics, and rearranged geomorphologic settings. Consequently, fluvial biota experiences disturbed functioning in the novel ecosystems. The case study is the large irrigation reservoir Alqueva in Guadiana River, Southern Iberia. The study area was divided into three zones: upstream and downstream of the dam and reservoir. For each zone, species composition and land use and land cover (LULC) were compared before and after the Alqueva Dam implementation. Data consist of aquatic and riparian flora composition obtained from 46 surveys and the area (%) of 12 classes of LULC obtained in 90 riverine sampling units through the analysis of historical and contemporary imagery. There was an overall decrease of several endemic species and on the riparian shrublands and aquatic stands, although di erences in the proportion of functional groups were not significant. Nevertheless, compositional diversity shows a significant decline in the upstream zone while landscape diversity shows an accentuated reduction in the reservoir area and downstream of the dam, which is likely related to the loss of the rocky habitats of the ‘old’ Guadiana River and the homogenization of the riverscape due to the irrigation intensification. The mitigation of these critical changes should be site-specific and should rely on the knowledge of the interactions between surrounding lands, ecological, biogeomorphologic, and hydrological components of the fluvial ecosystemsinfo:eu-repo/semantics/publishedVersio

Agriculturización e impactos ambientales en un área representativa de la ecorregión de las pampas, argentina.

Estudos prévios demonstram a existência do processo de agriculturização na ecorregião das Pampas, e o partido de Tandil constitui um exemplo desse processo. Esse trabalho compara as áreas ocupadas pelos distintos usos da terra e seus impactos ambientais na Bacia Superior do Arroio Langueyú e no Partido de Tandil, na qual ela está inserta, em três cortes temporais: 1988, 2002 e 2010. Aplicou-se uma classificação supervisada sobre imagens captadas pelo sensor TM com ajustes realizados no campo. Entre 1988 e 2002, os usos agrícolas têm aumentado significativamente na Bacia (159,5%), enquanto no Partido aumentaram 39,4%. Como conseqüência, os impactos ambientais sobre o meio natural, medidos com indicadores de sustentabilidade, foram mais intensos na Bacia do que no conjunto do Partido. Os resultados obtidos permitem colaborar no desenvolvimento de propostas de gestão ambiental tendentes à sustentabilidade agroecológica.Previous studies have shown the existence of the process of agriculturization in the Ecoregion of the Pampas, and Tandil County is a representative example of the process. This paper compares the areas occupied by different land uses and their environmental impacts in the Upper Basin of the Langueyú Creek and in Tandil County, in which the basin is located, in three points of time: 1988, 2002, and 2010. Supervised classification was applied on images captured by the sensor TM with adjustments to field. Between 1988 and 2010, agricultural uses in the Basin increased significantly (159.5%) while in the County, the agricultural areas increased 39.4%. Consequently, the environmental impacts on the environment, measured by sustainability indicators, were more intense in the Basin than in the County as a whole. The results allow collaborate in the development of environmental management proposals aimed at agroecological sustainability.Des études préalables démontrent l’existence d’un processus d’agriculturization dans l’écorégion des Pampas, et le département de Tandil constitue un exemple de ce processus. Ce travail compare des zones occupées par des différents usages de la terre et ses impacts environnementaux dans le Bassin Supérieur du Ruisseau Langueyú et dans le département de Tandil, où elle s’insère, dans trois périodes de temps: 1988, 2002 et 2010. On a appliqué une classification supervisée par des images captées avec le senseur TM et des ajustements réalisé sur le terrain. Entre 1988 et 2002, des usages agricoles ont augmenté considérablement dan le Bassin (159,5%), alors que l’augmentation dans tout le département a été de 39,4%. En conséquence, les impacts environnementaux sur le milieu naturel, mesurés avec des indicateurs de durabilité, ont été plus intenses dans le Bassin que dans la totalité du département. Les résultats obtenues permettent de collaborer dans le développement de propositions de gestion environnemental tendent à durabilité agroécologique.Estudios previos demuestran la existencia del proceso de agriculturización en la Ecorregión de las Pampas y el partido de Tandil constituye un ejemplo del proceso. Este trabajo, compara las áreas ocupadas por distintos usos de la tierra y sus impactos ambientales en la Cuenca Superior del Arroyo Langueyú y en el partido de Tandil, en el cual se haya inserta, en tres cortes temporales: 1988, 2002 y 2010. Se aplicó una clasificación supervisada sobre imágenes captadas por el sensor TM con ajustes realizados a campo. Entre 1988 y 2010, los usos agrícolas aumentaron significativamente en la Cuenca (159,5%), mientras que en el Partido 39,4%. En consecuencia, los impactos ambientales sobre el medio natural, medidos con indicadores de sustentabilidad, fueron más intensos en la Cuenca que en el Partido en su conjunto. Los resultados obtenidos permiten colaborar en el desarrollo de propuestas de gestión ambiental tendientes a la sustentabilidad agroecológica.Fil: Vazquez, Patricia Susana. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Humanas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Zulaica, Maria Laura. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Agronomia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Environmental effects related to the local absence of exotic fish

Given the extent of biological invasions in industrialized countries, our understanding of the determinants of overall patterns of biological invasions could gain most from consideration of why exotic species are absent from some areas, rather than from distribution patterns of exotic species. Fish communities were sampled at 381 sites representing 221 rivers in the Adour-Garonne stream system (116 000 km², SW France). Very few rivers were not colonized by exotic fish species, however, on a local basis, only 33% of the sampling sites hosted exotics. Using General Linear Modelling, we found that patterns of exotic fish (occurrence, number of species, proportion within assemblage) responded to both land-use and physical variables, whereas patterns of native fish only responded to the local meso-scale characteristics of each stream reach from headwaters to mouth. All fish communities were susceptible to invasion regardless of native species richness, and higher native species richness did not decrease the opportunity for establishment by exotic species. The likelihood that exotic fish are absent primarily increased with elevation and with lower human influence upon the land cover, while human-impacted landscapes (agricultural and urban areas) were more likely to host exotic fish and higher numbers of exotic species. In light of urban and agricultural development, our ability to detect responses of exotic species to landscape alterations using a combination of simple physical and land cover variables exemplifies a cost-effective technique for assessing areas at greater invasion risk in large stream systems

A baseline appraisal of water-dependant ecosystem services, the roles they play within desakota livelihood systems and their potential sensitivity to climate change

This report forms part of a larger research programme on 'Reinterpreting the Urban-Rural Continuum', which conceptualises and investigates current knowledge and research gaps concerning 'the role that ecosystems services play in the livelihoods of the poor in regions undergoing rapid change'. The report aims to conduct a baseline appraisal of water-dependant ecosystem services, the roles they play within desakota livelihood systems and their potential sensitivity to climate change. The appraisal is conducted at three spatial scales: global, regional (four consortia areas), and meso scale (case studies within the four regions). At all three scales of analysis water resources form the interweaving theme because water provides a vital provisioning service for people, supports all other ecosystem processes and because water resources are forecast to be severely affected under climate change scenarios. This report, combined with an Endnote library of over 1100 scientific papers, provides an annotated bibliography of water-dependant ecosystem services, the roles they play within desakota livelihood systems and their potential sensitivity to climate change. After an introductory, section, Section 2 of the report defines water-related ecosystem services and how these are affected by human activities. Current knowledge and research gaps are then explored in relation to global scale climate and related hydrological changes (e.g. floods, droughts, flow regimes) (section 3). The report then discusses the impacts of climate changes on the ESPA regions, emphasising potential responses of biomes to the combined effects of climate change and human activities (particularly land use and management), and how these effects coupled with water store and flow regime manipulation by humans may affect the functioning of catchments and their ecosystem services (section 4). Finally, at the meso-scale, case studies are presented from within the ESPA regions to illustrate the close coupling of human activities and catchment performance in the context of environmental change (section 5). At the end of each section, research needs are identified and justified. These research needs are then amalgamated in section 6

Integrated land and water management for food and environmental security

Water resource management / Food security / Environmental effects / Soil degradation / Water pollution / Watersheds / Urbanization / Public policy / Water quality / Ecosystems / Land resources / Water scarcity / Developing countries / Poverty / Households / Food supply / Economic aspects / Social aspects / Groundwater depletion / Salinity / Wetlands / Investment / Land use / Water use / Training needs assessment / Research priorities