Brigitta Schütt

Mapping Complex Patterns of Erosion and Stability in Dry Mediterranean Ecosystems

Parametrizing soil reflectance spectra with variables related to specific shape characteristics of the spectral profile permits organic carbon concentrations in soils to be estimated on the basis of regionally validated regression models. An important feature of the approach is that it can not only be applied to continuous spectra but, without notable loss in accuracy, also to the spectral resolution of operational earth observation satellites such as the Landsat-TM or -ETM systems. Using this type of imagery, it can also be shown that soil organic matter is positively correlated to growth conditions for cereal crops in dryland agriculture. Strong correlations with qualitative erosion indicators that can be derived through spectral unmixing approaches demonstrate that soil organic matter is an important indicator for assessing land degradation processes in dry ecosystems from space.

Soil erosion and conservation in Ethiopia: A review

This paper reviews Ethiopia’s experience and research progress in past soil and water conservation (SWC) efforts and suggests possible solutions for improvement. Although indigenous SWC techniques date back to 400 BC, institutionalized SWC activity in Ethiopia became significant only after the 1970s. At least six national SWC-related programs have been initiated since the 1970s and their focus over time has shifted from food relief to land conservation and then to livelihoods. The overall current soil erosion rates are highly variable and large by international standards, and sheet, rill, and gully erosion are the dominant processes. The influence of human activities on the landscape has traditionally been deleterious, but this trend seems to have recently reversed in some parts of the country following the engagement of the communities in land management. The efficiency of SWC measures show mixed results that are influenced by the type of measures and the agro-ecology under which they were implemented; in general, the relative performance of the interventions is better in the drylands as compared with humid areas. Methodological limitations also occur when addressing the economic aspects related to benefits of ecosystem services and other externalities. Although farmers have shown an increased understanding of the soil erosion problem, SWC efforts face a host of barriers related to limited access to capital, limited benefits, land tenure insecurity, limited technology choices and technical support, and poor community participation. In general SWC research in Ethiopia is fragmented and not comprehensive, mainly because of a lack of participatory research, field observations, and adoptable methods to evaluate impacts. A potentially feasible approach to expand and sustain SWC programs is to attract benefits from global carbon markets. Moreover, a dedicated institution responsible for overseeing the research–extension linkage of SWC interventions of the country should be established.

An assessment of the global impact of 21st century land use change on soil erosion

Human activity and related land use change are the primary cause of accelerated soil erosion, which has substantial implications for nutrient and carbon cycling, land productivity and in turn, worldwide socio-economic conditions. Here we present an unprecedentedly high resolution (250 × 250 m) global potential soil erosion model, using a combination of remote sensing, GIS modelling and census data. We challenge the previous annual soil erosion reference values as our estimate, of 35.9 Pg yr−1 of soil eroded in 2012, is at least two times lower. Moreover, we estimate the spatial and temporal effects of land use change between 2001 and 2012 and the potential offset of the global application of conservation practices. Our findings indicate a potential overall increase in global soil erosion driven by cropland expansion. The greatest increases are predicted to occur in Sub-Saharan Africa, South America and Southeast Asia. The least developed economies have been found to experience the highest estimates of soil erosion rates.Human activity and related land use change are the primary cause of soil erosion. Here, the authors show the impacts of 21st century global land use change on soil erosion based on an unprecedentedly high resolution global model that provides insights into the mitigating effects of conservation agriculture.

Reconstruction of palaeoenvironmental conditions by investigation of Holocene playa sediments in the Ebro Basin, Spain: preliminary results

Endorheic basins are typical landscape elements found in several parts of the Ebro Basin, Spain. Mineralogical and geochemical analysis of sediment cores from the endorheic basins facilitates the reconstruction of local palaeoenvironmental and palaeoclimatic conditions during the Holocene. The different morphogenetic and lithological environments of the areas investigated allows one to calibrate such information. First results of the analysis of the geochemistry and mineralogy of sediments from two endorheic basins within the central Ebro Basin indicate that the climatic conditions governing sedimentation during the Holocene changed from humid and subhumid to the present subarid conditions, but was interrupted by a phase of increased humidity. The varying character of solid bedrock caused different weathering products, which are reflected in the varying geochemical and mineralogical composition of lake deposits.

Holocene paleohydrology of playa lakes in northern and central Spain: a reconstruction based on the mineral composition of lacustrine sediments

Abstract The focus of this study is the reconstruction of Holocene limnic conditions of playa lakes in central Spain using inorganic components of their sediments. It is demonstrated that the mineralogical sediment characters provide valuable paleoenvironmental information: If dolomites originate from authigenic precipitation or early diagenetic dolomitization, the Mg–Ca-ratio of dolomites, derived from the position of dolomites major X-ray diffraction line, turns out to be an indicator for the reconstruction of paleosalinity. In contrast, the concentrations of carbonates and sulphatic evaporites and their changing proportion to siliciclastic sediments point to changing depositional environments. The comparison of investigations from different playa lakes and drainage basin systems shows that the interpretation of mineralogical sediment features always has to consider the petrographic, hydrologic, and geomorphic features of the catchment. As for the lacustrine sediments investigated there are no data available yet, a preliminary chronological framework is derived by comparison with results from neighbouring areas. Based on this the hypothesis is put forward that during the so-called Little Ice Age subhumid environmental conditions occurred over the central part of the Iberian Peninsula, while today climatic conditions are dry-subhumid to subarid. Also for times older than the Subatlantic distinct changes of environmental conditions are noticed, but various hiatuses in the sediments make correlation difficult.

Capability of feed-forward neural networks for a chemical evaluation of sediments with diffuse reflectance spectroscopy

Abstract Diffuse reflectance spectroscopy (0.4–2.5 μm) is evaluated as fast and non-destructive method for the analysis of sediments, characterised by a wide range of mineral constituents. Combined with feed-forward artificial neural networks (ANNs) this technique is used to estimate quantitatively the chemical composition from the sediments based on a supervised training with one model. The examined characteristics include contents of inorganic carbon, Fe, S, Al, Si, Ca, K, Mg and calcite. The efficiency of several learning algorithms (Backpropagation, Quickprop, Resilient propagation (Rprop), Cascade Correlation (CC)) is investigated. All learning algorithms perform well using principal component (PC) scores of the first derivative spectra as input for the supervised training. ANNs trained with Quickprop and Rprop produced most accurate estimations of the chemical characteristics and the performance was better than for standard multivariate statistical tools (stepwise multiple linear regression (SMLR), principal component analysis (PCA)). An interpretation of the results is given by a detailed consideration of the correlation structure among the chemical constituents.

The dimension of water in Central Asia: security concerns and the long road of capacity building

Central Asian water management has always been linked to energy and security politics. The region is abundant in water as well as in natural energy sources. However, distribution of these resources is a steady reason for quarrel within the region. In particular, the usage of mutually shared waterways creates tensions between different nation states. The five Central Asian republics Kazakhstan, Uzbekistan, Turkmenistan, Tajikistan and Kyrgyzstan seek energy independence and try to consolidate their position within this geopolitically important region. Despite their complex interdependencies, which affect all important social, economic, political and security relevant matters, Central Asian national states have initiated a disintegration process in the region. Economic crises after decades of mutual dependence make the region dependent on foreign investments. Within this complex setting, managing transboundary waters becomes a sensitive task that seems impossible to be resolved by the affected players themselves. Central Asian water management reaches beyond the borders of the region and has long become an international concern. This article analyzes how foreign geopolitical interests shape regional water management, and how capacity building measures can lead to sustainable management from within the region.

Managing the impact of climate change on the hydrology of the Gallocanta Basin, NE-Spain.

The Gallocanta Basin represents an environment highly sensitive to climate change. Over the past 60 years, the Laguna de Gallocanta, an ephemeral lake situated in the closed Gallocanta basin, experienced a sequence of wet and dry phases. The lake and its surrounding wetlands are one of only a few bird sanctuaries left in NE-Spain for grey cranes on their annual migration from Scandinavia to northern Africa. Understanding the impact of climate change on basin hydrology is therefore of utmost importance for the appropriate management of the bird sanctuary. Changes in lake level are only weakly linked to annual rainfall, with reaction times between hours and months after rainfall. Both the total amount of rainfall over the reaction period, as well as individual extreme events, affect lake level. In this study the characteristics and frequencies of daily, event, monthly and bi-monthly rainfall over the past 60 years were analysed. The results revealed a clear link between increased frequencies of high magnitude rainfall and phases of water filling in the Laguna de Gallocanta. In the middle of the 20th century, the absolute amount of rainfall appears to have been more important for lake level, while more recently the frequency of high magnitude rainfall has emerged as the dominant variable. In the Gallocanta Basin, climate change and the distinct and continuing land use change since Spain joined the EU in 1986 have created an environment that is in a more or less constant state of transition. This highlights two challenges faced by hydrologists and climatologists involved in developing water management tools for the Gallocanta Basin in particular, but also other areas with sensitive and rapidly changing environments. Hydrologists have to understand the processes and the spatial and temporal patterns of surface-climate interaction in a watershed to assess the impact of climate change on its hydrology. Climatologists, on the other hand, have to develop climate models which provide the appropriate output data, such as reliable information on rainfall characteristics relevant for environmental management.

Holocene morphodynamics in the Ugii Nuur basin, Mongolia : insights from a sediment profile and 1D electrical resistivity tomography

Sediment profile analysis and electrical resistivity tomography were applied in the Ugii Nuur basin, central Mongolia, in order to gain insight into the sedimentary architecture of valley fillings. It is shown that important constituents in the near surface ground are aeolian fines. Coarse grainsizes were predominantly deposited during the Late Pleistocene and the beginning of the Holocene indicating local dune activity and arid conditions. Since the Early to Mid Holocene a larger proportion of silt suggests an increase in mineral dust deposition. In combination with soil formation this points at dust trapping by a denser vegetation cover that reflects more humid conditions in the Ugii Nuur basin. Yet, 1D electrical resistivity tomography (VES) shows that Holocene deposits represent only a minor part of the thick valley fillings. Hence, it is assumed that there main extent has been established during the Pleistocene.

The chemistry of playa-lake-sediments as a tool for the reconstruction of Holocene environmental conditions - a case study from the central Ebro basin

The focus of the presented study is the reconstruction of the Holocene limnic and drainage basin conditions of the Laguna de Jabonera, a today playa-lake-system in the Desierto de Calanda, central Ebro Basin, using the inorganic characters of the lacustrine sediments. Mineralogical fabric helped to reconstruct the overall geomorphic processes and gives clues to the synsedimentary limnic environment (paleosalinity). The chemical composition of the lacustrine sediments largely reflects the mineralogical composition, but the higher resolution of the geochemical data compared to the mineralogical data enables to stratigraphically split the extracted core profile into three stratigraphic units. Supplementally, it is demonstrated that Statistics between chemical compounds point to the synsedimentary intensity of weathering and soil forming processes.