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Abstract: Southern Spain’s semi-arid habitats are a Mediterranean ecosystem modelled mainly by historic factors which make them unique in comparison with North African deserts. Southern Spanish vertebrates have adapted to the recent emergence of semi-arid habitats in varying degrees of success. This paper reviews the current status of these terrestrial vertebrates (amphibians, reptiles, birds and mammals), their origins and their main features in relation to this biogeographic area. The vertebrate fauna of the semi-arid southeast of the Iberian peninsula differs widely from the one in the semi-arid Maghreb mainly because the former is composed by generalist vertebrates and much less so by species adapted to arid conditions. Moreover, a large fraction of the vertebrates in the semi-arid Iberia does not exploit the semi-arid areas but depends on riparian and human-managed habitats. The species diversity is rather low since only a small fraction of Palaearctic, European or Mediterranean species can adapt to the ecological limitations imposed by aridity and dwell in these semi-arid habitats. Such adaptations comprehend features like trophic plasticity, low morphological specialization, high dispersal ability, shortened life cycles and behavioural mechanisms to exploit the limited resources available. This paper identifies major conservation issues and proposes specific courses of action. [Copyright &y& Elsevier]

Abstract: The changing climate is affecting biological and physical processes occurring in the biosphere, including the biogeochemical cycles of water and carbon. The response of ecosystem carbon exchange to changes in temperature and the water balance is still very uncertain, a fact that highlights the need for research in order to understand the role of the biosphere in the future global carbon budget. South east Spain is on the borderline between the tropical and mid-latitude climate zones, with climates ranging from sub-humid to arid, and the majority representing the driest area in Europe. Initial predictions on climate change for this region point to decreases in total precipitation and the number of precipitation events, meaning a decrease in water availability underlining the vulnerability of the region to desertification. This region, due to these special climatic conditions, has been the subject of experimental carbon and water field research in recent years. This paper defines the state of the art of carbon and water balance measurement and modelling studies in this region, analyses the different processes involved in aggregate exchanges (vegetation and soil; net ecosystem carbon balance–evapotranspiration, photosynthesis–transpiration, soil respiration–evaporation), and identifies needs for future research. [Copyright &y& Elsevier]

Abstract: Climate, lithology, soil and especially, intense land use/cover changes, make SE Spain very vulnerable to runoff generation and water erosion leading to loss of nutrients and organic matter and to infrequent but devastating floods, reservoir siltation and mass failures. This susceptibility has led to heavy economic investment and research efforts since the 1980s, making this region a worldwide reference for understanding the hydrology and geomorphology of semiarid ecosystems. Runoff and soil erosion have been intensively studied throughout the last decades in various natural ecosystems as well as in abandoned farmlands. Research has considered a wide range of methods and spatial and temporal scales. This paper reviews the methods and data describing runoff generation and water erosion, synthesising the key processes involved, rates, thresholds and controlling factors from a scale-dependent perspective. It also identifies the major gaps in current knowledge to provide recommendations for further research towards solutions that reduce the negative impacts of erosion. Research in SE Spain has contributed significantly to a better understanding of the effect of spatial and temporal scale on runoff and sediment yield measurements, and highlighted the important role of distinct erosion and sediment transport processes, hydrologic connectivity, spatial and temporal patterns of rainfall, the occurrence of extreme events and the impacts of land use changes. The most effective ways and challenges to predict runoff, soil erosion and sediment yield at the catchment scale are also discussed. [Copyright &y& Elsevier]

Abstract: As in most semiarid regions, the main source of freshwater in SE Spain is its aquifers, and their exploitation has enabled the development of highly profitable irrigated agriculture and tourism industries. The application of sustainable water management plans requires aquifer recharge to be quantified and its spatial pattern evaluated. This paper gives a comprehensive review of various recharge studies in mountainous carbonated aquifers, the most important groundwater reservoirs in SE Spain. Quantification of potential recharge rates and their spatial variability are illustrated using satellite-based modeling and tracer techniques. Actual recharge figures from the application of a lumped model based on water table fluctuations are also presented. Potential recharge relative to actual recharge is around 1 in small aquifers and flat areas and may increase up to 1.3 in heterogeneous mountainous aquifers with deep water levels due to losses of recharge in transit in the vadose zone. The complex interaction between climate, geology, aquifer geometry, topography, soil properties and the degree of karstification prevents the systematization of any particular technique to quantify potential recharge. The use of water table fluctuation methods for actual recharge evaluation requires daily time steps to compute unnoticed small recharge events. Therefore, the monitoring of environmental variables and the use of complementary techniques for comparison are recommended. Despite their importance for the correct assessment of recharge in the region, uncertainty analyses are still scarce, and the natural variability of recharge is unknown in most cases. Effort is required to improve the spatial and temporal characterization of recharge through the integration of interdisciplinary sciences. [Copyright &y& Elsevier]

Abstract: This paper analyses the role of climatic aridity on the spatial differences of vegetation activity and its inter-annual variability in a semi-arid region of the North East of the Iberian Peninsula. The vegetation activity was quantified by means of a monthly Normalized Difference Vegetation Index (NDVI) database from NOAA–AVHRR satellite images (1987–2000) at 1km2 of spatial resolution. Coefficients of variation (CoV) from temporal NDVI series were also calculated. The greater temporal variability of NDVI was recorded in areas with low vegetation cover (steppe and dry farming lands), whereas the lowest temporal variability of NDVI was recorded in the irrigated lands and forests located in the most humid areas. There is a strong and negative relationship between the CoV and the NDVI distribution, but we recorded important differences among land uses. Using maps of annual precipitation and temperature obtained by means of a regression-based method, we studied the influence of aridity on spatial patterns of NDVI and CoV values. The results show the high influence of aridity on the spatial distribution of vegetation activity in the Middle Ebro Valley. Aridity causes a general decrease of NDVI and an increase of CoV. Nevertheless, non-linear relationships between aridity and NDVI and CoV were recorded for the whole of the study area and for the different land uses. The relationships between aridity and vegetation patterns in the semi-arid region studied are discussed in depth. [Copyright &y& Elsevier]