Free advanced modeling and remote-sensing techniques for wetland watershed delineation and monitoring

Watershed scale studies focusing on hydrological pressures influencing freshwater ecosystem dynamics are necessary for the establishment of suitable wetland ecological indicators. Enhanced and reproducible methods for watershed modeling and land-cover assessment are thus essential tools for wetland monitoring and management. However, few integrated studies propose advanced open source methodologies for watershed modeling and assessment. In this study, a set of GIS methodological tools was applied and further developed in order to delineate wetland watersheds and map their land-cover changes over time. Watersheds draining to 11 semiarid Mediterranean saline wetlands were delimited and map algebra operations were applied on the digital elevation model in the Campo de Cartagena coastal plain to enhance watershed delimitation. land-use/land-cover maps of wetland watersheds were obtained for years 1987 and 2008 by means of supervised classification of Landsat images. A set of four spectral indices was included in the classification analysis using a combination of bands in order to improve the discrimination of vegetation, water bodies, infrastructure, and bare soil. An iterative classification procedure based on maximum likelihood and random selection of training areas was applied. Contextual information based on automatic image segmentation of Landsat scenes was also included as ancillary layers. Watershed areas obtained ranged from 70 to 17,000 ha and delineation was improved in the Campo de Cartagena coastal plain. The proposed image classification methodology showed high accuracies and improved standard classification techniques. The proposed methodology is based on free and open source tools, which makes it broadly applicable.     

Robust projections of Fire Weather Index in the Mediterranean using statistical downscaling

The effect of climate change on wildfires constitutes a serious concern in fire-prone regions with complex fire behavior such as the Mediterranean. The coarse resolution of future climate projections produced by General Circulation Models (GCMs) prevents their direct use in local climate change studies. Statistical downscaling techniques bridge this gap using empirical models that link the synoptic-scale variables from GCMs to the local variables of interest (using e.g. data from meteorological stations). In this paper, we investigate the application of statistical downscaling methods in the context of wildfire research, focusing in the Canadian Fire Weather Index (FWI), one of the most popular fire danger indices. We target on the Iberian Peninsula and Greece and use historical observations of the FWI meteorological drivers (temperature, humidity, wind and precipitation) in several local stations. In particular, we analyze the performance of the analog method, which is a convenient first choice for this problem since it guarantees physical and spatial consistency of the downscaled variables, regardless of their different statistical properties. First we validate the method in perfect model conditions using ERA-Interim reanalysis data. Overall, not all variables are downscaled with the same accuracy, with the poorest results (with spatially averaged daily correlations below 0.5) obtained for wind, followed by precipitation. Consequently, those FWI components mostly relying on those parameters exhibit the poorest results. However, those deficiencies are compensated in the resulting FWI values due to the overall high performance of temperature and relative humidity. Then, we check the suitability of the method to downscale control projections (20C3M scenario) from a single GCM (the ECHAM5 model) and compute the downscaled future fire danger projections for the transient A1B scenario. In order to detect problems due to non-stationarities related to climate change, we compare the results with those obtained with a Regional Climate Model (RCM) driven by the same GCM. Although both statistical and dynamical projections exhibit a similar pattern of risk increment in the first half of the 21st century, they diverge during the second half of the century. As a conclusion, we advocate caution in the use of projections for this last period, regardless of the regionalization technique applied.     

The 1877–1878 El Niño episode: associated impacts in South America

At times when attention on climate issues is strongly focused on the assessment of potential impacts of future climate change due to the intensification of the planetary greenhouse effect, it is perhaps pertinent to look back and explore the consequences of past climate variability. In this article we examine a large disruption in global climate that occurred during 1877–1878, when human influence was negligible. The mechanisms explaining this global disturbance are not well established, but there is considerable evidence that the major El Niño episode that started by the end of 1876 and peaked during the 1877–1878 boreal winter contributed significantly to it. The associated regional climate anomalies were extremely destructive, particularly in the Northern Hemisphere, where starvation due to intense droughts in Asia, South-East Asia and Africa took the lives of more than 20 million people. In South America regional precipitation anomalies were typical of El Niño events, with rainfall deficit and droughts in the northern portion of the continent as well as in northeast Brazil and the highlands of the central Andes (Altiplano). In contrast, anomalously intense rainfall and flooding episodes were reported for the coastal areas of southern Ecuador and Northern Perú, as well as along the extratropical West coast of the continent (central Chile, 30° S–40° S), and in the Paraná basin in the southeast region. By far the most devastating impacts in terms of suffering and loss of life occurred in the semiarid region of northeast Brazil where several hundreds of thousands of people died from starvation and diseases during the drought that started in 1877.     

Scientific management of Mediterranean coastal zone: a hybrid ocean forecasting system for oil spill and search and rescue operations

The oil spill from Prestige tanker showed the importance of scientifically based protocols to minimize the impacts on the environment. In this work, we describe a new forecasting system to predict oil spill trajectories and their potential impacts on the coastal zone. The system is formed of three main interconnected modules that address different capabilities: (1) an operational circulation sub-system that includes nested models at different scales, data collection with near-real time assimilation, new tools for initialization or assimilation based on genetic algorithms and feature-oriented strategic sampling; (2) an oil spill coastal sub-system that allows simulation of the trajectories and fate of spilled oil together with evaluation of coastal zone vulnerability using environmental sensitivity indexes; (3) a risk management sub-system for decision support based on GIS technology. The system is applied to the Mediterranean Sea where surface currents are highly variable in space and time, and interactions between local, sub-basin and basin scale increase the non-linear interactions effects which need to be adequately resolved at each one of the intervening scales. Besides the Mediterranean Sea is a complex reduced scale ocean representing a real scientific and technological challenge for operational oceanography and particularly for oil spill response and search and rescue operations.     

Interactions between rabbits and dung beetles influence the establishment of Erodium praecox

We examine the potential for two species – the wild rabbit Oryctolagus cuniculus and the dung beetle Thorectes valencianus – to affect the establishment of Erodium praecox, an endemic plant of the Iberian Peninsula. Rabbit latrines may be considered potential maternal parent areas of E. praecox. The spatial and temporal stability for nutrients and surface irregularities caused by the activity of rabbits increases bare soil areas. A negative relation between diameter of the basal rosettes of Erodium and the distance to the centroid of latrines was observed. Rabbit latrines were important for E. praecox distribution but their effect was higher when T. valencianus burrows exist. In laboratory conditions, a higher number of seeds buried was observed in latrines with dung beetles, while a lower number of seeds buried was observed in bare soil. T. valencianus activity plays the role of a soil fertilizer, increasing the rate of nutrient cycling and microbial activity which could raise the rate of decomposition of pellets and result in the further release of nutrients. The excavation of the dung beetles increases the soil fertilization and the surface irregularities required for the seeds of E. praecox to be easily self-buried.     

Reconstruction of the prograde PT history of high-P migmatitic paragneisses via melt-reintegration approach and thermodynamic modelling (Allochthonous Complexes,NW Iberian Massif)

The Upper Units of the allochthonous complexes of the NW Iberian Massif constitute a terrane with continental affinity. They represent the vestiges of a Cambrian magmatic arc developed in the periphery of Gondwana (West African Craton) which was involved in the Devonian Variscan collision, undergoing high-P, high-T metamorphism. This includes ultramafic rocks, high-P mafic rocks (eclogites and granulites) and high-P migmatitic paragneisses. The latter rocks show an extensive migmatization with the leucosomes oriented parallel to the regional foliation. The migmatitic paragneisses are composed of garnet, kyanite, biotite, quartz, plagioclase, K-feldspar, rutile and Ti-hematite. Thermodynamic modelling using the measured bulk composition in the NCKFMASTHO system indicates metamorphic peak conditions of ~15 kbar and ~800 to 835°C, followed by a significant cooling. The prograde evolution is assessed by means of a melt-reintegration approach, using the composition of the garnet and its inclusions. An appropriate composition of liquid is added to the measured bulk composition to emulate the pre-melting bulk composition. Modelling of this melt-reintegrated composition allows to identify a colder high-P episode below ~500°C. Zircon crystals extracted from the leucosomes show overgrowths crystallized from the partial melt at c. 389 Ma (U–Pb system). The P–T–t path proposed reveals a subduction of the peri-Gondwanan arc-derived section down to mantle depths. An isobaric heating stage occurred as a result of residence at great depths and/or inception of a transient oceanic basin at c. 395 Ma. The ensuing near-isothermal exhumation occurred due to the extension related to the inception of the basin, reaching the thermal peak shortly before c. 389 Ma. Subsequent cooling is related to the underthrusting of colder oceanic and transitional crust below the HP-HT Upper Units.     

Paleoshoreline reconstruction: A proposed method to approach submerged prehistoric landscapes of Espiritu Santo Island,Baja California Sur,Mexico

When the first Americans inhabited the area now known as Isla Espiritu Santo, around 12.5 and 6 ka, the sea level continuously rose. This resulted in the loss of the coastal territory and the retreat of the human population further inland. Part of the archaeological evidence of this period currently lies over the seafloor and under the seabed. Therefore, reconstructing paleoshorelines is a necessary first step toward submerged precontact archaeology and a broad understanding of the spatial context in which those human populations interacted and how the landscapes changed. Isla Espiritu Santo is of prehistoric importance as it contains numerous Paleocoastal tradition sites as early as ~12,400 Cal B.P. This research aims to reconstruct the changing shoreline positions as sea levels rose around Isla Espiritu Santo between 12.5 and 6.5 ka. We apply numerical modeling to map digital elevation models at 1 ka intervals by estimating the changes in the morphology of the seafloor according to the deposition rates and global sea-level curve. The results show the evolution of coastal morphology and paleoshoreline's position. Three primary geoforms are proposed: (1) coastal plains, (2) tombolo, and (3) a coastal lagoon–island barrier system. This also offers insights into the physical aspect of submerged prehistoric landscapes and the possible resource exploitation options of early societies. In this research, the reconstruction of submerged landscapes seeks to contribute to the long-term goal of locating submerged precontact sites.