Use of water from small alluvial aquifers for irrigation in semi-arid regions.

Water from small alluvial aquifers constitutes an attractive and low-cost option for irrigation and rural development in Northeastern Brazil. Based on piezometric measurements, geochemical analyses and electrical conductivity estimates, the present case study identified the main processes determining the hydrosaline dynamics of an alluvial aquifer in a small watershed inserted in the crystalline bedrock of a semi-arid region in Ceará and evaluated the availability of water for irrigation. Accumulation of salts in soil are related to evaporative flux from the aquifer and is increased by irrigation from the groundwater of the alluvial aquifer. The water in these aquifers may be used for irrigation, but represents a risk of soil salinization and alkalinization. Integrated management of surface and underground water resources in the Forquilha watershed may help control irrigation water quality (salinity and residual alkalinity), thereby rationalizing the use of local reservoirs and minimizing losses from evaporation. It has to take into account the complex dynamic of salts and water between the reservoirs, release of water into the river, floods and irrigations

Food or nesting place? Identifying factors limiting Wryneck populations

In recent decades, farmland bird populations have declined strongly as a consequence of agriculture intensification. Birds may have lost breeding sites, food supply or other crucial resources, with the role of multiple factors often remaining unclear. The ant-eating and cavity-breeding Wryneck (Jynx torquilla) may be limited by the availability of cavities, the number of ants or their accessibility. By comparing occupied and unoccupied breeding territories, we investigated the relative role of these factors in the decline of Wrynecks. We compared the characteristics of known Wryneck breeding territories (availability of breeding cavities, food abundance and ground vegetation structure) with randomly selected, fictitious territories (n=154) in Western Switzerland. We also studied environmental factors that may affect ant nest density. The probability of territory occupancy strongly increased with both nestbox availability and ant abundance. In addition, this probability peaked around 50% of bare ground cover. Habitat types that harbour low ant abundance such as cropland and grassland were avoided. Ant nest density decreased with increasing amounts of bare ground, and it was particularly high in vineyards. Our results showed that breeding cavities, food availability and its accessibility all limit Wryneck distribution. The maintenance and restoration of ant rich grassland, interspersed with patches of bare ground and with hollow trees or dedicated nestboxes in the surroundings, are essential to preserve Wryneck populations. Such a habitat structure could be achieved even in intensively farmed habitats, such as in vineyards or fruit tree plantation

One-year measurements of surface heat budget on the ablation zone of Antizana Glacier 15, Ecuadorian Andes

International audience[1] Meteorological variables were recorded (14 March 2002 to 14 March 2003) at 4890 m above sea level (asl) on the Antizana Glacier 15 (0.71 km 2 ; 0°28 0 S, 78°09 0 W) in the tropical Andes of Ecuador (inner tropics). These variables were used to compute the annual cycle of the local surface energy balance (SEB). The four radiative fluxes were directly measured, and the turbulent fluxes were calculated using the bulk aerodynamic approach, calibrating the roughness length by direct sublimation measurements. The meteorological conditions are relatively homogeneous throughout the year (air temperature and air humidity). There is a slight seasonality in precipitation with a more humid period between February and June. During June-September, wind velocity shows high values and is responsible for intense turbulent fluxes that cause reduction of melting. Considering the SEB over the whole year, it is dominated by net radiation, and albedo variations govern melting. During the period under consideration the net shortwave radiation S (123 W m À2) and the sensible turbulent heat flux H (21 W m À2) were energy sources at the glacier surface, whereas the net long-wave radiation L (À39 W m À2) and the latent turbulent heat flux LE (À27 W m À2) represented heat sinks. Since the O°C isotherm-glacier intersection always oscillates through the ablation zone and considering that the phase of precipitation depends on temperature, temperature indirectly controls the albedo values and thus the melting rates. This control is of major interest in understanding glacier response to climate change in the Ecuadorian Andes, which is related to global warming and ENSO variability

In Honor of Fred Gray: The Meaning of Montgomery

International audienceWe present a new method for depth estimation, based on a stereoscopic camera with various camera focus setting. Depth isestimated using a criterion derived from a maximum likelihood estimator, which jointly analyses the data likelihood with respect to the disparity and the defocus blur of each camera. Benefit of this approach is studied, in particular for scene having repetitive patterns with respect to classical stereoscopy, then we present experimental results on outdoor scenes from a real infra-red stereoscopic system.Nous présentons une nouvelle méthode d’estimation de profondeur, qui repose sur l’utilisation de deux caméras en configuration stéréoscopique avec chacune une mise au point différente. La profondeur est estimée via un critère dérivé d’un maximum de vraisemblance qui intègre conjointement des informations de disparité et les flous de défocalisation de chaque caméra. Nous étudions les apports de cette approche, notamment sur des scènes à motifs répétitifs, par rapport à la stéréoscopie classique sur des images issues de caméras opérant dans le visible.Enfin nous montrons des exemples de résultats sur des images IR thermique acquises en extérieur

The Anthropocene is shifting the paradigm of geosciences and science

Noting that humans are affecting the Earth’s envelopes, with geosciences becoming inseparable from social sciences and humanities, and acknowledging the increasing use of the word Anthropocene, the authors of this paper explore the possibility of a scientific paradigm shift. (1) Since the 17th century, modern science has developed in a context of naturalist worlding that favors its hegemony over other modes of existence and its paradigm of a quest to define the laws of nature. (2) Various manifestations attest to the emergence of a paradigm of knowledge diversity and the unravelling of the naturalist worlding. (3) The current boom in participatory science is a sign of this paradigm shift: through the fundamental changes to the Earth System that refer to it, the Anthropocene forces science to move towards action and interact with a society involved in adapting to changes and concerned with the threats to its territory’s habitability