No abstract

Afforestation has been widely encouraged with different goals, including as a strategy to tackle global warming. However, the side-effects of this land-use transformation have been in many cases underestimated. Particularly, the hydrological impacts may become relevant in (semi)arid regions where water is a key element. In this work, we evaluated the hydrological effects triggered by afforestation with ponderosa pine in the semiarid Argentine Patagonia that is currently a focus of afforestation programs. For this purpose, we used complementary approaches that included hydrological modelling (DINAQUA model), satellite image analysis, and soil wetness data. All analyses provided convergent results into hydrological effects of afforestation. The modelling results showed that afforestation significantly increased transpiration in relation to native grass-shrub steppe. In the steppe in degraded condition, transpiration accounted for only 10% (40 mm year −1 ) of total water flux, whereas in adult pine plantations, it accounted for up to 73% (277 mm year −1 ). Deep drainage was also severely affected by afforestation as it decreased from 182 mm year −1 in the steppe to zero in adult plantations, according to model simulations. Estimates from Landsat images also showed that evapotranspiration was higher in plantations compared with the steppe. Soil wetness data also revealed significantly drier soils in plantations. Our results indicate that pine plantations in the semiarid Patagonia evaporate all rainfall inputs, resulting in zero deep drainage and groundwater recharge. If the afforested area in the region increases, downstream meadow ecosystems, which are hotspots of primary productivity, may be negatively impacted.

Canine faecal contamination contributes to environmental degradation and increases the exposure of humans -mainly children -to helminth infections. We studied the magnitude and spatial distribution of faecal contamination on the pavements of two neighbourhoods representative of Buenos Aires suburbs. The pavements of a low-income neighbourhood (LIN) and a middle-income neighbourhood (MIN) were selected at random. Field maps including all substrates and objects observed on each pavement were drawn, viewed from above, on millimetre paper at 1:100 scale. Data were then loaded into a geographic information system (GIS) Arc View 3.1 with a digitiser board. The spatial distribution of faeces and its association with substrates or standing elements were analysed at three scales: substrate, pavement and neighbourhood.Permeable substrate cover was higher in LIN (75%) than in MIN (35%). The faeces were not homogeneously distributed on the substrates. In both neighbourhoods, the substrates with >50 per cent grass cover showed a significantly higher proportion of faeces than those with <50 per cent grass cover, bare soil and tile. At pavement scale, the number of faeces on pavements was not related to either the number of trees, posts and domiciled dogs in the block, or with the number of faeces and percentage cover of each substrate. At patch scale, substrate patches with faeces were larger than those without faeces. Patches with faeces did not differ in shape between neighbourhoods and were more regularly shaped than patches without faeces.The spatial distribution of faeces relative to each other was almost random, even when analysed in relation to trees or standing objects. Strategies for the sustainable control of this problem are suggested.