Land use and cover changes (LUCC) have been identified as one of the main causes of biodiversity loss and deforestation in the world. Fundamentally, the urban land use has replaced agricultural and forest cover causing loss of environmental services. Monitoring and quantifying LUCC are essential to achieve a proper land management. The objective of this study was to analyze the LUCC in the metropolitan area of Tepic-Xalisco during the period 1973-2015. To find the best fit and obtain the different land use classes, supervised classification techniques were applied using Maximum Likelihood Classification (MLC), Support Vector Machines (SVMs) and Artificial Neural Networks (ANNs). The results were validated with control points (ground truth) through cross tabulation. The best results were obtained from the SVMs method with kappa indices above 85%. The transition analysis infers that urban land has grown significantly during 42 years, increasing 62 km 2 and replacing agricultural areas at a rate of 1.48 km 2 /year. Forest loss of 5.78 km 2 annually was also identified. The results show the different land uses distribution and the dynamics developed in the past. This information may be used to simulate future LUCC and modeling different scenarios.

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In the Northeast Pacific the nonnative seagrass Zostera japonica frequently exists at the same sites as the native seagrass Zostera marina. Although at some sites their vertical distributions overlap, at most sites in the Pacific Northwest there is a distinctive unvegetated zone between them. The objective of this study was to better understand why a gap between the lower limit of Z. japonica and the upper limit of Z. marina exists. To address this issue we carried out transplant experiments, conducted in situ monitoring of existing Z. japonica patches, and collected sediment samples at South Beach on Shaw Island, Washington, during the spring and summer of 2006. Transplant and in situ monitoring data indicate that survival and performance of Z. japonica are reduced lower in the intertidal zone. In addition, Z. japonica patches tended to be smaller and more spaced out at lower tidal heights. Although we found no Z. japonica seeds within or outside extant Z. japonica patches, high transplant mortality indicates that Z. japonica dispersal limitation is an unlikely cause of the unvegetated gap zone. Our field observations further suggest that herbivory, bioturbation, and epiphytes are unlikely causes of the gap pattern at our study site. Instead, we hypothesize that light limitation prevents Z. japonica from occurring lower in the intertidal. A review of published vertical distribution data for both Zostera species indicates that the lower limit of Z. japonica is relatively invariant among sites. In contrast, the upper limit of Z. marina is highly variable, ranging by more than 4 m within some subregions in Washington State. Consequently we hypothesize that intersite variability in the vertical distribution of Z. marina is the primary driver of spatial variability in the presence of the unvegetated gap.

Contexto: El agua es esencial para la vida y la conservación de su calidad es vital. La cantidad de agua dulce existente en la Tierra es limitada, y su calidad está sometida a una presión constante. Esta problemática hace necesario generar herramientas que permitan medir los impactos potenciales que causan las actividades humanas sobre el recurso hídrico. Por ello, esta investigación determina la huella hídrica en la zona costera de San Blas, México. Método: Este trabajo estima la huella de agua en la zona costera del municipio de San Blas, Nayarit (México), a partir del método de escasez de agua, que tiene lugar cuando la demanda supera el suministro de agua dulce en un área determinada. Este método considera el índice de estrés hídrico en su cálculo. Resultados: La huella de agua para cuantificar el volumen total del líquido utilizado por los habitantes resulta inferior al promedio nacional. De esta manera, la zona de estudio no presenta estrés hídrico, ya que la extracción de agua no ha superado su disponibilidad. Conclusiones: La huella hídrica por el método de escasez puede considerarse como un indicador de la proporción de extracciones anuales y disponibilidad de agua; permite realizar comparaciones de la presión a la que está sometido el recurso hídrico entre zonas, regiones y países. Además, puede contribuir a la planificación de la distribución y gestión del agua en uso agrícola y urbano, en regiones como este estudio, donde el área de uso agrícola supera el 35 %. La estimación de la huella hídrica presentada en este trabajo considera la relación entre la extracción de agua dulce para uso humano y su disponibilidad total de agua en una región dada (WSI), el volumen distribuido y el porcentaje de cobertura de agua potable del área en estudio.