Combining multisensor images and social network data to assess the area flooded by a hurricane event.

In this study, multisensor remote sensing datasets were used to characterize the land use and land covers (LULC) flooded by Hurricane Willa which made landfall on October 24, 2018. The landscape characterization was done using an unsupervised K-means algorithm of a cloud-free Sentinel-2 MultiSpectral Instrument (MSI) image, acquired during the dry season before Hurricane Willa. A flood map was derived using the histogram thresholding technique over a Synthetic Aperture Radar (SAR) Sentinel-1 C-band and combined with a flood map derived from a Sentinel-2 MSI image. Both, the Sentinel-1 and Sentinel-2 images were obtained after Willa landfall. While the LULC map reached an accuracy of 92%, validated using data collected during field surveys, the flood map achieved 90% overall accuracy, validated using locations extracted from social network data, that were manually georeferenced. The agriculture class was the dominant land use (about 2,624 km2), followed by deciduous forest (1,591 km2) and sub-perennial forest (1,317 km2). About 1,608 km2 represents the permanent wetlands (mangrove, salt marsh, lagoon and estuaries, and littoral classes), but only 489 km2 of this area belongs to aquatic surfaces (lagoons and estuaries). The flooded area was 1,225 km2, with the agricultural class as the most impacted (735 km2). Our analysis detected the saltmarsh class occupied 541 km2in the LULC map, and around 328 km2 were flooded during Hurricane Willa. Since the water flow receded relatively quickly, obtaining representative imagery to assess the flood event was a challenge. Still, the high overall accuracies obtained in this study allow us to assume that the outputs are reliable and can be used in the implementation of effective strategies for the protection, restoration, and management of wetlands. In addition, they will improve the capacity of local governments and residents of Marismas Nacionales to make informed decisions for the protection of vulnerable areas to the different threats derived from climate change.

Social valuation of the ecosystem services from coastal wetlands: current status and perspectives / Valoración social de los servicios ecosistémicos de humedales costeros: estado actual y perspectivas

RESUMEN Los Servicios Ecosistémicos (SE) son bienes y servicios que la humanidad obtiene de la naturaleza y a los que se asigna valor ecológico, económico y social, aunque se ha brindado menor atención al estudio de este último. Esta deficiencia es más notable en el caso de los humedales costeros, que proveen importantes SE, escasamente explorados desde la perspectiva social y espacial, pese a su pertinencia en la planificación territorial. Para conocer el estado del arte relativo a la valoración social de SE de humedales costeros y la importancia del análisis espacial en el proceso, se realizó una revisión documental sistemática (2005-2018) que permitió observar una tendencia positiva en el número de publicaciones, en especial en el último trienio. Se identificó que el valor social carece de una definición estandarizada y se ha enfocado a servicios sin valor de mercado, mientras que en lo relativo a dimensión espacial, se encontró que se ha venido incorporando con esquemas de mapeo participativo, dirigido a determinar la accesibilidad a sitios de provisión de SE y a la identificación de sitios de valor social dentro de los humedales, sin que la producción de mapas sea relevante. No se encontraron elementos para determinar si la valoración social es complementaria o alternativa a la económica, pero se requiere crear un marco conceptual para la valoración integral basado en la pluralidad de valores de los SE como una estrategia de conservación de los humedales.

ABSTRACT Ecosystem Services (ES) include goods and benefits that people obtain from nature and to which ecological, economic and social values are assigned, although less attention has been given to the study of the latter. This deficiency is particularly notable for coastal wetlands, which provide important ES, rarely studied from a social and spatial perspective, despite their relevance in territorial planning. To define the state-of-the-art about social assessment of SE in coastal wetlands and the importance of spatial analysis in that process, a systematic documentary review (2005-2018) was carried out, finding a positive trend in the number of publications, with a notable increase in the last three years. It was found that social value lacks clear definition and has focused on services without market value, while in terms of spatial dimension it has been included with participatory mapping schemes, aimed at determining the accessibility to SE provision sites and the identification of social value sites within the wetlands, but with a little relevant map production. No elements were found to conclude if social valuation is complementary or alternative to the economic one, but it is necessary to create a conceptual framework for the integral valuation, based on the plurality of values of the SE as a strategy for the conservation of wetlands.

Effects of land use changes on the ecosystem service values of coastal wetlands.

Changes in the coastal landscape of Southern Sinaloa (Mexico), between 2000 and 2010, were analyzed to relate spatial variations in wetlands extent with the provision and economic value of the ecosystem services (ES). Remote sensing techniques applied to Landsat TM imagery were used to evaluate land use/land cover changes while the value transfer method was used to assess the value of ES by land cover category. Five wetland types and other four land covers were found as representative of the coastal landscape. Findings reveal a 14 % decrease in the saltmarsh/forested mangrove area and a 12 % increase in the area of shrimp pond aquaculture (artificial wetland) during the study period. ES valuation shows that the total value flow increased by 9 % from $215 to $233 million (2007 USD) during the 10-year period. This increase is explained as result of the high value worldwide assigned to saltmarsh. We recognize limitations in the transfer-based approach in quantifying and mapping ES values in the region, but this method provides with value estimates spatially defined, and also provides some guidance in the preliminary screening of policies and projected development in the context of data-scarce regions.

Assessment of runoff response to landscape changes in the San Pedro subbasin (Nayarit, Mexico) using remote sensing data and GIS.

Results on runoff estimates as a response to land-use and land-cover changes are presented. We used remote sensing and GIS techniques with rainfall time-series data, spatial ancillary information, and the curve-number method (NRCS-CN) to assess the runoff response in the San Pedro subbasin. Thematic maps with eight land-cover classes derived from satellite imagery classification (1973, 1990, and 2000) and hydrologic soil-group maps were used as the input for the runoff calculation. About 20% to 25% of the subbasin landscape has changed since 1973, mainly as consequence of the growth of agriculture. Forest is the main cover, although further analyses indicate that forest is degrading from good to poor conditions when evaluated as a function of the spectral response. Soils with low infiltration rates, classified as the hydrological soil-group "C", were dominant in the area (52%). The overlaying of all the hydrological soil groups with the land-use map produced a total of 43 hydro-group and land-use categories for which runoff was calculated using the curve-number method. Estimates of total runoff volumes (26 x 10(6) m3) were similar for the three dates analyzed in spite of landscape changes, but there were temporal variations among the hydro-group and land-use categories as a consequence. Changes are causing the rise of covers with high runoff potential and the increase of runoff depth is expected, but it can be reversed by different management of subbasin hydro-groups and land-use units.