The objective of this paper was to define indices based on reflectance measurements performed by the Landsat Thematic Mapper (TM) sensor for estimating water content of live Mediterranean fuels for fire danger estimation. Seven Landsat TM images were processed and correlated with fuel moisture content (FMC) of several live species of Mediterranean grassland and shrubland. Raw bands were converted to reflectances, and several indices potentially related to water content were calculated from them. Pearson r correlation coefficients and linear regression analysis were computed in order to estimate FMC. Those indices based on the short wave infrared bands (SWIR: 1.4-2.5 w m) and on the contrast between this band and the near-infrared band offered the best estimations. For grassland, the integral of visible and SWIR bands provided the highest correlation, but also raw reflectances and Normalized Difference Vegetation Indices (NDVIs) provide significant r values ( r 2 above 0.8). For shrub species, indices that include SWIR reflectances performed much better than NDVI, because the SWIR band is more sensitive to water absorption, whereas NDVI estimates FMC indirectly, only from the effects of chlorophyll changes due to water variation content and leaf area index. The most significant relations were found with the derivatives of bands 4-5 and 2-3, and again the integral of visible and SWIR bands. Multiple regression analysis provided adjusted r 2 values of 0.84 for grasslands and 0.74 for shrublands. Average errors of 23.45-40% in the estimation of FMC for grasslands were found, depending on which variables were included in the multiple regression. For the FMC estimation of shrub species, errors were lower (from 7.94 to 19.40%), since the range of FMC values was also lower.

The assessment of burning efficiency (BE) is a critical parameter for estimating gas emissions derived from biomass burning. Several authors have proven a strong dependence of BE on moisture conditions of the fuel. This paper presents an empirical study where the relationships between fuel moisture content (FMC) and satellite‐derived variables are evidenced. The study was conducted in Mediterranean ecosystems, using both high‐ and low‐resolution satellite images (Landsat‐TM, SPOT‐Vegetation and NOAA‐advanced very high resolution radiometer). First, theoretical relationships between FMC and reflected or emitted radiance are discussed. Second, multitemporal trends of vegetation indices and surface temperatures are compared with field measurements of FMC for Mediterranean grasslands and shrublands. Pearson r correlation coefficients were computed for a 4‐year series of field measurements of FMC and satellite images. Pearson r values show a good correlation between FMC and shortwave infrared (SWIR; 1.6–2 μm) reflectance, for both grasslands and shrublands, although the relations improve when near‐infrared (NIR) and SWIR reflectances are combined. “Traditional” spectral vegetation indices (based on the red and NIR reflectances) only work reasonably well with grasslands but not with shrublands. For shrublands a synthetic index mixing vegetation indices and surface temperature improves determination coefficients to estimate FMC. Finally, on the basis of these findings, multivariate fittings were computed and validated using AVHRR images. The assessment sample also provided high determination coefficients (r² > 0.75) in estimating FMC, both for the study site and other control sites.

Depopulation often leads to the abandonment of agricultural land and the resulting process of afforestation and reforestation. In this paper, we study the land use changes between 2000 and 2018 in two Spanish provinces, Soria and Teruel. The provinces chosen as case studies are of particular interest because they have some of the lowest population densities in Europe and continue to suffer depopulation processes that have been ongoing since the mid-20th century. The reasons for this are not immediately clear given that unlike other European regions with similar population density values, for example in Northern Scandinavia, they are not exposed to extreme climatic conditions, nor are they located in isolated mountain regions. Using the CORINE Land Cover database, we observed that in both provinces, there has been an expansion in shrub and forest land uses and a decline in agriculture due largely to the fact that certain areas have been abandoned by their inhabitants, although in other parts of these provinces, the amount of land used for agriculture has increased. Urban growth over this period has been minimal. In the coming years, it seems likely that the population of these areas will continue to fall, given that the policies carried out over decades to try to revert this trend have not been successful.