Adequacy of remote-sensing to assess productivity-habitat quality associations in Mediterranean-type ecosystems

One of the key ecological paradigms is on the relationship between biodiversity and productivity. Higher biodiversity leads to more productive ecosystems, and more productive environments support more biodiversity. At the population level, more productive ecosystems often provide a higher habitat quality in which species persist. Ongoing global changes are affecting ecosystem productivity, being expected to affect productivity-biodiversity and productivity-habitat quality relationships. Mediterranean-type ecosystems are hotspots of biodiversity threatened by ongoing changes in land use and climate, and these changes likely affect ecosystem productivity and the inherent habitat quality. Here we test to which extent are changes in land use and climate affecting habitat productivity, and whether productivity variation affect habitat quality and use by medium-sized mammals. To do this we analyzed the Enhanced Vegetation Index (EVI) for the Landsat time-series over an oak woodland ecosystem in southern Portugal and linked it to meteorological station data and to radio-tracking data of genets (Genetta genetta), stone martens (Martes foina) and badgers (Meles meles). We found that over the last 15 years: (1) on average EVI did not change while there was a significant decrease in max EVI and increase in min EVI, (2) EVI was strongly correlated with relative humidity and negatively correlated with temperature, (3) stone marten and badger presence was positively associated with productivity (EVI and NDVI) while genet habitat model was not significant, and (4) stone marten habitat preferences before and after a drought period showed that the species still preferred oak woodlands over other land cover types; cork oak woodlands are still the land cover type with higher EVI despite the significant reduction in EVI from 1997-1998 to 2005-2006 (EVI97-98=0.32, EV I05-06=0.25). These results suggest that despite changes in productivity, cork oak woodlands are still the most selected ecosystem. Cork oak woodland capacity to provide habitat is associated with a diversity of resources embedded within this ecosystem, i.e. due to its high biodiversity.