Combining Remote Sensing and Field Mapping Methods to Study the Vegetation Dynamics within a Coastal Wetland and Determine the Habitat Effects of a Threatened Bird Species (Emberiza schoeniclus witherbyi)

摘要

Coastal wetlands are highly dynamic changing ecosystems because of the effects of meteorology, wildlife interactions and human activities. They are one of the world's most threatened ecosystems, and threats to them drive the most specialist species to unfavorable conservation status and population trends. Therefore, it is important to frequently monitor the coverage changes of the different vegetation types to understand these species' population dynamics. However, frequent and detailed cartography entails costly efforts. Here, satellite images with field mapping were combined to create vegetation classification maps for past years from SPOT-5 images in the Pego-Oliva coastal wetland (Spain) and obtained classification accuracies above 85%. Together with habitat selection models, this information was used to understand the changes in the habitat of a threatened bird species, the Eastern Iberian reed bunting (Emberiza schoeniclus witherbyi), whose population has sharply declined in recent decades in Spain. A statistically significant reduction in reed-rush patches (positively selected habitat) and an increase in homogeneous reed patches (negatively selected habitat) were observed in those areas where the species disappeared as breeders. This study shows the potential of remote sensing and GIS techniques for the a posteriori monitoring of variation in the habitats available for threatened species to set up management and conservation measures.