Abstract
Appropriate management of (semi-)natural areas requires detailed knowledge of the ecosystems present and their status. Remote sensing can provide a systematic, synoptic view at regular time intervals, and is therefore often suggested as a powerful tool to assist with the mapping and monitoring of protected habitats and vegetation. In this study, we present a multi-step mapping framework that enables detailed NATURA 2000 (N2000) heathland habitat patch mapping and the assessment of their conservation status at patch level. The method comprises three consecutive steps: (1) a hierarchical land/vegetation type (LVT) classification using airborne AHS imaging spectroscopy and field reference data; (2) a spatial re-classification to convert the LVT map to a patch map based on life forms; and (3) identification of the N2000 habitat type and conservation status parameters for each of the patches. Based on a multivariate analysis of 1325 vegetation reference plots acquired in 2006–2007, 24 LVT classes were identified that were considered relevant for the assessment of heathland conservation status. These labelled data were then used as ground reference for the supervised classification of the AHS image data to an LVT classification map, using Linear Discriminant Analysis in combination with Sequential-Floating-Forward-Search feature selection. Overall classification accuracies for the LVT mapping varied from 83% to 92% (Kappa ≈ 0.82–0.91), depending on the level of detail in the hierarchical classification. After converting the LVT map to a N2000 habitat type patch map, an overall accuracy of 89% was obtained. By combining the N2000 habitat type patch map with the LVT map, two important conservation status parameters were directly deduced per patch: tree and shrub cover, and grass cover, showing a strong similarity to an independent dataset with estimates made in the field in 2009. The results of this study indicate the potential of imaging spectroscopy for detailed heathland habitat characterization of N2000 sites in a way that matches the current field-based workflows of the user.
Highlights
In Europe, the main regulations for biodiversity protection are found in the Habitats Directive (HabDir) [1] and the Birds Directive [2], which provide the legal basis for the NATURA 2000 network (N2000)
The objective of this study is to demonstrate the potential of Imaging spectroscopy (IS) in combination with ecological knowledge to both delineate and discern detailed N2000 heathland habitat patches, including valuable quality-indicating characteristics within each of the patches in a way that matches the current field-based workflows of the user, and produces maps and statistics that are familiar in both scale and content to local and national N2000 managers
Direct heathland habitat mapping using remote sensing is hampered by the high intra-variability of habitat patches, as well as the low inter-variability between different habitat types
Summary
In Europe, the main regulations for biodiversity protection are found in the Habitats Directive (HabDir) [1] and the Birds Directive [2], which provide the legal basis for the NATURA 2000 network (N2000). Of protected habitats and species present in the EU member states; and (2) the 6-yearly reporting to the European Commission on the ‘conservation status’ of these habitats and species [3] These commitments imply that EU member states are in need of accurate, simple and repeatable methods for habitat and species monitoring and surveillance. These habitat and species assessments require detailed, reliable and up-to-date habitat distribution maps, stretching further than merely attributing a given vegetation patch to a habitat type, and giving indications on its quality. Economically priced and as far as possible automated method is desired to meet these requirements [5,6]
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