Habitat heterogeneity from lidar and hyperspectral data: Implications for bird guilds and restoration management of coal mines

A global transition of energy production is underway. Coal-based power production is gradually being replaced by renewable energies, leading to the decommissioning of coal-mining sites. In Europe, this presents an opportunity for restoring degraded habitats, in alignment with the goals of the Nature Restoration Law. However, systematic approaches to monitoring restoration of mining sites are lacking as current practices are often labour-intensive and (both spatially and temporally) constrained. In this study, we evaluated the suitability of habitat heterogeneity metrics derived through airborne remote sensing for monitoring the restoration of coal-mining sites. Specifically, we tested the response of guild-specific bird species richness to various metrics of habitat heterogeneity, both at and around a restored coal-mining site. We (i) examined differences in habitat heterogeneity, including terrain characteristics, vegetation structure and senescent vegetation, between restored and surrounding areas; (ii) documented key aspects of habitat heterogeneity that influence bird richness and different bird guilds; and (iii) tested for significant differences among bird responses between restored and surrounding areas. Generalised additive models explained between 19% and 78% of the variability in guild richness. Canopy cover, understory cover, the standard deviation of vegetation height, and senescent vegetation positively affected overall bird richness, while terrain characteristics significantly influenced some guilds (e.g. ground-nesting birds). The effects of evaluated variables on guild diversity were generally similar in both restored and surrounding areas, with the standard deviation of vegetation height being the only exception. Increasing standard deviation of vegetation height positively affected the richness of understory nesters and foragers in the restored area but had no (or slightly negative) effect in the surrounding area. Synthesis and applications. This study underscores the need to design a mosaic of habitats with complex vertical structures, emphasising the critical role of senescent vegetation and unaltered terrain features in supporting biodiversity. Finally, it provides evidence that integrating habitat heterogeneity metrics derived from airborne remote sensing data into restoration success assessment can support biodiversity-promoting management measures.