The Mediterranean basin is a biodiversity hotspot which is being threatened by land abandonment and afforestation, most notably with eucalypt plantations, but little research has been done to assess their impact. This study evaluated the impact of eucalypt plantations on biodiversity in the Mediterranean area, taking Portugal as a case study and amphibians, bats and carnivores as the target groups.
The impact of eucalypt cover and other landscape, stand and local variables was evaluated in relation to: species richness and species occurrence for amphibians, namely if amphibian species occurrence is influenced by local characteristics (micro-scale), land-use cover (migration and dispersion-scale) or a mix of both and whether the effects differ if the main cover is eucalypt plantations or montado; species richness, bat activity, Kuhl’s bat Pipistrellus kuhlii (the most abundant bat species in the area) activity, for bats; and species occupancy and detection and spatial and temporal co-occurrence patterns for carnivores.
Amphibian species occurrence was, generally, not influenced by eucalypt cover, with the exception of the newt Lissotriton boscai, which was negatively affected, and Salamandra salamandra, which was positively affected. Overall, eucalypt plantations had a negative impact on bat activity, species richness and Pipistrellus kuhlii activity and negatively influenced carnivore detection probability across all species in both single and co-occurrence models. Eucalypt plantations had a negative effect on red fox (Vulpes vulpes) occupancy, whilst stone marten (Martes foina) and badger (Meles meles) preferred native land covers. However, eucalypt plantations had no effect on the interactions within this carnivore community.
This study confirms the negative impact of eucalypt plantations on bats and carnivores and suggests forest management guidelines to improve biodiversity at the stand and landscape scale. Namely, at a local scale, the implementation of a pond network of different hydroperiods and the exclusion/removal of exotic fish and promotion of understorey vegetation on eucalypt stands; at a landscape scale, it is suggested a multi-functional landscape, promoting eucalypt plantations with diverse age stands and the maintenance/promotion of native and patchy habitats.
