Hierarchisation of biodiversity hotspots from global to local scale: a concrete example with policy and conservation planning implications

The term, ‘biodiversity hotspot’, was coined in the late 1980s in order to identify priority conservation regions with a considerable loss of natural habitat and with a large number of endemic species (1). Since its introduction, the concept of hotspots has been used as a key strategy for global conservation actions, and it has become the principal global conservation prioritisation approach, attracting over $1 billion in conservation investment (2). Within the Mediterranean mega-hotspot, the levels of macro-hotspot (e.g. Tyrrhenian islands), meso-hotspot (e.g. Sardinia) and micro- (maximum extent of 500 km2) and nano-hotspots (maximum extent of 10 km2) have been applied at regional and local scales for endemic vascular plant species (e.g. 4,5). This approach has the advantage of being simply applicable and understandable through the selection process of areas for conservation, without recurring to extrapolations or automated computations. On the other side, the complete identification of such areas requires a−not always available−vast amount of information about the precise location of species. This study shows a replicable example of hotspot hierarchisation from the Mediterranean mega-hotspot up the finer level of nano-hotspots of Montarbu area (CE Sardinia), within the intermediate level of micro-hotpots of the Sardinian "Tacchi", a calcareous area in the central part of the Island. Such exercise has several policy implications and could represent a valuable tool for in situ conservation planning. Nonetheless, our example showed also gaps in efforts for the protection of endemic plant species.