Ecoregion-Based Conservation Planning in the Mediterranean: Dealing with Large-Scale Heterogeneity

Abstract

Spatial priorities for the conservation of three key Mediterranean habitats, i.e. seagrass Posidonia oceanica meadows, coralligenous formations, and marine caves, were determined through a systematic planning approach. Available information on the distribution of these habitats across the entire Mediterranean Sea was compiled to produce basin-scale distribution maps. Conservation targets for each habitat type were set according to European Union guidelines. Surrogates were used to estimate the spatial variation of opportunity cost for commercial, non-commercial fishing, and aquaculture. Marxan conservation planning software was used to evaluate the comparative utility of two planning scenarios: (a) a whole-basin scenario, referring to selection of priority areas across the whole Mediterranean Sea, and (b) an ecoregional scenario, in which priority areas were selected within eight predefined ecoregions. Although both scenarios required approximately the same total area to be protected in order to achieve conservation targets, the opportunity cost differed between them. The whole-basin scenario yielded a lower opportunity cost, but the Alboran Sea ecoregion was not represented and priority areas were predominantly located in the Ionian, Aegean, and Adriatic Seas. In comparison, the ecoregional scenario resulted in a higher representation of ecoregions and a more even distribution of priority areas, albeit with a higher opportunity cost. We suggest that planning at the ecoregional level ensures better representativeness of the selected conservation features and adequate protection of species, functional, and genetic diversity across the basin. While there are several initiatives that identify priority areas in the Mediterranean Sea, our approach is novel as it combines three issues: (a) it is based on the distribution of habitats and not species, which was rarely the case in previous efforts, (b) it considers spatial variability of cost throughout this socioeconomically heterogeneous basin, and (c) it adopts ecoregions as the most appropriate level for large-scale planning.

Coralligenous and maërl habitats: predictive modelling to identify their spatial distributions across the Mediterranean Sea

“…Spatial data on coralligenous and maërl habitats have become increasingly available during the last twenty years 11,15,45 , indicating that these bioconstructions occur widely across the Mediterranean basin 17 . The present study has provided (i) the most comprehensive update for the distributions of coralligenous outcrops and maërl beds across the Mediterranean Sea, going much further than previous studies, in particular for the eastern Mediterranean basin, and (ii) the first basin-wide and continuous distribution maps based on predictive modelling.…”

“…Recently, Giakoumi et al 15 assessed potential spatial priorities for the conservation of three Mediterranean habitats (Posidonia oceanica meadows, coralligenous formations, and marine caves) by considering their eco-regional representation, as well as the opportunity costs for fisheries and aquaculture. These efforts are partly driven by existing, as well as emerging policies at the national and international levels.…”

“…A similar process is emerging at the scale of the Mediterranean basin for the Contracting Parties to the Barcelona Convention (1976). To date, these efforts have documented important gaps in knowledge, especially on species and habitats that are considered of critical importance for the Mediterranean Sea and its conservation 15 .…”

“…The substantial lack of relevant geospatial data, however, significantly hinders the effective implementation of these policies 11,19 . Giakoumi et al 15 recently produced a basin-scale distribution map integrating all benthic assemblages thriving on hard substrata of biogenic origin and under low irradiance levels, along with rhodolith beds in coastal detritic bottoms, selected deep-sea habitats (e.g. seamount peaks, offshore rocky banks), and some deep coral communities.…”

Assembling Ecological Pieces to Reconstruct the Conservation Puzzle of the Aegean Sea

“…Yet again, most of these initiatives primarily focus on the distribution of few commercial or flagship species and priority habitat types (e.g., seabirds, cetaceans, Posidonia oceanica beds), while other equally important but less known biotic features-such as sponges and rocky habitats-are typically ignored. In the Mediterranean, the distribution of habitats or physical features has often been used as surrogate for the distribution of species (see, for example, Giakoumi et al, 2013), but such an approach has often been criticized as inadequate to properly represent species biodiversity (Pierson et al, 2015;Jackson and Lundquist, 2016). New efforts seeking to encompass a wider spectrum of key habitat types and species are therefore urgently needed to harmonize and advance conservation practices in the region, and design adequate and representative networks of MPAs.…”