When is a marine protected area network ecologically coherent? A case study from the North-east Atlantic

Abstract

Creating representative networks of marine protected areas (MPAs) as part of an ecosystem-based management approach is generally advocated to protect the full spectrum of marine ecosystems and vulnerable species. Core objectives for designing MPA networks incorporate issues of scale, size and spacing. Ascertaining when such objectives have been met, and thus when a network can be judged to be ecologically coherent, presents an ongoing challenge. This paper presents a broad-scale approach to assess the degree of ecological coherence within one such network.In 2013 an independent ecological coherence assessment was requested by OSPAR, the Regional Seas Convention for the North-east Atlantic, of the ecological coherence of its regional MPA network. As is often the case in the marine environment, the data were not sufficiently comprehensive or spatially inclusive to allow for a thorough assessment for the entire region. Consequently two levels of testing were applied: (1) basic tests applied to the whole OSPAR maritime area; and (2) a more sophisticated second level of tests directed at specific OSPAR regions and subregions for which more complete datasets were available. The former considered major gaps based on basic distribution thresholds and representativity (both biogeographic and bathymetric). The latter focused on broad-scale habitat presence to determine replication, adequacy and connectivity.On the basis of these tests it was concluded that while the OSPAR MPA network as a whole is not ecologically coherent, nonetheless significant progress towards global targets, such as protection of 10% of marine and coastal environments under the Convention on Biological Diversity (CBD) has been made. Gaps in the distribution of MPAs were identified, particularly under-representation of certain biogeographic provinces and bathymetric zones of depths greater than 75m including bathyal (200-3000m) and abyssal (3000-6000m) depths.To address such gaps, a cooperative region by region approach will be required by the OSPAR Parties to identify where positioning new MPAs can enhance ecological coherence.A limitation of the 2013 assessment was that it did not consider which MPAs are designated and managed for the protection of specific features; rather, it assumed that all features that fall within an MPA are protected. With a redevelopment of the OSPAR MPA database underway it is hoped that reporting of such details by Parties will improve, allowing for more specificity in future analyses. However, as the first such assessment of its kind our two-level approach serves as a case study of a pragmatic example of how assessments of ecologically coherent networks might be undertaken using GIS to contribute to systematic conservation planning.