The overall aim of this assessment is the identification of marine areas in the Western Indian Ocean (WIO) that could potentially be of Outstanding Universal Value (OUV). The challenge is to identify features and sites that exemplify the exceptional value and integrity of sites required to meet the criteria of OUV necessary for consideration for the World Heritage List.

The assessment did not involve any new research, but is based on analysis and synthesis of existing data and information following a three-step approach. The first step focused on identifying the key physical and biological features of the WIO that contribute to its uniqueness on a global scale. The second step considered and reviewed historical expert-led biogeographic and biodiversity prioritizations of sites in the region, as well as additional data and information from the literature or supplied by experts. The third step built up a list of those sites in the region that exemplify the features identified in step 1, that also are of sufficient integrity and scale, and with existing or potential management structures to maintain these features into the future against real and potential threats.

1) Unique regional features: The WIO has been recognized as a distinct region within the broader Indian Ocean and Indo-Pacific biome by a variety of historical studies (Briggs 1974, Kelleher et al. 1995), most recently embodied in the Marine Ecoregions of the World (MEOW) classification developed by Spalding et al. (2007). The latter document explains the hierarchical classification that defines the Realms, Provinces and Ecoregions, with the distinctive features relevant to the WIO described in the companion document by Spalding (2012). Within the WIO, Spalding et al. (2007) identified 9 Ecoregions, with additional support for these in Obura (in review) based on a detailed study of scleractinian corals. Obura (in review) extends the biogeographic analysis of Spalding et al. (2007) to include geological and oceanographic features that drive the region’s uniqueness on a global scale. Together, these provide a framework for describing those features of the WIO that make individual sites and zones globally unique.

We identified features in the WIO relevant to criteria 7, 8, 9 and 10 of the World Heritage List that make it unique, and on the basis of which OUV can be assessed. The main features were grouped into:
The first part of the results describes each of these in detail, with a focus on how they are manifest in the WIO.

2) Information sources: The primary sources of data include the two ecoregional prioritization exercises conducted for the mainland East African coast (WWF 2004) and the Indian Ocean Islands (RAMP-COI, unpublished). These studies considered a range of data, focusing on environmental factors driving biological patterns and ecoregional boundaries, habitat distributions and representation, and species diversity patterns. They were based on compilations of data where possible (see Appendix for list of variables), examples of these being temperature, currents, bathymetry and cholorophyll, for physical environmental variables, and maps of mangrove, coral and seagrass as examples of habitat distributions.

Species diversity was considered on the basis of reported species presence and species richness at individual sites, where such data is available, such as in Marine Protected Areas where surveys have been conducted in the past. It is important to note, however, that rigorous geographic databases for species and habitat distributions are not available for the WIO. Richmond (2001), Griffiths et al. (2005) and Wafar et al. (2010) all note the exceptionally large gaps in species distribution records across the WIO and the Indian Ocean. The same is true for habitat distributions, which are largely derived from localized studies or unverified interpretations from satellite images. These render quantitative assessments of habitat and species distributions inaccurate, requiring an approach based on expert knowledge to extrapolate beyond existing datasets. Both the WWF (2004) and RAMP-COI (unpublished) studies followed this approach, and this study builds on these interpretations with new data and additional insights.

An expert workshop will be held in La Reunion, from 14-16 February 2012, at which initial findings of this analysis will be presented to regional experts for comment and review, and consideration of additional features and sites if necessary.

3) Potential sites of Outstanding Universal Value: The final step is to identify a shortlist of sites that illustrate how the unique features of the WIO are expressed to the highest level at these locations. This approach emphasizes the fact that while many of the features are spread across the region, only a few sites express them to a sufficient level to meet the OUV criteria of the World Heritage Convention. At the same time, it is not only the sites mentioned here that might meet the criteria, and State Parties may consider other sites with sufficient value as alternatives. Following step 2, a priority list of sites was identified from which the sites presented here were selected. The selection criteria included representation of the features outlined in step 1, sites with the best expression of these at the regional and global?) level, and in some cases multiple features, values and criteria to maximize the values included in any once site.

The sites listed here are presented as examples of how the outstanding features of the WIO may be found and expressed at a particular site, in the context of criteria 7, 8, 9 and 10 of the World Heritage Convention. In the description of each site, the following aspects are presented: