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The layer was prepared as part of the spatial assessment of the threat status and protection levels of South African marine and coastal ecosystems for the 2011 National Biodiversity Assessment. Prepared by Stephen Holness, Trevor Wolf, Kerry Sink, Linda Harris and Mandy Lombard with inputs from Ben Halpern and Hedley Grantham.

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Derivation of ecosystem Threat status for features

The ecosystem threat status of a feature was determined by evaluating the area of each feature in a condition against thresholds or targets. This method is designed to give comparable answers and categories for the marine environment to those used in the South African National terrestrial, freshwater

and estuarine conservation assessments, and to ensure that the assessment remains within a systematic framework. The methodology and categories also allows quick conceptual links to be made to IUCN Red List categories for species which are immediately understood by a broad range of biologists and conservationists.

Biodiversity threshold (Targets): The basic biodiversity thresholds were set at 20% of the area of each ecosystem type. The 20% target is a default value commonly used in South Africa when targets derived from the underlying characteristics (e.g. species area curves) of biodiversity features are not available. A review of targets for marine systems is being undertaken by the South African National Biodiversity Institute, which will inform target setting for marine ecosystems in the future.

The ecosystem threat status of an ecosystem was determined by evaluating the area of each feature in a specific condition state against thresholds or targets. A number of categories were defined that are comparable with those used in the South African National terrestrial, freshwater and estuarine conservation assessments (Driver et al. 2005). The categories were:

Critically Endangered: These are ecosystems where the remaining area in good condition is less than the identified biodiversity threshold (20% of habitat). Conceptually, these are features where there are almost no remaining areas of pristine or natural habitat, and we expect that important components of biodiversity pattern have been lost and processes are heavily modified.

Endangered: These are ecosystems where the remaining area in good condition is less than the identified biodiversity threshold plus 15% (i.e. 35% of habitat). Conceptually, this is a "red flag" category for systems that are approaching the point where important components of biodiversity pattern will be lost, and which

already have significant impacts on processes.

Vulnerable: These are features where the remaining area in good condition is greater than the identified biodiversity threshold plus 15% (i.e. are not Critically Endangered or Endangered), but where the remaining area of good or fair condition habitat is less than 80% of habitat area. Conceptually, these are habitats where there are sufficient areas of intact biodiversity of this type to meet our targets, but outside of these areas there has been broad loss of ecosystem processes.

Least threatened: These are features where the remaining area in good condition is greater than the identified biodiversity threshold plus 15% (i.e. they are not Critically Endangered or Endangered), but where the remaining area of good or fair condition habitat is greater than 80% of habitat area. Conceptually, there are sufficient areas of intact biodiversity of this type to meet our biodiversity target, and there has been little broad modification of processes. Large portions of these systems remain in a natural or pristine state.

Input data:

NBA_benthic_and_coastal_condition_wgs84.shp

NBA_benthic_and_coastal_habitat_map_wgs84.shp

Available documentation and references:

Driver A, Maze K, Rouget M, Lombard AT, Nel J, Turpie JK, Cowling RM, Desmet P, Goodman P, Harris J, Jonas Z, Reyers B, Sink K, & Strauss T. 2005. National Spatial Biodiversity Assessment 2004: Priorities for Biodiversity Conservation in South Africa. Strelitzia 17. South African National Biodiversity Institute.

Holness, S., Sink, K., Harris, L., Wolf, T. and Lombard, M.. 2011. Spatial assessment of the threat status and protection levels of South African marine and coastal ecosystems for the 2011 National Biodiversity Assessment: Methods and Outputs, SANBI unpublished report.

SANS 1878

FGDC-STD-001-1998