2018 Marine Ecological Condition of South Africa’s Mainland Maritime Domain

A raster of marine condition made from cumulative mapping of marine pressures. Each grid cell has been coded as 1,2,3,or 4 to indicate its degree of modification: 1- Natural/ near natural, 2 - Moderately modified, 3 - Severely modified, and 4 - Very severely modified. In 2018, these were originally categories of degradation, but the word degradation was changed to modification in 2025 to better align with the other the realms. In 2018, 31 pressures on marine biodiversity were mapped to a 30 x 30 m pixel grid and their intensity in each grid cell was scaled to between 1 and 100. A pressure-impact matrix which indicates how serious a specific pressure intensity is for a particular broad ecosystem type (also scaled to between 1 and 100) was estimated for the ecosystem functional groups. The pressure intensity and matrix scores were multiplied for each grid cell to build individual pressure impact layers, which were then summed to create a cumulative impact layer. Modification (referred to as degradation in the 2018 National Biodiversity Assessment) of an ecosystem type was classified based on the cumulative impact scores at that site. Modification scores were assigned by distributing the mapped impact scores into 4 categories to align with the IUCN thresholds of less than 50% (natural/ near natural), more than 50% (moderately modified), more than 70% (severely modified) and more than 90% (very severely modified) based on natural breaks and expert inputs.