This goal measures the status of marine habitats that are particularly important in supporting large numbers of marine species.
Healthier habitats mean healthier species! Habitat is included as a subgoal of the Biodiversity goal to provide a more complete picture of diversity in the system than only considering the conservation status of species (the other subgoal for Biodiversity). This is because species assessments are often incomplete.
This goal assessess the condition of marine habitats that are particularly important in supporting large numbers of marine species. The status of each habitat is based on the current condition relative to reference condition, which is often based on historical area. A score of 1 indicates that the condition equals or exceeds the reference point. The subgoal score is then calculated by combining the habitat scores for each region.
For the global OHI assessment, we included mangroves, coral reefs, seagrass beds, salt marshes, sea ice, or subtidal soft-bottom habitats. All habitats measured contribute equally to the score, regardless of their extent, because the presence of a diverse set of habitats, as well as the level of conservation of each, is considered valuable to achieve this goal.
This sub-goal score contrasts with numerous scientific studies and media reports. The most important reason is the reference point used in the Ocean Health Index. There is no question that the extent of mangrove forests, salt marshes and seagrass beds have declined considerably compared to historic levels; that sea ice is steadily declining (especially in the Arctic) and that a number of pressures now seriously challenge coral reefs. Since it is not possible to return the ocean to pre-human or pre-industrial age conditions, the reference point for extent or condition of most of these habitats has been set at ~1980, a target that is achievable. Changes that have occurred since then are significant, but not as dramatic as when compared to conditions hundreds of years ago.
Explore the full description of the data and model used in the Global OHI MODEL. Or, take a look at PRACTICAL GUIDANCE for advice on adapting the goal for future assessments and to learn how previous OHI+ assessments have modified this goal to address differences in data availability or priorities.