Mapping the Health of the World's Ocean

The Ocean Health Index takes advantage of several key innovations to assess ocean health consistently and rigorously. First, we combine each of the 10 core goals of ocean health into a single index using explicit weights to transparently combine these many potentially conflicting benefits. This aggregation usually happens behind the closed doors of people’s cognitive machinations.  Second, we incorporate sustainability in the Index in three ways: (1) recent trends, (2) estimates of pressures that may worsen  expectations based on recent trends alone, and (3) estimates of factors that bolster resilience, improving the future outlook over recent trends alone.  Although imperfect, this approach avoids the need to simulate future scenarios of extraordinarily complex systems, which few could implement and replicate. As such, we democratize the Index. Finally, we convert measurement of each goal to a common scale that allows direct comparison and easy assessment of tradeoffs among different goals under different ocean conditions or in different locations.  Using this framework we calculate the first Ocean Health Index scores at global and country-level scales, highlighting key areas where strategic investment is needed to improve ocean health and how and why to prioritize different actions to improve chances of success.