More than three billion people rely on the ocean for their livelihoods and more than 80% of world merchandise trade by volume is carried by sea. The vast oceans, seas and marine resources are under continual threat from pollution, warming and acidification that are disrupting marine ecosystems and the communities they support. These changes have long-term repercussions that require urgently scaling up protection of marine environments, investment in ocean science and support for small-scale fishery communities and the sustainable management of the oceans.

While efforts to reduce nutrient inputs into coastal zones are showing success in some regions, algal blooms indicate that coastal eutrophication continues to be a challenge. Globally, chlorophyll-a (the pigment responsible for photosynthesis in all plants and algae) anomalies in country exclusive economic zones decreased by 20% from 2018 to 2020.

Ocean acidification is caused by the uptake of atmospheric CO2 by the ocean, resulting in a decreasing pH and acidification of the ocean, threatening marine organisms and ocean services. A limited set of long-term observation sites in the open ocean have shown a continuous decline in pH over the last 20 to 30 years.

Mean protected area coverage of marine Key Biodiversity Areas increased globally from 28% in 2000 to 44% in 2020. However, there is considerable spatial variation in this progress, with coverage still less than a quarter in Oceania (excluding Australia and New Zealand).

Improved regulations, together with effective monitoring and surveillance, have proven successful in reverting overfished stocks to biologically sustainable levels. However, the adoption of such measures has generally been slow, particularly in many developing countries. In thirteen countries that have active assessment and management systems in place, the proportion of fish stock within biologically sustainable levels is higher than the world average of 65.8% based on data collected in 2019.

Between 2018 and 2020, the average degree of implementation of international instruments to combat illegal, unreported and unregulated fishing has improved across the world, with the global score of a composite measure of the degree of implementation of the five principal instruments rising from 3/5 to 4/5. Close to 75% of States scored highly in their degree of implementation of relevant international instruments in 2020 compared to 70% percent in 2018.