Plastic will outweigh fish in the ocean by 2050 - unless countries start to limit the number of manufactured products that end up as marine debris. This is one way governments are now pledging to reach the United Nations' Sustainable Development Goal (SDG) 14 - to 'conserve and sustainably use the oceans, seas and marine resources for sustainable development'.
Preventing nutrient pollution of seas, oceans and African lakes and rivers is another. With this type of pollution, the flow of nutrient-rich water, in Lake Victoria for example, from maritime activities leads to excessive plant growth which depletes the amount of oxygen in the lake, suffocating marine life such as fish. While not part of the oceans, inland lakes and rivers are considered part of Africa's maritime domain.
Rising sea levels, temperatures and acidity, the loss of vital habitats such as coral reefs and with them the destruction of marine life and associated biodiversity, also threaten our seas.
Never before has the health of our oceans been more in peril.
Marine pollution of all kinds can be significantly reduced by 2020
At the UN Ocean Conference in New York from 5 to 9 June, world leaders discussed the importance of healthy oceans - and international cooperation - for the future of the planet. Governments agreed on a Call for Action to cooperate on achieving SDG 14, and over 1 300 voluntary commitments for implementing it were announced.
But states must demonstrate that this political will is genuine, and translates into properly implemented national strategies and action.
If SDG 14 is achieved, marine pollution of all kinds can be significantly reduced by 2020. The sustainable management and protection of marine and coastal ecosystems and numerous restorative actions to undo past harms should also be seen in that year.
A good example of the ecosystem approach for governing the oceans is taking place between South Africa, Angola and Namibia, who have agreed to cooperate for the protection and management of the Benguela Current Large Marine Ecosystem (BCLME).
Given that the populations of many African shore-lying cities are increasing - Lagos and Dar es Salaam are turning into megacities - this approach must be swiftly adopted throughout the continent to ensure the sustainable management of available oceanic resources in the areas of greatest population growth.
African maritime policy is increasingly seen from an economic point of view
Perhaps the most ambitious SDG 14 target for 2020 is the conservation of at least 10% of coastal and marine areas. Declared Marine Protected Areas (MPAs) cover over 5% of the world's oceans, but time is running out to ensure that further important areas are adequately protected in this period.
African countries are starting to play a leading role in this regard. On 5 June, Gabonese President Ali Bongo Ondimba announced the creation of Africa's largest network of MPAs in Gabon's waters.
Governments hoping to achieve SDG 14 must also provide effective regulation of fishing, end destructive fishing practices, and prohibit harmful fisheries subsidies.
Many developed and industrialised countries subsidise their fishing fleets long after their own domestic fishing stocks are exhausted. This enables fishing vessels and fleets to both survive this hardship of their own making, and sail around the world to fish from stocks that have not been exhausted.
Those stocks are often located in African waters, where states mostly lack the law-enforcement capability to protect local and artisanal fishing, and prevent illegal fishing. However some strides are being made in West Africa to arrest illegal fishermen.
African maritime policy is increasingly seen from an economic point of view - that is, wealth creation from the sustainable development of ocean resources; but this will be impossible if the oceans are in danger.
Blue economies are crucial for Africa's social and economic transformation
The AU's Agenda 2063, the Revised African Maritime Transport Charter and 2050 Africa's Integrated Maritime Strategy are African frameworks that commit states to implementing policies that can contribute to the creation of healthier oceans.
These need to be vigorously implemented for the prompt achievement of SDG 14, and will lead to the creation of ocean or blue economies that have been identified as crucial for Africa's eventual social and economic transformation.
The 2016 Lomé Charter is now the most significant initiative for keeping healthy oceans central to African policies for enhancing development, and would be even stronger if it incorporated SDG 14-derived targets and indicators in its annexes. The AU is in the process of clarifying the appropriate intergovernmental institutions and mechanisms to implement the provisions of the charter.
Current ocean policies have harmed the health of the oceans, and the sustainable development of ocean resources will be impossible without real and urgent change. Our oceans will only become healthier through continual and concerted global agreement, and individual countries' achievement of SDG 14.
Timothy Walker, Researcher, Peace Operations and Peacebuilding Programme, ISS Pretoria