A snapshot of climate change impacts on South Africa’s oceans

Our oceans are just as valuable as the species that depend on them and have absorbed approximately 28% of the carbon dioxide emitted through human activities and more than 90% of the added heat since the 19th century. This system is critical to our survival yet our oceans are changing right on our doorstep. To celebrate National Marine Month, WWF-SASSI shared a deep dive on climate change and our oceans, starting with setting a foundation of what climate change is and exploring global and local ocean impacts. Five of the major threats causing this are: overfishing;  pollution; habitat destruction; invasive species; and climate change. Healthy ecosystems are resilient ecosystems that are better equipped to adapt to change, but the combined effects of these environmental threats sadly reduce the ability of our precious species and ecosystems to adapt to change.

Climate impacts on our oceans globally, are showing up as:

  • Sea level rise -having implications for low-lying islands, coasts and communities
  • Changing marine ecosystems and species distributions
  • Ocean acidification causing coral bleaching
  • Effects on dependent communities
  • Extremes in weather and abrupt changes

South Africa’s unique ~3000km coastline is a mix of different systems and currents that underpin these ecosystems. In short, the cool west coast is getting cooler and the warm east coast is getting warmer.  Globally, South Africa shows the highest regional variability in oxygen, acidity and temperature. This means our dissolved oxygen is decreasing, whilst ocean acidity and sea temperatures are increasing. Why is this a problem, you may ask?

Marine species are moving out of their normal habitats to more favourable areas as waters temperature changes. Experiments have shown warmer and more acidic water disrupting fishes’ ability to find food, find a home, and preventing beneficial relationships with other creatures. This too impacts population dynamics and entire ecosystems. As the ocean acidifies and dissolved oxygen decreases, physiology and ecology of marine species are also expected to be affected. Changes in oxygen can affect survival, reproduction and growth of numerous species, as well as their resistance to diseases. Acidification  affects growth, larval mortality and behaviour in certain groups of marine organisms. This affects especially the calcifiers (e.g. shellfish) in natural environments as acidification alters the calcium carbonate in skeletons or shells of organisms. Changes in marine species distributions can alter the combination of predators, parasites and competitors in an ecosystem, resulting in changes to ecosystem function and productivity.

Pretty much EVERYTHING can change when climate changes.

South Africa’s marine fisheries depend on coastal and offshore ecosystems with the main commercial stocks being sardine, anchovy, Cape hake, horse mackerel, rock lobsters, tuna, shark, squid and prawns. Anchovy and sardine are fished the most by volume, and adult stocks depend on the upwelling west coast region while the south coast is important for their spawning. Hake, abalone, rock lobsters and squid are among our most valuable resources. A study on the vulnerability of South African fisheries to climate change identified the line fish and small pelagic fisheries as the most vulnerable. West Coast rock lobster, squid and marine aquaculture were identified as sectors with medium vulnerability.

Rising sea levels have been recorded all along South Africa’s coastline, and increased coral bleaching on the north east coast has affected reef health. Overfishing may result in reduced genetic variability of fish, which may negatively affect an evolutionary response to climate change and the ability of depleted stocks to recover. Stocks under intense exploitation pressure are likely to be more vulnerable to the effects of climate change than optimal exploited populations.

Everyone can help in the fight to save our oceans. The most important thing you can do is to buy sustainable, SASSI green-listed fish. Sustainably managed fish stocks will cope better with the changing environment. Healthy stocks and sustainable fisheries governance means fishing has a reduced footprint on the ecosystem: this leads to more resilient ocean populations and habitats. Healthy stocks mean less fuel and other resources needed to harvest them. Other lifestyle behaviour changes to reduce your carbon footprint include auditing your consumption which includes: your clothing, means and frequency of travel, plastic-use (made from fossil fuels), reducing food and other waste, buying local and being energy smart. There is no Planet B, and this is our shared home. With climate change effects being seen and greater impacts looming, we can all be part of the solution if we take small yet meaningful actions now.

Kirtanya Lutchminarayan WWF-SASSI Project Officer