Climate study: Sushi and oysters may soon be meals of the past

The world’s oceans may soon be transformed from resilient, biodiverse environments to simple ecosystems that can no longer support basic human needs according to a powerful new climate change study. Sarah Keenihan writes.

The analysis – which combines data from 632 recent experiments published across the world – measures likely ecological change resulting from ocean acidification and warming due to increasing atmospheric carbon dioxide.

“This study is the most comprehensive forecast we have so far of the impact of climate change and ocean acidification on our global marine communities and species,” said Associate Professor Ivan Nagelkerken, lead author on the paper and ASC Future Fellow at the University of Adelaide’s Environment Institute in South Australia.

“Our analysis projects decreases in species abundance across many types of organisms.”

In particular, numbers of zooplankton (tiny animal life) and smaller fishes are predicted to drop away in response to rising ocean acidification, with follow-on effects for larger carnivorous fish.

“There will be a species collapse from the top of the food chain down,” said Professor Nagelkerken.

Humans will feel the impact through dramatic reductions in the availability of key predator species we currently enjoy on our dinner plates. Coral and oyster reefs are also expected to be hit hard by rising water temperature and acidity. In fact, such changes are already being observed.

“Large amounts of money are being spent right now to study and try to mitigate the negative effects of ocean acidification on oyster farms in the USA,” said Professor Nagelkerken.

“These sorts of research programs will likely be expanded in the USA, Australia and other countries as we start to see more and more impacts of climate change on seafood species.”

With global carbon dioxide emissions unlikely to grind to a halt in the near future, Professor Nagelkerken suggests there are actions that can be taken to slow down the impact of climate change on ocean biodiversity.

“Anything we can do to reduce the burden of stressors applied to our oceans will have a positive impact,” said Professor Nagelkerken.

“We may achieve this by reducing overfishing, thereby maintaining healthy populations and a diverse gene pool in our fishes, and providing them with the chance to possibly adapt.”

“We can also reduce local stressors like pollution,” he said.

The meta-analysis approach utilised by Professor Nagelkerken in this study overrides the limitations of applying one-off research papers to predict ocean diversity.

“It’s hard to see overarching patterns if you look only at individual studies,” said Professor Nagelkerken. “It’s almost like a ‘can’t see the woods for the trees’ scenario.”

“Our approach allows us to combine and weigh up the strengths of each of the studies appropriately, and come up with a prediction with a higher degree of confidence,” he said.

The paper Global alteration of ocean ecosystem functioning due to increasing human CO₂emissions was published in the journal Proceedings of the National Academy of Sciences (PNAS).