A review by the University of Adelaide of 632 studies on biological changes in the oceans, all of which are down to rising anthropogenic CO2 emissions, forecasts a massive reduction in marine life.
It concludes that very few marine species will avoid the deleterious effects of an increase in CO2, and that there will be a dramatic reduction in species diversity and abundance throughout the world’s oceans.
This much needed overview of data from the numerous studies covered all forms of ocean ecosystem, and every trophic level. Prof Sean Connell, co-author of the report, outlines that “until now, there has been almost total reliance on qualitative reviews and perspectives of potential global change. Where quantitative assessments exist, they typically focus on single stressors, single ecosystems or single species.”
One exception to the trend will be microorganisams, which are more resistant to ocean acidification and are likely to see an increase in number and diversity.
Additionally, ocean acidification from dissolved CO2 will lead to a decline in dimethylsulfide production by plankton. This is a gas released from the oceans which contributes to the formation of clouds, thus maintaining the Earth's heat balance.
This marine devastation will have drastic implications for marine ecosystems, as well as for coastal populations and for people and industries dependent on ocean-based products. Half the world's population lives within 60km of the sea, and three-quarters of all large cities are located on the coast. Fisheries and aquaculture account for the livelihoods of 10-12 % of the world’s population, and provide 16 % of the total global animal protein.
Aquaculture practices are likely to change, which will have environmental impacts as well and societal and human rights concerns. Access to adequate protein from ocean products is also on the human rights agenda.
The relative resistance of microorganisms to acidification means that the collapse of the ocean food-web will be from the top down, impacting the species that are most valuable to fish stocks sooner rather than later.
Could we see a change in consumption towards lower-level species, or those with less predation? Jellyfish already represent a multi-million dollar business in Asia, and their population is booming due to over-fishing of their predators and also their food competitors.
Additionally, a reduction in dimethylsulfide production will result in fewer, smaller clouds. Clouds play an important role in reflecting the sun’s heat away from the Earth because of their colour (known as the albedo effect). Therefore, fewer clouds will lead to greater warming, thus forming a positive feedback loop.
All of these impacts are interwoven. Will this stark research go some way to inform much-needed solutions?
Image credit: Sam DeLong / Flickr
The University of Adelaide (October 13, 2015) Global marine analysis suggests food chain collapse
Proceedings of the National Academy of Sciences (September 10, 2015) Global alteration of ocean ecosystem functioning due to increasing human CO2 emissions