By Barend ter Haar.
Science, the famous weekly of the American Association for the Advancement of Science, published on July 3 a review article[1] that deserves wide attention, because the conclusions are of concern to us all.
The title Contrasting futures for ocean and society from different anthropogenic CO2 emissions scenarios might not directly seem very interesting, but the abstract certainly is. To put it in perspective, we should start with noting that the oceans and seas cover about two thirds of the earth’s surface, provide food for millions of people and other services such as coastal protection and play an important role in regulating global climate.
The researchers, from renowned institutes in inter alia Australia, Canada, France, Germany, Switzerland, Great Britain and the United States, have compared two contrasting CO2 scenarios. The first scenario is based on continuation of current emissions, the business-as-usual scenario. The second scenario is based on the hypothesis that the mean increase of global temperatures will be kept below 2°C, as agreed at the Copenhagen summit.
The authors note first of all that the until now limited warming and acidification of surface ocean waters has already affected many marine organisms and services provided by the ocean’s ecosystem. The question they try to answer is what the impact will be on marine organisms and the ocean’s ecosystem when CO2 emissions continue to grow.
On the basis of field observations and of experiments and models, the experts predict that even under the second restrictive scenario inter alia corals, clams, mussels and oysters will be “at high risk” by 2100. Under the business-as-usual many of the marine organisms evaluated will be at “very high risk” by 2050.
In the below 2°C scenario the impact on most of the ocean’s ecosystem services is expected to remain moderate during this century, but the business-as-usual scenario would put ecosystem services “at high or very high risk”.
These problems would moreover be aggravated by the impact of other human activities, such as overexploitation of living resources, habitat destruction and pollution.
The authors state that international climate negotiations have so far paid too little attention to the impact of climate change on the oceans. They point to the high risk of impacts well before 2100, even under the second scenario and add that these impacts “will occur across all latitudes, making this a global concern beyond the north/south divide”.
They argue that immediate reduction of CO2 emissions is required “to prevent the massive and mostly irreversible impacts on ocean ecosystems and their services” and warn that as the level of CO2 in the atmosphere increases “protection, adaptation, and repair options for the ocean become fewer and less effective”.
It will be interesting to see how governments will react and whether the coming Paris Climate Conference will decide on measures that minimize the impact of climate change on the oceans.
[1] Science 3 July 2015: Vol. 349 no. 6243. See also the editorial: The beyond-two-degree inferno
