The ocean moderates human-induced global warming but at the cost of profound alterations to its physics, chemistry, ecology and ecosystems services. These are the findings of a report published today in Science by the Oceans 2015 Initiative and co-authored by IUCN World Commission on Protected Areas Marine Vice Chair, Dan Laffoley.
The report evaluates and compares two scenarios under two potential carbon dioxide emissions pathways over this century. Both carry high risks to vulnerable ecosystems, such as warm-water corals and mid-latitude bivalve species (molluscs), but a business-as-usual scenario was projected to be particularly devastating with a high risk of widespread species mortalities.
Lead author, Jean-Pierre Gattuso, Senior Scientist at CNRS (Centre National de la Recherche Scientifique, France), hopes that the findings of the report will generate the political will to enforce meaningful cuts in carbon dioxide emissions, stating "The oceans have been minimally considered at previous climate negotiations; our study provides compelling arguments for a radical change at COP21 (the UN climate summit in Paris in December)".
Driven by 40% increases in atmospheric carbon dioxide (CO2), the oceans have already undergone a series of major environmental changes in terms of ocean warming, ocean acidification and sea level rise. Whilst the report finds that emissions cuts in line with the Copenhagen Accord target of less than 2 degrees temperature rise by 2100 would ensure moderate impacts to all but the most vulnerable of species, failure to achieve this goal would lead to high impacts on all the marine organism groups considered. These include high-value species such as corals and finfish as well as pteropods (shell-bearing zooplankton) and krill that form the base of the oceanic food chain.
The report singles out ocean acidification as one of the highest risks with the biggest impacts; shellfish, corals and zooplankton are particularly at risk. "Signs of ocean acidification have now been detected in both hemispheres," warns Carl Gustaf Lundin, Director of IUCN's Global Marine and Polar Programme. "Once thought to be a problem for the future, acidification is already having economic repercussions today and, if carbon emissions continue to grow, these are set to grow rapidly."
What can be done?
Beyond the stringent emissions cuts needed to meet the Copenhagen Accord target, the authors stress the need for recognition of the ocean's important role in climate regulation and acknowledgement of its particular vulnerability. "Any new climate regime that fails to minimise ocean impacts will be seen as incomplete and inadequate,” says Laffoley. "Implementation of further Marine Protected Area networks and investment in coastal ecosystem restoration are two important ways to ensure the ocean can remain resilient and can continue to regulate the Earth's climate."