The oceans cover two thirds of the Earth’s surface, and in the words of renowned oceanographer Dr Sylvia Earle, were once thought to be “too big to fail”.
But 90% of the excess heat from greenhouse gas emissions has been absorbed by the oceans, and this heat is now finding its way to the deepest layers. Absorption of CO2 from the atmosphere is causing the oxygen content of seawater to decline, and the level of acidity to increase. Increasing acidity is affecting the reproduction, growth and activity levels of many marine species, including corals.
waters are also affecting the distributions of species, with many plants and
animals from tropical areas now turning up in more temperate regions, while
declining within their original range. This includes many fish species
important for human nutrition and livelihoods. Marine diseases and introduced
species are also becoming more evident in many parts of the ocean.
Coral reefs are especially at risk. Increasing acidity is already affecting the ability of many coral species to make their skeletons. Add on rising sea levels, increased intensity of tropical cyclones, and underwater heat waves in summer months and it’s not to imagine what sort of stress our reefs are under! More detail on the impact of climate change on our oceans can be found here: IPCC summary at http://ipcc-wg2.gov/publications/ocean.
The impending oceans crisis has been recognised as a key issue at the Paris Climate Summit. Day 5 of the summit was a specially designated Oceans Day, with a host of events highlighting the risks our oceans face.
The threats for coral reefs were highlighted by a special screening of the first instalment of a new David Attenborough documentary on the Great Barrier Reef at the La Maisons Des Oceans during the Paris meeting. Prior to the screening, a panel discussion between Sir David, Dr Earle, Sir Richard Branson and Marco Lambertini, Director General of WWF International, was facilitated by the University of Queensland’s Prof. Ove Hoegh-Guldberg.
Sir David recounted his first visit to the Reef in 1957 when he experienced his first scuba dive. Home to over 1500 fish species, and one of the richest storehouses of biodiversity on the planet, the Reef set in train his lifelong fascination with nature – something the world has benefited from many times since.
The documentary showcased technology of the 21st century – a mini Triton submersible submarine, allowing the filmmakers to go deeper on the Reef than had been previously possible, revealing the extraordinary beauty and diversity of this icon. The second part of the series will showcase the dependence on the reef by some of the oceans most majestic creatures – the rays, sharks and whales while the final episode will explore the many risks, including climate change, that are already transforming this ecosystem.
As we look ahead to the conclusion of the summit and to the international agreement being negotiated, there is perhaps no greater symbol of what is truly at risk if the world’s nations do not increase their ambitions for emissions reduction. The Paris agreement will likely nominate a 2oC limit for global ambition – but the pledges on the table thus far will, even if fully implemented, deliver 2.7-3oC.
And this is just not enough – as Ove Hoegh-Guldberg said bluntly: “The Great Barrier Reef’s upper limit of temperature for survival is 1.5oC”.
Australia has so much to lose yet continues to be a global laggard in addressing the problem. The Climate Change Performance Index is a comparison of climate protection performance of 58 countries that are, together, responsible for more than 90% of global energy-related CO2 emissions. The latest assessment, released during the summit, ranks Australia as 3rd last of 58 countries assessed, with only Kazakhstan and Saudi Arabia rate below.
Surely we can do better!
1. Coral reef, Shark Island, French Frigate Shoals from Flickr user usfwspacific CC BY 2.0
2. Image from Keith Tuffley (https://twitter.com/KeithTuffley/status/6731996298...)
3. Great Barrier Reef, from Flick user farbenfrohewunderwelt CC BY-ND 2.0