Cut Back On CO2 to Save Corals
Lowering CO2 Emissions is Vital to Protect the World’s Coral Reefs
Nov 23, 2008
The scientists led by Dr Ken Anthony of the ARC Centre of Excellence for Coral Reef Studies and Professor Ove Hoegh-Guldberg, Director of the University of Queensland’s Centre for Marine Studies, set up experiments on Heron Island on the Great Barrier Reef in Southeast Queensland, simulating the effects of human-caused CO2 emissions and the resultant warming and acidity of the waters around the reef.
The experiments measured the combined effects of warming, high CO2 and sunlight on reef organisms placed in large aquariums for two to six months.
Professor Hoegh-Guldberg stressed that the combination of rising temperatures and rising acidity from the CO2 was contributing to the damage.
“Both are very serious and will destroy coral dominated reef systems if carbon dioxide rises above 450 ppm (parts per million)
“This [level] is one of the lower scenarios predicted by the Intergovernmental Panel on Climate Change. The two factors do not operate on their own, and combined have a much greater impact.
“Basically, corals become much more susceptible to the effects of temperature (bleaching, disease and mortality) when daily experiencing acidified conditions.”
CO2's Impact On Reef Biodiversity
He warned that it would not only be coral species that would suffer from increasing temperatures and acidity in the oceans.
“Corals are like the trees of rainforest, and provide habitat for as many as a million species of animals, plants and protists,” Professor Hoegh-Guldberg said.
“If you remove the corals from a coral reef, you lose the habitats and homes of these organisms. What happens to the fish that live on coral reefs when coral has been removed, by either mass coral bleaching or predators such as the crown of thorns starfish, is that 50% of the species of fish on coral reefs disappear.
“These fishes require corals for their reproduction, food and shelter. If this is multiplied for all of the other creatures that live on coral reefs, the losses of species from coral reefs is likely to be catastrophic if we go into a warmer and more acidified world.”
High CO2 Levels Threaten More Than Corals
It’s not just the ocean dwellers that would suffer from levels of CO2 above 450ppm.
“It is important to realise that exceeding 450ppm CO2 in the atmosphere will remove tropical rainforests like the Daintree, Amazon and Monte Verde,” he warned.
“It will also destroy major wetland habitats such as Kakadu, alpine ecosystems and a whole series of other natural ecosystems.
“With these things on the cards, life on planet Earth for humans could become untenable.
"Any government that is contemplating emission levels that would result in anything more than about 450 ppm, is flirting with the earth's future.”
Good Management Key to Rescuing Reefs
While the picture is grim, and he is dubious about governments’ political will to tackle global warming, there are some steps that can be taken to minimise damage to coral reefs.
“Minimising the effects of local factors such as overfishing and poor water quality can have a very important role in reducing the impact of the warming and acidification of the world's oceans,” he said.
“Fishing activities cover almost every coastline throughout the tropics and subtropics.
"While this is an important source of protein for over one billion people, the removal of key species is causing some ecosystems to change from coral dominated ones to those dominated by seaweeds.
“Marine pollution from chemicals and rubbish such as plastic bags play havoc with marine organisms and ecosystems all over the world.
“Reef managers will be focusing on reducing these local stresses while we struggle to get global emissions of CO2 under control.”
See also: CO2 Increase Killing Corals
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