Death sentences

In Coral Reefs Under Rapid Climate Change and Ocean Acidification, Ove Hoegh-Guldberg and sixteen other distinguished marine scientists call for... decisive action.


Photos: extant examples of reefs from the Great Barrier Reef that are used as analogs for the ecological structures anticipated under the paper's coral reef scenarios. Photos by O. Hoegh-Guldberg.

A post on Dot Earth, Carbon Dioxide Is Double Threat to Reefs, summarises non-technically.

P.S. 14 Dec: The Guardian reports this as Acidic seas may kill 98% of world's reefs by 2050.

Reefs and carbon sequestration

On 7 Dec, the Jakarta Post reported Asia to push coral reef into Kyoto system:

Indonesia and five other countries within the Asia and Pacific regions announced Thursday they will propose a huge global contribution from their marine and coral reefs to absorb carbon, to be taken into account...within the protocol.

But leading marine scientists say there slim to no grounds for claiming reefs as carbon sinks. Stuart Campbell of the Wildlife Conservation Society wrote on Coral List (7 Dec):

today’s Jakarta Post...claim[s] that the reefs of the Coral Triangle....act as sink for around 245 million tons of carbon per year. My reading of the literature suggests that reefs both act as sinks and sources of atmospheric carbon - depending on their productivity rates and many other factors - this is a complex issue and a publication by Kinsey and Hopley (1991) suggests that globally coral reefs act as a sink for 111 million tons of carbon each year, "the equivalent of 2% of present (that was 1991) output of anthropogenic CO2". But there are many complicating fators including production rates of reefs and their effect on the reduction of pH, solubility of CO2 and its release to the atmosphere. Generally the literature I have read suggests that coral reefs contribute to the global greenhouse effect, but in a way that is part of the natural cycle of inorganic carbon in and out of the atmosphere. I'd be interested in any recent publications that provide updated information on this issue or anyone who knows where the estimate of 245 millions tons of CO2 for the Coral Triangle Region came from?

Tom Goreau responded:

The claim that coral reefs are a CO2 sink is completely incorrect. They are in fact a source of CO2 to the atmosphere even while they remove carbon from the ocean. This has been understood by carbonate chemists for a long time but we keep having to deal with this popular error over and over again.

Because the ocean is a pH buffered system in which electrical charge is conserved, for every atom of bicarbonate in seawater that is converted to carbonate and deposited as limestone one molecule of bicarbonate is converted to carbonic acid and then to CO2 to balance the charge. So in effect for each atom of carbon removed from the ocean into limestone, one atom is released as CO2 to the atmosphere.

On a geological time scale limestone deposition and volcanic emissions are the two major sources of atmospheric CO2 (since photosynthesis and respiration plus decomposition balance). Atmospheric CO2 in turn dissolves in fresh water, where it is the major acid once it ionizes, and is then neutralized by chemical weathering of limestone on land and of igneous and metamorphic rocks, being converted into bicarbonate which washes into the sea, resuming the cycle.

Half of all the limestone buried in the sea is buried in coral reefs (since most open oceanic production dissolves in the deep sea), but to put it into perspective, this natural source of CO2 is 50 times smaller than fossil fuel input, showing how seriously we have perturbed the natural carbon cycles.

The only way that reefs could be a CO2 sink would be if they were autotrophic ecosystems that buried most of the algae carbon before it could decompose. But in fact reef sediments have very low buried organic carbon content, because the organic carbon is almost entirely decomposed. In fact, reefs are not autotrophic at all, they are heterotrophic systems that rely on external organic carbon input from land and oceanic zooplankton. Whenever I have measured oxygen in a reef it has always been below saturation, except directly over dense shallow seagrass beds in full sunlight. Overall the reef organic carbon cycle is consuming oxygen and producing CO2, as well as the CO2 produced by limestone deposition.

Coral reefs are the first and worst victims of global warming, but they do not contribute to removing CO2 form the atmosphere at all. We must save them for their biodiversity, fisheries, shore protection, and tourism services, not because of false and misguided claims that they are carbon sinks.

Catch less to get richer

Economics of Overexploitation Revisited shows in four disparate fisheries that dynamic maximum economic yield can exceed maximum sustained yield.

"This means that if you reduce the harvest now, you'll actually be better off", says co-author Quentin Grafton
(Catch cuts 'bring bigger profits').

The fisheries studied include long-lived and slow-growing orange roughy which live on seamounts rich in benthic life including cold water corals.

Ecotourism 'benefits nature and reduces poverty'

I've been critical of ecotourism in the past, perhaps intemperately so. Conceding that "there is substantial evidence that well run eco-tourism projects can bring substantial benefits to a few poor communities", I have asserted:

too many poor people in the world are dependent on primary resources such as reefs and forests ever to be reached by eco-tourists. This great majority will not receive the benefit of eco-tourist dollars but will suffer the impact of the tourists’ pollution. Very often eco-tourism is a stalking horse mass tourism, which is hugely destructive of the environment in both the short and long run. (from Holidays on Death Row at Climatedenial.org)

Still, it is good to see further evidence that well run eco-tourism projects can benefit communities that depend on coral reefs. Nature's Investment Bank, a report from The Nature Conservancy draws on interviews with more than 1000 people in four recently protected marine zones in Fiji, Indonesia, the Philippines and the Solomon Islands. "In every case, the conservation schemes had boosted fish catches and helped create new jobs." The common factor in each case, say co-authors Craig Leisher, Peter van Beukering and Lea M. Scherl were:

the heavy involvement of the local community in the creation of the protection zone, the legal designation of "no catch" zones where fish could breed, and the policing of these zones by government agencies. In all four cases, action was taken after a collapse in fish populations through overfishing by outsiders.

But:

There has to be a sense of crisis before people are willing to change the status quo dramatically.

News reports here and here.