Two recent reports on the state of the world’s coral reefs appear to contradict each other. But which is right?
Johnny Langenheim The Guardian 2 Aug 16;
Over the last six weeks, scientists have published two major reports on coral reef resilience that appear to contradict each other. The first - “Bright spots among the world’s coral reefs” was produced by 39 scientists led by Professor Josh Cinner of James Cook University in Australia and drew on data from 6000 reef surveys from all over the world. Cinner et al concluded that those reefs that were sustainably managed had a much better chance of withstanding bleaching impacts related to global warming and periodic climate events like El Niño. The second however suggested remote coral reefs not subject to human stressors like overfishing or pollution were faring no better than those close to populated areas and that ecosystems management made no real difference to the overall health of reefs. So which is right?
“Coral reef degradation is not correlated with local human population density,” by Professor John Bruno and co-author Abel Valdivia of the University of North Carolina was published on 20 July. It suggests that contrary to prevailing scientific opinion, local pressures do not act synchronously with global stressors (most notably warming) and that their impact on reefs is negligible. According to Valdivia “Widespread arguments that coral reef degradation is mostly caused by local factors are unsupported. We found the problem is better explained by global impacts such as climate change.”
This is controversial because it throws into question the efficacy of current marine conservation strategies that attempt to mitigate human impacts and the “widespread argument that human-dominated reefs can be made more resilient to global stressors.” The overriding message is a simple one according to the report’s author & lead researcher John Bruno - it “illustrates the far-reaching effects of global warming and the immediate need for drastic and sustained cuts in carbon emissions to help restore the health of coral reefs.”
The first report - published in June - identified 35 “dark spots” where coral reefs were suffering the greatest degradation and 15 “bright spots” that were, if not flourishing, certainly faring better than most. Many of these bright spots are in the Coral Triangle in countries like Indonesia, the Solomon Islands and Papua New Guinea.
Like Bruno & Valdivia, Cinner et al found that remote reefs did not necessarily fare better than those close to high population densities. What they did find though is that bright spots tend to be in locations where local communities have ancestral systems of reef tenure that protect fishing grounds from outsiders (such as West Papua in eastern Indonesia and some Pacific countries). The paper found that far from over-harvesting their reefs, these communities were acting as custodians.
“Bright spots are characterized by strong sociocultural institutions such as customary taboos and marine tenure, high levels of local engagement in management, high dependence on marine resources, and beneficial environmental conditions such as deep-water refuge,” the report concludes.
The apparent contradictions here are partly due to each report analysing different types of data. According to Bruno “Cinner et al was about spatial patterns in fish populations while we asked how coral and macroalgal cover are related to human population density.” Put simply, one was looking at fish, the other at coral cover.
Still, the question remains, is local management of the kind highlighted by Cinner et al having a real impact on the health of reef ecosystems? Says Bruno, “Although I doubt most coral bright spots are bright because of local management, I do agree that... we should throw all our conservation dollars at them to keep them that way as long as possible.”
The problem is in how each of these reports is interpreted. Cinner et al imply that sustainable management means healthy reefs - even though they are harvested by local populations. A positive message for conservationists and the local programmes they support. Bruno’s point however seems to be that all of this is academic in the face of climate change, lulling us into a dangerous and altogether unjustifiable sense of security. If we fail to drastically reduce the volume of CO2 entering the atmosphere, coral reefs everywhere will bleach and die, however well they are being managed.
But while Bruno & Valdivia frame their argument very carefully, it is possible that unscrupulous policy makers could seize upon their study to justify continued exploitation of marine resources, claiming that it makes no difference to the bigger picture. Professor Avigdor Abelson of Tel Aviv University who works on restoration ecology such as building artificial reefs fears it “may lead to undesirable consequences of accelerated coral reef degradation.”
Both reports are right. The danger is that they will be misinterpreted.
