In a commentary Shifting Baselines, Local Impacts, and Global Change on Coral Reefs in PLoS Biology coral reef ecologists Nancy Knowlton and Jeremy Jackson write:
Imagine trying to understand the ecology of tropical rainforests by studying environmental changes and interactions among the surviving plants and animals on a vast cattle ranch in the center of a deforested Amazon, without any basic data on how the forest worked before it was cleared and burned. The soil would be baked dry or eroded away and the amount of rainfall would be greatly decreased. Most of the fantastic biodiversity would be gone. The trees would be replaced by grasses or soybeans, the major grazers would be leaf-cutter ants and cattle, and the major predators would be insects, rodents, and hawks. Ecologists could do experiments on the importance of cattle for the maintenance of plant species diversity, but the results would be meaningless for understanding the rainforest that used to be or how to restore it in the future.
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This lack of a baseline for pristine marine ecosystems is particularly acute for coral reefs, the so-called rainforests of the sea, which are the most diverse marine ecosystems and among the most threatened [4–8]. Most of the world’s tropical coastal oceans are so heavily degraded locally that “pristine” reefs are essentially gone, even if one ignores changes associated with already rising temperatures and acidity [3]. Most modern (post-SCUBA) ecological studies have focused on reef ecosystems that are moderately to severely degraded, and we have a much better understanding of transitions between human-dominated and collapsed reefs than between human-dominated and quasi-pristine reefs.
Knowlton and Jackson’s essay is a comment on an article in PLoS One Baselines and Degradation of Coral Reefs in the Northern Line Islands by Stuart Sandin and others that describes a large scale marine community assessment across a gradient of human dominated to relatively little impacted reefs in the Pacific. The study found that large predatory fish and reef-building organisms dominated the reefs around unpopulated islands, but around populated islands the reefs were dominated by small planktivorous fishes and fleshy algae. The reefs around populated islands exhibited more coral disease and less coral recruitment, suggesting that protection from overfishing and pollution may increase the resilience of coral reefs. The authors write:
Thus, local protection from overfishing and pollution may enhance ecosystem resilience to warm episodes and coral bleaching that result from global warming. To test this we need to determine how do coral recruitment, growth, and survivorship respond to changes in local community structure due to fishing, and how do these responses interact with episodes of warming measured by DHW. We also need to determine how fish productivity, i.e., the key currency of fisheries management, varies with changes in food web structure such as those observed between Kingman and Kiritimati. The only way to answer these questions is by investigation of reefs like the northern Line Islands that have remained remarkably intact in comparison to the global norm. They are among the only baselines that remain.
Continue reading ‘Coral Reefs in the Anthropocene’
At Crooked Timber, Australian economist John Quiggin reflects on the recent Coral Reef Futures Forum, which was recently organized by Resilience Alliance member Terry Hughes group at the ARC Centre of Excellence for Coral Reefs Studies in Australia. The forum aimed to discus how global changes such as fishing, climate change, and ocean acidification are threatening coral reefs. John Quiggin writes:
I spent the last couple of days in Canberra at the Coral Reef Futures Forum, as part of my new Federation Fellowship is to look at economic approaches to management of the Great Barrier Reef. As one of the speakers said, a lot of the talks had people staring at their shoes in gloom, though the tone got a little more positive towards the end. …
The most hopeful view is that, if we can fix the local threats like overfishing and poor water quality, the resulting increase in resilience (part of my project is to develop a more rigorous understanding of this popular buzzword) will offset moderate global warming, so that if we can stabilise the climate (an increase of no more than 2 degrees) we might save at least some reef systems.
It will be interesting to see what type of resilience economics John Quiggin develops. Several other economists have been working on the economics of resilience, such as Wisconsin econmist Buz Brock, Charles Perrings at Arizona State U, as well as Anne Sophie Crepin and others at the Beijer Institute, but the there is a lot that needs to be done to create a broadly useful resilience economics.
The paper by coral reef researchers Bellwood, Hughes, & Hoey, Sleeping functional group drives coral-reef recovery in Current Biology (2006 16(24):2434 -9) shows that hidden ecological functions can be critical for ecological restoration and provides further evidence for the importance of hysteresis in ecological regime shifts.
The researchers were examining the frequently observed shift of coral reefs from being dominated coral to macroalgae. This change is often due to the overharvesting of herbivorous fishes, particularly parrotfishes and surgeonfishes, that maintain the coral regime. They showed that a shift to the marcoalgae dominated regime on the Australian Great Barrier Reef was reversed not by parrotfishes or surgeonfishes, but rather by a species of batfish, Platax pinnatus, which is relatively rare on the Great Barrier Reef, and was thought to feed only on invertebrates.
Their finding suggests three things:
- that conserving ecosystem functioning is important for both for the maintenance and recovery of ecosystems,
- that successful functional conservation requires that we need to greatly increase our functional understanding of ecosystems, and
- that research into ecosystem functioning should examine function in different ecological contexts.
Interestingly, this research finding is similar to that of common property researchers who have discovered that many local resource management institutions contain “hidden” resources management practices, that are only activated during special environmental conditions - for example a fishery may have alternative property rights emerge during periods low fish abundance.
Press coverage of this research can be found in a press release from James Cook University, the New Scientist, and the Washington Post.