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Avoiding confusion for stabilization targets for climate change and ocean acidification

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Long Cao and Ken Caldeira from the Carnegie Institution at Stanford have a new paper in Geophysical Research Letters on atmospheric carbon dioxide (CO2) stabilization and ocean acidification, a critical topic for current marine science and public policy. Hoegh-Guldberg et al (2007) illustrated the essential chemistry at the heart of this problem as follows:

Essentially, as CO2 dissolves into the oceans it forms an acid leading to decreased coral calcification and growth through the inhibition of aragonite formation (the principal crystalline form of calcium carbonate deposited in coral skeletons). The increased acidity caused by increasing atmospheric CO2 is known as ocean acidification and it is a separate, though inter-related, phenomenon to increased temperatures caused by CO2 acting as a greenhouse gas.

Cao and Caldeira (2008) found “that even at a CO2 stabilization level as low as 450 ppm, parts of the Southern Ocean become undersaturated with respect to aragonite [and] therefore, preservation of existing marine ecosystems could require a CO2 stabilization level that is lower than what might be chosen based on climate considerations alone.”

These results are similar to Hoegh-Gulberg et al (2007), who concluded “… contemplating policies that result in [CO2]atm above 500 ppm appears extremely risky for coral reefs and the tens of millions of people who depend on them directly, even under the most optimistic circumstances.”

Hoegh-Guldberg et al (2007) illustrated the expected the conditions of coral reefs under different levels of atmospheric carbon dioxide and temperature increases as follows:

These findings are very significant for governments around the world and other policy-makers because much of the current policy debate on climate change focuses on stabilizing greenhouse gases, including carbon dioxide, between 450-550 parts per million carbon dioxide equivalents, thereby allowing a rise in mean global temperatures of around 2-3°C (e.g. Stern 2007; Garnaut 2008; Australian Treasury 2008).

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“Great Barrier Reef could adapt to climate change, scientists say” – Facts, fallacies and fanciful thinking.

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The Australian newspaper published an article this weekend entitled “Great Barrier Reef could adapt to climate change, scientists say”.

THE prediction of a prominent marine biologist that climate change could render the Great Barrier Reef extinct within 30 years has been labelled overly pessimistic for failing to account for the adaptive capabilities of coral reefs.

University of Queensland marine biologist Ove Hoegh-Guldberg said yesterday that sea temperatures were likely to rise 2C over the next three decades, which would undoubtedly kill the reef.

But several of Professor Hoegh-Guldberg’s colleagues have taken issue with his prognosis.

Andrew Baird, principal research fellow at the Australian Research Council’s Centre for Excellence for Coral Reef Studies, said there were “serious knowledge gaps” about the impact rising sea temperatures would have on coral.

“Ove is very dismissive of coral’s ability to adapt, to respond in an evolutionary manner to climate change,” Dr Baird said.

“I believe coral has an underappreciated capacity to evolve. It’s one of the biological laws that, wherever you look, organisms have adapted to radical changes.”

Dr Baird acknowledged that, if left unaddressed, climate change would result in major changes to the Great Barrier Reef.

“There will be sweeping changes in the relative abundance of species,” he said. “There’ll be changes in what species occur where.

“But wholesale destruction of reefs? I think that’s overly pessimistic.”

Dr Baird said the adaptive qualities of coral reefs would mitigate the effects of climate change.

I must say I’m a little amazed that Andrew Baird has come out with such poorly supported statements.  In fact, his conclusions seem to depend almost entirely on his personal opinion!  The argument that corals are able to magically “adapt” over one or two decades to climate change (even though their generation times are often longer) has come up many times over the years – always, with a complete dearth of evidence to support it.

I wrote to Andrew Baird yesterday, to try and understand if there was something that he knew that I might have missed in the scientific lecture.  In response, Andrew sent me a recent article published by Jeff Maynard and himself (Maynard et al 2008).

Unfortunately, the article is an opinion piece (a bit like the newspaper article) that is poorly supported by anything but the most scant evidence (if you could actually call it that) from literature.   I have responded to these types of articles before, but frustrated, here we go again:

Maynard et al (2008) state the following as important evidence that corals can adapt to changes in the environment, and therefore that they can adapt to the current very rapid changes in ocean temperature and acidity.

“..geographic variation in bleaching thresholds within species, sometimes over scales <100km, provides circumstantial evidence for ongoing evolution of temperature tolerance between both species and reef”

Let me start by saying that no credible biologist would doubt the role of evolution in the shaping of the physiology and ecology of corals with respect to temperature.  Biological populations evolve in response to stress.  However, the mere observation of geographic variation in thermal tolerance, does not give any hint  about the rates or the length of time that these changes have taken to occur.  Importantly, this statement does not equate to evidence that thermal tolerance can evolve in ecological time.  The only way that Andrew Baird could convince anyone of this particular somewhat fanciful leap of logic is to present data that show that coral populations can rapidly evolved in the period of years.  They can’t, and they haven’t.

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Jacques Piccard, deep sea explorer dies at age 86

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Jacques Piccard, the legendary scientist, explorer (and childhood hero of mine)  passed away yesterday at his home in Lake Geneva.

Jacques Piccard helped his father invent the bathyscaphe, a vessel that allows people to descend to great depths. On Jan. 23, 1960, he and Lt. Don Walsh of the United States Navy took the vessel, named the Trieste, into the Mariana Trench in the Pacific to a depth of 35,800 feet, nearly seven miles below sea level. It remains the deepest human dive ever.

“By far the most interesting find was the fish that came floating by our porthole,” Mr. Piccard said. “We were astounded to find higher marine life forms down there at all.” Solar Impulse said the discovery of living organisms at such a depth played a crucial role in the prohibition of nuclear waste dumping in ocean trenches. (link to NY Times obituary)

“Estate agents told me not to talk: climate expert”

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ABC News, 29th October 2008

A climate change scientist says real estate agents have threatened to make his life difficult if he continues to publish research about how vulnerable particular properties are to rising sea levels and coastal erosion.

Professor Andrew Pitman works at the Climate Change Research Centre at the University of New South Wales.

He says real estate agents do not like potential buyers asking questions about climate change based on his research.

Professor Pitman has told the ABC’s Local Radio that several agents have asked him to stop talking about how vulnerable certain properties are.

“More explicitly [they said] ‘We’re nervous about our particular market niche in a particular suburb’,” he said.

“And, ‘We are going to start making your life difficult if you keep pointing to climate change affecting our particular location’.”

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Origins of sea fan aspergillosis

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Infectious disease outbreaks are a major cause of coral loss and reef degradation.  Evidence from paleontological studies and ecological monitoring indicate that coral disease prevalence, variety, and host range have all increased over the last 30 years.  But what is the origin of coral pathogens?  Even in the few cases where the causal pathogen has been identified, we don’t know where it came from, if it is new or newly introduced or whether it was always present on reefs, but only recently became virulent due to a mutation or environmental change.

Identifying the source of coral pathogens is a key goal of coral disease ecology with obvious importance for disease mitigation and reef management.  Coral pathogens could originate in terrestrial habitats and be introduced to the ocean following deforestation and soil runoff.  They could also be added via sewage outfalls, transported from faraway reefs in the ballast water of cargo ships, and might even be spread within and among regions by human travel.

A pair of exciting new studies clarifies the origins of sea fan aspergillosis, a major Caribbean epizootic caused by the pathenogenic fungus Aspergillus sydowii.  In the first paper, Rypien et al. (2008) used molecular markers to determine patterns of relatedness among strains of Aspergillus sydowii collected from a variety of hosts and environments. Specifically, they tested four hypotheses:

1) The Endemic Marine Hypothesis predicts that corals are infected by fungus that is native to marine habitats and therefore phylogenetically distinct from nearby terrestrial isolates.

2) The Terrestrial Runoff Hypothesis predicts that isolates from diseased corals will be most closely related to terrestrial isolates from nearby landmasses.

3) The single-origin African Dust Hypothesis predicts that isolates will have reduced genetic diversity and allelic richness, with evidence of a recent bottleneck in coral disease-causing isolates. This hypothesis also predicts that isolates will be most closely related to terrestrial isolates from Africa.

4) The multiple origins African Dust Hypothesis predicts no evidence of a recent bottleneck, with disease-causing isolates being most closely related to terrestrial isolates from Africa.

Their results essentially refute all four hypotheses and reveal a pattern of global panmixia and multiple origins, suggesting that a single source of Aspergillus sydowii into reefs is unlikely.  The results illustrate the opportunistic nature of the fungal pathogen and suggest that a diversity of isolates can cause aspergillosis.

Despite coming from very different geographic locations (Japan to North America to Europe) and different sources (diseased corals, diseased humans, dried fish), we found that all strains form a single well-connected global population. – lead author Dr. Krystal Rypien, currently a post doc at Scripps Institution of Oceanography

Aspergillus sydowii fungi in culture

Dr. Rypien added; This has important implications for the management of disease, as it means that any isolate of this fungus has the potential to cause disease in coral, and that we are not dealing with a specialized group of pathogens.  Interestingly, this is similar to a close relative, Aspergillus fumigatus, a common fungal pathogen of immune compromised humans.  Given the global distribution of A. sydowii, and evidence for multiple introductions into marine systems, it seems that this pathogen has always been present in marine systems, and changes in environmental conditions and host immune status are likely to be more important in driving patterns of disease outbreak.

The second study (Rypien 2008) tested the widely-believed hypothesis that African dust plays a role in coral epizootics in general and sea fan aspergillosis in particular.  Each year hundreds of millions of tons of dust is transported from the Sahara desert to the Caribbean.  There are indications that the volume of dust has increased as the Sahara expands and atmospheric conditions and wind patterns change.  The idea is that African dust can cause or exacerbate coral epizootics by depositing nutrients and trace elements that benefit pathogens or by transporting pathogens from terrestrial African habitats to Caribbean coral reefs.  Past studies have indeed found Aspergillus spp. in dust samples collected from the Caribbean, but none have identified the fungi to species, which turns out to be a critical shortcoming.

Dr. Rypien collected dust samples from the Caribbean and Africa, isolated Aspergillus, and identified the isolates to species using standard colony-level and microscopic morphological characteristics.  Despite yielding seven different species of Aspergillus and related taxa, there was no A. sydowii in airborne dust samples from Africa and the Caribbean or in sediment samples from Africa and the Cape Verde Islands.

The lack of A. sydowii in airborne dust and sediment samples suggests that African dust is an unlikely source of the marine pathogen A. sydowii.  Given the high richness of fungi observed, even under selective growth conditions, identification of potential pathogens to the species level is critical.

The study doesn’t entirely refute African dust as a source of Aspergillus sydowii – it is nearly impossible to prove the absence of something – but it does cast doubt on much-heralded theory.

References

Rypien, K. L. 2008. African dust is an unlikely source of Aspergillus sydowii, the causative agent of sea fan disease. Marine Ecology Progress Series 367:125-131.

Rypien, K. L., J. P. Andras, and C. D. Harvell. 2008. Globally panmictic population structure in the opportunistic fungal pathogen Aspergillus sydowii. Molecular Ecology 17:4068-4078.

Will we leave the Great Barrier Reef for our children?

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Amidst the current policy debate in Australia on climate change is a surreal argument that policies that will destroy the Great Barrier Reef (GBR) are acceptable and economically rational. Ross Garnaut was alive to the damage to the GBR when saying Australia should initially aim for a global consensus to stabilise greenhouse gases in the atmosphere at 550 parts per million. Garnaut (2008a: 38) was brutally frank in his supplementary draft report:

“The 550 strategy would be expected to lead to the destruction of the Great Barrier Reef and other coral reefs.”

His final report does not shy away from this conclusion (Garnaut 2008b).

The Australian and Queensland governments have always silently avoided this point when explaining the costs and benefits of their climate policies. Neither has ever stated a stabilisation target for the rise in global temperatures or greenhouse gases. To do so would expose them to the criticism that their policies will not save the GBR or a host of other ecosystems.

Garnaut’s frank admission reflects the findings of research of the impacts of climate change to the GBR since mass coral bleaching occurred globally in 1998 and 2002. Rising sea temperatures and increasing acidity of the oceans due to our use of fossil fuels are now well-recognized as major threats to coral reefs and the marine ecosystem generally in coming decades.

Coral bleaching and partial recovery on Pelorus Island, GBR: (a) 1998; (b) 2002; and (c) 2004. Source: Schuttenberg H and Marshall P, A Reef Manager’s Guide to Coral Bleaching (GBRMPA, Townsville, 2006), p12.

Coral bleaching and partial recovery on Pelorus Island, GBR: (a) 1998; (b) 2002; and (c) 2004. Source: Schuttenberg H and Marshall P, A Reef Manager’s Guide to Coral Bleaching (GBRMPA, Townsville, 2006), p12.

In relation to coral bleaching the IPCC (2007b: 12) found that:

“Corals are vulnerable to thermal stress and have low adaptive capacity. Increases in sea surface temperature of about 1 to 3°C are projected to result in more frequent coral bleaching events and widespread mortality, unless there is thermal adaptation or acclimatisation by corals.”

The findings of the IPCC suggest that a rise of 1°C in mean global temperatures and, correspondingly, sea surface temperatures above pre-industrial levels is the maximum that should be aimed for if the global community wishes to protect coral reefs. The range of 1-3°C is the danger zone and 2°C is not safe. Supporting this conclusion Ove Hoegh-Guldberg and his colleagues concluded in a review of the likely impacts of climate change to the GBR edited by Johnson and Marshall (2007: 295):

“Successive studies of the potential impacts of thermal stress on coral reefs have supported the notion that coral dominated reefs are likely to largely disappear with a 2°C rise in sea temperature over the next 100 years. This, coupled with the additional vulnerability of coral reefs to high levels of acidification once the atmosphere reaches 500 parts per million [CO2], suggests that coral dominated reefs will be rare or non-existent in the near future.”

The IPCC’s (2007a: 826) best estimate of climate sensitivity found that stabilising greenhouse gases and aerosols at 350 parts per million carbon dioxide equivalents (ppm CO2-eq) would be expected to lead to a rise in mean global temperatures of 1°C, stabilising at 450 ppm CO2-eq will lead to a rise of 2°C, and stabilising at 550 ppm CO2-eq will lead to a rise of 3°C.

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Rare corals may be smarter than previously thought

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Following on from a previous article at Climate Shifts, a recent article published in PLoS One shows that corals are proving to be even more non-conformist than previously thought. Zoe Richards and co-authors from the ARC Centre of Excellence for Coral Reef Studies found that ‘rare’ species of branching corals are able to cross breed with other branching corals to create hybrids, therefore avoiding probable extinction:

“Coral reefs worldwide face a variety of marine and land-based threats and hundreds of corals are now on the red list of threatened species. It is often assumed that rare coral species face higher risks of extinction than common species because they have very small effective population sizes, which implies that they may have limited genetic diversity and high levels of inbreeding and therefore be unable to adapt to changing conditions.

When we studied some particularly rare species of Acropora (staghorn corals), which you might expect to be highly vulnerable to extinction, we found some of them were actually hybrids – in other words they had cross-bred with other Acropora species.  This breaks all the traditional rules about what a species is. By hybridising with other species, these rare corals draw on genetic variation in other species, increasing their own potential to adapt to changing conditions.

When we looked at the genetic history of rare corals, we found that they exhibited unexpected patterns of genetic diversity.  This suggests that, rather than being the dying remnants of once-common species, they may actually be coral pioneers pushing into new environments and developing new traits by virtue of the interbreeding that has enabled them to survive there.

This is good news, to the extent that it suggests that corals may have evolved genetic strategies for survival in unusual niches – and may prove tougher to exterminate than many people feared. With such tricks up their sleeve, it is even possible that the rare corals of today could become the common corals of the future.”  (Link)

CoralCoralCoral

Grazer composition an important factor in controlling macroalgae

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The redband parrotfish was one of the species studied as part of research into the importance of fish diversity for the health of coral reefs.

The redband parrotfish was one of the species studied as part of research into the importance of fish diversity for the health of coral reefs.

We know the biomass of macroalgae on coral reefs is largely controlled by herbivory and that one of the most important groups of grazers are parrotfish.  A new study published in PNAS (Berkepile and Hay 2008) indicates that the richness and composition of grazer species is also important.  In a nutshell, different fish consume different seaweeds because of their differing chemical defenses.  Similar work in other benthic marine systems has found that consumer species richness can be an important determinant of ecosystem functioning, yet this is the first such study on a coral reef.

Our study shows that in addition to having enough herbivores, coral ecosystems also need the right mix of species to overcome the different defensive tactics of the seaweeds.  explained Mark Hay, the Harry and Linda Teasley Professor of Biology at the Georgia Institute of Technology.

Despite different species of parrotfish in the Caribbean having different feeding behaviors, bioerosion rates, and preferred diets, parrotfishes are often considered as a unified functional group when inferring their effects on community structure. However, we found that redband and princess parrotfish had considerably different effects on communities, suggesting that grouping all parrotfishes may blur important distinctions among species.

Despite their different feeding morphologies, ocean surgeonfish and princess parrotfish generated similar macroalgal communities dominated by upright brown macroalgae (e.g., L. variegata and Sargassum spp.). In contrast, despite their more similar jaw morphology, the communities generated by redband and princess parrotfish differed considerably in the abundance of upright macroalgae. Similar to the work of Bellwood et al., these results show that fishes with different feeding morphologies can have similar effects on community structure, suggesting that relying primarily on jaw functional morphology to construct functional groups or infer a species’ impact may be unreliable.

Working out of the underwater Aquarius laboratory off Key Largo Florida, Hay and co-author Deron Burkpile – who is now at Florida International University in North Miami – constructed 32 cages on the reef. Each cage was about two meters square and one meter tall and was sealed so that larger fish could neither enter nor leave.

The number and type of fish placed into each four-square-meter cage varied. Some cages had two fish that were able to eat hard, calcified plants; some had two fish able to eat soft, but chemically-defended plants; some had one of both types, and some had no fish at all

For the cages in which we mixed the two species of herbivores, the fish were able to remove much more of the upright seaweeds, and the corals in those areas increased in cover by more than 20 percent during ten months, Hay said.

The data we are seeing in Fiji [from similar experiments] suggests that diversity may be even more important there than it was in the Caribbean.  There are a lot of different species doing a lot of very different things. These consumers are very important, and in areas where they are over-fished, the reefs are crashing.

Reference

Berkepile, D.E. and M.E. Hay. 2008. Herbivore species richness and feeding complementarity affect community structure and function on a coral reef. PNAS 105: 16201–16206

Diver Todd Barsby secures a cage to the coral reef during a study of the role of diversity among herbivorous fishes.

Diver Todd Barsby secures a cage to the coral reef during a study of the role of diversity among herbivorous fishes.

The missing link in the “solutions” to climate change

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The recent Garnaut report states that “the solutions to the climate change challenge must be found in removing the links between economic activity and greenhouse gas emissions.” In order to successfully mitigate climate change impacts on both the environment and the economy, we need to go a step further and replace those links with avenues for sustainable economic activity. This can effectively begin with innovative designs for improving efficiency in energy production and usage.

Rather than compensating mining companies that are vulnerable to the new emissions trading scheme, the pledged compensation should be used to train employees of these companies with skills that will help them develop innovative designs for efficient energy usage to the commercialisation level. These high emission companies should begin investing in new technologies which could eventually be traded instead of coal to countries like China, in order to spread the improvements in carbon emissions to a global scale. Of course, this is the ten billion ton gorilla in the room that no one quite wants to recognise (at least not publicly!)

Credits to trade-exposed companies and low income households should only be considered to the extent that benefits are not initially received for their investment. Once benefits are realised, this monetary gain must be re-invested into future innovative solutions, thereby replenishing the funding for green solutions. Essentially, we need to amp up the green investment cycle.  For example, in the above situation a mining company burdens the cost of training some employees and using their work hours for sustainable development avenues.

Once the company receives return on their investment, re-investment into development of sustainable technologies should occur to the extent of the original “loan” or government credit. Similarly, households given credits, for example, to install solar panels should be encouraged to re-invest the savings on their electricity bills into new innovative technologies. The establishment of this positive feedback loop should be a condition of receiving the credits in order to prevent the misuse of the credits or the undermining of carbon trading.

The missing links in the solutions to climate change are the real ideas that will drive the economy towards sustainable development. Treading softly on this issue is not an option – time is of essence.  Another weak link in this much needed cycle is the fact that economic gain is our society’s key motivation and the environment is severely undervalued. The Garnaut Review states that environmental and social costs “are not amenable to conventional measurement”.

In other words, any cost-benefit analysis will not be accurate. Society’s real motivation needs to come from desire to maintain and conserve the environment for future generations. There is no adequate or accurate way to quantify this desire. And there is no way to ensure that that this desire is a top priority of world citizens. It seems that the best way to achieve this goal is to steer people’s actions economically. However, it is unlikely that the outcome will exhibit the same strength when motivated by monetary value.