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Are the impacts of climate change on coral reefs exaggerated? Questions and Answers (Part 1)

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For a long time the New Scientist has waged an ongoing battle with the climate change “skeptics”, and have produced some thorough articles such as “Climate change: a guide for the perplexed“, a round-up of the 26 most common climate myths and misconceptions. Time and time again I see people use similar myths and misconceptions regarding corals and coral reefs that are used as an argument as to why global warming is clearly a hoax, how warm water is good for corals (and the list goes on). In response to recent debates, below is the first part of a series called “Are the impacts of climate change on coral reefs exaggerated? Questions and Answers” in which I hope to address these misconceptions following the scientific evidence. Over the coming weeks I will aim to add more in the series: please feel free to add or ask any further questions in the comments below or email me at climateshifts @ gmail.com


1. “Warm water is good for corals”

Corals are locally adapted to the water temperature that they live in. This has taken many hundreds if not thousands of years to occur. It does not happen over decades, which would be the requirement if corals were to tolerate and survive the very rapid changes in sea temperature that we are currently facing.

The statements that “corals calcify faster in warmer waters” and “hotspots of coral diversity are found in warm waters close to the equator” are indeed true, but these conditions are only good for those corals that have adapted to these warmer conditions. For example, if you take corals from the southern end of the Great Barrier Reef and put them at the northern end of the Great Barrier Reef, these corals will suffer from being exposed to warmer than normal conditions and will die.

Although corals thrive within the upper limits of their thermal tolerance (within 1-2ºC), coral bleaching occurs when this tolerance is exceeded, resulting in loss of photosynthetic function, expulsion of symbiotic algae, and ultimately death of the coral. Clearly warm water is beneficial to those corals that are adapted to these warmer temperatures, although exceeding these thresholds results in mortality – a precarious balance.

With respect to the statement “corals in Moreton Bay are regularly stressed as the water is too cold” – it is well-known that corals in Moreton Bay (and other high latitude regions) where conditions that drop below 18°C in the winter lead to coral death. Just like they are sensitive to being too hot, they are also sensitive to becoming too cold. This is called the physiological range or tolerance of species. Conditions at places like Moreton Bay are marginal and therefore an outlier in global coral reefs and are restricted by their latitudes by cold winters.

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Status of Caribbean coral reefs after bleaching and hurricanes in 2005

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The “Status of Caribbean coral reefs after bleaching and hurricanes in 2005” is an excellent account of the impact of mass bleaching and hurricanes that hit the Caribbean in 2005. As you will remember, sea temperatures rose sharply in this region in May 2005, intensifying until October by which time hotspots covered most countries in the eastern Caribbean.  This occurred during the hottest year on record for the northern hemisphere at that time, and resulted in a massive die off of corals.

As pointed out by the editors, Clive Wilkinson and David Souter, the 2005 event provided an important opportunity to study the impact of extreme thermal stress on coral reefs.  Via network of hundreds of scientists that were linked by the Internet and backed up by sophisticated monitoring tools, key information and insights would gained into the relationship between thermal stress, bleaching and coral mortality.

Overall, coral reefs in eastern Caribbean were severely damaged by anyone’s estimate in 2005.  What is perhaps most alarming is that the mortality ranged up to 50% in places like the US Virgin Islands and the Greater and Lesser Antilles.  This came on top off a rapid deterioration of reefs that has been occurring over the past few decades.  The coral cover of most (if not all) coral reefs in this region have been sliding rapidly downwards.

This is a useful collection of papers which I recommend that you read (link).  My good friend Billy Causey, who has a long and proud history of fighting for the protection of Florida’s coral reefs, provides a very useful account of the history of bleaching in his region. There is also some useful information as well on the hurricane story, including on what drives their intensity and how they impacted reefs in 2005.

“Climate change could be the next subprime meltdown”

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Financial Post, 14th February 2008

Another subprime-mortgage-meltdown-sized risk could be looming for investors: global warming. That alarm was sounded Thursday at an investor summit at the United Nations headquarters, at which 480 investors, pension fund leaders and corporate executives from around the globe were warned that the vast majority of companies are ill-prepared for the Earth’s changing climate.

Many oil producers, utilities and manufacturing plants have yet to factor in the added expense if the United States – as is expected in the next few years – imposes caps on carbon-dioxide emissions. Similarly, many companies with big real-estate holdings in U.S. coastal regions haven’t calculated their exposure to increased tropical storms and rising seas.

Most of the financial institutions that lend to these companies and the insurance companies that protect them also have yet to adequately consider how they might get burned.

"It’s like subprime mortgages…one of longest kept secrets of uncalculated risk," said Mindy Lubber, president of Ceres, a coalition of investors and environmental groups, which co-hosted yesterday’s event. "By not acting on climate change…we face the same kind of [risks] with what we’re seeing in subprime."

Former U.S. vice president Al Gore, who was awarded the Nobel Peace Prize last year for bringing attention to the issue of climate change, echoed that theme as keynote speaker, urging investors to dump any assets they hold in businesses that are heavily reliant on carbon-intensive energy – or risk losing a ton of money down the road.

"You need to really scrub your investment portfolios, because I guarantee you…that if you really take a fine-tooth comb and go through your portfolios, many of you are going to find them chock-full of "subprime" carbon assets," Mr. Gore said according to an Associated Press report of the speech, which was closed to the press.

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Further calls for dramatic reductions in carbon emissions in the news

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Climate report calls for 2008 commitment to target
The Age, 21st February 2008

Greens leader Bob Brown has described a report that urges action on global warming as “spot on” but says he is worried the Federal Government will back away from adopting its recommendations.

Economist Ross Garnaut’s interim report on climate change, released today after being commissioned by Kevin Rudd and his colleagues while in opposition last year, has recommended Australia commit to a 2020 greenhouse target this year.

So far the Rudd Government has only adopted a long-term goal of cutting greenhouse emissions by 60% by 2050, but Professor Garnaut’s report says action needs to be taken immediately because recent scientific data indicates the global climate is changing faster than expected. (Read More)

Adaptation ‘key to climate deal‘
BBC News, 20th February 2008

The UK’s former top diplomat has called for a massive increase in the amount of money available to help developing countries to adapt to climate change.Lord Jay was speaking in Brazil, ahead of a two-day meeting of lawmakers from 13 key countries. The Global Legislators’ Organisation for a Balanced Environment conference will discuss the shape of a long-term deal to tackle global warming.

The discussions will not determine policy but they may influence it. The aim is to show what kind of future agreement would have enough support to be politically viable.

The Globe meeting brings together 100 leading politicians from the group of eight richest economies (G8) and five key developing countries: Brazil, China, India, Mexico and South Africa.On the table is a document drawn up by the former head of the UK Foreign Office, Lord Jay, sketching out the key principles of a global deal on climate change which the world’s leaders have pledged to negotiate by 2009, the timetable agreed at December’s UN climate meeting in Bali. (Read more)

Hammerhead in need of protection

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BBC News, 18th February 2008

Over-fishing and demand for shark fins, an expensive delicacy, have pushed one of the world’s iconic animals towards the brink of extinction, say experts.

The scalloped hammerhead shark is to be added to the official endangered species list this year, under the heading “globally endangered”.

Their plight has been discussed at the American Association for the Advancement of Science annual meeting. It was told that enforcement of marine reserves would aid shark protection.

The observation takes account of new research that shows hammerhead and great white sharks patrol fixed routes in the ocean, gathering at hotspots to mate or feed.

Dr Julia Baum, a marine ecologist at the Scripps Institution of Oceanography, US, and a member of the World Conservation Union (IUCN), said excessive fishing was putting many of the ocean’s “most majestic predators” at risk of extinction.

Speaking at the Boston meeting, she said: “Sharks evolved 400 million years ago, and we could now lose some species in the next few decades – so that would be just a blink of an eye in evolutionary time.”

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First map of threats to marine ecosystems shows all the world’s oceans are affected

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EurekAlert, 14th February 2008

As vast and far-reaching as the world’s oceans are, every square kilometer is affected by human activities, according to a study in the journal Science by researchers at the University of North Carolina at Chapel Hill and others.

The international team of scientists integrated global data from 17 aspects of global change – from overfishing to global warming – that threaten 20 different marine ecosystems, such as coral reefs and continental shelves. Similar to an online satellite map that lets you add layers of highways, retail stores, schools, parks, etc., to find the most congested areas or the highest concentration of fast food restaurants, the global threat map highlights areas in the ocean where threats overlap.

The researchers scored the potential threats – from having very-low to very-high impacts – and found that affects were ubiquitous, and more than 40 percent of the oceans experience medium- to very high-impact threats.

“For the first time we can see where some of the most threatened marine ecosystems are and what might be degrading them,” said Elizabeth Selig, an author on the study and a doctoral student in UNC’s curriculum in ecology in the College of Arts and Sciences.

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Desktop Darwin’s surprise discovery

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The Age, 12th February 2008

One day late last year, Chris Simpson was looking at the waters off the coast of Western Australia on Google Earth when he made an unusual discovery.

Just west of the Kimberleys, a remote area in northern Western Australia, there was an extensive formation of fringing coral reefs – a sight rarely seen anywhere in the world.

“I feel like bloody Charles Darwin up here discovering these new reefs!” Dr Simpson told his boss.

It was a significant find for the coral reef specialist at West Australia’s Department of Environment and Conservation. Most coral reefs occur as isolated reefs and atolls, such as the Great Barrier Reef off the coast of Queensland.

But fringing coral reefs are much rarer. As freshwater kills corals, such reefs can only occur if they are off the coast of an arid location, such as a desert, where no rivers flow out into the waters.

So it was only in locations such as the Red Sea, in south-west Madagascar and at Ningaloo Marine Park off Western Australia where extensive formations were found.

And while the Kimberleys were always a candidate for marine park status, their inaccessibility, turbid waters, massive tides and the presence of crocodiles have deterred would-be explorers from finding out the extent of the reefs.

So when Dr Simpson was exploring the Kimberleys through Google Earth, a practice he has incorporated into his job, he did not expect to spot such a major formation.

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More disinformation from Dr Peter Ridd in response to the ocean thermostat study

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I see over on “The Politics and Environment Blog” in response to the ocean thermostat study published recently that the following comment from the ill-informed Dr Peter Ridd’s diatribe “The Great Great Barrier Reef Swindle” is again being misconstrued as evidence that warmer waters will be beneficial for corals:

“The scientific evidence about the effect of rising water temperatures on corals is very encouraging. In the GBR, growth rates of corals have been shown to be increasing over the last 100 years, at a time when water temperatures have risen. This is not surprising as the highest growth rates for corals are found in warmer waters. Further, all the species of corals we have in the GBR are also found in the islands, such as PNG, to our north where the water temperatures are considerably hotter than in the GBR. Despite the bleaching events of 1998 and 2002, most of the corals of the GBR did not bleach and of those that did, most have fully recovered.

Of course, some corals on the Queensland coast are regularly stressed from heat, viz. the remarkable corals of Moreton Bay near Brisbane which are stressed by lack of heat in winter. A couple of degrees of global warming would make them grow much better.”

See my response to Dr Ridd’s comments here. I’d like to extend an open invitation to Dr Jennifer Marohasy, the blog’s main author (or anyone else) to provide evidence from the scientific literature that warmer waters will be holistically beneficial to corals from the Great Barrier Reef, and look forward to your response.

Flood waters on the Great Barrier Reef – a report from the Keppels

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On the topic of Great Barrier Reef flood waters posted last week, a rapid response team from my lab, headed by Dr Guillermo Diaz-Pullido and backed by the remote sensing capabilities of Dr Scarla Weeks was busy conducting coral and algal surveys in the Keppels region to determine baselines of coral health before the flood waters hit the reef. Dr Diaz-Pullido and two volunteers (Pim Bongaerts and Norbert Englebert) joined researchers from JCU to determine levels of coral and algae at reefs across the region. Flying out from Rockhampton over the ever rising flood waters confirmed the MODIS satellite images (see bottom left), and shows the level of water damage to the region (see centre): the waters were clearly heading outwards of the reef forming a freshwater lens (see bottom right picture).

Satellite image showing the Fitzroy river (Jan 21st 2008) View of the Fitzroy River in full flood (22nd Jan 2008) Flood plume extending out to the inshore reefs (22nd Jan 2008)

 

As a bit of background to this region: the Fitzroy catchment at nearly 150,000km2 is the largest of the Great Barier Reef, and is dominated by agriculture (grazing, irrigated cotton and horticulture) and by mining (coal production of 100 million tonnes/year, magnesite and nickel), and significant flooding events have been recorded in 1918, 1954, 1978, 1983, 1988 and 1991 (see below from the Bureau of Meterology). The ABC News site has some astounding images from the 2008 flood here.

 

Following the high levels of rainfall in January this year, many have predicted significant flooding and impacts to the inshore coral reefs of the Keppel region. Such disturbances are far from unusual in the Keppels – in 1991, over 85% of coral in shallow reefs died following severe flood events, and again on November 2006, significant mortality occured within 8 hours on the reef flats in the Keppels due to a lethal combination of high rainfall and low tides.

The team surveyed shallow and deep reefs of five islands using belt transects, including more than 300 1×1 m photo quadrats. At the time of the surveys, the freshwater plume from the Fitzroy River had already reached the leeward side of some islands, although at the time of surveying Dr Diaz-Pullido reported no visible impacts on the coral reef benthic community. Benthic macroalgae (seaweeds) usually colonise weakened and dead corals, and during the last coral beaching event in 2006, seaweeds experienced an unprecedented macroalgal bloom. Despite the severity of these disturbances and algal blooms, many coral reefs of the area have recovered and currently flourish (see images below)

 

Dr Guillermo Diaz Pullido surveying coral and algal cover prior to the flooding Research assistants Pim Bongaerts and Norbert Englebert collect algal samples Healthy inshore reefs at the Keppels with high coral cover (Acropora sp.

 

The impacts on the reef communities will depend on the residence time of the freshwater plume on the area, the nature and quantity of the sediments and contaminant associated. The team are closely monitoring the oceanographic and meteorological patterns, and depending on the developments of the plume, the research team will head back to the Keppel Islands in the coming weeks. The offshore surface flow in the region is strongly influenced by wind direction, whilst surface flow is primarily offshore (cross-shelf) limited in offshore extent by the frontal boundary created by inflow of oceanic waters due to eddy dynamics further south. Therefore, the Fitzroy outflow will be deflected to the left due to geostrophy (due to rotation of the Earth ) moving along this front.

Coral Reefs May Be Protected By Natural Ocean Thermostat

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Science Daily, Feb 8th 2008

Natural processes may prevent oceans from warming beyond a certain point, helping protect some coral reefs from the impacts of climate change, new research finds. The study, by scientists at the National Center for Atmospheric Research (NCAR) and Australian Institute of Marine Science (AIMS), finds evidence that an ocean “thermostat” appears to be helping to regulate sea-surface temperatures in a biologically diverse region of the western Pacific.

The research team, led by NCAR scientist Joan Kleypas, looked at the Western Pacific Warm Pool, a region northeast of Australia where naturally warm sea-surface temperatures have risen little in recent decades. As a result, the reefs in that region appear to have suffered relatively few episodes of coral bleaching, a phenomenon that has damaged reefs in other areas where temperature increases have been more pronounced.

The study lends support to a much-debated theory that a natural ocean thermostat prevents sea-surface temperatures from exceeding about 88 degrees Fahrenheit (31 degrees Celsius) in open oceans. If so, this thermostat would protect reefs that have evolved in naturally warm waters that will not warm much further, as opposed to reefs that live in slightly cooler waters that face more significant warming.

“Global warming is damaging many corals, but it appears to be bypassing certain reefs that support some of the greatest diversity of life on the planet,” Kleypas says. “In essence, reefs that are already in hot water may be more protected from warming than reefs that are not. This is some rare hopeful news for these important ecosystems.”

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