Shifting Baselines, Local Impacts, and Global Change on Coral Reefs – a note from Nancy Knowlton & Jeremy B. C. Jackson

Healthy Reefs, Dying Reefs, and Corals in Bocas del Toro, Panama:(A) Example of a healthy reef with abundant living coral. (B) Example of a reef in which most coral has died and been replaced by macroalgae. (C) Bleached and healthy coral colonies; both are alive but the bleached colony has lost its symbiotic algae. (D) Coral suffering from disease and with encroaching macroalgae.

PLoS ONE, February 26th 2008

Nancy Knowlton & Jeremy B. C. Jackson

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.

Fortunately, ecologists began to carefully describe tropical forests more than a century ago, and vast areas of largely intact forests have persisted until today, so there are meaningful baselines for comparison. Networks of 50-hectare plots are monitored around the world [1], and decades of experiments have helped to elucidate ecological mechanisms in these relatively pristine forests [2]. But the situation is very different for the oceans, because degradation of entire ecosystems has been more pervasive than on land [3] and underwater observations began much more recently. Monitoring of benthic ecosystems is commonly limited to small intertidal quadrats, and there is nothing like the high-resolution global monitoring network for tropical forests for any ocean ecosystem.

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. Even the classic studies of Caribbean reefs that began in the 1950s were based on reefs that had very high coral cover but were severely overfished, and the first systematic surveys of subtidal Australian reefs in the late 1960s began after a severe outbreak of the crown-of-thorns starfish Acanthaster planci had devastated coral populations along much of the Great Barrier Reef. We are thus left without a clear understanding of how reefs functioned in the absence of major human impacts.

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More torrential rainfall in the Great Barrier Reef catchment: La Nina coming to an end?

After the flooding in late January in the Fitzroy catchment, and the downpour in Mackay causing rising levels in the Pioneer river earlier this month, the turbulent Queensland weather has caused more phenomenal localised rainfall in Rockhampton this morning, with over 200mm of rain falling in less than 2 hours. As residents in Rockhampton begin the cleanup process, the Chief executive officer of the Fitzroy Basin Association (Suzie Christensen) discussed management principals and how to reduce the impact of the recent flooding in the catchment on the inshore reefs of the Great Barrier Reef.

“The Fitzroy Basin is the largest river system draining to the east coast of Australia, with 20,850 kilometres of waterways all leading to the reef lagoon.

“The effect of this flood would have been worse if landholders weren’t already taking steps to reduce impact on the land by retaining ground cover and using best practice farming techniques.”

“In particular where land practices had allowed the ground to be disturbed such as some mining on floodplains and some areas cleared for cropping and grazing.”

Ms Christensen said the flood water plume into the Great Barrier Reef lagoon would have consequences for the reef ecosystem.

“The flood waters are flushing sediment, fertilisers, pesticides, herbicides and other run-off several kilometres out onto the reef.

“The delicate balance of the reef ecosystem is upset by changes in water quality, and the thick cloud of sediment will also block sunlight and prevent coral from photosynthesizing.” (Link)

Further north in Mackay the Mayor of Mackay is quoted as saying that last week’s flooding could be classified as a “one in 200 year event“. Over 625mm of rain fell in 6 hours on February 15th, averaging 132mm per hours (double the total of the classification of a one in 100 year event), peaking at 184mm in a one hour period – quite an event! After such a substantial wet season, the director of meteorology at the Australian Bureau of Meteorology, Dr Geoff Love, stated that the La Nina event identified last November is “probably reaching its peak“. However, according to the World Meteorological Organization, the La Niña period is expected to last until June or July this year, and could last longer.

  • La Niña conditions have become slightly stronger in the last three months
  • Sea surface temperatures are about three to four degrees colder than average over the central and eastern equatorial Pacific Ocean
  • La Niña already has influenced climate patterns in many parts of the globe.
  • La Niña is the meteorological opposite of the better-known El Niño
  • La Niña. Central and eastern Pacific Ocean areas are generally cool, while those in the west remain warmer. This is associated with the frequency of heavy rainfall on the western side of the Pacific Rim.
  • El Niño. The El Niño phenomenon is linked with warmer temperatures in the central and eastern Pacific areas and can lead to drier conditions
  • The El Niño/La Niña cycle historically happens every four to seven years and is strongly linked to major world climate fluctuations:
  • Typically, La Niña will follow an El Niño event and last up to 12 months.
  • Exceptionally, it lasted for two years from early 1998 to 2000. (Link)

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

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

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”

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

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

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

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

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

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.