Coral reefs and climate change

A colleague of mine, Dr John Bruno forwarded me an excellent article that he wrote for The Encyclopedia of the Earth, titled “Coral Reefs and Climate Change

“A healthy reef ecosystem literally buzzes with sounds, activity and colors and is populated by incredibly dense aggregations of fish and invertebrates. In this respect, tropical reefs are more reminiscent of the African Serengeti than of the tropical rainforest they are often compared to, where the resident birds and mammals can be secretive and difficult to see. A coral reef can contain tens of thousands of species and some of the world’s most dense and diverse communities of vertebrate animals. Unfortunately, very few remaining coral reefs resemble this pristine condition; on most, corals and fishes are much less abundant than they were only a few decades ago”

John’s expert write-up and summary of threats to coral reefs related to climate change (coral bleaching, disease, ocean acidification) provides an excellent background of the literature and current threats, and is a worthy read for scientists, managers and the general public alike.

Healthy Great Barrier Reef reefscape A recovering Jamaican coral reef Bleached corals off Puerto Rico in 2005

 

Coral in Crisis – Science Friday interview with Ken Caldeira

Below is a great interview by Science Friday of my colleague, Dr Ken Caldeira on the topic of ocean acidification of the worlds coral reefs (as a co-author on the recent science paper, Ken clearly echoes my sentiments on this issue) – click below to listen.

The world’s coral reefs are in great danger, threatened by climate change and rising carbon dioxide levels. In an article published in the journal Science, researchers provide provide three different scenarios for the fate of reef-building corals worldwide as they face higher concentrations of atmospheric carbon dioxide and the related ocean acidification that slows coral calcification, the process needed for a reef to grow. Increasing CO2 levels have the potential to greatly shift the chemistry of ocean waters, threatening the existence of most coral species.

The fragile corals also face a phenomenon known as ‘bleaching,’ caused by rising temperatures, and damage from overfishing, pollution, and oil and gas exploration. We’ll hear about the forecast for the future of the world’s coral”


[audio:https://climateshifts.org/sciencefriday.mp3]


Barrier Reef’s future clouded (The Australian Newspaper)

The Australian, 14th December 2007
It is probably too late to save the Great Barrier Reef and other coral reefs from global warming.
Even if governments implement far-reaching measures to cut greenhouse gas emissions, they will not prevent the annihilation of coral reefs around the world.

These are the conclusions of analysis by leading marine scientists to be published today in the prestigious journal Science.

“There is a terrible future in front of us for the reefs,” said Canada-based United Nations University professor Peter Sale, one of 17 authors from seven nations of the Science paper.

On Wednesday, Kevin Rudd told the UN’s Bali climate change conference that global warming was threatening Australian natural wonders such as the Great Barrier Reef, Kakadu National Park and rainforests, killing rivers and exposing people to more frequent and ferocious bushfires.

The scientists present three scenarios for the future of coral reefs – the world’s largest lifeforms – under different climatic conditions.

If current conditions continue, with the stabilisation of temperatures and emissions at today’s level of 380 parts per million, reefs will survive but undergo fundamental changes.

However, scientists agree that stabilisation of current conditions is not possible. The paper warns that if emissions rise to between 450 and 500ppm, with an associated temperature rise of 2C by 2050 – the most optimistic outcome predicted by the landmark study by British economist Nicholas Stern – reefs will suffer “vastly reduced habitat complexity and loss of biodiversity”.

But if they rise above 500ppm, the minimum emission level forecast by the UN’s Intergovernmental Panel on Climage Change by 2050, reefs will become “rapidly eroding rubble banks”.

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Global action call to save reefs

Eminent coral scientists have given world leaders in Bali more reason to act urgently against climate change, by producing a new report that warns coral reefs will disappear within decades if atmospheric CO2 levels continue to rise.

Their paper, published today in the prestigious Science magazine, is the most compelling scientific case yet that unchecked global warming will be a disaster for coral reefs and the 100 million people and one million species depending on them.

CO2 concentration in the earth’s atmosphere is currently 380 parts per million (ppm) but the authors say if future emissions exceed 450ppm we risk losing reefs.

“This is a very ambitious target and should represent yet another reality check for world leaders meeting in Bali,” lead author UQ Professor Ove Hoegh-Guldberg said.

Reducing CO2 emissions must also be accompanied by reducing reef risks such as overfishing, pollution and unsustainable coastal developments, a cross-section of the report’s authors (all of whom are members of the Coral Reef Targeted Research and Capacity Building for Management Program, CRTR) said at UQ.
Tools needed to reduce stress on coral reefs already exist, and include: increased protection of river catchment and coastal areas; co-management arrangements between governments and local communities; improved catchment, water quality and environmental flow measures; fishing regulation enforcement; restoration of reefs and coastal vegetation; and sustainable tourism.
The study has found serious consequences follow on from even small increases in CO2.

“The warmer and more acidic oceans caused by the rise of CO2 from the burning of fossil fuels threaten to destroy coral dominated reef ecosystems, exposing people to flooding, coastal erosion and the loss of food and income from reef-based fisheries and tourism,” Professor Hoegh-Guldberg said.
“This is happening just when many nations are hoping that growing industries like tourism and fisheries will allow them to develop beyond their often impoverished state.
“Increased CO2 not only warms the climate but also dissolves in sea water making it more acidic.
“This, in turn, decreases the ability of corals to produce calcium carbonate, which is what the all-important framework of coral reefs is made of.”

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Facing up to the realities of climate change

Developed countries must ‘show some spine’ on climate change
ABC News, 19th November

Some 2,500 scientists worked on the IPCC’s findings. The UN believes the worst case scenarios of global warming could be avoided if there were sharp reductions in greenhouse gas emissions. The economic cost it argues, is minimal compared with the cost of doing nothing.

Professor Ove Hoegh-Guldberg is the Director of Marine Studies at the University of Queensland and also contributed to the IPCC report. “The report points out that if we are going to avoid those catastrophic scenarios, we actually have to peak our emissions in 2015, which is just around the corner, eight years away,” he said. “Now to do that, we have to have really major efforts to change the way we use energy and we’re going to have to have a range of international treaties in place not in 2012 but literally tomorrow.”

Professor Hoegh-Guldberg says it is imperative that developed nations such as Australia and the US set an example by cutting emissions immediately through reducing energy needs, better insulation and construction standards and use of technology that currently exists, like solar energy. “It’s up to the developed countries to show some spine on this issue and avoid what will be a global catastrophe. It’s relatively cost effective – in fact it’s you know, really quite cheap – to address the issue and achieve that level of stabilisation.

“If we go down the street of trying to stabilise at about 450 parts per million, it will shave only, and this is an upper estimate, only about 0.12 per cent of the average annual growth in GDP.” (Read more)




Oceans fail the Acid Test

Science Alert, 22nd November

Acid oceans are the elephant in the room of global change – an event potentially so massive and profound in its implications for life on Earth that the world media has largely avoided it, governments shunned it and scientists discussed it mostly in muted tones, usually behind closed doors.The acid oceans theory is quite straightforward: the CO2 emitted by human activity dissolves out of the atmosphere into the seas, gradually turning them more acidic. This is largely independent of global warming or other effects. It is a straight equation – about half of all the CO2 produced since the start of the industrial revolution has ended up in the sea, reducing the surface pH by 0.1 (some experiments indicate as much as 0.3 pH).

The change in acidity may seem minor but experiments by the Centre’s Professor Ove Hoegh-Guldberg suggest it could be enough to shut down coral growth and kill the calcareous algae that hold together the fronts of reefs. He has warned that Australia risks losing the Great Barrier Reef if atmospheric CO2 levels rise above 500 parts per million from their current level of 385ppm, as they are currently expected to do by mid-century.

If that were not serious enough, an even more profound impact is likely to occur among calcareous plankton which will be unable to form their chalky skeletons as the water acidifies. The vulnerable corals and plankton make up about a third of all life in the oceans. (Read more)

CO2 emissions rising faster than expected

A new study published in the Proceedings of the National Academy of Sciences from an international team of scientists (headed by Josep Candell of the Global Carbon Project, CSIRO) shows that the recent increases in CO2 are rising faster this decade than during the 1990’s (link to pdf). The authors blame rapid increases in a synergy of factors, primarily economic growth, fossil fuel usage and somewhat more worryingly a decline in the efficiency of natural sinks, such as ability of the oceans to absorb CO2 from the atmosphere (read more). It looks like we may be reaching the upper end of the modeling predictions (the 500ppm tipping point) sooner than anyone thought: these findings are alarming, and strongly imply that the UN Climate Report may already be out of date.

Someone yesterday reminded me of a great analogy similar to that of the rise in CO2 emissions: for example, if you start driving from point A to point B, and half-way there realise that you are driving north instead of south (and hence that you are likely to arrive in point C rather than point B), the only way of getting to point B is to stop and turn around – slowing down isn’t going to help the situation. Given the evidence presented in this paper – It is too late to alleviate or ‘slow down’ fossil fuel usage. And with that, do we need a global revolution in what we do rather than pretending we can ease our way out of this problem with waterdowned commitments and wishy washy policy (remember the ‘aspirational’ non-existent targets of APEC?).

Ocean acidification blog

Jean-Pierre Gattuso, a senior research scientist at theLaboratoire d’Océanographie over in France has started a coral & ocean-acidification related blog entitled “Ocean acidification: An information outlet on ocean acidification“. His site is well worth reading (see Corals May Have Defense Against Global Warming, Acidic oceans may threaten fisheries) as an upto date resource on global warming and the impacts upon the worlds oceans.

CO2 emissions could violate EPA ocean-quality standards within decades

In a commentary in the September 25, 2007, issue of the Geophysical Research Letters (GRL), a large team of scientists state that human-induced carbon dioxide (CO2) emissions will alter ocean chemistry to the point where it will violate U.S. Environmental Protection Agency Quality Criteria [1976] by mid-century if emissions are not dramatically curtailed now. This is the first recognition that atmospheric CO2 emissions will cause ocean waters to violate EPA water quality criteria.

 

The paper also says that carbon-dioxide induced “changes in ocean chemistry within the ranges predicted for the next decades and centuries present significant risks to marine biota” and that “adverse impacts on food webs and key biogeochemical process” would result.

 

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