Captions for photos provided by

Professor Ove Hoegh-Guldberg
Centre for Marine Studies
The University of Queensland

©2007 The University of Queensland
CO2 Scenarios      

  Photo 1:  Coral reefs like the Great Barrier Reef are wonderfully diverse and productive habitats, important to both tourism and fisheries.  Large predatory fish such as those seen here with the diver, perform important ecological roles on coral reefs, and important as a source of food to many millions of people in tropical regions.
(Coral community in the marine protected area at Heron Island, southern Great Barrier Reef)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 2:  Fisheries along the coasts of Asian countries feed at least one billion people.  The demand for this food has meant that the populations of many marine species that perform important ecological roles like grazing seaweeds have been decimated.
(Hong Kong fish market)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 3:  Large urban centres have fueled the need for large mechanized fishing fleets and have driven a rapid escalation of fishing pressure on coral reefs throughout the world.  Overexploitation of fisheries, together with climate impacts, has turned many tropical reef ecosystems from coral into seaweed dominated ecosystems.
(Hong Kong fish market)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 4:  Coral reefs provide at least one billion people in Asia alone with daily protein.  Unfortunately, in many parts of world, fishing pressure exceeds the capacity reefs to regenerate fisheries stocks.  This has led to rapid declines in importance species, and large-scale ecological change.  Coupled with climate change, these pressures are leading to more and more declining reefs.
(Hong Kong fish market)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 5:  Increasing heat stress from global climate change coupled with declining calcification rates due to ocean acidification may mean that coral dominated reefs may become a distant memory.  High latitude reefs such as this one in Western Australia illustrate the struggle between coral and seaweeds.
(High latitude coral Reefs off Jurien Bay, Western Australia).
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 6:  Coral reefs are likely to have reduced numbers of corals on them as sea temperature and acidity increases in the sea surrounding them.  This is likely to affect the structural complexity of coral reef ecosystems, with dire consequences for the diversity of organisms that live in and around them.
(High latitude coral Reefs off Jurien Bay, Western Australia).
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 7:  Rising carbon dioxide concentrations in the atmosphere may eventually lead to conditions that favor organisms other than reef building corals.  This may mean major changes to the biodiversity of tropical nearshore reef systems.
(High latitude coral Reefs off Jurien Bay, Western Australia).
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 8:  Marine pollution from chemicals and rubbish such as plastic bags play havoc with marine organisms and ecosystems all over the world.  More than half of the more than 500 billion plastic bags end up in waterways and in the ocean, where they kill wildlife and clog ecosystems.
(High tide mark in Karimunjawa, Java Sea, Indonesia)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 9:  Fishing activities cover almost every coastline throughout the tropics and subtropics.  While this is an important source of protein for over one billion people, the removal of key species from ecosystems like coral reefs is causing some ecosystems to change from coral dominated ones to those dominated by seaweeds.
(Fishing boats in Karimunjawa, Java Sea, Indonesia)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 10:  The equipment used to catch fish on coral reefs has become more and more efficient over time leading to the collapse of fish populations in many parts of the world.  This has had consequences coral reefs that have been amplified by other stressors such as global climate change.
(Fishing boats in Karimunjawa, Java Sea, Indonesia)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
   
  Photo 12:  The collapse of coral reefs would have significant ramifications the many societies that depend on fishing for a large part of their food.
(Fishing boats in Karimunjawa, Java Sea, Indonesia)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 13:  The competition between fishermen for an ever dwindling source of protein from the marine ecosystems has caused huge changes to ecosystems along coastlines of many developing countries.
(Fishing boats in Karimunjawa, Java Sea, Indonesia)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 14:  Almost one billion people depend on fish they catch on coral reefs.  This often leads to the decline of fish species that play key ecological roles such as grazing and predation.  Without these species, reefs can change dramatically from being coral dominated to reefs dominated by less slightly sea weed.
(Fishermen sharing a meal in Karimunjawa, Java Sea, Indonesia)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 15:  The combination of local (over-fishing, declining water quality) and global (global warming and ocean acidification) can often reduce coral reefs to nothing more than a slimy rubble heap.  Often, it is difficult to get coral reefs to grow back in these places.
(Destroyed coral reefs in Java, Indonesia)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 16:  The loss of corals from human associated impacts on tropical Reef systems often has major impacts on biological diversity, with big impacts on tourism and fisheries.  As these industries are important parts of the economy of many developing countries, the impact on human well-being and income can be enormous.
(Destroyed coral reefs in Java, Indonesia)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 17:  Coral reefs that have lost the corals and the associated biological diversity are stark and disappointing places to visit.  After a while, coral frameworks that often protect coastlines from wave impacts also start to crumble and disappear.
(Destroyed coral reefs in Java, Indonesia)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 18:  It will only take a little bit more carbon dioxide in the atmosphere before conditions on planet Earth exceed those coral reefs need to grow and prosper.  This is expected to have huge impacts on marine biodiversity and on the human societies that depend on coral reefs for their livelihood.
(Destroyed coral reefs in Java, Indonesia)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
    Photo 19:  Increasing carbon dioxide levels above 500 ppm will lead to conditions that will exceed those that corals need to live.  This will mean that coral reefs that currently line tropical coastlines will begin to crumble and disappear.  Similar problems are appearing in other ecosystems.
(Destroyed coral reefs in Java, Indonesia)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 20:    Global climate change by reducing the growth of corals, and by increasing sea levels and storm intensity, may reduce corals and the reefs they build to simple piles of rubble.  Gone will be the marine biodiversity and the ecosystem functions that currently support over 100 million people worldwide.
(Destroyed coral reefs in Java, Indonesia)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 21:   Hollywood icons like clownfish are highly dependent on coral reef ecosystems, which are in turn dependent on having healthy populations of reef-building corals.  Rising carbon dioxide in the atmosphere from the burning of fossil fuels threatens to make clownfish like Nemo extremely rare or extinct in many parts of the world..
(Clownfish swimming among the tentacles of a sea anemones in Indonesia)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 22:   Many tropical countries still have pristine coastline where tropical rainforest meets tropical coral reefs.  Unfortunately, both ecosystems are highly threatened by climate change. 
(A tropical coastline in Karimunjawa, Java, Indonesia)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 23:   Coastal fishing and trading vessels are a regular sight throughout tropical regions.  Many millions of people depend on fish and other food items that they derive from coral reefs.  In many cases, these resources also contribute to export earnings through trade.
(Fishing boat in Karimunjawa, Java, Indonesia)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 24:   Coral reefs are spectacular underwater forests full of magical creatures.  Over one million species are estimated to live on coral reefs, but only 10% are estimated to have been described by science.   It is tragic then, that much of despite adversity may disappear if we don't get global emissions of carbon dioxide under control.
(Coral reef in Karimunjawa, Java, Indonesia)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 25:   Coral reefs are still a source of much mystery and intrigue.  The biology of these mushroom corals is only just becoming known to science.  Climate change is threatens species such as these with becoming either rare or extinct.  Either way, it appears a pity that the stories of species such as the mushroom coral may remain untold for ever as they become rare or extinct along with coral reefs.  (Coral reef in Karimunjawa, Java, Indonesia)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 26:   Reef building corals (such as the one shown in this picture) provide the source of calcium carbonate which builds the frameworks of coral reef ecosystems.  Within this framework, it is estimated that over a million species would have nowhere to live.
(Coral reef in Karimunjawa, Java, Indonesia)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 27:   Diving tourism is a global business worth billions of dollars.  Increasingly, tourists are becoming sensitive to the health of coral reefs and where they spend their tourist dollars.  If global climate change continues unchecked, many reefs will deteriorate causing a decline in the precious international earnings of many developing countries.
(Coral reef in Karimunjawa, Java, Indonesia)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 28:   Reef building corals can take a number of wonderful shapes such as this species, Turbinaria.  The delicate shapes and colors produced a beautiful backdrop to the enormous biodiversity of coral reefs. 
(Coral reef in Karimunjawa, Java, Indonesia)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 29:   In addition to being important as draw card is the tourism, coral reefs also support over 100 million people through the food they provide.  Indigenous fishermen in Indonesia (shown) derive almost 100% of their food from health of coral reefs.  Global climate change threatens the health of coral reefs and their ability to provide food.
(Indigenous fisherman on a coral reef in Karimunjawa, Java, Indonesia)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 30:   There are many wonderful shapes and colors on coral reefs.  This species of soft coral has pulsating polyps that are mesmerizing to watch.
(Soft coral on a coral reef in Karimunjawa, Java, Indonesia)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 31:   Clownfish like this pair provide color and humor amid the riotous landscape of a coral reef in Indonesia.   Popularized by a recent movie in Hollywood, clownfish like Nemo have helped highlight the plight that coral reefs face from climate change and other local factors such as overfishing and declining water quality.
(Clownfish on sea anemones on a coral reef in Karimunjawa, Java, Indonesia)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 32:   Corals form a symbiosis with simple plant like organisms called of zooxanthellae.  These brown organisms trap sunlight and allow corals to grow quickly in tropical seas.  If the waters get to warm for too long, the symbiosis breaks down and corals bleach.  As global temperatures have increased, coral bleaching and resulting coral death have increased.
(Bleached corals on coral reef on southern Great Barier Reef in January 2002). 
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 33:   When corals get too warm, the symbiosis they enjoyed with brown plant like organisms known as zooxanthellae breaks down.  The result is coral bleaching as shown here.  The beautiful blue colors are due to animal pigments while the pale brown color remaining at the base of the branches is due to the remaining zooxanthellae that have not left yet.
(Bleached corals on coral reef on southern Great Barier Reef in January 2002).  
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 34:   Coral bleaching occurs when waters get to warm.  Corals may die afterwards in large numbers.  Global warming is increasing the frequency and intensity of bleaching events on coral reefs around the world.
(Bleached corals on coral reef on southern Great Barier Reef in January 2002). 
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 35:   Coral bleaching primarily affects reef building corals when conditions get too warm.  Increasingly, corals are dying after bleaching events affecting their role as habitat for hundreds of species including fish.
(Bleached corals on coral reef on southern Great Barier Reef in January 2002). 
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 36:  Coral reefs build extensive ramparts made of calcium carbonate which act as barriers to the power of oceanic waves.  Without coral reefs, other natural ecosystems such as mangroves and sea grass meadows, as well as human infrastructure lying in coastal regions, becomes vulnerable to ocean waves.
(Coral reefs photographed from the air are insurrounding Heron Island on the southern Great Barrier Reef)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 37:  Coral reefs build extensive structures which can cover hundreds and thousands of square kilometres.  Seen from space, coral reefs represent one of the few signs of life on our planet.
(Coral reefs photographed from the air are surrounding Heron Island on the southern Great Barrier Reef)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Photo 38:   Clownfish have become great ambassadors for coral reefs having been popularized by recent movies in Hollywood.  Clownfish, however, will disappear if coral reefs degrade under further global warming and ocean acidification.  They represent just one of a million reasons (species) why the world needs to constrain its carbon dioxide emissions and switched to renewable fuels. 
(Clownfish on sea anemones on a coral reef in Karimunjawa, Java, Indonesia)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Fig5A:   If carbon dioxide concentrations remain at around today's levels (380 ppm), reefs will continue to experience coral bleaching events that will mean the occasional loss of coral and associated biodiversity.  However, coral dominated reefs will continue to persist over time.  In this state, coral reefs will need to be protected from other stresses such as declining water quality and over exploitation of fishery stocks.  These local stresses, in combination with the effect of global warming and ocean acidification, could still push reefs close to the edge of functional collapse.
(Coral Reef at Heron Island on the southern Great Barrier Reef)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Fig5B:   As concentrations of carbon dioxide continue to rise above where they are today, coral reefs will shift from coral dominance to reefs that have less coral and more macroalgae (seaweeds).  Under these conditions, protecting coral reefs from other disturbances such as declining water quality and overfishing will become increasingly important.  A significant amount of the biodiversity of coral reefs will disappear as reefs become increasing dominated by organisms other than corals.
(Reef ecosystem surrounding St Bees Island on the central Great Barrier Reef)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Fig5C:   Coral dominated Reef systems are likely not to exist if atmospheric concentrations of carbon dioxide rise significantly above 500 ppm.  Under these conditions, coral mortality will escalate under an increasing severity and frequency of coral bleaching events, and increasing ocean acidification will set reefs into net erosion and dissolution.  The effect will be similar to this reef on inshore Great Barrier Reef where corals have disappeared and the forces of erosion dominate the landscape.
(Eroding and crumbling reef crest at the Low Isles in the Great Barrier Reef)
Please credit:  Ove Hoegh-Guldberg, Centre for Marine Studies, The University of Queensland
  Fig 1.pdf:  A.  Ocean acidification involves the dissolution of carbon dioxide in the ocean, where it forms an acid.  The acid converts carbonate ions into bicarbonate, removing them from processes such as calcification.  The net effect on marine calcifiers such as Reef building corals is that they slowly fail to calcify. If concentrations get too high, ecosystems such as coral reefs may begin to crumble and dissolved.  B.  Conditions in tropical oceans over the past 420,000 years.  These data were calculated from carbon dioxide and temperature date derived from the Vostok Ice Core data set.  The calculated values fall in a tight cluster where tropical oceans have been for the past 420,000 years least.  Today's conditions are significantly different and will become an increasingly different as the carbon dioxide content of the atmosphere is increased by the burning of fossil fuels.  If conditions rise above 500 ppm carbon dioxide, global temperatures will exceed the thermal as well as carbonate thresholds for coral reefs.  This will put coral reefs in the upper right-hand sector of the diagram, which is where corals will be rare organisms on tropical Reef systems.
  Fig2.pdf  A model that relates grazing pressure to the amount of coral cover on coral reefs.  If the growth rate of corals is diminished by global warming and ocean acidification, there will be an increasing need to preserve grazing pressure on coral reefs.  This can only come about through the protection of fish like parrotfish, and invertebrates such as sea urchins.
  Fig3.pdf  Simplified network diagram showing the interaction between components of coral Reef ecosystems.  Both global warming and ocean acidification are set to massively interfere with these interactions if carbon dioxide concentrations continue to grow unchecked in the earth's atmosphere.
  Fig4.pdf   Calculated values for the tendency of calcium carbonate crystals to form  (termed aragonite saturation) as a function of location on the planet.   Coral reefs today only form when aragonite saturation concentrations exceed 3.25, which is illustrated by the panel showing 380 in the corner (coral reefs found today are indicated in this panel by the pink dots).  As the concentration of carbon dioxide in the atmosphere increases, the extent of conditions that are suitable (any cool color in the figure) for the formation of carbon coral reefs dwindles until there are few areas with these conditions left at 550 ppm and above.   Ocean acidification represents a serious threat to carbonate reef systems and may see the loss and decay of reef structures across the entire tropical region of the world.
 
Fig5-comp.pdf:  Predicted scenarios for coral reefs under increasing amounts of atmospheric carbon dioxide.  If concentrations of carbon dioxide remain at today's level, many coral dominated reefs will survive (left-hand panel) although there will be a compelling need to increase their protection from local factors such as deteriorating coastal water quality and overfishing.  If carbon dioxide concentrations continue to rise as expected, reefs will become less dominated by corals and increasingly dominated by seaweeds (middle panel).  If carbon dioxide levels continue to rise as we burn fossil fuels, coral reefs will disappear and will be replaced by crumbling mounds of eroding coral skeletons.  In concert with the progression from left to right is the expectation that much of the enormous and largely unexplored biodiversity of coral reefs will disappear.  This will almost certainly have major impacts on the tourist potential of coral reefs as well as their ability to support fisheries, both indigenous and industrial.