STRICT EMBARGO: June 18, 4.00am AEST
The first comprehensive synthesis on the effects of climate change on the world’s oceans has found they are now changing at a rate not seen for several million years.
In an article published today in Science magazine, scientists reveal the growing atmospheric concentrations of man-made greenhouse gases are driving irreversible and dramatic changes to the way the ocean functions, with potentially dire impacts for hundreds of millions of people across the planet.
The findings of the report, “The impact of climate change on the world’s marine ecosystems” emerged from a synthesis of recent research on the world’s oceans, carried out by two of the world’s leading marine scientists, one from The University of Queensland in Australia, and one from The University of North Carolina at Chapel Hill, in the USA.
Professor Ove Hoegh-Guldberg, lead author of the report and Director of The University of Queensland’s Global Change Institute, says the findings have enormous implications for mankind, particularly if the trend continues.
He said that the Earth's ocean, which produces half of the oxygen we breathe and absorbs 30% of human-generated CO2, is equivalent to its heart and lungs.
“Quite plainly, the Earth cannot do without its ocean," he said.
"This study, however, shows worrying signs of ill health.
“It’s as if the Earth has been smoking two packs of cigarettes a day!”
Professor Hoegh-Guldberg said: “We are entering a period in which the very ocean services upon which humanity depends are undergoing massive change and in some cases beginning to fail.
“Further degradation will continue to create enormous challenges and costs for societies worldwide.”
He said that we may soon see “sudden, unexpected changes that have serious ramifications for the overall well-being of humans,” including the capacity of the planet to support people.
“This is further evidence that we are well on the way to the next great extinction event.”
The “fundamental and comprehensive” changes to marine life identified in the report include rapidly warming and acidifying oceans, changes in water circulation and expansion of dead zones within the ocean depths.
These are driving major changes in marine ecosystems: less abundant coral reefs, sea grasses and mangroves (important fish nurseries); fewer, smaller fish; a breakdown in food chains; changes in the distribution of marine life; and more frequent diseases and pests among marine organisms.
Report co-author, Dr John F. Bruno, an Associate Professor at The University of North Carolina, said greenhouse gas emissions were modifying many physical and geochemical aspects of the planet’s oceans, in ways “unprecedented in nearly a million years”.
“This is causing fundamental and comprehensive changes to the way marine ecosystems function,” Dr Bruno said.
“We are becoming increasingly certain that the world’s marine ecosystems are approaching tipping points. These tipping points are where change accelerates and causes unrelated impacts on other systems, the results of which we really have no power or model to foresee.”
The authors concluded: “These challenges underscore the urgency with which world leaders must act to limit further growth of greenhouse gases and thereby reduce the risk of these events occurring. Ignoring the science is not an option.”
In their study, the researchers sought to address a gap in previous studies that have often overlooked the affects of climate change on marine ecosystems, due to the fact that they are complex and can be logistically difficult to study.
Renowned coral reef scientist and former chief scientist at the Australian Institute of Marine Sciences, John “Charlie” Veron, says studies of coral reefs have previously dominated investigations into climate change impacts on marine environments, giving rise to the impression that this is simply a “reef problem”.
“This paper gives a refreshingly holistic approach to this subject where reefs have no more profile than other marine ecosystems: the subject is bigger than reefs,” Dr Veron said.
Media: Further information:
Global Change Institute
The University of Queensland
tel +61(0) 401 106 604
mobile/cell: 61(0) 401 106 604
John F. Bruno PhD
Department of Marine Science
University of North Carolina at Chapel Hill
mobile/cell +61 (0)432 942 618
Global Change Institute
The University of Queensland
tel: (+61 7) 3346 9041
mobile/cell: +61(0) 410 491 159
About the Global Change Institute
The University of Queensland established the Global Change Institute (GCI) to provide a vehicle for collaborative research, learning, engagement and advocacy in major global change issues.
The GCI will contribute to evidence-based, progressive solutions to the problems of a rapidly-changing world within the existing and projected frameworks of those problems: political, environmental, social, economic and technical. The GCI will investigate complex, interconnected issues in innovative ways, in order to achieve multi-disciplinary, integrated solutions.
The Impact of Climate Change on the World’s Marine Ecosystems
Why is this report significant?
This report is the first to produce a holistic view on how the world’s oceans are changing with respect to anthropogenic climate change, bringing together ‘big picture’ changes within marine ecosystems
Oceans are critical to all life on our planet.
• They cover 71% of our planet, and are critical to the health of our atmosphere, producing approximately 50% of the oxygen that we breathe.
• Oceans absorb 30% of the carbon dioxide produced by humans and more than 85% of the extra heat trapped as a result of global warming.
• It is estimated that 80% of people now live within 60 miles/100 kilometres of the coast, and more than 3.5 billion people depend on the ocean for their primary source of food. In 20 years, this number could double.
Despite all this, however, only 5% of the articles published on climate change in the past decade have focused on the ocean and its responses.
What did the study involve?
The authors reviewed hundreds of articles on the impact of climate change on the ocean ecosystems, and identified a number of universal ways that these important ecosystems are changing.
What are the study’s general findings?
The study found that ocean ecosystems are changing at rates that dwarf anything seen in the past several million years.
Other key findings relating to the changes on the ocean’s ecosystems as a result of climate change include:
• No ocean or coast appears to be exempt from these changes: all marine ecosystems from intertidal to deep ocean and from tropics to polar oceans are all changing rapidly, directly impacting the ability of fisheries and other coastal resources to provide support for coastal populations worldwide; and
• These changes are so rapid and complex that our ability to predict responses and hence manage marine ecosystems services such as fisheries is diminishing.
• Ocean ecosystems appear to be approaching a number of critical thresholds at which the risk of non-linear and catastrophic changes increases sharply.
What particular changes are occurring to the world’s oceans?
Some of the key findings from this study centre on reduced habitat complexity, reduced primary productivity, altered life history traits and changing food web dynamics.
Reduced habitat complexity
The scientists found that key habitat-forming organisms such as corals, sea grasses, mangroves, salt marsh, and oysters are starting to disappear as a result of global climate change. Hundreds of thousands of species depend on these habitats, further emphasising the major threat that rapid anthropogenic climate change poses to biological diversity in the ocean.
Example: half of the species that live on coral reefs need to have the carbonate structures that corals build, but corals have been disappearing at a rate of roughly 1% per year around the world. If this rate of loss continues, most reefs will have negligible numbers of coral on them by 2050, putting at risk the habitat of many hundreds of thousands of species.
Altered life history traits
The study found that changes in sea temperature are having direct effects on the ocean’s species, with fundamental implications for reef connectivity and conservation.
There are also shifts in the timing and life histories of marine organisms caused by ocean warming. Changes in the metabolism of marine animals driven by warming oceans are causing subsequent changes to reproductive timing and other related key biological events (phenology). Though subtle, these changes have huge ramifications.
Example: many species have planktonic larvae which disperse using ocean currents. As temperature increases, the length of time and hence the distance these larvae will travel will get smaller. Reef systems may experience a loss of some species due to the fact that they no longer can disburse far enough to reach these locations.
Altered life history traits
The study found that changes in sea temperature are reducing mixing of the water column and consequently the replenishment of nutrients in the upper layers the ocean. The reduced amount of nutrients means less primary productivity by marine phytoplankton, which is critically important to the basic food chains of the ocean.
Example: This has led to reduced ocean productivity in many parts of the world, and the least productive waters of the Pacific and Atlantic oceans have expanded by 6.6 million km2 or by about 15.0% from 1998 through 2006.
Changes to appearance and spread of species and disease
The study found that diseases and troublesome invasive species are becoming more common, with many examples of diseases spreading rapidly as a result of warming conditions. Organisms are moving towards higher latitudes and are causing massive changes in ecosystems as they do.
There are also numerous examples of novel communities within ecosystems that are popping up which have no known precedent. Managing these risks is going to be very difficult.
Example: The black spined sea urchin, Centrostephanus rodgersii, has migrated south from New South Wales and increasingly removing Tasmania’s kelp forests and replacing them with “barrens”.
Links between global factors and local stresses
The study found evidence of an interaction between local stressors and global climate change. For example, recovery from climate impacts is faster where ecosystems are protected and are less stressed by declining water quality and overfishing.
There is growing evidence of significant synergies between different global factors on their own.
Example: corals are more susceptible to thermal stress when exposed to the acidic conditions caused by the warming of the ocean. They also recover better from mass coral bleaching events (caused by elevated sea temperatures) when coral reefs are protected from local factors such as fishing and pollution.
The research also revealed that temperatures of +2°C and atmospheric carbon dioxide concentrations of 450 parts per million cause major changes to ocean ecosystems from polar to tropical oceans, meaning that it is now even more important that we avoid exceeding these concentrations of carbon dioxide and other greenhouse gases, and global temperatures.
According to the researchers, these changes combined are making management of marine ecosystems extremely difficult, and suggest that we are entering a period in which we will no longer have the ability to influence the direction of marine ecosystems.