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The state of the oceans
In early 2011 a cross-disciplinary group of scientists met in Oxford to discuss the current ecological
state of the world’s oceans. The meeting was coordinated by the International Programme on the State
of the Ocean (IPSO) and the International Union for the Conservation of Nature (IUCN). The
scientists’ conclusions were alarming, and a report of the meeting describes widespread damage to the
seas and predicts species loss at a level not seen since the extinction of the dinosaurs. The report led to
headlines such as ‘Oceans on the brink of catastrophe’ in the press.
Key findings of the report were:
 The rate of degeneration of the oceans is faster than has
previously been predicted.

Many of the negative impacts are greater than the worst predictions.

A globally significant extinction event in the oceans may have
already begun.
Causes of the environmental damage and associated species loss include:
 the effects of climate change

overfishing

nutrient run-off from farming

acidification from increased CO2 levels (CO2 dissolved in water creates acidic conditions)

increasing hypoxia (low oxygen levels) and anoxia (absence of oxygen)

pollutants, such as flame retardant chemicals and other substances found in detergents.
Scientists believe that a combination of these factors is leading to unprecedented species loss: when
pressures are added together, the ocean ecosystems are unable to recover as they are constantly being
bombarded by different threats (what the panel call ‘multiple stressors’). The scientific panel report
severe declines in many fish species, regional extinction of certain habitats (such as mangrove and
seagrass meadows), and predict the loss of whole marine ecosystems within a generation (such as coral
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reef). Professor Alex Rogers, IPSO's scientific director and professor of conservation biology at Oxford
University, described the findings as ‘shocking’. The marine scientists at the meeting suggest that the
potential loss of species is directly comparable to the five past mass extinctions.
Read a summary of the report:
 Report summary (short)
 Report summary (long)
Past extinction events
The figure shows the changes in marine species during the last 542 million years (the Phanerozoic
eon). The five mass extinctions in geological time are shown (see also textbook page 191).
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Cretaceous-Tertiary extinction (or K-T extinction) – 65 mya
Thought to be caused by an asteroid strike (or possibly volcanic action) and caused the extinction of the
non-avian dinosaurs. In the seas, photoplankton (the start of oceanic food chains) was severely
affected, and giant mosasaurs and plesiosaurs were wiped out.
Triassic-Jurassic extinction – 199-214 mya
This period saw 20% of all marine families disappear. In total, approximately half of all species on the
Earth at the time went extinct. The extinction event may have been caused by climate change,
fluctuating sea levels and volcanic eruptions.
Permian-Triassic extinction – 251 mya
This was the most severe of the Earth’s extinction events to date, with 96% of marine species lost, as
well as around 75% of land-based species. Cause: volcanic eruptions leading to global warming by
triggering a ‘runaway greenhouse effect’, and floods of lava destroying algae and plants in the sea
leading to a reduction in oxygen levels. It took 100 million years for species diversity to recover.
Late Devonian extinction – 364 mya
Three quarters of species on Earth are believed to have been wiped out in this period, which may have
occurred over several million years. Shallow seas were badly affected, leading to loss of coral reef that
took millions of years to recover. Climate change and sea level changes are believed to have been the
cause.
Ordovician–Silurian extinction – 439 mya
During the Ordovician period, much of life on Earth existed in the seas, and so it was oceanic life that
was most affected by this extinction event, with trilobites, brachiopods and graptolites drastically
reduced in numbers. 85% of sea species became extinct. The event is thought to have been caused by a
drop in sea levels as glaciers formed, then by rising sea levels as the ice melted.
The IPSO/IUCN panel describes a ‘deadly trio’ of factors that are affecting the Earth’s oceans: global
warming, ocean acidification, and anoxia: the same factors that are believed to have played a part in
past oceanic mass extinctions. Because these factors are all linked to changes in atmospheric carbon
dioxide levels, they are known as ‘carbon perturbations’.
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Species under threat

The giant Chinese bahaba (Bahaba taipingensis) has gone from first discovery in the 1930s to
near extinction in less than 70 years. The fish, once common, is now critically endangered. A
recent study showed that of the assessed world fish stocks, 63% are over-exploited or depleted.

Other critically endangered marine species include:
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Black sea bass
Bowhead whale
Caribbean electric ray
Leatherback sea turtle
Mediterranean monk seal
Queensland sawfish
Staghorn coral
Strawberry grouper.
For further threatened species see the IUCN Red List of Endangered Species.
A call for action
Marine scientists call for a range of urgent measures to try to turn back the tide of environmental
destruction in the oceans – these include:

cutting global carbon emissions

reducing overfishing

shutting unsustainable fisheries

creating protected areas in the seas

reducing the input of pollutants, e.g. plastics, agricultural fertilizers and human waste.
Professor Dan Laffoley, marine chairman of the World Commission on Protected Areas, and advisor to
the IUCN, says ‘The challenges for the future of the oceans are vast, but, unlike previous generations,
we know now what needs to happen. The time to protect our planet is now.’
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Questions and activities
1. What environmental services do the world’s oceans provide for humanity?
[3 marks]
2. What factors make the protection of oceanic ecosystems especially difficult to achieve? Outline
possible solutions to these problems.
[3 marks]
3. (i) Outline two historic causes of mass extinction.
[2 marks max.]
(ii) What is the main difference between the current mass extinction (the ‘sixth’ mass
extinction) and the previous five?
[2 marks max.]
4. Check out the award winning documentary The End of the Line, and read more about the issues
in Professor Callum Robert’s book The Unnatural History of the Sea. Pick one of these two
sources, or another you have found, and produce a PowerPoint for the rest of your class
summarizing the main points: make links to as much of the ESS syllabus as possible. [10 max]
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Suggested answers
1. Photosynthetic organisms in the sea (e.g. algae) yield most of the oxygen in the atmosphere; the
oceans take up and store large quantities of carbon dioxide; the seas are an essential element of
the global water cycle; other valid arguments.
[3 marks]
2. The world’s oceans largely cover international waters and so are difficult to protect legally; as
the seas of the planet are in general seen as a common resource, they are open to exploitation:
this is an example of the Tragedy of the Commons; the report calls for states, regional bodies
and the United Nations to adopt better governance of the largely unprotected high seas, and to
enact measures that would better conserve ocean ecosystems.
[3 marks]
3. (i) global volcanic eruption leading to rapid climate change; catastrophic events such as
meteorite impact leading to rapid climate change; over hunting of e.g. large mammals by
man in the Holocene to the extent that populations became reproductively unviable/wiped
out; NOT Ice Age.
[2 marks max.]
(ii) previous mass extinctions were caused by physical (abiotic) factors whereas current one is
due to humans (biotic factors); current extinctions happening over human lifespan to
hundreds of years whereas past extinctions happened over long time-spans, often millions
of years.
[2 marks max.]
4. PowerPoint presentation:
The rest of the class can give you marks out of 10 for:
 coverage of ESS syllabus (award 3 points max.)
 scientific accuracy (award 4 points max.)
 creativity and flair (award 2 points max.)
 quality of the presentation (award 1 point max.).
Work out the average marks from the class, out of 10.
[10 marks]
Total: [20 marks]
© Pearson Education Ltd 2011. For more information about the Pearson Baccalaureate series please visit
www.pearsonbacc.com