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Summary for policy-makers
The latest
research findings show that climate change will subject the marine environment
and the coasts to major change and damage that are likely to have severe
consequences for humankind. Ocean surface waters are warming, the sea
level is rising ever faster, the oceans are becoming increasingly acidic
and marine ecosystems are under threat. Human activities are unleashing
processes of change in the oceans that are without precedent in the
past several million years. Due to the considerable geophysical time
lags, these processes will determine the state of the world’s
oceans for millennia to come. Humanity is thus intervening in a pivotal
mechanism of the Earth System, and many of the consequences cannot yet
be predicted accurately. Resolute and forward-looking action is needed
in order to ensure that the oceans do not overstep critical system boundaries.
The way we handle the oceans will be a decisive test of humankind’s
ability to steer a sustainable course in the future.
Climate mitigation for marine conservation
Ocean
warming, ocean acidification and a distinct sea-level rise are all already
measurable. The causes are clear: elevated concentrations of greenhouse
gases in the atmosphere caused by human activities have led to a global
warming that has also increased temperatures in the surface waters of
the oceans. This leads to rising sea levels due to thermal expansion
of the water and due to melting ice masses. At the same time, the continuously
rising carbon dioxide concentration in the air causes CO2 to be absorbed
by the sea where, through chemical reactions, the seawater acidifies.
These changes can only be mitigated by means of drastic reductions in
anthropogenic greenhouse gas emissions. Rapid action is therefore required:
• Ambitious climate protection measures are needed to limit the
consequences of warming, acidification and sea-level rise for the marine
environment and human society. WBGU therefore recommends that global
anthropogenic greenhouse gas emissions must be approximately halved
by 2050 from 1990 levels. Adaptation measures can only succeed if the
present acceleration of sea-level rise and the increasing acidification
of the oceans are halted.
• The guard rail already recommended previously by WBGU –
namely limiting the rise in near-surface air temperature to a maximum
of 2 °C relative to the pre-industrial value while also limiting
the rate of temperature change to a maximum of 0.2 °C per decade
– is essential not only to prevent dangerous climatic changes
but also to maintain the state of the oceans.
Bolstering the resilience of marine ecosystems
Compared
to terrestrial ecosystems, marine ecosystems respond much more sensitively
and rapidly to climatic changes, for example through spatial shifts
of populations. As a result, human-induced warming of the surface waters
can cause changes in food webs and species composition that are difficult
to predict. A further increase in water temperatures, in combination
with continuing acidification, will have major overall impacts on marine
ecosystems and also on fisheries.
The
fisheries sector is thus facing two further threats in the future in
the shape of climate change and ocean acidification, in addition to
the consequences of overfishing, which are already drastic enough in
themselves. Taken together, and in view of the continuing growth of
the world population, these anthropogenic factors will jeopardize a
sufficient supply of food from the oceans.
Tropical
coral reefs, by far the most species-rich ecosystems in the ocean, are
acutely threatened by climate change. Most reefs may be destroyed within
the next 30–50 years, because many corals are not viable at higher
water temperatures. The local ramifications are vast, reefs being indispensable
for coastal protection and in supplying protein for millions of people.
One of the most visible consequences of warming is the retreat of Arctic
sea ice. Over the past 30 years, summertime ice cover has declined by
15–20 per cent. Model scenarios for the future indicate that,
unless action is taken to mitigate climate change, the Arctic Ocean
will be practically ice-free in summertime by the end of the 21st century.
This would have severe consequences for ecosystems and climatic processes.
•
To preserve marine biodiversity and strengthen the resilience of marine
ecosystems, WBGU proposes the following guard rail: at least 20–30
per cent of the area of marine ecosystems should be designated for an
ecologically representative and effectively managed system of protected
areas. There is a particular need to enhance marine conservation significantly
for coral reefs and areas that are nursery grounds for fish populations.
Goals for marine protected areas already agreed by the international
community need to be implemented, and the regulatory gap in this regard
for the high seas should be closed by adopting an agreement under the
United Nations Convention on the Law of the Sea (UNCLOS).
• Marine resource management should follow the ‘ecosystem
approach’. In particular, the publicly subsidized overfishing
of the oceans must be terminated, not least in order to strengthen the
resilience of fish stocks to the impacts of climate change. This necessitates
not only removing fisheries subsidies, but also dismantling excess fishing
capacity and taking measures to combat destructive fishing practices
and illegal or unregulated fisheries.
• Our understanding of the linkages between anthropogenic disturbances,
biological diversity and the resilience of marine ecosystems needs to
be improved. Intensive monitoring is a precondition for the further
development of coupled ecosystem-climate models.
Limiting
sea-level rise and reorienting coastal zone management strategies
Climate change causes sea-level to rise, particularly due to ocean warming
and the melting of inland glaciers and continental ice sheets. Throughout
the 20th century, global sea-level rise averaged 1.5–2.0 cm per
decade. Satellite measurements show that the decadal rate already reached
3cm in the past decade. If warming continues, there is a risk of further
acceleration of sea-level rise. There are indications that the continental
ice sheets on Greenland and in the Antarctic are beginning to disintegrate.
This has the potential to cause several metres of sea-level rise in
the next centuries.
Besides
sea-level rise, the increasingly destructive force of hurricanes is
a further factor threatening many coastal areas. Theory, observed data
and mathematical models agree that while climate warming does not increase
the number of hurricanes, it does boost their destructive energy. Tropical
sea-surface temperatures have warmed by only half a degree Celsius,
while an increase in the energy of hurricanes by 70 per cent has been
observed.
Sea-level
rise and extreme events such as hurricanes and storm surges are threatening
the coasts. Coastal protection is thus becoming a key challenge for
society, not least in economic terms. Past strategies for protecting
and utilizing coastal areas fail to do justice to this development.
Novel combinations of measures (portfolio strategies) are called for,
whereby the options of protection, managed retreat and accommodation
need to be weighed against each other. In particular, coastal protection
and nature conservation concerns must be better linked, and the people
affected by adaptation or resettlement measures need to be involved
in decision-making on such measures.
•
Absolute sea-level rise should not exceed 1m in the long term, and the
rate of rise should remain below 5cm per decade at all times. Otherwise
there is a high probability that human society and natural ecosystems
will suffer unacceptable damage and loss.
• Because of anticipated sea-level rise, national and international
strategies need to be developed for protection and accommodation, but
also for a managed retreat from endangered areas.
• There is a need to improve the linking of nature conservation
with coastal protection. The process of drawing up coastal protection
plans and strategies for the sustainable use and development of coastal
zones must integrate all key policy spheres (integrated coastal zone
management).
Adopting innovative instruments of international law for refugees
from sea-level rise
Sea-level
rise will lead to the inundation of coasts and small island states and
thus to migration of ‘sea-level refugees’. Under international
law as it stands at present, there is no obligation to receive refugees
from coastal areas, nor is the question about costs resolved. In the
long term, however, the international community will not be able to
ignore the problem of refugees from coastal areas and will therefore
need to develop appropriate instruments to ensure that affected people
are received in suitable areas, ideally areas corresponding to their
preferences.
•
There is a need for agreements on the reception of refugees from coastal
areas and on the apportionment of the associated costs, e.g. by means
of a compensation fund. It would be expedient to develop a fair burden-sharing
system, under which states make a binding commitment to assume responsibility
for the migrants.
• To inform the policymaking process, studies should be undertaken
in the fields of law and social sciences.
Halting
ocean acidification in time
The dissolution
of carbon dioxide in seawater leads to considerable acidification (decrease
in pH) and thus to changes to the biogeochemical carbonate balance.
The oceans have absorbed about one-third of all anthropogenic CO2 emissions
to date, which has already caused a significant acidification of seawater.
Such emissions thus influence the marine environment directly –
in addition to the route via climate change. Unabated continuation of
this trend will lead to a level of ocean acidification that is without
precedent in the past several million years and will be irreversible
for millennia. The effects upon marine ecosystems cannot yet be forecast
exactly but there is a risk of profound changes to the food web, as
calcification of marine organisms may be impeded or in some cases even
prevented. We are now seeing on a global scale problems similar to those
that arose regionally when lakes acidified in the 1970s and 1980s (‘acid
rain’).
•
In order to prevent disruption of the calcification of marine organisms
and the resultant risk that marine food webs will be fundamentally altered,
the following guard rail should be obeyed: the pH of ocean surface waters
should not drop more than 0.2 units below the pre-industrial level in
any larger ocean region (i.e. also in the global mean).
• Engineering approaches to mitigate acidification, such as large-scale
liming, are not feasible in the oceans. It is therefore important to
ensure that anthropogenic CO2 emissions are limited, regardless of reductions
of other greenhouse gas emissions. WBGU thus recommends taking the special
role of CO2 compared to other greenhouse gases into account in the negotiations
on future commitments under the United Nations Framework Convention
on Climate Change. The consequences of acidification for marine ecosystems
and for biogeochemical cycles are still insufficiently understood. Considerable
further research is needed in this regard.
Regulating CO2 storage
Engineering
approaches can be used to capture the carbon dioxide arising from the
utilization of fossil energy sources, and to compress it and transport
it via pipelines or by ship to permanent repositories. CO2 can be stored
in geological formations on land or under the sea floor. Theoretically,
the CO2 could also be injected into the deep sea. Such approaches, however,
involve a risk of continuous, slow release of the stored CO2 into the
atmosphere, which runs counter to long-term climate mitigation. The
specific benefits and drawbacks of the technical and economic development
of sequestration technologies therefore need to be balanced against
other climate mitigation approaches such as improving energy efficiency
or switching to renewable energy sources.
•
The precautionary principle indicates that introducing CO2 into seawater
should be prohibited, because the risk of ecological damage cannot be
assessed and the retention period in the oceans is too short.
• Storing CO2 in geological formations under the sea floor can
only be an ‘emergency’ solution for a transitional period.
Permits for such measures should only be granted if they meet strict
criteria with regard to technical safety and, above all, with regard
to the permanence of storage and its low environmental impact. These
criteria should also apply to the use of CO2 for ‘Enhanced Oil
Recovery’. CO2 sequestration must not lead to neglect of sustainable
emissions reduction strategies (such as efficiency improvement and the
promotion of renewable energies) and should therefore not be supported
with public funds.
• Only a proportion of the CO2 stored under the sea floor should
be eligible as prevented emissions when drawing up emissions inventories
and for the purposes of the flexible mechanisms in international climate
policy. This is necessary in order to take the risk of leakage into
account. Specific liability rules also need to be established.
Imposing
strict conditions upon methane hydrate mining
Quantities
of carbon are stored in the sea floor in the form of methane hydrates
that are of the order of magnitude of total worldwide coal reserves.
Methane hydrates are only stable under high pressure and at low temperature.
Such conditions typically prevail on the sea floor from depths of around
500 m downwards; in the Arctic this boundary is somewhat higher. The
stability of methane hydrate stocks can be compromised by climate change,
by disturbances resulting from mineral oil and natural gas production,
or, in the future, possibly by direct mining of the hydrates themselves.
WBGU takes the view that the hazard of a sudden release of larger, climate-relevant
quantities of methane within this century is very small. Over the long
term, however, the slow penetration of global warming to lower ocean
layers and sediments could cause gradual methane releases over many
centuries to millennia.
•
Because of the potential instabilities of deposits, it is important
to ensure even now that methane hydrate mining in the oceans is only
permitted under very strict conditions. Existing regulatory systems
governing ocean mining should be amended and adjusted accordingly.
Complementing the existing financing mechanisms
Measures
to mitigate and cope with the anticipated adverse effects of climate
change upon the marine habitat can be funded from existing international
funds whose task is to finance emissions reductions or adaptation projects.
It must be expected, however, that these resources will not suffice
for the tasks outlined in the present report, above all because they
do not budget for specifically ocean-related projects. To complement
these resources, WBGU therefore recommends:
•
Fisheries subsidies must be removed in order to avoid providing misplaced
incentives for overfishing. The public funds thus released could then
be invested partly in marine conservation.
• Charges should be levied on the use of the oceans by shipping,
and the revenues earmarked.
• The establishment of microinsurance systems to protect individual
assets should be supported as a component of a more comprehensive
precautionary strategy, e.g. through public co-financing, especially
in developing countries.
• Some of the official development assistance (ODA) resources
presently deployed to provide emergency relief worldwide should be
diverted into preventive measures.
With
this special report, WBGU has taken up an issue that until now has attracted
little attention, and whose profound implications are largely underestimated.
The state of the marine environment is of elementary importance to the
future of the blue planet Earth. Through overexploitation and pollution,
humankind has already inflicted great damage on the oceans. Global climate
change is presenting a further, completely new dimension of threat. The
present report pinpoints the threats and identifies required actions and
options that arise at the interface of climate change and the oceans.
The report hopes to encourage policy-makers to tackle the necessary measures
in time and with resolve, to prevent the oceans from becoming too warm,
rising too high and turning too sour.
1 Introduction
The
oceans are changing rapidly. Surface waters are warming, sea-level
rise is accelerating and the oceans are becoming increasingly acidic,
jeopardizing many marine ecosystems. Human activities are unleashing
processes of change in the oceans that are without precedent in the
past several million years. Humanity is thus interfering with pivotal
mechanisms of the Earth System. The oceans play a key role in the
carbon cycle of our planet and have absorbed about one-third of total
anthropogenic CO2 emissions until now. Covering more than two-thirds
of the Earth’s surface, the oceans initially take up the greater
part of incoming solar heat and thus determine our climate system.
Similarly, the global water cycle is driven mainly by evaporation
from the oceans. Finally, the oceans harbour a great wealth of biological
diversity and, through fisheries, supply humankind with vital proteins.
An intact marine environment is also an important factor for economic
development, social well-being and human quality of life.
Recent research is making it increasingly
clear that climate change will reconfigure and wreak major damage
upon the marine environment and the coasts. These effects will also
impact severely upon human society. A large and ever growing part
of the population now lives close to coasts. The threats posed to
coastal populations and infrastructure by rising sea levels and extreme
events such as storm surges or hurricanes will mount in coming decades.
Furthermore, coupled with drastic overfishing, climate change and
acidification can endanger food supply from the oceans. There is an
urgent need for action now in order to limit the adverse effects of
climate change upon ecosystems and human society, especially because,
due to the considerable time lags, the present behaviour of humankind
will determine the state of the world’s oceans for millennia
to come. A strong research effort is also needed, for the oceans are
still terra incognita in many respects.
One important reason to produce this special report is the changed
scientific understanding of sea-level rise and ocean acidification
since the Intergovernmental Panel on Climate Change published its
last assessment report (IPCC, 2001). Furthermore, recent events such
as the unusual hurricane season of 2005, or the ongoing debate on
methane hydrates and carbon storage, present a need for WBGU, the
German Advisory Council on Global Change, to state its views. By analysing
the climatic impacts upon the oceans, WBGU draws attention to the
need for and urgency of efforts to engage in vigorous climate mitigation
activities and develop appropriate adaptation strategies. WBGU also
wishes to contribute its findings to the process of shaping a new
European Union policy on seas and oceans.
This special report does not seek to
paint a comprehensive picture of the state of the oceans. It does
not, for instance, set out to recapitulate the many years of debate
on ocean overfishing. WBGU concentrates instead on those key linkages
between climate change and the oceans that are the topic of new scientific
insights. These insights include new findings on warming, ocean currents,
sea-level rise, carbon uptake and acidification, and on the impacts
of these factors upon marine ecosystems. The report also discusses
in detail the development of tropical cyclones, the issues surrounding
carbon storage in the ocean or under the seabed, and the risks associated
with methane hydrate deposits in the sea floor. Many of these issues
are closely interlinked – coral reefs, for instance, are affected
simultaneously by warming, sea-level rise, storms and acidification.
Each theme is explored systematically, starting with the physical
and chemical fundamentals, proceeding to the ecological impacts, moving
on to the consequences for human society, and finally deriving policy
and research recommendations on that basis. WBGU embeds its analysis
within a normative framework that it has developed – the ‘guard
rail’ approach (Box 1-1). Analogous to the ‘climate guard
rail’ that it developed previously, WBGU now proposes a set
of ‘ocean guard rails’ for the sustainable management
of the oceans. These are quantitative boundaries that must not be
overstepped.
Resolute and forward-looking action
is needed to ensure that the oceans do not cross critical system boundaries
within a matter of decades. Overstepping these boundaries would lead
to severe and partly irreversible damage to nature and human society.
The way we manage the oceans now will thus be a decisive test of humankind’s
ability to steer a sustainable course in the future.
| Box
1-1
The guard rail concept
WBGU
has developed the idea of guard rails to operationalize the
concept of sustainable development (e.g. WBGU, 2004). Guard
rails are limits on damage and can be defined quantitatively;
a breach of these limits would give rise either immediately
or in future to intolerable consequences so significant that
even major utility gains in other fields could not compensate
for the damage. Guard rails thus demarcate the realm of desirable
and sustainable development trajectories. For instance, WBGU
has argued repeatedly in previous reports that the average mean
temperature should not be allowed to rise more than 2°C
above the pre-industrial level. Beyond that value, a domain
of climate change begins that is characterized by non-tolerable
developments and risks.
The guard rail approach proceeds from the realization that it
is scarcely possible to define a desirable and sustainable future
in positive terms, in other words as a specific target or state
that should be achieved. It is, however, possible to agree on
the demarcation of a domain that is recognized as unacceptable
and which society wishes to prevent. Within the guard rails,
there are no further requirements at first. Society can develop
in the free interplay of forces. Only if a system is on course
for collision with a guard rail must measures be taken to prevent
it crossing the rail. Compliance with all guard rails does not
mean, however, that all socio-economic abuses and ecological
damage will be prevented, as global guard rails cannot take
account of all regional and sectoral impacts of global change.
Moreover, knowledge is limited and misjudgement is possible.
Compliance with guard rails is therefore a necessary criterion
for sustainability, but it is not a sufficient one.
The
analogy of road traffic may serve to illustrate the guard rail
concept. Guard rails have a function similar to that of speed
limits, e.g. a limit permitting a maximum of 50 km per hour
in built-up areas. The outcome of setting the limit at 40, 50
or 60 km per hour can be determined empirically, but in the
final analysis the choice of figure is a normative decision,
representing an expedient way to handle a risk collectively.
Compliance with the speed limit cannot guarantee that no serious
accidents will occur, but it can keep the risk within boundaries
accepted by society. The guard rails formulated by WBGU build
upon fundamental norms and principles agreed by the international
community in various forms. They can be no more than proposals,
however, for the task of defining non-tolerable impacts cannot
be left to science alone. Instead, it should be performed –
with the support of scientists – as part of a worldwide,
democratic decision-making process. For instance, compliance
with the climate guard rail (no more than 2 °C global warming)
has now been adopted as a goal by the European Union. .
Guard rails for marine conservation
In the present report, WBGU applies its guard rail approach
to the field of marine conservation. This builds upon earlier
reports, in which WBGU has repeatedly argued for a two-fold
climate guard rail (WBGU, 1995, 2003). The environmental changes
in the oceans discussed in this report further underpin the
need for the climate guard rail. In addition, the report develops
further guard rails. Each is concerned with a specific aspect
of the interplay between climate change and the oceans, and
is elucidated and argued in a separate chapter. The full set
of guard rails is as follows:
•
Climate protection: The mean global rise in near-surface
air temperature must be limited to a maximum of 2 °C relative
to the pre-industrial value while also limiting the rate of
temperature change to a maximum of 0.2 °C per decade.
The impacts of climatic changes that would arise if these
limits are exceeded would also be intolerable for reasons
of marine conservation.
• Marine ecosystems: At least 20–30 per
cent of the area of marine ecosystems should be designated
for inclusion in an ecologically representative and effectively
managed system of protected areas.
• Sea-level rise: Absolute sea-level rise should
not exceed 1m in the long term, and the rate of rise should
remain below 5 cm per decade at all times. Otherwise there
is a high probability that human society and natural ecosystems
would suffer non-tolerable damage and loss.
• Ocean acidification: In order to prevent
disruption to calcification of marine organisms and the resultant
risk of fundamentally altering marine food webs, the following
guard rail should be obeyed: the pH of ocean surface waters
should not drop more than 0.2 units below the pre-industrial
level in any larger ocean region (i.e. also in the global
mean).
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