7 Core
messages
Climate
mitigation for marine conservation
The future of the marine environment will depend crucially upon whether
human-induced disruption of the climate system can be limited to a tolerable
level. It follows in WBGU’s view that global anthropogenic greenhouse
gas emissions will need to be approximately halved by 2050 from 1990.
Because of the geophysical time lags, the climate protection policies
adopted in the next few decades will determine the state of the oceans
for millennia to come. Adaptation measures can only succeed if the present
acceleration of sea-level rise and the increasing acidification of the
oceans are halted.
WBGU
has already formulated a ‘climate guard rail’ in earlier
reports as a contribution to making a sustainable development pathway
operable: to prevent dangerous climatic changes, the mean global rise
in near-surface air temperature must be limited to a maximum of 2 °C
relative to the pre-industrial value and the rate of temperature change
must be limited to a maximum of 0.2 °C per decade. The present report
shows that marine conservation is a further reason why it is essential
to obey this guard rail.
Bolstering the resilience of marine ecosystems
Fish stocks and coral reefs will only retain their productivity and
diversity if sustainable marine resource management is ensured worldwide.
The mounting direct and indirect pressures generated by anthropogenic
greenhouse gas emissions are making adoption of an ‘ecosystem
approach’ for the conservation and use of the marine environment
ever more important. To that end, the establishment of marine protected
areas, an approach already agreed by the international community, must
be pushed forward energetically, and the regulatory gap for the high
seas must be closed by adopting a corresponding agreement within the
framework of the United Nations Convention on the Law of the Sea (UNCLOS).
To
conserve marine ecosystems and strengthen their resilience, WBGU proposes
the following guard rail: at least 20–30% of the area of marine
ecosystems should be designated for inclusion in an ecologically representative
and effectively managed system of protected areas.
Limiting sea-level rise and reorienting coastal zone management strategies
The strategies hitherto adopted to protect and utilize coastal areas
are no longer adequate to cope with climate-driven sea-level rise and
the mounting destructive force of hurricanes. 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 must be involved in the planning and implementation
of such measures. To this end, WBGU recommends creating integrative
institutions that combine all key competencies.
To
prevent severe damage and losses from occurring, and to avoid overstretching
the adaptive capacity of coastal ecosystems and infrastructure, WBGU
proposes the following guard rail for sea-level rise: absolute sea-level
rise should not exceed 1 m in the long term, and the rate of rise should
remain below 5 cm per decade at all times.
Adopting innovative instruments of international law for
refugees from sea-level rise
At present no nation has any obligation under international law to receive
migrants whose homeland has been lost due to climate-induced flooding.
In the long term, however, the international community will not be able
to ignore the issue of ‘sea-level refugees’ and will therefore
need to develop appropriate instruments for the secure reception of
affected people in suitable areas, ideally in areas that correspond
to their preferences. It would be expedient to develop a fair burden-sharing
system, under which states make a binding commitment to assume responsibility
for these people in line with their greenhouse gas emissions. To inform
the policymaking process, studies in the fields of law and social sciences
should be undertaken.
Halting ocean acidification in time
The oceans have absorbed about one-third of all anthropogenic CO2 emissions
to date, which has already caused a significant acidification (decrease
in pH) of seawater. These 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
be forecast exactly but profound changes to the food web are conceivable,
as calcification of marine organisms may be impeded or in some cases
even prevented. WBGU recommends fostering internationally coordinated
research and monitoring programmes on this issue. Furthermore, the negotiations
on future commitments under the United Nations Framework Convention
on Climate Change need to take into account the special role of CO2
compared to other greenhouse gases. Besides stabilizing the overall
package of greenhouse gases, it will be important to also seek explicitly
to stabilize CO2 concentrations.
To
protect the oceans against acidification, WBGU proposes the following
guard rail: in order to prevent disruption to calcification of marine
organisms and the resultant risk of fundamentally altering marine food
webs, 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).
