World in Transition: Climate Change as a Security Risk - WBGU

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7 Hotspots of climate change
rapid glacier melt that this causes and increasing precipitation
variability. Above all, serious impacts on
the population’s water supply and on agriculture are
to be expected. The societies concerned already face
major political and socio-economic challenges and
are characterized by political disputes and conflicts
over the allocation of scarce resources. The (partial)
destruction of the rainforest and water scarcity –
amplified by largely non-sustainable water usage and
population growth – have so far resulted mainly in
conflicts that are limited to local and regional areas.
Even though it is likely that there will be a gradual
shift in awareness among the population and some
sections of the political elite as a result of the increasing
pressure of problems in the region, countries
other than Chile are comparatively poorly equipped
to meet the additional challenges arising from climate
change effectively. As a result of political instability
and economic pressure, political planning is
extremely short-sighted; there are serious defects
in the administrative structure of the state, deficiencies
in the rule of law and a low level of cooperation
between countries. Hence, in the near term, iterative
learning processes are possible, but the development
of a long-term adaptation strategy is unlikely. It must
therefore be assumed that climate change and the
environmental changes that it causes will in future
exacerbate existing political tensions and conflicts in
the Andes region.
7.10
Amazon region
7.10.1
Impacts of climate change on the biosphere and
human society
The Amazon rainforest is the largest contiguous
expanse of tropical forest in the world, harbouring
a significant proportion of all terrestrial plant
and animal species (IPCC, 2007b). The Amazon
basin extends over eight Latin American countries;
around 60 per cent of the basin lies in Brazil, while
the remaining 40 per cent is divided among Bolivia,
Peru, Colombia, Venezuela, Ecuador, Suriname and
Guyana. Around 50 per cent of precipitation in the
Amazon region is generated by evapotranspiration
in the region (Schubart, 1983; Salati, 1987). The most
major problem in the Amazon region is continuing
deforestation. If present trends continue, 30 per cent
of the Amazonian forest could have disappeared by
2050. The resulting regional climatic changes could
lead to ‘savannization’, particularly of the eastern
Amazon area; this will be significantly amplified by
global climate change. The transformation of tropical
rainforest into dry grassland savannah would lead
to the extinction of a significant number of species
(IPCC, 2007b).
For the Amazonas region of northern Brazil,
regional climate projections based on the A1B scenario
predict a rise in temperature by 2100 of 2.6–
3.7 °C against a 1990 baseline; such a level of warming
is 30 per cent above the global mean (IPCC, 2007a).
These model projections are robust and accord well
with the warming already recorded in the 20th century.
The seasonal change in temperature distribution
shows a trend towards more marked warming in the
months of June to August compared to the months
of December to February, thus reducing the annual
temperature range (IPCC, 2007a).
Changes in the regional distribution of precipitation
are always hard to predict, and in the Amazon
region the difficulty is increased by the very important
interactions between vegetation and climate, and
by the effect of the high but narrow mountain range
of the Andes. Both factors are poorly depicted in current
models. A further factor contributing to the level
of uncertainty is the future trend of the El Niño phenomenon,
which leads to significant droughts in the
Amazon region. At present, therefore, it is impossible
to make any statement about future changes in mean
precipitation (IPCC, 2007a). However, droughts will
occur in future as a result of the significant warming
of the Atlantic and the associated changes in atmospheric
circulation, irrespective of the El Niño phenomenon
(Cox et al., 2004; Shein et al., 2006).
In the Amazon region, the year 2005 was notable
for its extraordinary dryness. This unusual event
could be a herald of the drought years that, according
to climate projections, will occur ever more frequently
in the region. According to model calculations
of the Hadley Centre (HadCM3), from 2050
onwards the Amazon region will be able to absorb
less and less carbon from the atmosphere. Higher
air temperatures combined with increasing dryness
will reduce carbon fixing by the rainforest; the effect
will be amplified by a further decrease in the area of
the rainforest. In the models of Cox et al. (2000), this
reduction of carbon storage in the Amazon region
results in the terrestrial biosphere becoming a global
source of carbon in future. More recent predictions
assume that, in the extreme case, 65 per cent
of the Amazon forest area will disappear by 2090 as
a result of increasing incidence of droughts (Cox et
al., 2004; Hutyra et al., 2005). The transformation of
the Amazon basin into a savannah landscape (IPCC,
2007a) would release additional carbon dioxide into
the atmosphere, which would in turn accelerate climate
change (Section 5.3.4).