Geoscience Reference
In-Depth Information
woodland - crossing the threshold is more likely than not to occur this century.
Others become more likely if the temperature continues to rise beyond 4°C.
The consequences for human society of crossing these tipping elements are
particularly serious in three major areas. First, loss of large amounts of ice from
the polar ice sheets would contribute to sea-level rise that would continue
for centuries and would ultimately be measured in metres. Second, changes
in oceanic and atmospheric circulation would change regional precipitation
patterns, further affecting agriculture and urban water supplies. Third, rapid
changes in the composition, structure and functioning of large ecosystems on
land and in the ocean would result in significant losses of biodiversity, under-
mining the capability of these ecosystems to provide services that benefit
humanity. Adapting to shifts in these tipping elements would undoubtedly
present formidable challenges to contemporary society in their own right, but
such changes will not occur in isolation from other changes occurring in the
socio-economic sphere and in the environment at local levels.
Compounding global crises
As noted earlier in the discussion about the changing human-environment
relationship in the past and in contemporary society in the Anthropocene,
environmental pressures, such as changes in climate, do not act in isolation in a
simple cause-impact relationship. Rather, they are invariably intertwined with
other changes in the environment as well as changes in the human enterprise,
ranging from alterations of economic policy to changes in demographic patterns
and shifts in underlying core values of society. Until the recent past, most of
these interacting stresses have acted upon societies at local and regional levels,
in contrast to the novel situation of a globalized contemporary society in which
our own planetary-level life support system is in question.
Recent analyses of the challenges facing humanity in the 21st century have
highlighted the risks associated with compounding global crises resulting from these
complex interactions between society and environment (e.g. Walker et al., 2009;
Biggs et al., 2011; Folke et al., 2011).
Figure 7.4
, adapted from Walker et al. (2009),
is an elegant visual representation of the nature of these compounding crises. In
addition to the multiple, interacting drivers of change, two other features of these
crises stand out in the figure. First, many of the unwanted outcomes are the result
of feedbacks in the system (the broken arrows in the figure) rather than the initial
impacts of the global drivers on the system. Second, the major sectors - climate,
ecosystems, human health and economy - cannot be treated in isolation from one
another. In short, simple cause-effect logic will fail in understanding these global
crises; they lie squarely in the realm of complex system science.
Some progress has been made in understanding the nature of these compounding
global crises despite their complexity. For example, many crises are typified by
largely independent stressors acting on interconnected systems, thus generating
feedbacks and often surprising outcomes that are difficult to predict and manage.
A good example is the global food crisis of 2008.
