5. Ecosystem limits
Climate Change and Biodiversity Conservation
Human civilizations and the natural
ecosystems that we know today have evolved to be well adapted
to the current climate, which has been relatively stable during
the last 7,000 years. Thus we can be confident that dangerous
interference with the climate system would be prevented only if
greenhouse gas concentrations could be returned to preindustrial
levels (i.e. 280 parts per million of CO2, 700 parts
per billion of CH4, 270 parts per billion of nitrous
oxide (N2O), zero parts per trillion of CFCs, HFCs,
and PFCs). As stabilization of greenhouse gas concentrations at
these levels does not appear to be feasible during at least the
next century, the risk of adverse impacts from climatic change
cannot be completely avoided. Furthermore, the risks of severe
negative impacts and undesirable synergistic effects will grow
if concentrations are allowed to increase further.
Scientists have begun to identify several key principles that
can be used in assessing potential ecosystem vulnerability to
climate change. For example, it can be said with some certainty
that:
- The faster the rate of climatic change, the higher the probability
of substantial disruption of ecosystem structure and function,
and surprise within natural ecosystems, and the greater the risk
of serious ecosystem degradation.
- Ecosystems will not react wholesale in response to climate change.
Rather, each species will respond differently. Existing species
associations will break up and new communities of plants and animals
will take their place.
- Ecosystem response to climate change will depend largely on
competition between species to maintain themselves in new geographic
areas or under changing conditions. In many cases, species such
as pests, parasites, and opportunists will benefit.
- Ecosystems already stressed by human activities will be more
vulnerable to climatic threats and among the first to show the
effects of climate change. However, the multiple factors affecting
these ecosystems will complicate the identification of strictly
climatic effects.
- Species' adaptive abilities depend not only on genetic variability
but also on dispersal and migration capacity. Ecosystem resilience
and genetic variability within populations are being reduced through
habitat fragmentation. They will be further reduced by pressures
resulting from humaninduced climate change.
- For many ecosystems, increases in the frequency and severity
of extreme weather events such as drought, storms, and floods,
and changes in their geographic distribution, will lead to some
of the most serious impacts. Changes in seasonal precipitation
patterns and weather variability will also be critical. These
changes are likely under any climate change scenario.
Back to the previous page
|