Executive summary
Climate Change and Biodiversity Conservation
A main objective of the UN Framework Convention on Climate
Change (UNFCCC) is to stabilize levels of greenhouse gases in
the atmosphere within a time frame that ensures the rate of climate
change is slow enough to allow ecosystems to adapt naturally.
Current levels of greenhouse gas emissions will cause climatic
changes that many species and ecosystems will not be able to adapt
to.
The observed warming trend over the last 100 years is probably
due to the buildup of greenhouse gases in the atmosphere.
Evidence of recent global warming comes from temperature records
and analysis of tree growth rings. Worldwide, melting glaciers
provide physical evidence of warming, as does the catastrophic
drought in subSaharan Africa.
Ecological indicators of warming are being recorded from
around the globe:
- Yellowstone National Park, USA: increased risk of wildfires
due to warming and drying trends
- Caribbean and Pacific islands: warm water episodes cause
coral reefs to die from "bleaching"
- Barro Colorado Island, Panama: longterm drying trend
leading to extinction of tropical forest species
- Bermuda: die back of coastal mangrove forests as a result
of sealevel rise.
Certain ecosystems can be identified as most vulnerable to climate
change. These "front line" ecosystems include:
- Temperate and boreal forests
- Tropical montane cloud forests
- Coastal mangrove forests
- Coastal marshes
- Coral reefs
- Alpine/high montane systems
- Arctic ecosystems.
Predicting climate change impacts on species and habitats is
difficult because of the complexity of ecosystems. Each species
will react differently, and many ecosystems will break up and
disappear entirely. Ecosystems already under stress from human
pressures such as pollution or development are likely to be the
most sensitive. Uncertainty as to the degree of threats is not
a reason for inaction, but rather an argument for greater precaution.
Despite surviving past climatic changes, for instance between
ice ages, many species will be unable to adapt to a rate of warming
which will be the fastest experienced in at least 10,000 years.
For many tree species, such as Scots pine and Douglas fir, the
speed of change will be more than 20 times the speed with which
they can "migrate" to keep up with suitable climatic
conditions.
There are clear limits of ecosystem tolerance to climatic change.
A 1°C
warming will have significant negative impacts on many ecosystems,
and a rate of change of 0.01°C
per decade is probably a threshold level for many species. This
means an order of magnitude less than IPCC (Intergovernmental
Panel on Climate Change) predictions of global warming. Sealevel
rise of less than 1 cm per decade can harm many coastal habitats.
One response to expected climate change is to increase investment
in conservation and protected area management. The more resilient
ecosystems are to current environmental pressures, the better
they will be able to cope with global warming. Larger protected
areas, better managed buffer zones and corridor systems between
reserves will help to soften the blow of climate impacts.
The best strategy to reduce climate impacts is to reduce greenhouse
gas emissions down to levels which will ensure that climatic changes
will remain within the boundaries of known ecological limits.
A first step towards this objective would be to cut industrialized
country greenhouse gas emissions to 20 per cent below 1990 levels
by the year 2000.
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