STATE OF THE RAINFOREST 2014
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Considerable attention is given to the deforestation of tropical
forests and its devastating effects on societies, biodiversity
and carbon emission. However, forest degradation and forest
fragmentation also have adverse impacts on forest ecosystems and
on the goods and services they provide, but receives less attention.
Forest degradation
Forest degradation is perceived differently by different actors: a
2009 survey found more than 50 definitions of ‘forest degradation’.
26
Most definitions focus on changes in the composition of tree
species, loss of biodiversity, or long-term reduction in crown cover.
27
The most widely used definition is the rather broad one developed
by a FAO expert meeting in 2002:
a reduction of the capacity of a
forest to provide goods and services
.
28
The lack of a commonly agreed-upon definition may hamper
conservation efforts. Policymakers need to have information about
what degradation is, what causes it, and how serious the impacts
are, in order to tackle the problem. International conventions, like
the United Nations Framework Convention on Climate Change and
the Convention on Biological Diversity, requires countries to report
on their efforts to mitigate forest degradation. Without a suitable
threshold defining ‘degraded ‘and ‘non-degraded’ forest, it is
difficult to report on the status and quality of forests.
29
It is hard to measure and estimate degradation on the global level,
partly due to the lack of a common definition, and partly because
it occurs in different forms and with varying intensity. However, in
2002, the International Tropical Timber Organization indicated that
up to 85.000 km
2
of tropical forest and forest land could already
be regarded as degraded – a figure larger than the area of non-
degraded tropical forest.
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The underlying causes of forest degradation vary globally, and
may be natural- (fire, storm, drought or pests) or human-induced
(logging, grazing, fuelwood gathering, agriculture expansion).
Selective logging is the primary cause in many areas, as in
rainforests which are rich in attractive, high-value timber. According
to research based on national data from 46 tropical and sub-tropical
countries, timber extraction and logging are involved in half of the
forest degradation in tropical countries.
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Fire, the other primary
force driving forest degradation, is however also closely connected
to logging. Once the canopy cover has been opened up, the forest
floor is more vulnerable to drought and the spread of fire.
32
Even if degradation does not directly result in the complete
loss of forest, the opening up of the canopy by selective logging
and often road building, is often the first phase of a process that
leads to deforestation – degradation transforms into slow-motion
deforestation.
33
Studies have shown that degraded forests are
considerably more likely than intact ones to over time be completely
deforested,
34
and even selective logging may develop into complete
forest loss.
35
One study from the Amazon showed that selective
logging destroyed up to 62% of the trees in a forest, even if only the
most valuable ones were directly harvested.
36
Forest degradation is
also one of the major sources of greenhouse gas emissions.
37
Forest fragmentation
Forest fragmentation occurs when large areas of forests are split
into smaller areas,
38
for example by roads or agriculture expansion.
The ecosystem in the remaining forest blocks may be disrupted
when plant species behaviour and the mix of species is altered with
the changes in the habitat.
39
Plant recruitment, seed dispersal and
seedling survival can be negatively affected.
40
Animal populations are also affected. When a forest area is reduced,
it becomes more difficult for some species to breed or find food.
In addition, ‘edge effects’ can cause further trials for the forest
through drought, wind and fires. A study from the Brazilian Amazon
shows that forest-fragmentation-related edge effects are one of the
major causes of forest degradation. Large trees on the forest fringes
succumb to wind- and drought mortality much faster than similar
trees in the forest interior.
41
A major task for global forest policy today is to restore and
rehabilitate the huge areas of forest lands that have already been
lost or degraded. This is essential for long-term food security,
climate stability, biodiversity conservation and human well-being.
Forest degradation and forest fragmentation
