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Many of the controversial aspects of tropical (industrial)
forestry are associated with the destructive activities of
felling and extracting trees. Heavy machinery can compact
the soil and destroy vegetation while high-volume harvesting
can contribute to erosion, and reduce species diversity and
regenerative capacity. Excess organic debris can make forests
more vulnerable to destruction in the event of fire. While
damage is an unavoidable consequence of logging, poor planning
and execution of logging cause much unneeded damage. Damage
is influenced by several factors, such as harvest intensity,
the topography of the terrain and logging method.
Harvest intensity in the tropics varies from < 1 m3 to
>100 m3 per ha, depending of the range of species harvested,
their spatial distribution, accessibility of the terrain and
presence of regulatory controls such as minimum felling limits
and maximum felling intensities. The presence of markets strongly
influences the selection of trees and species and thus harvest
intensity. Logging intensities in SE Asia are highest, often
in the range 50-100 m3/ha. This is a consequence of the high
abundance of suitable species concentrated in a single family
(Dipterocarpaceae). In Africa the harvest is concentrated
in very few but very large individuals, leading to harvest
intensities of 10-40 m3/ha. In South America harvest intensities
are lowest, between 5-30 m3/ha, as a result of the low proportion
of species with suitable timber properties. In terms of proportion
damaged, increasing harvest intensity leads to increased damage
to the residual stand and increased soil compaction by heavy
machinery. Both types of damage are known to vary widely between
5-50%.
The main agent of damage is log extraction. Least damaging
are manual extraction and extraction by draught animals such
as elephants, oxen, mules or horses. Agricultural tractors
require narrow skid trails and are less damaging than the
large wheeled or tracked skidders that are used in most industrial
logging operations. Bulldozers are also frequently used and
may be extremely damaging. Technologically advanced extraction
methods such as helicopter, balloon and skyline extraction
are often less damaging but apply mainly to high value operations.
Reduced (or Low) Impact Logging (RIL or LIL) is increasingly
propagated as an approach to reduce unwanted side-effects
while at the same time increasing efficiency of the logging
operation. It is defined as "Intensively planned and
carefully controlled implementation of harvesting operations
to minimise the impact on forest stands and soils" RIL
addresses the entire logging cycle, from pre-harvest planning
to post-harvest measures to protect forest stands, and emphasises
the critical role of training and adequate supervision of
logging crews for reducing the deleterious impacts of logging.
Applying RIL is not equivalent to sustainable forest management,
but it is an indispensable tool in achieving it. Most RIL
guidelines call for at least the following:
Elements of Reduced Impact Logging operations (from
FAO 2001).
Characteristics
stand entries at pre-determined cutting cycle landings planned
< 1/3 the basal area removed tree marking, location mapping
& felling direction
pre-harvest operational inventory operations only under favourable
conditions
advanced access road construction maximum utilization of all
trees felled
minimize extraction trails minimal residual damage
climber cutting if required rehabilitation of negative impacts
worker and supervisor training post-harvest assessment
safe felling and extraction practices
RIL requires increased investments in training and planning
(e.g., a detailed inventory needs to be done). This is justified
by savings achieved in more efficient use of expensive equipment
(e.g. reduced skidding distances, faster skidding), improved
log recovery (fewer logs are "lost", fewer logs
are wasted due to improved felling techniques) and a more
efficient organisation of the operation (leading to fewer
unproductive delays). More and more information is becoming
available regarding the costs and benefits of implementing
RIL. In many instances, it has been demonstrated that per
m3 of timber harvested, RIL indeed is more cost effective
than conventional logging. However, in areas with high biodiversity
values, a large area of streamside buffers or steep slopes
the balance of costs and benefits may be different due to
the large quantity of foregone timber. High wages relative
to machine costs may also contribute to higher costs for RIL
compared with conventional logging. From the viewpoint of
the forest owner, RIL may be advantageous, as reduced damage
to regeneration will translate into a higher yield in the
second cycle of logging. Whether costs savings demonstrated
in relatively small experimental settings would be achieved
when RIL is applied to large-scale operations remains to be
seen. It should also be realised that applying RIL changes
the distribution of costs and benefits among stakeholders.
As conventional logging may be excessively profitable to the
logger, even though it may be detrimental to other interests,
incentives to switch to RIL must be very strong. This is one
of the reasons why, in spite of the many obvious advantages
of RIL, poor logging is still the rule in the tropics.
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TBI sources
 Hout,
P. van der (1999). Reduced Impact
Logging in the Tropical Rain Forest of Guyana: Ecological,
Economic and Silvicultural Consequences.
Hout,
P. van der & Leersum, G.J.R. van
(1998). Reduced impact logging: a global panacea?
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