Environmental Impacts of Logging
THE WELL-DOCUMENTED environmental impacts of logging167 are summarised below. Environmental impact assessments of logging operations in a number of different countries (Papua New Guinea, Solomon Islands and Cameroon, for instance) clearly demonstrate that destructive logging practices using heavy machinery seriously reduce the forest's ability to carry out vital environmental and ecological functions.
Watershed Management and Soil Erosion
Forests provide a buffer to filter water and to hold soil in place. They sustain water and soil resources through recycling nutrients. In watersheds where forests are degraded or destroyed, minimum flows decrease during the dry season, leading to drought, while peak floods and soil erosion increase during
Tributary meets Melinau River, upper reaches of Baram river. Tributary water (left of picture), from preserved, non-logged and non-eroded watershed. Water from main river is cloudy with sediment from logging operations.
Flooding along the Baram River in Sarawak has increased significantly since logging began, the major floods occurring in 1979 and 1981.168 Massive floods, directly linked to excessive logging, have caused hundreds of deaths in the Philippines169 and Thailand.170
Much of the current logging carried out in Sarawak and other places is on steep lands dominated by surface materials that are highly susceptible to erosion when disturbed.171 Data collected by the Malaysian Department of Environment in 90 long-term sampling site locations within 21 river basins has detected incredibly high suspended sediment loads in most rivers and tributaries. This mainly originates from upstream soil erosion caused by the indiscriminate construction of logging roads and camps, skid trails and logging itself.172 Dr Saulei of the University of Papua New Guinea also blames the logging industry for 'accelerating erosion, weathering and humus decomposition, and leading to widespread formation of soils with low nutrient and absorptive capacities'.173
A skid track with severe erosion. More than a metre of topsoil has been lost and the bedrock exposed along many metres of this skid track on Isabel Island, Solomon Islands (see Kumpulan Emas, page 44).
The scale of inputs of mobilised sediment is clearly seen in this photograph where many tonnes of material are being made transportable from machinery-mediated topsoil disturbance and the loss of vegetative cover and litter layers.
Local Climate Regulation
Beside the implications of large-scale logging for global warming, drastic changes in precipitation are direct and immediate when the forest cover is removed.174 Changes in transpiration result in a greater intensity of tropical rainfall, enhancing both run-off and erosion, even if the total amount of rainfall remains unchanged. Forest loss can also make rainfall more erratic, thus lengthening dry periods.175
Most of the destructive forest fires that have recently raged out of control across the world, from the Amazon to Indonesia, are widely acknowledged to have been either started by and/or exacerbated by logging and agricultural development companies, such as the oil palm industry. One of the most detailed studies on the effects of fires in Kalimantan, Indonesia, concludes that the considerable decrease in foliage and related changes in the stand structure, increase of albedo, and horizontal and vertical air movements caused by fires, may produce significant and lasting effects on the regional climate.176
Impacts on the Marine Environment
Unsustainable logging mobilises debris that not only finds its way into the streams and rivers but also to the marine environment, where it damages mangroves and coral reefs, habitats crucial for aquatic life. In the Solomon Islands, the unique Marovo Lagoon, a proposed World Heritage Site, is threatened by the ecologically-destructive logging operations occurring in the surrounding forests. In Papua New Guinea, coral reefs have been destroyed to construct log ponds.
Loss of Biodiversity
Logging often destroys natural habitats, resulting in the loss of biodiversity and sometimes leading to the local, and possibly global, extinction of species. Although estimates of the rates of loss vary, few deny the reality of the current losses of both flora and fauna.177
According to a joint report by the Worldwide Fund for Nature and the Sarawak Forest Department, "Logging causes immediate forest disturbances, long-term habitat changes (e.g. damage to food trees and salt-licks), increased hunting by timber company workers and availability of logging roads as hunting routes. The destruction of wildlife from habitat loss must be recognised to be on an enormous scale".178 In Central Africa, the opening-up of the forest by logging facilitates the illegal hunting of wildlife, including protected species such as primates, and is leading to a decline in wildlife populations.179 Deterioration in water quality has caused a decline in fish stocks and has affected aquatic biological diversity because indigenous animals and plant life are highly vulnerable to oxygen depletion, suspended particulate matter and a lack of light.180
Even so called selective logging severely affects the complex and rich biodiversity of forests through excessive damage to residual stands, destruction of other plant and tree species and the creaming-off of species which are the most valuable for timber. An FAO study in Malaysia has shown that as much as 50% of the standing forest may be damaged and the surface soil destroyed when up to 30% of the ground surface is exposed. During silvicultural treatment in logging operations in Sarawak, so-called uneconomic forest species are deliberately poisoned. This reduces the complexity and species diversity of the tropical forests to only 10% of the original condition, resulting in the systematic elimination of tree genetic resources and contamination of the environment.181 According to the IUCN the most frequently recorded of all threats to globally endangered tree species is 'felling'.182
Destructive logging practices using heavy machinery seriously reduce the forest's ability to carry out vital environmental and ecological functions.