Environmentally sound forest infrastructure development and harvesting in Bhutan

Rom

1999

67 S.

Bandaufführung

57079

The study was carried out in natural forests of the Himalayan range in Bhutan in the spring of 1998. Although the concept of opening up forests by a permanent road network as a precondition for forest management and utilization of forests in a sustainable manner is widely accepted, it is a difficult concept to put into effect, paricularly in sensitive forest ecosystems. Holistic, interdisciplinary approaches that take account of the need for landscape and wildlife considerations should replace purely technology-oriented solutions. The Third Forestry Development Project (TFDP) in Eastern Bhutan was selected to demonstrate that "Environmentally Friendly Forest Engineering" considerably reduces the effect of damaging elements of forest road construction. The study documents each phase of both, environmentally sound road construction by excavator and traditional road construction by bulldozer and compares environmental impacts of both construction techniques. Another objective was to provide on "long-distance cable crane logging" which appears that it will continue to be the most common harvesting system applied throughout Bhutan in the near future. The traditional clear-felling practices as well as a modified technique both with subsequent cable logging were studied. Data on road construction were collected for both construction techniques under similar formation conditions in forest management units (FMU) of the TFDP. Work and time studies on construction operations by excavator were carried out in the Kharungla unit and on construction operations by bulldozer in the Korila unit. The work and time studies on long-distance cable logging were in the Korila unit for the traditional way of harvesting and in the Champang-Helela unit which is not part of TFDP. On average the productive work time required per metre in length of road constructed was 8.69 min for the excavator used in the Kharungla road project and 3.48 min for the bulldozer used in the Korila road project. These figures on productivity can be considered indicative for favourable construction conditions in mountainous terrain of the Himalayan range of Bhutan. A productivity of 5.60 m in length of road constructed per hour of workplace time was found for environmentally sound road construction by excavator. The corresponding figure for traditional road construction by bulldozer was 13.61 m/h workplace time. All figures stated above on efficiency and production rates of excavator and bulldozer refer to the establishment of the cross-section excluding the hillside ditch which was to be established manually, and do not cover any further activities usually carried out by excavator or bulldozer in finishing the road (e.g. installation of culverts). The cost per metre of road constructed is based on the production rates established by the work and time studies at each construction site and amounts to US$ 9.28 per metre of road constructed by excavator and US$ 6.07 per metre by bulldozer construction. The stated figures on cost per metre refer to the particular road sections under review only. Furthermore, it has to be noted that the cost for excavator construction is based on the purchase price of this particular excavator used at the Kharungla construction site. This excavator is the most recent model manufactured, whereas the bulldozer is an older one. This has to be kept in mind, otherwise the short-term economic advantage in bulldozer construction might mislead to favouring the bulldozer. On average the productive work time required per cubic metre of timber extracted by long-distance cable crane was 15.34 min for the traditional practice at the Korila logging site and 10.52 min for the modified system used at the Helela logging site. A productivity of 3.88 mß/h workplace time was found for cable logging applying the traditional clear-felling practice. The corresponding figure applying the group selection felling system was 5.01 mß/h workplace time. The cost per cubic metre of timber extracted by long-distance cable crane is based on the production rates established by the work and time studies at each logging site and amounts to US$ 25.53/mß for the traditional system at the Korila site and US$ 20.13/mß for the modified system at the Helela site. The results of this case study show that environmentally sound road construction, as applied in the Kharungla road project, is superior to road construction in the traditional way by bulldozers as applied at the Korila construction site from the environmental point of view. The short-term economic benefits from use of bulldozers in forest road construction in mountainous terrain are likely in the longer run to create evnironmental damage on a considerable scale as side slopes increase. The traditional harvesting system in Bhutan, strip-wise clear-felling with subsequent long-distance cable logging, can be modified towards more environmentally sound harvesting practice. The adverse environmental impacts such as loss of biodiversity, creation of monocultures or forest with a poor species composition as well as erosion can be reduced. This solution makes use of the available skills and equipment in the country, contributes to the livelihood of the people and improves the overall development in rural areas.