FOREST HARVESTING CASE-STUDY 12
Environmentally sound forest infrastructure development and harvesting in Bhutan
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Case studies on environmentally sound harvesting operations form part of a series of initiatives undertaken by the Forest Harvesting, Trade and Marketing Branch of FAO to promote environmentally sound forest harvesting and engineering practices. These will serve the unquestionable continuing need to refine harvesting systems and techniques so that they become fully compatible with the objectives of sustainable forest management contributing to the economic, ecological and social aims of sustainable development.
This study, initiated by FAO, meets the need to thoroughly document and establish data on environmentally friendly forest engineering practices. The marked superiority of sophisticated construction equipment and advanced techniques in forest road construction should encourage the adoption of such practices for the opening up of forests by roads in mountainous and difficult terrain.
The results of the study demonstrate that the efficiency and the low environmental impact of “environmentally sound road construction methods”, already generally used in semi-natural forests of the Alps (see Forest Harvesting Case Study 10: “Environmentally Sound Road Construction in Mountainous Terrain”, 1998) are also appropriate for the Himalayan region in Bhutan. Although a case study is just a snapshot, it is hoped that this case study will contribute to raise interest in introducing environmentally friendly forest engineering practices, not only in mountainous terrain but also for areas where sensitive forest ecosystems are to be opened up.
The Forest Harvesting, Trade and Marketing Branch wishes to express its gratitude to the Third Forestry Development Project and the Royal Government of Bhutan for their kind support.
This case study was made possible through a special contribution by the Austrian Government for the FAO programme on environmentally sound forest harvesting and engineering.
Officer in Charge
Forest Harvesting, Trade and Marketing Branch
Forest Products Division
Forestry Department, FAO
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, particularly 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 information 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 Chamgang-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 m3/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 m3/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/m3 for the traditional system at the Korila site and US$ 20.13/m3 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 environmental 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.
FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS
Rome, © FAO 1999
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SYMBOLS, ABBREVIATIONS AND EXCHANGE RATE
2. GENERAL INFORMATION ON BHUTAN AND THE FORESTRY SECTOR
3. DESCRIPTION OF THE PROJECT AREA
3.1. Forest type classification by satellite images compared to field assessments
3.2. Description of the study areas
4. INTEGRATED PLANNING OF FOREST INFRASTRUCTURE
5. DESCRIPTION OF ROAD CONSTRUCTION TECHNIQUES CURRENTLY USED IN BHUTAN
5.1. Clearing of the construction area
5.2. Road construction by excavator and bulldozer
5.3. Mass transport
5.4. Road drainage
5.5. Surfacing and shaping
5.6. Slope protection and stabilization
6. DESCRIPTION OF LONG-DISTANCE CABLE LOGGING IN BHUTAN
6.1. Logging operation
6.2. Operations at the landing and hauling
7. DESCRIPTION OF EQUIPMENT
7.1. Description of the road construction equipment
7.2. Description of the logging equipment
8. STUDY METHODOLOGY AND ANALYSIS OF DATA
8.1. Work and time studies on forest road construction
8.2. Estimating production rates in road construction
8.3. Estimating costs of road construction
8.4. Qualitative assessments of environmental impacts
8.5. Work and time studies on logging operations
8.6. Estimating production rates in cable logging
8.7. Estimating costs of long-distance cable logging
8.8. Qualitative assessments of environmental impacts in cable logging
9. CONCLUSIONS AND RECOMMENDATIONS
Appendix 1. Operable forest by subcatchment
Appendix 2. Time table on excavator operations
Appendix 3. Time table on bulldozer operations
Appendix 4. Time tables on long-distance cable logging operations
cm = centimetre
h = hour
ha = hectare
l = litre
kg = kilogram
km = kilometre
kN = kilonewton
kPa = kilopascal
kW = kilowatt
km2 = square kilometre
m = metre
mm = millimetre
m3 = cubic metre
min = minute
AAC = Annual allowable cut
FDC = Forest Development Corporation
FMU = Forest Management Unit
FSD = Forest Services Division
LUPP = Land Use Planning Project
LUWM = Land Use Working Map
MoA = Ministry of Agriculture
TFDP = Third Forestry Development Project
Exchange rate applied (as of March 1998)
US$ 1 = Nu 39 (Nultrum) = Rs 39 (Rupes)