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6. Reduced impact logging in Bhutan - Ugyen Thinley*

* Director of Forestry Services, Ministry of Agriculture, Kingdom of Bhutan, Tel: ++(975 2) 32 1185/32 3055, Fax: ++(975 2) 32 2395, E-mail: [email protected]


Bhutan is known as the land of the thunder dragon. It is a mountainous country nestled in the heart of the Himalayas. It has a total land area of 40 077 km2, of which 72.5 percent is covered by forests. Bhutan’s elevation ranges from 150 m to more than 7 500 m above sea level. This wide range in elevation has resulted in a tremendous biological variation that makes Bhutan one of the most biologically diverse countries in the world.

Although the total area under forest management, where active timber harvesting takes place, is only 3.45 percent of the geographical area of the country, forests play a major role in Bhutan. Most people live in a rural, forested landscape and depend on the forest for their livelihoods. The international community acknowledges Bhutan’s progressive conservation and development policies, which include preserving its near pristine environment through the conservation of extensive areas under forest cover.

The Government of Bhutan recognizes the importance of forests vis à vis the well-being of its people and for a long time has made the conservation of forests and the natural environment top priority in the national development policy. The generation of direct economic revenue from commercial forest harvesting is given low priority. Commercial timber harvesting and processing contribute 5 percent to the total national revenue. The export value of forest products is approximately Nu. 80 million per year[4].

The credit for Bhutan’s visionary policies belongs to His Majesty the King who decreed that a minimum of 60 percent of the country should be kept under forest cover forever. In 1999, the Government banned the export of logs to conserve forests further and to provide timber for local people at affordable prices in the interest of rural development and the maintenance of cultural values.

Logging operations were nationalized in 1979. Since then, forest management practices have moved steadily towards more sustainable management with the introduction of more intensive inventories, better data analysis, improved planning and more environmentally sound harvesting and road construction methods. Bhutan is now in the process of preparing a national Code of Best Practice, which is nearing completion.


The paper addresses a number of issues concerning better forest management and has the following four objectives:

It is hoped that sharing the Bhutanese experience will help to improve forest-harvesting practices and promote the adoption and effective implementation of RIL in Asia and the Pacific.


Bhutan has developed its own approach to forest harvesting in a very mountainous environment. Ground-based systems that are common in much of the tropical world cannot be applied in Bhutan, since this would result in large-scale environmental degradation. Currently, all commercial harvesting is based on cable logging systems. Cable logging, using fixed skylines, was first introduced in the early 1970s. Gradually, other equipment was introduced such as skidders, mini-tower yarders, hydraulic loaders and backhoes (for road construction).

The long-distance cable logging system is the most suitable option for commercial timber harvesting in the mountainous terrain of Bhutan. Both gravity and haul-back machines using a mini-tower are used. On average, the time required for the extraction of one cubic meter of timber using long-distance gravity skylines is 15.34 minutes while the shorter distance machines, using a haul-back line, take an average of 10.52 minutes/m3.

Gravity machines (cable cranes) can have a logging reach of up to 1 500 m. The distance between the two consecutive cable crane lines is usually 60 m or less. Over such a long distance, cable lines usually require intermediate support. They can lift a total weight of 2 500 kg (carriage and transport load).

This type of logging system requires careful planning, engineering and surveys to meet technical conditions for establishing and operating the cable crane.

Felling and bucking is done once the skyline corridor and the trees to be felled have been marked and enumerated. Care is taken to fell towards the extraction corridor or into the logging opening. After felling is completed, the long-distance cable crane is set up.

The whole logging operation is radio controlled. The forest management unit is divided into compartments or coupes. Usually, natural features such as rivers, creeks and ridges are chosen as boundaries. Utilization maps are prepared using these boundaries. The selection of annual logging coupes is in line with the management plan and according to annual targets. In selecting the coupe, stand volume and the quality of trees are determined. Normally, a system of parallel cable lines is used to develop a logging coupe. This systematic approach is suitable for the steep terrain prevalent in most logging areas.


The traditional silvicultural system in Bhutan is a selection-and-improvement method of harvesting and regeneration. The natural forest is in many cases over-mature, with little regeneration in the understorey. Older and poorer quality trees are marked for felling to open the forest and assist natural regeneration. The first entry into the natural forest seeks to remove approximately 25 percent of the standing stock.

With the use of skyline systems, a narrow corridor is clear-felled to allow unobstructed installation of the cable line. The adjacent forest is marked and felled according to the silvicultural objectives. This clear-felling corridor approach is still the common silvicultural system applied in the hardwood forests.

In the conifer zone, the preferred silvicultural system is the group selection method. Small openings, varying from 0.2 to 0.3 ha in size, are created by felling trees along the skyline corridor. The single tree selection system has not been successful in stimulating regeneration in the conifer zone whereas the group selection system results in good natural regeneration. Where natural regeneration has difficulty becoming established, planting is carried out using the species naturally occurring on that site.

The productivity of the group selection system is also greater than the traditional single tree selection system. The traditional single tree selection system has an average productivity of 3.88 m3/hour while the group selection system averages a productivity of 5.01 m3 per working hour (FAO, 1999).


Adoption of mechanized extraction

Most early logging in Bhutan used manual labour. Long, continuous slopes made the manual rolling of logs to a road possible. Initially, trees were felled and bucked manually. Gradually chainsaws were introduced but the manual extraction remained. Trees were marked and felled using a single tree selection system, cut into short logs (usually not more than 4 m) and rolled down the slope, sometimes for as far as a kilometer.

All undergrowth and regeneration along the rolling path had to be cleared. Rolling paths were often in small gullies or depressions. The ground would become compacted causing accelerated runoff and erosion, which made regeneration very difficult. Remaining trees often were damaged by the rolling logs, which frequently resulted in decay and disease. This method of harvesting had a high impact and was slow and inefficient.

Cable logging, using fixed skylines, was first introduced in the early 1970s. As Bhutan introduced more commercially oriented harvesting of its forests, more skyline equipment was purchased. Now, all of the commercial harvesting is based on cable skyline logging systems.

The conversion to skyline logging posed many challenges. Skyline logging requires good planning, engineering and surveying skills. The entire planning and location of the road system must be done to facilitate the most efficient use of the skyline equipment. The task of installing and operating a skyline system requires many specialized skills that were not available in the country when this technology was first introduced.

The environmental benefits of this change to mechanized logging are obvious. Soil disturbance is very low since the fixed skyline system fully suspends logs during the extraction process. Damage to logs is minimized. Landings are usually smaller, particularly if mechanized loading using small, hydraulic loaders is used. With the skyline system, regeneration is left largely undisturbed, since logs are lifted out of the forest, even in a single tree selection system.

Improvements in road construction

Road construction in the mountainous areas of Bhutan creates probably the biggest environmental impact. In the past, roads were constructed entirely by manual means. This was slow and inefficient.

Small, crawler tractors such as the D-6 were introduced as the first step in the mechanization process. With the use of this machinery, Bhutan was able to open up its forest areas and introduce commercial utilization of the forest resource. However, the crawler tractor creates a high degree of soil disturbance. In the sedimentary geology of the Himalayas, the soils and underlying schist and gneiss are highly erodible. The very steep banks of the road excavation often failed and fill slope failures and erosion were common problems.

In recent years, a major step has been taken towards reducing the impact of road construction through the introduction of hydraulic excavators or back-hoes. With these machines, cut slopes can be tapered easily and fill material can be placed to create a more stable roadbed and to minimize erosion. Culverts are easier to install and ditch lines can be maintained easily. All of these improvements have reduced the environmental impact of forest road construction significantly, while simultaneously improving the quality of the roads.

However, construction costs have increased with the more environmentally sound method. Using the excavator as the main construction machine, on average, 5.60 m of road can be constructed per working hour. Using the bulldozer to construct the road under similar terrain conditions results in productivity of 13.61 m/hour. The cost of road construction was found to be US$9.28/m using the excavator compared to US$6.07/m by bulldozer (FAO, 1999).

Summary of improvements

The changes to harvesting and road construction methods through the introduction of more appropriate equipment and techniques and through better planning and training, have contributed greatly to the achievement of sustainable forest management. Refinements to the silvicultural system to reflect the regeneration requirements of the different forest ecosystems in the Bhutanese forest complex have also helped Bhutan to move toward sustainable forest management.

These benefits can be summarized as follows:

Challenges and constraints

Despite the progress that has been made in forest harvesting, road construction, and environmental management, there is room for improvement.

The greatest challenge is to strike a balance between commercial timber harvesting, traditional utilization for domestic consumption and the national goals of maintaining the environmental values of forest cover, soil conservation, clean air and water.

Another area that impacts negatively on the achievement of sustainable harvesting and natural regeneration, is grazing in forest areas. Bhutan has a rural culture in which ownership of cattle and yaks is prized. These animals graze throughout the forest areas and damage regeneration through trampling and browsing. This has a negative impact on the harvesting cycle and ultimately, on the annual allowable cut.


Strengthening the legal forest management framework is an important element in achieving sustainable forest management. The Forest and Nature Conservation Act (1995) of Bhutan requires an approved forest management plan for all forestry operations. No forest harvesting is permitted until there is an approved management plan.

A code of practice, adapted to the Bhutan situation, is now under preparation and is nearing completion. This code will strengthen institutional arrangements further and will benefit Bhutan’s efforts to achieve sustainable forest management.

The existing equipment of the forest development agency is old and outdated. It is recommended to purchase new road construction equipment and cable cranes to improve the efficiency of harvesting and forest road construction. Cable cranes with a lift capacity of 5 tonnes will be acquired to further improve efficiency and reduce environmental impact.

Training remains a priority and a challenge. Only adequately trained, skilled and experienced machine operators will be employed for road construction and timber extraction in sensitive forest ecosystems and difficult terrain. The adoption of environmentally sound techniques requires additional skills and more qualified human resources.


Prior to the early 1970s, logging was carried out manually and impacts on the soil, the residual stand and hydrology were high. Bhutan has endeavoured to achieve high standards of environmental protection by adopting more appropriate management, road construction and harvesting techniques.

Bhutan’s development policies are aimed also at maintaining cultural values for its population, which is heavily dependent on the forests. The pursuit of these policies has required a limited amount of commercial forest exploitation in order to create revenues for national development.

Generally, Bhutan has been successful in achieving its environmental and social development goals, partly through the adoption of appropriate technology and techniques and partly due to a clear vision that has allowed decision-makers to follow a consistent course of action.


FAO. 1999. Environmentally sound forest infrastructure development and harvesting in Bhutan. Food and Agriculture Organization of the United Nations, Rome.

[4] US$1 = Nu 46

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