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21. Reduced impact logging in Sarawak, Guyana and Cameroon - the reasons behind differences in approach - W.B.J. Jonkers*

* Wageningen University, Silviculture and Forest Ecology Group, P.O. Box 342, 6700 AH Wageningen, The Netherlands Tel: ++(31 317) 47 8035, Fax: ++(31 317) 47 8078, E-mail: [email protected]


Pinard et al. (1995) first used the term “reduced impact logging (RIL)” in 1995. They defined RIL as efficient timber harvesting, which is executed in such a way that damage to the forest ecosystem is minimized. The first efforts to reduce logging damage in the tropical rain forest date from the 1950s, when directional felling was introduced in the Philippines to avoid damage to potential crop trees (Reyes, 1968). In the same period, the first publications on logging damage in Malaysia appeared (Nicholson, 1958; Wyatt-Smith and Foenander, 1962). This led to the introduction of pre-felling climber cutting in the late 1960s (Fox, 1968). However, serious efforts to modify the complete logging operation with the dual aim to reduce damage and to improve efficiency were not undertaken in Southeast Asia until the late 1970s, and even later in Latin America and Africa.

The first true RIL system for tropical rain forests was developed in the late 1970s in Sarawak, Malaysia (Mattson-Marn and Jonkers, 1981). In the 1980s, other RIL systems were developed in Australia (Ward and Kanowski, 1985) and in Suriname (Jonkers and Hendrison, 1987; Hendrison, 1990). In the meantime, concern over continuing deforestation placed the need for improved management of tropical forests on the international political agenda. Consequently, RIL research really gained momentum in the 1990s. Many studies were initiated, for example in Indonesia (Bertault and Sist, 1995), the Malaysian state of Sabah (Pinard et al., 1995; Cedergren et al., 1994), Brazil (Johns et al., 1996; Blate, 1997), Guyana (van der Hout and van Leersum, 1998; van der Hout, 1999; 2000; Armstrong, 2000) and Cameroon (van der Hout and van Leersum, 1998; Jonkers and van Leersum, 2000; Jonkers, 2000; Durrieu de Madron et al., 1998). Furthermore, a code of practice was formulated, which applies worldwide (Dykstra and Heinrich, 1996).

Research results showed that logging damage can be reduced substantially, and that introducing improved logging techniques could be financially attractive for logging firms. However, most timber companies are reluctant to change their operations in spite of the favourable research findings (Putz et al., 2000a). Furthermore, RIL studies relate mainly to efficiency and costs, and to damage to vegetation and soil, which do not address fully the impediments to adoption. During the 1990s, many organizations made efforts to develop criteria and indicators for sustainable forest management and many of them are also relevant to logging. It may be that current RIL methods have to be adjusted to meet the requirements of sustainable forest management.

In this paper, four cases are discussed in which the author was involved directly: the RIL methods developed in Sarawak in the 1970s, in Suriname in the 1980s and in Guyana and Cameroon in the 1990s. This paper explains how and why these approaches differ from one another and what steps should be taken to improve them further as well as other methods. The methods are described briefly. For more complete descriptions, the references at the end of each case study can be consulted.


Case 1: Sarawak

The site

The Sarawak method was tested in a dipterocarp forest on undulating terrain, in a logging concession approximately halfway between the towns of Miri and Bintulu. The dipterocarp forests in Sarawak are generally richer in commercial timber than forests in Africa and South America, although the yield in this particular experiment was rather low by Malaysian standards of the 1970s. About 14 trees/ha were harvested, yielding about 54 m3/ha. Large commercial timber trees were scattered over the whole experimental site without an obvious spatial pattern, although there may have been a slight tendency to clumping. Before logging operations started, the area was uninhabited; the opening up of the area soon attracted a small number of settlers.

The method

Designing an improved logging method was one of the activities of a project implemented by the Food and Agriculture Organization of the United Nations (FAO). The project also dealt with silviculture, forest management and timber processing. Mattson-Marn, the project’s logging expert, had come to Sarawak to design a logging system which was less costly and more efficient than the existing methods, but reducing logging damage was not explicitly part of his terms of reference. Nonetheless, his method contained most elements used in more recent RIL methods:

Efforts focused on activities within the logging compartments and improvements in planning, and construction of roads and truck transport were not investigated.

The results

As a result of this planned way of working, logging costs per cubic meter extracted were reduced by 23 percent, which is due partially to lower skidding costs and partially because less timber had been wasted. Although the method had not been designed to reduce logging damage, the number of trees destroyed by logging had almost been halved.

Reference: Mattson-Marn and Jonkers, 1981.

Case 2: Suriname

The site

Suriname is a small country in South America. The Celos Harvesting System developed by Hendrison (1990) was meant for the “Forestry Belt”, a 40 to 120 km wide and 400 km long zone in the northern part of the country. The terrain is flat to undulating. The forest contains fewer timber trees than the Sarawak forest, and these trees are considerably smaller. Some 5-8 trees/ha are harvested, seldom yielding more than 20 m3/ha. The spatial distribution of commercial timber trees is usually random. The Forestry Belt is virtually uninhabited by humans.

The method

The Celos method was similar to the one developed in Sarawak, with the following modifications in felling and skidding:

The results

The results were comparable to those obtained in Sarawak: additional expenditures for surveys, planning and pre-harvesting operations added about 5 percent to the logging costs. This increase was more than compensated for by reduced skidding costs and improved efficiency. The Celos method also significantly reduced logging damage. The area under skid trails was reduced by about 50 percent to a mere 5 percent of the total area.

References: Jonkers and Hendrison, 1987; Hendrison, 1990.

Case 3: Guyana

The site

Forests in Guyana are, as in neighbouring Suriname, relatively poor in timber trees and log dimensions are rather small, usually less than 70 cm in diameter. Traditionally, logging has targeted mono-dominant groves of exploitable species in the forest, the most important being greenheart (Chlorocardium rodiei). Recently, the range of commercial species has been broadened by an increased demand for peeler species.

Several RIL studies have been conducted in Guyana, but only the activity at the Tropenbos site near Mabura Hill is discussed here. Logging in this concession, although influenced by an increased marketability of lesser-used species, still focuses on greenheart. Because this species is limited to certain parts of the forest, selective logging is disturbing the landscape in a patchy fashion. Although the average yield is not higher than in Suriname, exploitation locally can reach 20 stems/ha or 60 m3/ha. The terrain in the study area is almost flat. Like most forested regions in Guyana, the area is almost uninhabited by humans. The population of the only settlement nearby, Mabura Hill, consists almost entirely of the personnel of the timber company and their families.

The method

Logging was confined to those parts of the forest where greenheart was present. The method was adapted from the one developed by Hendrison (1990) in Suriname. The most important modifications were:

The reason for the last two adaptations of Hendrison’s method was the high local logging intensity. In Suriname, there was usually ample space for the skidder to manoeuvre in case a tree had been felled in the wrong direction or in case of other unforeseen obstacles. In Guyana, however, much more timber and logging debris remains on the forest floor after felling, thus reducing the manoeuvring space of the skidder. Felling trees in the same direction and allowing the skidder operator to adjust the course of a trail if necessary allows operators to avoid obstacles.

The results

Again, RIL reduced the area under skid trails by about 50 percent. The number of trees damaged by skidding was reduced by the same percentage. Felling damage was not reduced, however, and may even be more severe than in conventional operations if felling intensity is high. This is because in conventional logging, trees are more likely to be felled into existing felling gaps, thus creating less damage but larger canopy openings. Research had shown that such multiple tree gaps are not favourable for regeneration of commercial species; nevertheless, they were preferred to avoid large gaps.

The costs per cubic meter extracted under RIL were slightly less than under conventional logging. The difference would have been more substantial if the same felling limits had been applied in both methods.

References: van der Hout and van Leersum, 1998; van der Hout, 1999; 2000.

Case 4: Cameroon

The site

Two RIL studies have been conducted in Cameroon, but only the Tropenbos study is discussed here. The Tropenbos site is located in the southwest of the country. The physiography is undulating in parts, but more often hilly or mountainous and highly dissected. An important difference from the other three cases is that people reside in the area. They practice shifting cultivation, hunt and gather non-timber forest products. Population density is about 7 persons/km2. Easily accessible parts are used mostly for shifting cultivation, and logging has to be practised mainly in difficult terrain. The forest differs in many respects from the forests in Sarawak, Suriname and Guyana. The high number of tall emergent trees with trunk diameters of 1 to 2.5 meters or more (about 7/ha in the logging experiments) is remarkable. Only a few of these giants belong to marketable species, and the average logging intensity is well below one tree/ha. Only very large trees are cut, and the average volume extracted is about 10 m3/ha. As in Guyana, the bulk of the production comes from one species, in this case azobé (Lophira alata). Large azobé trees as well as some other timber species tend to clump, but seldom stand close together. Felling tends to be concentrated in such clumps, and substantial parts of the forest are not affected by felling.

The method

The RIL method developed by the Tropenbos-Cameroon Programme is again based on the method of Hendrison (1990) described above. The following adjustments were made:

The first adjustment was made because medium-sized and small trees of commercial species are relatively scarce and often occur in groups. This makes it highly desirable and feasible to reduce the damage caused by falling stems. Furthermore, it is less critical to pay special attention to avoiding large gaps. Under the prevailing harvest intensity, multiple tree gaps are rare and some timber species regenerate poorly in small gaps. This does not apply to most timber species, however, and preferably, felling should not lead to gaps exceeding 1 300 m2.

The results

At the onset of the project, there was doubt if directional felling and winching would be feasible, given the large tree sizes and the heavy weights of the logs. However, it appeared that winching over distances up to 20 m was applied already in conventional logging to recover logs on steep slopes. Furthermore, the experienced felling instructors could direct virtually all trees to be felled in any direction within 90° of the tree’s natural lean. Although the local fellers were less successful than their trainers in this respect, felling damage to trees of commercial species could be reduced by more than 40 percent.

In conventional logging, the area under skid trails was only 4.3 percent. With RIL just a modest reduction to 3.9 percent could be realized. More important is that after RIL skidding, part of the vegetation had survived on 47 percent of the trail length, compared to 29 percent after conventional logging. These parts of the trail network had been used for the extraction of one or two felled stems only, and are likely to recover more rapidly than other sections because some vegetation remained and because the soil had been less compacted.

A difference in costs between RIL and conventional logging could not be demonstrated, although the RIL method is probably somewhat less expensive.

References: van der Hout and van Leersum, 1998; Jonkers and van Leersum, 2000; Jonkers, 2000.

Discussion and conclusions

All four methods discussed lead to reductions in damage to vegetation and soil, higher recovery of usable timber and safer working conditions. Furthermore, they do not require major investments. The RIL methods discussed are remarkably similar. Differences in approach relate mainly to differences in logging intensity and forest composition. This probably applies also for most other RIL methods.

Some issues, like incentives for logging operators to stimulate them to produce quality work, still need to be resolved. Otherwise, the methods are ready to be implemented by the logging companies. Further technical refinements are certainly possible. For instance, use of the global positioning system (GPS) can improve the accuracy of mapping and planning. These are not the most important issues for the near future, however. Two crucial questions remain:

Acceptance by the industry

There are many explanations for the reluctance of the timber industry to accept RIL (Putz et al., 2000a), but none apply to all companies. Some relate to constraints in introducing new methods. Change always brings unexpected problems and costs, which may outweigh financial gains in the short term. Furthermore, improvements in mapping and planning mean extra office work and more coordination, supervision and communication, and therefore a change in the logging company’s organization, which may be quite fundamental.

Many timber companies also doubt the profitability of RIL after the introduction period. When improved logging techniques are combined with other measures to achieve sustainable forest management, RIL may indeed be more expensive (see Tay et al., this volume). Examples of such measures are the application of higher felling limits or restricting logging in parts of an area for environmental and other reasons. Introducing such elements may be good forest management, but may lead to higher costs. Applying RIL without such additional prescriptions will generally be less costly than conventional logging.

Another explanation is that conventional logging has at least one important advantage for timber companies in comparison to RIL. The prime objective of timber companies is to maximize profits from timber processing and timber sales. Hence, they want to be able to respond flexibly to changes in timber prices and orders from buyers. Timber prices fluctuate considerably and unpredictably. It is therefore difficult to predict if logs of lesser quality can be sold or processed profitably. This applies also to good-quality logs of tree species that yield low-priced timber or are less in demand. In conventional logging, timber companies respond to poor market conditions by leaving trees for which there is no demand uncut, and return later, when market conditions have improved, to the same tract of forest to harvest the remaining timber. This flexibility is not foreseen in RIL. An assumption of RIL is rather that all timber is removed in one single logging operation, as re-entry always causes extra damage and costs. One may of course consider allowing re-entry under specified conditions, but it would be better if the problem could be resolved through better marketing, long-term sales contracts and other market-oriented strategies.

Aspects of sustainable management

Sustainable rain forest management has to meet many ecological, social, economic and technical criteria. As RIL is supposed to contribute to sustainable forest management, it is logical that RIL has to comply with these standards also. RIL research has focused so far on efficiency and reduction of damage to vegetation and soil. In addition, safety aspects and the impact of gap size on regeneration of timber trees have been taken into consideration. Some important aspects, which have received little attention so far, are discussed below.

Impacts on wildlife

There are many studies on ecological impacts of logging, such as consequences for floral and faunal biodiversity, but these studies were seldom in relation to RIL (Putz et al., 2000b). Although it is likely that RIL’s impact on biodiversity is lower than conventional logging, the impact on fauna requires more attention. Logging affects fauna indirectly through hunting (Bennett and Robinson, 2000), because it opens up the forest for hunters and because of hunting by logging personnel. Direct impacts include damage to vegetation (changes in microclimate and availability of food plants) and habitat disturbance caused by the mere presence of logging personnel and the noise of machinery. The last aspect, which affects especially the larger mammals, is documented poorly. At the Tropenbos site in Cameroon, Bagyeli pygmies and other hunters complain that larger game is chased away by the noise of logging operations, and that it takes many years for populations to recover (van den Berg and Biesbrouck, 2000), which is supported by other, yet unpublished evidence (van Dijk, pers. comm.; Tovar, pers. comm.). In fragmented forest areas surrounded by shifting cultivation, game may even disappear forever.

RIL does not reduce hunting pressure, but it diminishes damage to vegetation and it also reduces the duration of the entire logging operation. The impact on fauna should be reduced further by preventing logging operations from being executed concurrently over large continuous areas, that is, by ensuring that the animals have a place to where they can flee and from where they can return after logging has been completed.

Social impacts

Social impacts have been neglected in RIL research. Where logging operations are in uninhabited areas this is justified, as the only social function of logging is providing employment. However, most logging companies have to deal with local people, who also use the forest, inter alia, for hunting and gathering of non-timber forest products. Logging interferes with the lives of villagers in both positive and negative ways. Logging roads make it easier for them to trade and travel. The company may also provide some employment and compensation for inconveniences caused by logging. These benefits are offset by substantial social and direct financial costs. During the harvesting operations, it is not safe for the villagers to enter a forest where logging is in progress; thus, their access to forest resources is reduced. The aforementioned impact on fauna also has social consequences. At the Tropenbos site in Cameroon, wildlife provides virtually all of the proteins for the local population (van Dijk, 1999), which means that continuous access to the forest is vital. This illustrates that social aspects have to become an integral feature of RIL planning, and that this planning should be discussed with the people to ensure their interests are taken into account adequately. Logging should be planned in such a way that individual villages always have access to a considerable part of the forest. Furthermore, prescriptions for directional felling may have to be adjusted to preserve treesthat produce non-timber forest products.

Yield regulation

A basic assumption of sustainable management is that the amount of timber harvested per year is equivalent to the potential annual volume increment. This means that the allowable cut should be integrated in RIL planning. When the methods discussed in the case studies were developed, growth and mortality data were insufficient to assess the allowable cut with satisfactory accuracy, although yield prediction models were developed by the Sarawak and Cameroon projects (Jonkers, 1982; Eba’a, 2000). Reliable data from growth and yield experiments established in the 1970s in Sarawak and Suriname now exist, and introducing the allowable cut in the RIL methods concerned is therefore possible and recommendable. In Sarawak, steps in this direction have been undertaken already (see also Ago Dagang et al., this volume). Diameter limits set for trees to be logged should well exceed the size at which the species flowers for the first time, and be at least 20 cm below the maximum diameter at which the species starts to develop unacceptable decay, even if the yield prediction model suggests otherwise.


This paper is based on results of projects executed by FAO and the Sarawak Forest Department (Sarawak), Celos (Suriname), Wageningen University (Suriname, Cameroon), Institut de Recherche Agronomique (IRAD) (Cameroon) and Utrecht University and the Guyana Forest Department (both Guyana), in collaboration with their industrial partners. The projects received financial support from the Tropenbos Foundation (Cameroon, Guyana), the United Nations Development Programme (Sarawak), the International Tropical Timber Organization (ITTO) and the Common Fund for Commodities (Cameroon). The author would like to thank these organizations, and the numerous individuals who contributed to the success of the projects concerned.


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[26] This phenomenon is not unique to Suriname. The author also observed it in Peninsular Malaysia, when visiting the logging experiment of Wyatt-Smith and Foenander (1962) in 1977.

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