* International Forestry Consultant, BLUE OX FORESTRY, 9770 SW Vista Place, Portland, OR 97225-4251, USA, Tel. 503-292-9311, Fax 775-514-1088, E-mail: [email protected] or [email protected]
INTRODUCTION
In this paper, two apparently contradictory conclusions are drawn: First, that reduced impact logging (RIL) involves the application of technologies that have been known for many years and are utilized as a matter of common practice in many industrialized countries; and second, that RIL is something new, requiring both a new mindset and also a new approach to tropical forest management. It is hoped that the reader will be convinced that these assertions are true in spite of the apparent contradiction between them.
TERMINOLOGY
In forestry, a distinction is often made between ‘timber harvesting’ and ‘logging’. Logging generally refers to the process of felling and extracting timber from forests, whereas timber harvesting includes pre-harvest planning, technical supervision and post-harvest assessments that reflect concern about non-timber resource values and about the future state of the forest. The term ‘reduced impact logging’ however, has become essentially interchangeable in the vernacular with timber harvesting. ‘Reduced impact logging technology’ is a collective term that refers to the use of scientific and engineering principles, in combination with education and training, to improve the application of labour, equipment and operating methods in the harvesting of industrial timber.
A BRIEF HISTORY OF RIL IN THE TROPICS
Until after World War II, logging operations in tropical forests were for the most part unmechanized, relying largely on human and animal power. As such, they involved only small areas of forest and had little impact on the resource. Even so, some of the best early work on management of tropical forests emphasized the importance of careful logging to protect future crop trees. An example of this is the management system for teak developed by Sir Dietrich Brandis in Burma during the second half of the nineteenth century (Dawkins and Philip, 1998).
Beginning in the 1950s, industrial logging of tropical forests became widespread as the worldwide demand for timber increased dramatically due to the rapid postwar economic expansion. Mechanized logging technologies developed in industrialized countries were introduced into the tropics quickly, and both the scale of operations and their intensity changed substantially. Tropical foresters began to recognize that many industrial logging operations were leaving forests in a seriously degraded condition (Dawkins, 1958; Nicholson, 1958; Redhead, 1960; Wyatt-Smith and Foenander, 1962; Fox, 1968). Some authors, most notably Dawkins (1958), went so far as to suggest that selective harvesting of moist tropical forest might be incompatible with the goal of sustained-yield management because of the excessive damage to residual vegetation that resulted from mechanized logging. At the same time, other tropical foresters (Bruenig, 1957) had begun to develop and test prescriptions for mechanized logging that would minimize damage to residual vegetation and soils and thus foster sustained-yield forest management. Even so, comparisons over time by authors such as Fox (1968), Nicholson (1979), Ewel and Conde (1980), Marn and Jonkers (1982), Estève (1983), DeBonis (1986), Jonkers (1987), Hendrison (1989), and Bruijnzeel and Critchley (1994) suggested that as increasingly powerful machinery was being introduced into tropical forests, the scale of damage to residual vegetation and to soils was rising proportionally.
By 1992, when the United Nations Conference on Environment and Development convened in Rio de Janeiro, it had become clear that at least in some instances the mechanization of logging operations in the tropics posed a serious threat to long-term sustainability of the resource, particularly if impacts on non-timber values were added to the equation (Dykstra and Heinrich, 1992).
Around the same time, the first publications were appearing, in which the term reduced impact logging was used (Putz and Pinard, 1993). Somehow this term and its acronym “RIL” proved more broadly acceptable than ‘environmentally sound timber harvesting’, an alternative that was being promoted by the FAO Forestry Department (Dykstra and Heinrich, 1992). The Tropical Forest Foundation (TFF) introduced the related term ‘low-impact logging’ but this was not generally adopted by environmentalists who felt that ‘low-impact’ and ‘logging’ were mutually exclusive terms. The more neutral term reduced impact logging was picked up quickly and widely used, both in technical articles and in news releases. The concept of forest management technologies that reduced logging impacts resonated not only with foresters but also with the general public. Importantly, the concept also was supported by influential environmental organizations such as WWF and IUCN. As a consequence, RIL gained a legitimacy that foresters themselves could never have provided.
Also around this time, a concerted effort was underway on a variety of levels to assess the effectiveness of tropical forest management and to develop and implement guidelines to improve management practices. Influential publications stemming from this activity included Poore et al. (1989), ITTO (1990), Poore and Sayer (1990), FAO (1993a) and FSC (1994, revised 2000). Building on these efforts, a number of initiatives were undertaken to develop codes of practice for logging in tropical forests. Many of these codes of practice borrowed heavily from guidelines developed for Australian tropical forests during the 1970s and 1980s (Queensland Forest Service, undated; Ward and Kanowski, 1985). An early effort was the Fiji National Code of Logging Practice (Fiji Ministry of Forests, 1990), developed with assistance from the International Labour Office (ILO). By 1996, FAO had published a model code of forest harvesting practice (Dykstra and Heinrich, 1996), and this spurred a large number of tropical countries to develop their own codes of practice, often with assistance from FAO, the International Tropical Timber Orgainization (ITTO), the European Union, or bilateral development-assistance agencies such as GTZ (Germany), USAID (USA), AusAID (Australia), French Cooperation, DFID (UK), and others. FAO’s Regional Office for Asia and the Pacific subsequently worked with member countries of the Asia-Pacific Forestry Commission to develop the Code of Practice for Forest Harvesting in Asia-Pacific (FAO, 1999) and is also assisting with the development of national codes of practice as extensions to the regional code.
LOGGING IN TROPICAL VERSUS TEMPERATE FORESTS
In spite of very high biomass levels, tropical forests generally support much lower volumes of merchantable timber than temperate forests (Wadsworth, 1997). The volume of timber harvested from an average hectare of tropical forest worldwide is less than 30 m3 and usually involves 10 or fewer trees, each of which is a different species (FAO, 1993b). In Africa, some highly selective operations remove only one tree in 10 ha. By comparison, a typical operation in the coniferous forests of the Pacific Northwest of the USA extracts 500 m3/ha from 200-300 trees, most of which are a single species. As a consequence of the relatively low volume of merchantable timber harvested per hectare of tropical forest, the area disturbed by logging to obtain a given volume of industrial roundwood is substantially larger than in temperate forests. This means that logging operations in the tropics are spread over extensive areas, making them obvious to large numbers of people. Although spreading operations over large areas may reduce impacts on a per hectare basis, it can result in a greater total impact because of the many additional kilometers of skidtrails and roads that are required. One analysis comparing operations in West Africa with those in Europe found that the effective road density, measured in meters of road per cubic meter of roundwood extracted, was fifty times higher in the African operations than in the European operations (Dykstra and Heinrich, 1996). Perhaps more importantly, the many additional kilometers of road built into tropical forests to extract timber makes the forest more attractive for colonization.
An important demographic difference between temperate and tropical forests is that the latter are often populated, and the people who live in them depend upon the forest for their livelihoods. This was once true of temperate forests, but by the time mechanized logging was being applied in temperate forests, those forests had largely become unpopulated. It remains true in tropical forests, in spite of a worldwide trend toward increasing urbanization. Even remote areas like the forests of Borneo support relatively large populations of both indigenous people and migrants, and these people often make extensive use of non-timber forest products. For example, at CIFOR’s Bulungan Research Forest in East Kalimantan, Indonesia, a survey of several communities of Dayaks - forest-dwelling indigenous people who inhabit remote areas on the island of Borneo - indicates that of 383 plant taxa identified in the area, 236 (62 percent) are used in some way by the local people. Non-timber forest products (NTFPs) are the single most important source of cash income for these people, accounting for as much as 80 percent of an average household’s annual cash income (Wollenberg, 1998). Furthermore, a comparison with town dwellers suggests that the forest dwellers’ total annual incomes, including imputed values for the NTFPs they use, average almost one-third more than the average incomes of town dwellers who do not have regular access to forests. This indicates the importance of considering local populations and the potential impacts of logging on non-timber forest resources when planning forestry operations in the tropics.
A recent study in Cameroon (Nef, 1997) demonstrated that by avoiding timber species from which local people harvest NTFPs, timber companies might be able to gain the support of local populations and thereby avoid chronic theft and operational disruptions. There may be significant costs associated with such a strategy, however; in Nef’s study, 24 NTFPs used by local people were produced by tree species that were also used for commercial timber. Designating as ‘off limits’ to logging the 10 tree species considered most valuable as sources of NTFPs would, according to Nef’s analysis, reduce the company’s aggregate timber stumpage value per hectare by about 20 percent.
WHAT IS NEW ABOUT RIL?
To a large extent, RIL technologies that are being promoted for adoption in tropical forests have been developed in temperate forests and are utilized as a matter of common practice there. In this sense, they represent nothing new. Because of the differences between tropical and temperate forests, however, many of these practices require significant adjustment in order to be economically and technically viable in the tropics. Also, protection of non-timber values in areas where local populations utilize NTFPs requires considerable evaluation and planning.
Although it varies somewhat with the local situation, RIL in tropical forests generally requires the following (see, for example, Sist et al., 1998):
Pre-harvest inventory and mapping of individual crop trees.
Pre-harvest planning of roads, skidtrails and landings to provide access to the harvest area and to the individual trees scheduled for harvest while minimizing soil disturbance and protecting streams and waterways with appropriate crossings.
Pre-harvest vine cutting in areas where vines bridge tree crowns.
The use of appropriate felling and bucking techniques, including directional felling, cutting stumps low to the ground to avoid waste, and optimal crosscutting of tree stems into logs in a way that will maximize the recovery of useful wood.
Construction of roads, landings and skidtrails so that they adhere to engineering and environmental design guidelines.
Winching logs to planned skidtrails and ensuring that skidding machines remain on the skidtrails at all times.
Where feasible, utilizing yarding systems that protect soils and residual vegetation by suspending logs above the ground.
Conducting post-harvest assessments in order to provide feedback to the concession holder and logging crews and to evaluate the degree to which RIL guidelines were applied successfully.
Nearly all of these practices are common in temperate forests. Two that are not are the requirement for mapping individual crop trees, and the need for preharvest vine cutting.
Numerous studies have shown that mapping of individual crop trees is essential in tropical forests where only a small number of trees per hectare can be harvested commercially. Information on locations of individual crop trees can be used to locate roads, landings and skidtrails so that the crop trees can be extracted without disturbing soils in areas where no trees are to be harvested. In spite of efforts to develop improved systems for mapping individual trees (Hendrison, 1989), this remains both a logistical headache and a cost that is not readily accepted by operators. Nevertheless, recent analyses such as Holmes et al. (2000) indicate that this additional cost is more than offset by the benefits provided through the effective planning that the individual tree maps provide. Still, research is needed to streamline this process and to make use of recent developments in remote sensing that might reduce the cost of pre-harvest mapping.
Beginning with a rather important and influential paper published by Fox (1968), it has been recognized for a long time that pre-harvest cutting of vines can significantly reduce damage associated with felling in areas where climbing vines are present. Historically, a common procedure has been to cut all vines within a harvest block, regardless of whether the vines are associated with crop trees. It now appears that this is both unnecessary and wasteful; instead, vine cutting should concentrate in the area around individual crop trees and their neighbours, and often the cost can be reduced by coordinating this activity with pre-harvest inventory and mapping. It is also important to recognize that some vines are used by local people, and that certain vine species, such as figs, are important sources of fruit for wildlife.
As mentioned earlier, most RIL technologies have been developed in temperate countries and are applied there widely. In this sense, RIL is not new - it is simply the transfer of well-established technologies from temperate forests to the tropics. Because of the important differences that exist between temperate and tropical forests, however, the correct application of RIL in the tropics involves several new steps. The section that follows argues that some of these differences require both a new mindset and also a new approach to tropical forest management.
ISSUES IN RIL
Philosophical acceptance by foresters. Many foresters, often including those responsible for the education of forestry students in universities and technical institutes, consider logging to be a subject that should not be discussed in polite society (Dykstra 1994). Although most foresters recognize that harvesting is essential if income is to be generated from forestry investments, there is a tendency to treat the logging operation in the way farmers treat the slaughterhouse - hide it away in the hope that it will not disturb the customers.
There are at least three consequences of this tendency. First, logging operations seldom get the professional attention required and therefore are often poorly planned, improperly executed, and inadequately supervised. Second, foresters and forestry technicians frequently have little appreciation for the positive benefits of timber harvesting and only a vague, uncomfortable sense of the very real environmental hazards that are associated with logging operations. Third, foresters often come to believe that environmentally sound harvesting is impossible at a level of cost that will permit an economically viable forest industry. They are thus often willing to accept poor logging practices because the alternative does not seem feasible. This is partly due to the fact that few logging operations in tropical forests can truly be described as environmentally sound, so there is little opportunity to see such practices being applied. In addition, conventional wisdom holds that environmental protection always costs more, so it is generally assumed that RIL must be more costly than conventional logging.
The cost of RIL. The opposite holds true. Studies by Marn and Jonkers (1982), Hendrison (1989), and most recently by Holmes et al. (2000) have demonstrated conclusively that properly planned and supervised harvesting operations not only meet conditions for sustainability but also reduce harvesting costs by a substantial margin as compared to conventional logging. The difficulty is that these cost savings are due to better planning, better supervisory control and better utilization of felled timber. To obtain these savings, therefore, it is necessary to have technically competent planners, loggers and supervisors.
Training. The most critical single requirement for the successful application of RIL on a wide scale in tropical forests is the availability of skilled logging personnel at all levels. The fact that almost no tropical countries presently offer such training effectively dooms their forests to poor logging practices. Unless these countries and the development-assistance agencies that work with them begin to recognize this constraint and work to overcome it, there is little hope that timber concession holders will be able to implement RIL effectively on a large scale, simply because they will be unable to find skilled personnel who understand both why and how to carry out RIL. Efforts by organizations such as TFF to train loggers, planners and supervisors in Brazil and more recently in Indonesia have shown the way forward to overcoming the training vacuum, but this is a problem of enormous proportions that will require intensive, coordinated efforts on the part of government agencies, development-assistance organizations, and non-governmental organizations like TFF.
Active supervision of loggers. Well-trained loggers need equally well-trained supervisors to ensure that their work is carried out properly and to provide feedback that will help them to improve their practices continually. It is important that supervisors understand not only what to do and how to do it, but also why, and they must be able to communicate this understanding in an effective way. Supervisors must be on the ground every day, not confined to an office where they can only supervise by remote control.
Aerial logging systems. By adhering to the above requirements for RIL practices, virtually any type of logging machinery can reduce impacts as long as the operation is properly controlled and supervised. But it must be recognized that there is an optimal logging system for any given situation, and that a low-impact system in one situation might become a high-impact system in another situation. Most logging in tropical forests relies on ground-based skidding machines. Such systems can achieve acceptably low impacts when operators are trained properly and slopes are of low to moderate steepness. Unfortunately, in many forests, especially in developing countries, ground skidding is used even when slopes are very steep. Under such conditions, the environmental impacts associated with ground skidding are often unacceptably high. Aerial logging alternatives such as cable systems and helicopters can reduce direct impacts associated with ground disturbance during logging substantially, and because of their extended yarding capabilities can also reduce the density of haul roads needed to support logging operations. As most soil erosion associated with logging operations can be traced directly to roads and skidtrails, reducing the density of this infrastructure will lessen stream sedimentation and all its related offsite impacts, such as the siltation of reservoirs and irrigation ponds, high treatment cost for drinking water, and reduced fishery values. Unfortunately, both cable systems and helicopters require highly skilled crews and specialized knowledge that is often in scarce supply in developing countries. This emphasizes the need, again, for effective and widely available logger training.
Some RIL technologies are indigenous to the tropics. Several types of RIL systems are unique to tropical forests. The kuda-kuda system still used in some swamp forests probably exists nowhere outside the tropics, although the concept of moving logs along a ‘corduroy road’ of logs was often used in temperate forests until the middle of the last century. Although animal-powered skidding systems have been important historically in temperate forests, it is safe to say that logging with elephants and with water buffalo (carabao) has always been limited to the tropics!
Improving harvest recovery. Regardless of the type of logging equipment used, the amount of usable wood recovered from forest harvesting can be improved by reducing wood residues at all stages of production, from felling to skidding to transportation and final processing. In tropical forests particularly, improved utilization has tremendous potential for reducing the area of forest disturbed annually through timber harvesting. A study initiated by FAO (Dykstra and Heinrich, 1997) and continued by the Center for International Forestry Research (CIFOR) and the World Forestry Center (WFC) suggests that the volume of wood recovered from harvesting operations in managed tropical forests could be increased by perhaps 10-30 percent without a significant increase in harvesting cost. In fact, Dykstra and Heinrich (1997) argue that improved utilization in most situations should reduce harvesting cost (see also Holmes et al. 2000).
On the basis of the FAO-CIFOR-WFC study, Figure 1 shows how the area of tropical forest disturbed annually through harvesting operations might be reduced if utilization were improved. The scenarios assume that the demand for industrial roundwood is driven by population growth, and that a one percent increase in population results in a 0.75 percent increase in demand for industrial roundwood. Under this assumption, the expected world population of 8.9 billion in 2050 implies a level of demand for tropical industrial roundwood to the order of 453 million m3 per year.
Scenario 1. Three projections are shown in the figure. The upper projection line assumes no change in utilization standards as compared to the period 1961-1990. Under this level of utilization, 16.6 million ha of tropical forest would need to be disturbed in 2050 in order to harvest 453 million m3 of industrial roundwood. Compared to 2000, when the harvest of tropical industrial roundwood is approximately 195 million m3, this represents an increase of more than 130 percent in the area of tropical forest disturbed annually by timber harvesting.
Scenario 2. The middle projection line assumes an improvement in utilization of one percent annually beginning in 2001. Even such a modest improvement would result in a significant reduction in the area disturbed. In 2050, the area of tropical forest disturbed annually in order to harvest 453 million m3 of industrial roundwood under this scenario would be 11.1 million ha. Compared to Scenario 1, this represents a reduction of one-third in the area of tropical forest that would be disturbed each year by timber harvesting. Perhaps more importantly, the one percent annual improvement in utilization would reduce the total area of tropical forest disturbed over the 50-year period from 2001-2050 by almost 150 million ha. This is a huge reduction, equivalent in area to more than one-tenth of all of the world’s protected areas combined.
Scenario 3. For comparison, Figure 1 also shows the area of tropical forests that would have been harvested annually between 1961 and 2050 if the tropical harvesting recovery rate were equal to the utilization rate reported for the USA around 1990. Although far better than current practice in tropical forests, this level of utilization is judged by FAO experts to be achievable over the long run with reasonable improvements in training and management of tropical forest operations. As the figure indicates, a one percent annual improvement in felling utilization beginning in 2001 would result in a utilization rate around 2050 that is very close to the 1990 USA rate.
A reduction in the annual area of tropical forest harvested in the order of magnitude suggested by this analysis would benefit both timber and non-timber forest resources substantially. In addition, the improved utilization of felled timber would reduce forest residues significantly, thus decreasing the risk of destructive fires of the type that occurred during 1997 and 1998 in Brazil and Indonesia. There is little doubt that the large volume of forest residues left behind by past logging operations contributed to the destructiveness of those fires and to the large amount of smoke and haze that drifted over neighbouring countries for several months.
CONCLUDING REMARKS
This paper suggests that RIL is not a new concept because its technologies are generally well understood from many years of application in temperate forests. At the same time, it can be perceived as both new and different because of important dissimilarities between temperate and tropical forests that require a new mindset by logging operators and a new approach to tropical forest management. The new approach will have to recognize that tropical forests are places where people live, and will need to directly and specifically accommodate the many ways in which these people depend upon the forest for their livelihoods and their well-being. The new approach will also have to provide effective training for logging personnel and their supervisors if RIL is ever to become a widespread reality in tropical forests.
REFERENCES
Bruenig, E.F. 1957. Waldbau in Sarawak. Allgemeine Forst- und Jagdzeitung 128:156-165.
Bruijnzeel, L.A. & Critchley, W.R.S. 1994. Environmental impacts of logging moist tropical forests. IHP Humid Tropics Programme Series No. 7, UNESCO, Paris, France.
Dawkins, H.C. 1958. The management of tropical high forest, with special reference to Uganda. IFI Paper 34. Imperial Forestry Institute, Oxford.
Dawkins, H.C. & Philip, M.S. 1998. Tropical moist forest silviculture and management: A history of success and failure. CAB International, Wallingford, UK.
DeBonis, J.N. 1986. Harvesting tropical forests in Ecuador. Journal of Forestry 84 (4): 43-46.
Dykstra, D.P. & Heinrich, R. 1992. Sustaining tropical forests through environmentally sound timber harvesting practices. Unasylva 169: 9-15.
Dykstra, D.P. 1994. Teaching ecologically benign logging methods in the professional and technical-level forestry schools of the Asia-Pacific Region. Food and Agriculture Organization of the United Nations, Rome, Italy. FAO Forestry Paper 123 (report of the 17th Session of the FAO Advisory Committee on Forestry Education, combined with Regional Expert Consultation of the Asian Network on Forestry Education, 13-15 Dec 1993, Bangkok, Thailand). p. 164-180.
Dykstra, D.P. & Heinrich, R. 1996. FAO Model Code of Forest Harvesting Practice. Food and Agriculture Organization of the United Nations, Rome, Italy.
Dykstra, D.P. & Heinrich, R. 1997. Forest harvesting and transport: old problems, new solutions. Keynote presentation for Session 14 (Forest Harvesting and Transport) at the World Forestry Congress, Antalya, Turkey, 13-22 October 1997. Proceedings Vol. 3, pp. 171-186.
Estève, J. 1983. La destruction du couvert forestier consecutive à l’exploitation forestière de bois d’oeuvre en forêt dense tropicale humide africaine ou américaine. Bois et Forêts des Tropiques 201:77-84.
Ewel, J. & Conde, L.F. 1980. Potential ecological impact of increased intensity of tropical forest utilization. Biotrop Special Publication 11.
FAO 1993a. The challenge of sustainable forest management: What future for the world’s forests? Food and Agriculture Organization of the United Nations, Rome, Italy.
FAO. 1993b. Forest resources assessment 1990: Tropical countries. FAO Forestry Paper No. 112. Food and Agriculture Organization of the United Nations, Rome, Italy.
FAO. 1998. State of the World’s Forests 1997. Food and Agriculture Organization of the United Nations, Rome, Italy.
FAO. 1999. State of the World’s Forests 1999. Food and Agriculture Organization of the United Nations, Rome, Italy.
FAO. 1999. Code of Practice for Forest Harvesting in Asia-Pacific. RAP Publication: 1999/12. Food and Agriculture Organization of the United Nations, Regional Office for Asia and the Pacific, Bangkok, Thailand.
FAOSTAT. 2000. FAO Forestry Database. Food and Agriculture Organization of the United Nations, Rome, Italy. http://apps.fao.org/page/collections?subset=forestry.
Fiji Ministry of Forests. 1990. Fiji National Code of Logging Practice. Ministry of Forests, Suva, Fiji. (Plus a 7-page booklet on chainsaw use and safety).
Fox, J.E.D. 1968. Logging damage and the influence of climber cutting prior to logging in the lowland dipterocarp forest of Sabah. Malaysian Forester 31 (4): 326-347.
FSC. 1994, revised 2000. FSC Principles and Criteria. Forest Stewardship Council, Oaxaca, Mexico. Available at http://www.fscoax.org/principal.htm.
Hendrison, J. 1989. Damage-controlled logging in managed tropical rain forests in Suriname. Series on the Ecology and Management of Tropical Rain Forests in Suriname, Wageningen Agricultural University, The Netherlands.
Holmes, T.P., Blate, G.M., Zweede, J.C., Pereira, R., Jr., Barreto, P, Boltz, F. & Bauch, R. 2000. Financial costs and benefits of reduced impact logging in the Eastern Amazon. Tropical Forest Foundation, Alexandria, Virginia.http://www.tropicalforestfoundation.org/costbenefits.html
ITTO. 1990. ITTO guidelines for the sustainable management of natural tropical forests. Technical Series 5, International Tropical Timber Organization, Yokohama, Japan.
Jonkers, W.B.J. 1987. Vegetation structure, logging damage and silviculture in a tropical rain forest in Suriname. Number 3 in the series on Ecology and Management of Tropical Rain Forest in Suriname, Wageningen Agricultural University, The Netherlands.
Marn, H.M. & Jonkers, W. 1982. Logging damage in tropical high forest. In: Srivastava, P. B. L. et al., Editors, Tropical forests - source of energy through optimisation & diversification. Proceedings of an international conference held 11-15 November 1980 at Penerbit Universiti Pertanian, Serdang, Selangor, Malaysia. pp. 27-38.
Nef, R. 1997. Socio-economic impacts of forest exploitation on the livelihoods of local people in Southern Cameroon: Timber versus non-timber forest products. Master of Science thesis, Department of Forestry, Wageningen Agricultural University, The Netherlands.
Nicholson, D.I. 1958. An analysis of logging damage in tropical rain forests, North Borneo. Malayan Forester 21(4): 235-245.
Nicholson, D. I. 1979. The effects of logging and treatment on the mixed dipterocarp forests of South-East Asia. Report FO:MISC/79/8, Food and Agriculture Organization of the United Nations, Rome.
Poore, D., Burgess, P., Palmer, J., Rietbergen, S. & Synott, T. 1989. No timber without trees: Sustainability in the tropical forest. Earthscan Publications Ltd., London.
Poore, D. & Sayer, J. 1990. The management of tropical moist forest lands: Ecological guidelines, Second Edition. IUCN Tropical Forest Programme, publication no. 2. Gland, Switzerland.
Putz, F.E. & Pinard, M.A. 1993. Reduced-impact logging as a carbon-offset method. Conservation Biology 7(4): 755-757.
Queensland Forest Service. Undated. Guidelines for the selective logging of rainforest areas in North Queensland state forests and timber reserves. Queensland Forest Service, Brisbane, Queensland, Australia.
Redhead, J.R. 1960. An analysis of logging damage in lowland rain forest in Western Nigeria. Nigerian Forestry Information Bulletin (New Series), No. 10, p. 5-16.
Sist, P., Dykstra, D. & Fimbel, R. 1998. Reduced impact logging guidelines for lowland and hill dipterocarp forests in Indonesia. Bulungan Research Report Series No. 1, September 1998, Center for International Forestry Research, Bogor, Indonesia.
Ward, J.P. & Kanowski, P.J. 1985. Implementing control of harvesting operations in north Queensland rainforests. In: Shepherd, K. R., and H. V. Richter, Editors, Managing the tropical forest. Proceedings from a workshop held at Gympie, Australia, from 11 July to 12 August 1983. Development Studies Centre, The Australian National University, Canberra. p. 165-186.
Wadsworth, F.H. 1997. Forest production for tropical America. Agriculture Handbook 710. USDA Forest Service, Washington, DC.
Wollenberg, E. 1998. Unpublished notes for the “People and Forests” presentation at the CIFOR Public Forum, United Nations University, Tokyo, Japan, 10 April 1998; supplemented by personal communication. Senior Scientist (Local Forest Management), Center for International Forestry Research, Bogor, Indonesia.
Wyatt-Smith, J. & Foenander, E.C. 1962. Damage to regeneration as a result of logging. Malayan Forester 25(1): 40-44.
