Previous - Next
This is the old United Nations University website. Visit the new site at http://unu.edu
2.1.The environmental consequences of forestry and forest industries
Commercial forestry operations have both immediate and longterm physical impacts on the forest ecosystem and on its biological and physical environment. Not uncommonly, the impacts of the industry on the moist tropical forest ecosystem are severe. For the most part, the immediate consequences of forestry operations result from: the effect of harvesting (and in particular the "creaming" of the most desirable species) on timber-size trees; the effect of silvicultural operations on trees of all sizes; a reduction of plant biomass; soil disturbance; the increased exposure to sunlight, rain and wind; and the increased quantity of deadwood and debris left behind. The principal long-term environmental consequences of the industry are its effects on soil processes; impacts on hydrology; modification of climate and micro-climates; and changes in the carbon cycle and atmospheric oxygen.
Harvesting trees according to species and stem form and diameter causes an immediate change in the species composition of all remaining trees of harvestable size; a reduced population of the larger-sized, commercially valuable trees; and a relative increase in the number of large trees of unharvestable species. The volume of timber harvested and the proportions of the remaining species depends on the original species composition of the forest, the forestry technology employed and the efficiency with which operations are carried out.
In Southeast Asia only a small percentage of the standing stock of timber is harvested. In Malaysia this amounts to an average of only some 30 to 40 species, owing principally to the "creaming" of about a dozen preferred species with high commercial value, and to regulations limiting the minimum size class for harvesting.21 Only about 10-20 per cent of the available tall species in the moist tropical forest are regularly utilized by the timber industry, and this selective harvesting pressure is also applied to individual specimens within a particular species. The continued selective removal of the most valuable individuals detrimentally changes the specific and genetic composition of the forest and contravenes the basic principles of conservation for sustained yield.
The species composition of all sizes of trees is affected through forestry operations that use such selective treatments as poisoning, girdling, selective cutting for fuelwood or charcoal manufacture, and by clearing operations such as weeding. The longterm future composition and quality of a forest is affected by operations aimed at reducing the stock of species with little or no commercial value and thus to relatively increase the proportion of those species producing saleable timber. When damaged or poor quality individuals of the valuable species are also killed along with the species of low value, some eugenic effects in future forest regeneration may occur to counteract the possible dysgenic effects of selective harvesting, especially where selected seedlings are also used to effect forest enrichment. 22
Harvesting, weeding and opening the forest canopy by forestry operations causes a reduction in the total biomass of forest plants. This in turn causes an immediate alteration in the cycling and availability of water and soil nutrients. Felling, extracting and transporting logs and construction of the infrastructure for forestry operations and industries also disturbs the soil and disrupts hydrological systems. Watercourses may be blocked or otherwise disrupted, and erosion and landslides occur, particularly where fire, a common tool of tropical forestry, causes changes in the structure and nutrient status of the topsoil.
It is clear that among the major long-term consequences of forestry operations is the disruption of micro-climates. Changes in the physical and chemical properties of soils rates is a major interference in forest ecosystems and one that varies considerably depending. in particular, on the original fertility levels of undisturbed soils, local rainfall, degree of slope, and the rate of recovery of wild vegetation after large-scale disturbance.
Mechanical logging results in extensive soil damage through the use of heavy vehicles and log transport action. In East Kalimantan, with an intensity of log extraction of 25 trees per hectare, tractor paths amount to 30 per cent of the ground surface 23 Thus, physical damage such as compaction, structural deterioration and reduced aeration of the soil is widespread and is detrimental to seed germination and to the regeneration of logged-over forests. The tracts of bare soil left by forestry operations provide a nursery bed for pioneer species of the regenerating secondary growth. However, the species adapted to those habitats are not necessarily those of economic importance, and only a few species can grow in secondary growth on tractor trails. Moreover, the recovery of such tracts is extremely slow: evidence from Sabah indicates that 40-45 years are required after disturbance, assuming that seed supply is adequate and other factors amenable, for the normal species composition of the mature forest to reconstitute itself.24
Within a logged-over area the major categories of landuse prone to accelerated erosion and excessive run-off of surface waters are skidding roads, daylighting areas (cleared, safety areas along both sides of the access roads), and landing or log yards. In East Kalimantan some 4.2 km of road are needed to log 1 km2 of forest, and for a road 10 m wide a daylighting area about 80 m in width is required. On the concession of the International Timber Corporation Indonesia (East Kalimantan) alone, there are more than 500 km of logging roads (much more than the total length of the public road network in the province), with a total cleared daylighting area of some 40,000 ha. 25 Projected throughout the whole of Southeast Asia, the alarming extent of land disturbance and its resultant problems as a consequence of forestry operations is not difficult to envisage.
Forestry operations are a cause of major micro-climatic changes in soils, particularly in soil temperatures, as a consequence of increased exposure to sunlight and of burning, which is an important tool of tropical forestry. Under normal lowland moist forest conditions, temperatures in tropical soils fluctuate little, and usually remain between 23°C and 26°C. After logging they, may reach as high as 40°C. 26
Such greatly increased temperatures raise the evaporation rate of the soil and accelerate the rate of transpiration of seedlings. This may lead to such a degree of seedling mortality as to inhibit the regeneration of valuable species. Dipterocarps are especially hard hit by soil desiccation, since their seedlings require cool and moist conditions for germination.
Soil quality is also affected by the reduced uptake of water and nutrients from the soil, as a consequence of plant mortality, and by the increased volume of nutrients added to the soil by decomposing plant material and wood ash.
Relatively little is known about how human intervention in the humid tropical forest ecological system affects the atmospheric environment. From the limited available evidence it can be concluded, however, that partial destruction of the forest canopy leads to greater windspeeds and increased diurnal fluctuation of air temperatures, relative humidities and related characteristics, particularly in periods of clear weather. Seasonal fluctuations also increase, and with increased and persistent disturbance, the forest microclimate more closely resembles that of an open forest or even the external climate. Little research has directly analyzed the changes in the solar radiation environment as a consequence of forestry operations, but inferences can be drawn from measurements taken in different areas of humid tropical forest. Forestry operations that permit the entry of more solar radiation will tend to equalize the spectral composition of the radiation inside and outside the forest. Such changes may be partially responsible for alterations in the growth rates of understory plants and in the species composition of forests regenerating after disturbance. 27
Forest cover on a water-catchment area is an important regulator of seasonal streamflow, via the vegetation's capacity to facilitate infiltration of rain into the soil during the wet season and its slow release of stored water to maintain streamflow during the dry season. Removal of forest cover for alternative land use is known to have a serious impact on streamflow28 and a similar interference has been noted as consequence of logging operations. 29 Forest cover may reduce streamflow volumes because of water loss through evapotranspiration, evaporation and interception. Interception of rainfall over humid tropical forests, which has been calculated at 30-50 per cent of total rainfall,30 appears to be markedly reduced in more open canopies. Hence if the canopy cover is reduced by forestry operations. interception of rainfall and other water losses may be reduced and streamflow increased as a con sequence .
Destruction or degradation of forests is often followed by increased rates of water runoff, erosion, sedimentation and reduced streamflow in the dry season. Soil and nutrient losses through erosion vary greatly, depending on differences in soil type, topography, climatic regime and the technology employed in logging. Erosion problems are generally increased by ill-planned and poorly constructed logging roads, and when roads are built and used repeatedly during the rainy season.32 The sediment load and concentration of dissolved organic and mineral compounds in streams is increased by forestry operations. Although eutrophication of streams and lakes can be advanced by forestry operations, this is not yet generally regarded as a problem in humid tropical forest zones.33
Log skidding trails and hauling roads frequently cut across water courses, with little regard for local hydrology, and thereby often cause the formation of swamps and semipermanent ponds, which kills seedlings and mature trees alike. If widespread, this may be of considerable ecological and economic significance. More severe damage is reported for timber operations in Sabah, where the residual stock of one sample tract consisted of 68.2 per cent damaged trees.34
Regardless of how carefully felling is undertaken with the techniques employed at present, damage to surrounding vegetation will always ensue, since exploitable tropical high forest trees with a girth of 2.5 m have such large crowns that when felled they will damage or destroy surrounding vegetation over an area of at least 0,02 hectares.35 In East Kalimantan, for every 39 trees felled, the damaged area covers 0.78 hectares.36
Forestry operations and their various environmental impacts result in complex, interactive biological consequences that are still poorly understood. Primary forest species may decline if biologically mature trees are eliminated when no seeds are available for regeneration. They may also decline because forestry operations alter the relative competitive status of different species, particularly if enrichment planting with one or a few species accentuates the change in species composition. Fungal decay and insect attack are facilitated by the large quantities of dead wood and drying trees generated by logging and other forestry operations; yet the significance of this is not well understood. partly because so little is known about the functions of microflora and microfauna in relatively undisturbed forests. The biological consequences of forestry operations may be more severe for some life forms and in some niches than in others. For example, epiphytes dependent on bark conditions found in older trees may have their habitats severely reduced or eliminated. The faunal populations of the humid tropical forest all have their environments altered - some adversely and some for the better- by changes in the species composition and physical structure of the forest. And changes in animal populations may be of major importance for the pollination of flowers or the distribution of seeds. This, in turn, feeds back to affect species composition in all the ensuing stages in the forest succession.
Logging and the forest products industries in the humid tropical forests have major short- and longterm consequences on the forest itself, on its biological and physical environment and on the regenerative and interactive processes of plants and animals. More alarming perhaps than the direct threat of forest operations, which also produce clearly demonstrable social and economic benefits, is the acute shortage of scientific knowledge about the consequences of disturbance for the forests of the humid tropical zone. In many areas such knowledge is limited to just a crude understanding of the species composition of secondary regrowth plants.37 It is imperative that reliable quantitative information be quickly assembled, for as many different parts of the humid tropical zone as possible, on the consequences and importance of changes resulting from the disturbance of biologically mature humid forest ecological systems.
Pressures on the humid tropical forests have, in the last few years, been exacerbated by the increasing use of natural forests to provide pulpwood. Unlike selective logging for timber and veneer logs, clear-felling for the woodchips used in pulping means the virtual destruction of the forest ecological system. Clear-felling for pulpwood production should not be treated as a specialized form of forestry which harvests specific logs but rather as a form of land clearance for which distinct resource use guidelines must be established. Because of the speed and scale with which trees are removed to provide pulpwood there is little chance of natural regeneration and it is almost impossible to control logging or to organize replanting schemes in an area cleared for woodchips and then abandoned by commercial interests. 38
Chemical arboricides, defoliants and pesticides are widely used in the management of tropical forests to reduce unwanted tree and other plant species, to contain harmful pests and to control the vectors of human disease. They are also used in enrichment planting or stand improvement to open the forest canopy and permit more sunlight to reach the desired species, as well as for controlling the growth of vegetation along forest roads and trails, particularly in countries where labour costs are high and where rapid vegetation growth necessitates frequent plant clearance. Although the judicious use of chemicals offers practical advantages in forestry it does involve the now clearly-recognized risks of detrimental side-effects that may be harmful to non-target tree species, wild and domestic fauna, and aquatic habitats, and may endanger human life and health. Most arboricides are of relatively low toxicity for mammals, but since in many cases lethal doses have been established through laboratory experiments using rats and mice, they can offer only an approximate guide to the hazards involved for humans and fauna. Moreover, only a few experiments have been conducted in the humid tropical zone.
Experiments now underway on the dipterocarp forests of Sabah in connection with regeneration operations that involved the application of sodium arsenite indicate that destruction of the understory vegetation resulted in soil degradation and a high mortality of dipterocarp seedlings and that, as a consequence of dormancy and the increase of light availability through canopy openings, death of the seedlings of undesirable species cannot be guaranteed. The application of this herbicide did not appear to facilitate regeneration by accelerating the transition toward climax forest.
In some countries, chemicals are viewed as an essential tool of modern, sustained-yield forest management. Elsewhere the use of herbicides in forestry is less common or is restricted to selected uses where no herbicide may be applied aerially. Application may be either by spraying or by direct injection into undesired trees. Although more time consuming and expensive, particularly in terms of labour requirements, direct injections as opposed to aerial releases involves little risk to non-target organisms. Yet by taking the precautions prescribed for the handling and application of pesticides it appears that the use of arboricides poses little or no direct threat to humans and other organisms.
Pesticides are becoming more widely used in the humid tropical forest in connection with human health programmes. Sufficient data have not been accumulated to assess such pesticides' impact on forested areas, but it would probably be similar to that observed in savanna areas. The subject is complicated by the evolution of chemical-resistant strains of certain insects, particularly mosquitos; controlling them requires the application of pesticides such as DDT at levels higher than those believed to be safe for human drinking water and foodstuffs. As a consequence of such problems many programmes of pest control by chemical means are widely regarded as failures. Although DOT and other pesticides have found application in the tropical forest for insect control, their use is not as common as in temperate zone forests, nor is it as widespread as in agriculture.
Chemical pesticides have impacts on the biological and physical environment that are essentially ecological, physiological or chemical. It is therefore imperative that in the humid tropical zone research be conducted to assess the relative ecological importance and abundance of particular plant and animal species, as well as possible alterations in the metabolism, reproductive behaviour and other aspects of these organisms, whether the target or not of the application of chemicals. Information is also urgently required for the tropical environment on the persistence, degradation and accumulation of different pesticides in the various components of the humid tropical forest ecological system.
Damaged and undamaged residual trees are commonly removed by "artisanal foresters" for fuelwood and smallscale timber uses, particularly in the more populous and accessible areas. Undamaged trees, including those left as "core trees" to provide a source of seeds for the natural regeneration of economically valuable species, also die through their inability to adapt to changed ecological conditions and as a consequence of competition with more aggressive components of the secondary growth that compete for light, water and nutrients.
Seedlings and saplings are even more heavily damaged, being crushed by the falling crowns of the felled trees, covered by the fallen vegetation, or destroyed by tractors during yarding. Those that survive slightly damaged are prone to mildew attack in wet weather. In a study conducted on sample plots in Sabah, between 1966 and 1970, it was found that 60 per cent of a original seedling population of 47,814/ha was destroyed by logging operations.39
In addition to trees damaged beyond usefulness during forestry operations, considerable wastage of resources results from the excessive numbers of trees removed or destroyed in creating the physical infrastructure for the forestry operation, from the percentage of timber rejected in bucking, hauling and shipping, and from potentially harvestable trees that are left uncut. Wastage rates from these sources are estimated at 40 per cent in the Philippines and at 30 per cent in Indonesia.40
Destruction of the mature moist tropical forest through inappropriate forestry activities resulting in land clearance can also increase the incidence of diseases harmful to humans. Under undisturbed forest conditions, forest mammals are frequently infected with blood parasites and scrub typhus (Ricketsia tsutsugamushii). but man seldom contracts disease and endemic pathogens do little harm to normal hosts.41 But once the normal forest cycle is disturbed - or, in secondary forests, once animal species not adapted to the parasites or parasites not adapted to the forest commonly invade the area - the endemic phase of the disease becomes epidemic. The incidence of filariasis and malaria is also increased by forest clearance.42 The mature forest provides the habitat for Anopheles spp. mosquitos that are the vectors of parasites in animals; but after man's intervention in the forest these are replaced by A. maculates, a vector of malaria.
2.2.Impact of forestry in uplands and on linked resource systems
Forestry and forest industries are not inherently deleterious for the biological and physical environments and for traditional economies. But in the absence of strictly enforced national and international controls to ensure forest conservation for the sustained yield of timber and other economic and ecological benefits, logging operations, particularly those conducted in uplands and on steeply sloping terrain, invariably have deleterious consequences both for the former relatively undisturbed forest area itself and for linked ecosystems and resource systems at lower elevations. Thus forestry and forest industries contribute to the process of marginalization both in situ and in other parts of river basins and adjacent marine waters. However, large-scale, commercial forestry operations create niches for other resource systems, especially for shifting cultivation and artisanal forestry, which more often than not severely exacerbate the environmental degradation initiated by forestry operations and greatly accelerate the process of marginalisation. Hence in the absence of detailed data collected at specific periods during the different resource use stages of a sequent occupance, for many parts of Southeast Asia it is impossible to isolate the contribution of forestry to the process of marginalisation from that attributable to other resource systems, particularly shifting cultivation. On the other hand, forestry operations, especially when conducted as part of land clearance schemes for commercial plantations or commercial smallholder agriculture, as in Malaysia, have a far less deleterious impact. However, since their vegetation cover is more open, run-off rates and sediment loads are greater from plantations than from areas under undisturbed forest.
3. Implications for national development planning
The complex and multiple linkages between international and national development policies and the use and transformation of natural resources require more careful analysis and planning if development policies are not to deplete renewable resources further and continue to impoverish people living in marginal areas. As United Nations reports on environmental and natural resources have concluded for more than a decade, the purpose of a more integrated, multidisciplinary analysis of the potential long-term impacts of development policies on natural resource systems is intended "not so much to define and control the future," which is clearly impossible even with the most sophisticated analytical models and planning procedures, "as to establish present conditions and capacities to plan better the requirements of future population." UN officials argue that there is a need for greater awareness of the critical interactions between physical and socio-economic processes; diagnosis of current weaknesses and potentials in the functioning of these processes; and the planning of appropriate adaptations of economic activities, social institutions, value structures and patterns of living to ensure equitable and sustainable development in the longer term.43
The implications for how national development policies are formulated have been suggested by United Nations committees that have examined environmental and natural resource issues over the past two decades. They conclude that
1. More attention must be paid to potentially adverse effects
of international economic and political activities on the natural
resources of developing countries. Although individual developing
nations may have little direct control or influence over these
activities, a better understanding of the impacts could lead to
collaborative efforts to offset or mitigate them.
2. More attention must be given to critical or strategic
intersectoral relationships in national and sectoral development
planning. Although it is difficult, if not impossible, to
identify and control all of the interactions among sectors as
they affect natural resources, a better understanding of natural
resource systems within developing countries can provide planners
with better information by which to identify those relationships
through which the most serious and widespread impacts of
development policies may occur. Little is gained in national
development by undertaking projects and programmes in one sector
that produce adverse effects in other sectors or by pursuing
shortterm policies that lead to the long-run depletion of
renewable resources or the destruction of nonrenewable resources.
3. More attention must be given to programmes of human resource
development that have a direct impact on the use and
transformation of natural resources. U.N. reports point out that
the existence of interrelationships means that, in many
situations, improvements in one area may obviate the need for
investment in another area. For example, in Sri Lanka, when
people were taught the benefits of boiling water, education
proved an effective substitute for more costly and less-immediate
improvements in the quality of the water. In this case.
improvement in human capabilities constitutes a point of leverage
which substantially reduces the financial cost and administrative
burden of development programmes 44.The identification of
strategic interventions that change human behaviour patterns or
that set in motion other interactions to improve or transform
natural resources without extensive controls or investments lies
at the heart of the concept of transformational development.
4. More attention must be paid to non-economic variables in the
evaluation of national development projects, especially
large-scale capital projects that have serious impacts on natural
resources. Costbenefit analyses that do not consider impacts on
the natural resource base of a country and that do not value the
loss of nonrenewable resources may be misleading and inaccurate.
Moreover, projects must be designed in ways that allow for
changes or modifications as unanticipated and uncontrollable
adverse effects, especially those that affect the population
living in areas where such projects are located, become apparent.
5. Because all of the interactions and relationships in natural
resource systems cannot be easily identified and controlled,
development policies must give more attention to decentralized,
participatory forms of planning and management. UN analysts note
that frequently "local communities have a fuller
understanding of local conditions and the necessary
interrelationships between people, resources and the
environment."45 Decentralization requires
regional and local planning of development activities and greater
community participation in the management of natural resource use
and transformation.
Thus, it is to the roles of regional planning and household and community decision-making in the use, management and transformation of natural resources that Chapters 5 and 6 turn.
Notes
1 World Bank, World Development Report, 1980 (Washington, D C.: World Bank, 1980), p. 3.
2 Ibid, p 13
3. H. Santa Cruz, "The Three Tiers of 'Basic Needs' for Rural Development," Finance and Development, Vol 16 (1979), pp 2531, quote at p. 31.
4. Ibid., quote at p 25
5. For an elaboration of this section, see Kenneth Ruddle, 1981 "Pollution in the Marine Coastal Environment of ASEAN Countries," in: L S. Chia, and C. McAndrews (eds ), Frontiers for Development The Southeast Asian Seas. Singapore McGraw-Hill 1981, pp. 136 176; and Kenneth Ruddle. "Environmental Pollution and Fishery Resources in the Coastal Zone," In C H Soysa, et al (eds ), Man, Land and Sea Coastal Resource Use and Development in Asia. Bangkok: Agricultural Development Council, 1982, pp 15-35.
6. Smithsonian Institution, Office of International and Environmental Programs, Coastal Zone Pollution in Indonesia. A Reconnaissance Survey Washington, D C: Smithsonian Institution, 1974
7 R W Spears, "An Evaluation of the Effects of Oil, Oilfield Brine and Oil Removing Compounds," in: Proceedings AIME Environmental Quality Conference, 7 9 June, 1971 Washington, D C: American Institute of Mining, Metallurgical and Petroleum Engineers, 1971, pp 199-216
8 D E Wohischlag, and J N Cameron, "Assessment of a Low-Level Stress on the Respiratory Metabolism of the Pinfish (Lagodon rhomboides)," Contributions in Marina Science, Vol 16 (1967), Austin: University of Texas Press, pp 160-171, and T C Kloth and D.E Wohischlag, "Side Related Metabolic Responses of the Pinfish Lagodon rhomboides to Salinity Variations and Sublethal Petrochemical Pollution," Contributions in Manne Science, Vol 26 (1972), Austin: University of Texas Press, pp 125-137
9 Smithsonian Institution, op cit.
10 Ibid
11. E M Grant, "Notes on an Experiment upon the Effects of Crude Oils on Live Corals," Fiascends Notes N S.. Vol. 1 (1970), pp. 1-3; R E. Johannes, J Maragos, and S.L. Coles, "Oil Damages Coral Exposed to Air," Manne Pollution Bulletin, Vol. 3, No. 2 (1972), pp 29-30
12 U S Environmental Protection Agency (EPA), Studies and Investigations of the Fate and Effect of the Shell Oil Spill, Platform B. Block 26, South Timbalier Bay (Dec. 1 1970-Nov 30, 19711, Washington, D C.: EPA, Office of Water Programs, 1972.
13 D P. Finn, Y Hanayama, M.J Meimandi-Nejad, T. Piyakarnchana, and J N Reeves, Oil Pollution from Tankers in the Straits of Malacca: Policy and Legal Analysis. Open Grants Paper No 6, Honolulu: East-West Center, 1979
14 R Nuzzi, "Effects of Water Soluble Extracts of Oil on Phytoplankton," Proceedings, Joint Conference on Prevention and Control of Oil Spills 13 15 March, 1973 Washington, D.C: American Petroleum Institute, 1973, pp 809 813.
15 A Sommer, Attempt at a Global Appraisal of the Tropical Moist Forests Committee on Forest Development in the Tropics, Fourth Session, Rome, 15-20 November, 1976 (FO/FDT/76/4) Rome: FAO (mimeo ), 1976
16 Ibid
17 The environmental consequences of forestry and the future of tropical forests are discussed more fully in Kenneth Ruddle and Walther Manshard, Renewable Resources and the Environment: Pressing Problems in the Developing World, Tokyo and Dublin: The U.N University and Tycooly International Publishing Ltd.. 1981, pp. 20-70; and in Jose I D.R Furtado and Kenneth Ruddle, "The Future of Tropical Forests," In: G A. Knox and N. Polunin (eds ) Ecosystem Theory and Application, Chichester (U.K.): John Wiley (in press, 1983), respectively
18 Ruddle and Manshard, op cit.
19 D E Earl, Forest Energy and Economic Development Oxford The Clarendon Press, 1975
20 Ibid
21 J l.D.R. Funtado, "The Status and Future of the Tropical Moist Forest in Southeast Asia," In: C McAndrews and L S. Chia (eds.), Developing Economies and the Environment The Southeast Asian Expenence, Singapore: McGraw-Hill, 1979, pp 73 120
22. T J. Synnott, The Impact Short- and Long-Term of Silviculture, Logging and Other Operations on Tropical Moist Forests, Oxford: Commonwealth Forestry Institute (mimeo.), 1975
23 K Kartawinata, "Biological Changes after Logging in Lowland Dipterocarp Forest," In: Proceedings, Symposium on the LongTerm Effects of Logging in Southeast Asia (Bogor, Indonesia, June, 1975) Biotrop Special Publication No 3 Bogor: Biotrop, 1978, pp 27 34
24 W. Meijer. "Regeneration of Tropical Lowland Forest in Sabah, Malaysia, Forty Years after Logging," Malayan Forester, Vol 32 (1970), pp. 204 229
25 Z. Hamzah, "Some Observations on the Effects of Mechanical Logging on Regeneration, Soil and Hydrological Conditions in East Kalimantan," In Proceedings. Symposium on the LongTerm of Logging, op cit. pp 73 87
26. P W. Richards, The Tropica) Rainforest, London: Cambridge
University Press, 1966, Meijer, W., "A Botantist's View of
the Use of
Arboricides in Forestry in Sabah," In: Consenvation in
Tropical South
East Asia, lUCN Pub. N.S. No. 10, Morges: IUCN, pp 164-167
27 K A Longman, and J Jenik, Tropica/ Forest and its Environment, London: Longman Group, 1974
28 H C Pereira, Land Use and Water Pesources in Temperate and Tropical Climates, Cambridge: Cambridge University Press, 1973.
29 D.A. Gilmour, "The Effects of Logging on Streamflow and Sedimentation in a North Oueensland Rainforest Catchment," Commonwealth Forestry Review, Vol 50, No 1, (1971), pp 39 48; T C. Liew, "A Nole on Soil Erosion Study at Tawan Hills Forest Resenve," Malayan Nature Journal, Vol 27. Nos. 1-2, (1974), pp. 20-26.
30 A G. Clegg, "Rainfall Interception in a Tropical Forest," Caribbean Forester, Vol. 24, No. 2 (1963), pp. 75-79.
31. Ibid.
32. Synott, op. cit.
33. S.H. Kunkle, "Water-Its Ouality often Depends on the Forester," Unasylva, Vol. 26, No 105 ( 1974), pp. 10 16
34 D I. Nicholson, "An Analysis of Logging Damage in Tropical Rainforest, North Borneo," Malayan Forester, Vol 22 (1959). pp. 235-245.
35 H C Dawkins, "The Voiume Increment of Natural Tropical High Forests and Limitations on its Improvement," Empire Forestry Review, VoL 38 (1959), pp 173-180
36 K Kantawinata, "Keterangan tambahan tentang hutan di Kalimantan," Kompas, 27th July, 1974, cited in Hamzah, 1978, op. cit
37 Synott, op. cit.
38 L.J Webb, Ecologica/ Considerations and Safeguards in the Modern Use of Tropica/ Lowland Rainforests as a Source of Pulpwood: Example, the Madang Area, Papua New Guinea. Port Moresby Office of Environment and Conservation, Department of Natural Resources, 1977.
39 T.C. Liew, and F O. Wong, "Density Recruitment, Mortality and Growth of Dipterocarp Seedlings in Virgin and Logged-Over Forests in Sabah," Ma/ayan Forester, Vol 36 (1973). pp. 3-21.
40 H Adeli, "Timber Logging Waste," Benta Hasi/ Hutan II, (1973), p 564; and Anon. "Ikhtisar keadaan den perlusan industri kertas di Indonesia," Kebut. Indonesia Maret (1974), pp. 112-126, both cited in Hamzah, 1978, op. cit.
41. B L. Lim, L Muul.. and K S. Chai, "Zoonotic Studies of Small Animals in the Canopy Transects at Bukit Lajan Forest Resenve, Selangor, Malaysia," IBP Synthesis Meeting, Kuala Lumpur, 12 18 May, 1974
42 W.H Cheong, "The Changing Pattern of Vector-Borne Disease Transmission due to Ecological Changes Resulting from Development and Human Activities," IBP Synthesis Meeting, Kuala Lumpur, 12-18August, 1974
43 United Nations Social and Economic Council. Interrelationships Between Population, Resources, Environment and Development: Report of the SecretaryGeneral Doc No E/1981/65, New York: UNSEC, 1981, p 31
44 Idem.
45 Ibid p 32