L.S. Hamilton
Lawrence S. Hamilton is Research Associate al the Environment and Policy Institute. East-West Center, Honolulu. Hawaii.
Note. This article is based on a paper prepared for a meeting of the Tropical Forests Task Force of the Pacific Economic Cooperation Council, Kuala Lumpur, 25-29 September 1990.
This article holds up for scrutiny eight forestry issues that are currently making headlines. Several of them are based on myth, misunderstanding, misinformation or misinterpretation. Nevertheless, they must he dealt with, not simply to dispel any misinformation, but to clarify and to try to identify problems and valid solutions and opportunities. The article does not attempt to place the blame or responsibility for the origin of these myths, a number of which originate in forestry itself. The point is that to identify the real targets and problems so that progress can he made in tropical forest conservation, governments, the media, environmental groups and, not least, the forestry profession must he helped to eschew these slogans, repetitive claims, misdirected solutions and panaceas.
All too often statistics on the extent of tropical forests and the rates of deforestation or alteration are followed by a narrative that deals almost entirely with tropical rain forests. This would appear to be deliberate, since rain forests stir the emotions more than their more prosaic cousins. Hardly anyone can view or experience them with equanimity, or refrain from verbal excesses. They have been described as dangerous and impenetrable jungles of dank vegetation inhabited by fierce beasts, on the one hand, and as verdant Gothic cathedrals with clear expanses between trees, comfortably smelling like a well-tended greenhouse on the other (Colinvaux, 1979).
Indeed, it is the tropical rain forests that serve as the great storehouses of biological diversity, exhibit the diversity-rarity complex that leads to the ready extinction of species; have soils which are usually unsuited to sustained agriculture after clearing: have the greatest number of unknown species: and so forth. It is a mistake, however, and mischievous, to lead readers or listeners to assume that the rates of clearing or alteration for all tropical forests apply to tropical rain forests, or that all tropical forests have infertile soils that become hard red deserts (as a result of laterization) when cleared. Statements implying that the heavy impact of felling for fuelwood is a major source of tropical rain forest destruction are nonsense, although they may be true of tropical dry forests. Statements such as "following wood harvesting the land remains bare of trees for decades, or needs artificial planting to restore cover", are simply untrue for evergreen rain forests. In most of the ones I have encountered, one can hardly jump out of the way before green woody perennials engulf the scene (except on compacted landings and logging roads - as discussed later in this article).
We need to use more precise descriptors, remembering that there are many kinds of tropical forests, each with its own set of problems and opportunities: mangroves; cloud forests; riverine forests; woodlands; tropical dry forests; seasonal tropical forests; evergreen tropical rain forests, etc. It is more than a matter of semantics, for we must seek solutions to specific problems.
A good argument can be made for the elimination of the word "deforestation" from our vocabulary. It has no generally accepted definition. It has been used to indicate the consequences of a multitude of actions: fuelwood cutting; commercial logging; shifting cultivation; forest clearing; and conversion to annual cropping, grazing, horticultural tree crops and forest plantations; grazing or burning in existing forest: flooding with reservoirs; gathering non-wood forest products; and the killing of wildlife (Bowonder, 1982). Each of these activities has different biophysical and socioeconomic effects, and each is initiated by a varying mixture of socio-economic forces, yet we label all of them "deforestation" and look vainly for a simple panacea to solve the problem (Hamilton, 1988a). We read that "deforestation" results in accelerated erosion; catastrophic floods; dried-up springs, wells and streams; decreased rainfall; reservoir sedimentation; savannah and desertification; landslides where none occurred in the undisturbed forest; loss of biodiversity; large releases of carbon dioxide and methane that accelerate global warming; and so forth. Moreover, it is always referred to as an undesirable action with evil consequences, yet the productive, sustainable, hydrologically benign, terraced paddy systems of Southeast Asia are unquestionably the result of "deforestation".
A single, ambiguous word is not appropriate for such disparate actions as clearing land with bulldozers and other heavy equipment and planting a monocultural annual crop, and cutting and harvesting rattan or even timber (of which much original forest vegetation consists). Instead, let us describe the exact nature of the activities responsible for changes in forest conditions, whether they be desired or undesired.
In spite of the frequency with which logging is blamed for the loss of tropical rain forests, it is not a general truth; moreover, it diverts attention from the real causes and, therefore, from the solutions. Statements affirm that the decrease in forest area in Thailand from 70 percent of land area in 1950 to 18 percent in 1989 was the result of logging (The Economist, 1989). Nonsense! It was caused by a combination of planned and spontaneous clearing of forest for rice and cassava production. In the tropical dry forest, because of minimal reproduction, improper logging alone may result in deforestation, but in tropical rain forests it is surely the actions of burning, grazing and cropping, with or without prior logging, that result in the loss of forest.
Certainly, commercial logging as it is commonly carried out cannot be considered benign: it can temporarily eliminate the habitats of many primary forest species; it can result in increased landslips, greater surface erosion on the trails, roads and landings, consequently increasing short-term sediment discharges; and it can adversely affect the livelihood of indigenous forest dwellers. Logging roads that give greater access to the forest provide the landless as well as the speculators with an easier route to land occupancy or control, and hence clearing. But landlessness and land speculation must be faced as problems in their own right, and not overlooked in the process of blaming the loggers. Attention must be directed to these root causes of forest loss.
Many newspaper and journal articles (even in scientific publications) have blamed devastating floods on logging or fuelwood cutting in upper watersheds (Openshaw, 1974; Corvera, 1981). Typical of these was an article in Asia 2000 (Sharp and Sharp, 1982) which stated: "overlogging is now officially recognized as the cause of the July 1981 severe flooding of the Yangtze" in China. Reporting on the Bangladesh floods of August 1988, which killed 1 600 people and left 30 million homeless, an article from the Knight-Ridder news service (Kaufman, 1988) was entitled "Bangladesh flood disaster blamed on deforestation", and it went on to say: "By almost all accounts, the main environmental problem is the widespread and growing deforestation of the Indian and Nepalese mountains to the north of Bangladesh."
In both of these cases, the flooding was caused by unusually heavy or prolonged rains that exceeded soil water-storage capacity and the ability of streams and rivers to contain the extra volume without overflowing their banks. These were major monsoon rains, cyclones or unusual storms where the presence or absence of logging, or even the presence or absence of trees, would have had only a negligible effect on the downstream flood level of a major river (Hamilton, 1987, 1988b). But if it is said often enough that logging or "deforestation" causes major floods, it will be believed and may influence major policies. An example is the prohibition of logging in Thailand, instituted after the terrible flooding and consequent damage from sediment in the southern portion of the country in November 1988 (Nation, 1989). In reality, as pointed out by Rao (1988), almost all of the landslips occurred not on logged land, but on cleared land, much of it consisting of young rubber tree plantations on steep slopes which received rains of between 450 and 1 000 mm in two days. A subsequent mission, fielded by the Economic and Social Commission for Asia and the Pacific, confirmed Rao's observations (ESCAP, 1988).
A logging ban may be a temporary measure of some value; the pace of logging has been so rapid and the problem of illegal cutting so rife that a temporary respite can allow time for the development of better policies with respect to parks and reserves, and the control of logging concessions. However, the cessation of logging in Thailand increased pressure on the forests of its neighbours (such as Myanmar), who have even less capacity to control poor logging practices or illegal logging. The selective prohibition of land clearing on critical sloping areas would have been a much more appropriate response.
Erosion in various tropical moist forest and tree crop systems (tonnes/ha/year)
|
|
Minimal |
Median |
Maximal |
|
Multistoried tree gardens (4 locations, 4 observations) |
0.01 |
0.06 |
0.14 |
|
Shifting cultivation, fallow period (6 Locations, 14 observations) |
0.05 |
0.15 |
7.40 |
|
Natural forests (18 locations, 27 Observations) |
0.03 |
0.30 |
6.16 |
|
Forest plantation, undisturbed (14 locations, 20 Observations) |
0.02 |
0.58 |
6.20 |
|
Tree crops with cover crop/mulch (9 locations, 17 Observations) |
0.10 |
0.75 |
5.60 |
|
Shifting cultivation, cropping period (7 locations, 22 Observations) |
0.40 |
2.78 |
70.05 |
|
Taungya cultivation (2 locations, 6 observations) |
0.63 |
5.23 |
17.37 |
|
Tree crops clean-weeded (10 locations, 17 observations) |
1.20 |
47.60 |
192.90 |
|
Forest plantations burned/litter removed (7 locations, 7 observations) |
5.92 |
53.40 |
104.80 |
Source: Wiersum (1984)
There may indeed be increased stone flow volumes and peaks in streams emanating from a logged area during small, frequent storms, and local flooding can have adverse effects on people, infrastructure and land use, especially if desirable water management practices are not instituted on tracks, roads and landings. However, as storms increase in intensity and longevity, and as one moves farther down the watershed into increasingly large basins and river systems, the effects of logging dwindle to insignificance with respect to major floods from unusual storms (Hamilton and King, 1983).
Much popular and quasi-technical writing about tropical forests dwells on the importance of the tall tree canopy in reducing the impact of falling rain and thereby protecting the soil from erosion (MacKenzie, 1983). The theory on which this argument is based is sound, for reducing the kinetic energy of rainfall by inserting a barrier can reduce particle detachment and subsequent displacement by splash erosion. On slopes, splash erosion can initiate sheet erosion, then channels (rills) and substantial downward soil movement.
The problem is that the tall tree canopy is not effective in reducing the energy of falling rain. If the distance from the canopy to the ground is more than about 10 m, the raindrops achieve terminal velocity again after interception, and the leaves cause the rain to coalesce into larger drops which then have an even greater impact. For instance, Albizia falcataria (now Peraseriathes falcataria), with a canopy height of 20 m, yielded drops with an erosive energy equivalent to 102 percent of rainfall on open ground; Anthocephalus chinensis, with its large leaves, gave 147 percent energy with a canopy height of only 10 m (Lembaga Ekologi, 1980). Mosley (1982) found that the total kinetic energy of rainfall per unit area at the ground was greater under a New Zealand rain forest than in the open.
Studies have shown that it is the leaf litter, humic horizons and low understorey that provide protection from erosion (Wiersum, 1985). If these are removed, the presence of trees alone will not prevent surface erosion on slopes. For example, it is common practice for Nepalese, Indian and Bangladeshi hill farm families to gather forest litter for livestock bedding and fuel. This practice increases the risk of surface erosion, the reduction of which was one of the reasons for the development of efforts aimed at afforestation. Recognition of this problem has led the Nepal-Australia Community Forestry Project to promote the practice of frequent prunings rather than the collection of the annual leaf or needle fall on the ground surface. Wiersum (1984) has synthesized much of the research literature on erosion under various forest and tree crop systems and has presented a table of averages (see Table). It is noteworthy that as soon as the litter is removed, the erosion rate increases substantially.
It is important, therefore, to focus on ground-level activity, rather than observing the crowns. If we are worried about surface erosion and sedimentation, for instance, it is not the tree cutting that is the problem, but what happens to the ground cover when tree products are extracted. Thus, in this arena too, it is easy to misidentify the cause of the problem because of the rhetoric and, therefore, fail to come up with the appropriate remedy.
However, it must be pointed out that the simple cutting of trees can increase another kind of erosion - shallow landslips. If the species cut does not coppice and keep its root system alive, the result can be a lower shear strength of slip-prone soils. A greater incidence of shallow slips has been reported by O'Loughlin (1974) and O'Loughlin and Ziemer (1982) in cut, as opposed to uncut, forests. Fortunately, there are ways of predicting which slopes and soils are prone to mass movement, and these areas should be left largely undisturbed.
Agroforestry has many potential benefits. Particularly for small-scale upland farmers, it can help ease resource pressure, provide needed products, supply cash and permit crop improvement. When properly instituted it can also help to stabilize shifting cultivation, thus relieving pressure on natural forest.
However, it has been claimed by some promoters that the addition of trees to the system will automatically control erosion, reduce floods and restore low stream flows in the dry season. Not so! Short-statured agroforestry trees can indeed reduce the impact of splash erosion beneath their crowns, particularly if the leaves are not large. They can also provide leaf litter which has the potential to protect the surface. But if the litter is removed to prevent it from interfering with the undercrops, there is no benefit derived. It will be largely the undercrop and soil management practices that reduce surface erosion, not the trees themselves.
In basins where soils are compacted over large areas as a result of overgrazing, or in heavily eroded lands, the introduction of agroforestry systems to the rural parts of such watersheds could assist in reducing overland flow, but only if sound soil and water conservation measures are applied to the other components of the system to improve infiltration capacity. Counteracting this, however, is the fact that deep-rooted trees make a demand on soil water during the dry season, possibly "robbing" the base flow to streams. The establishment of trees in cropland or grazing land can lower groundwater levels, a fact which surprises many. Yet it is precisely this phenomenon that is responsible for the promotion of agroforestry in areas where rising saline water tables following land clearing have presented problems which must be reversed (e.g. in the Western Australia wheat belt).
At first, timber-exporting governments, foresters and tropical land-use experts were inclined to dismiss the environmentalist call for a boycott of tropical timber imports as an aberration. At this juncture, the environmentalists appear to be serious. Goodland (1990) has listed examples of tropical timber trade boycott initiatives and a few recent ones have been added by the author (see Box).
The concern of those advocating a boycott is commendable and valid but they are not attacking the real problem, and what they are proposing may, in some cases, result in more loss of forest rather than less. We need to be concerned with forest loss and not logging per se. Rather than boycott tropical timber we need to implement sound management practices, of which logging is an integral part, and look outside the forestry sector to such measures as the reform of land tenure arrangements; the intensification of production on existing agricultural lands; the creation of new employment opportunities; etc. (Rambo and Hamilton, in press; Westoby, 1989). In many cases, shutting off the markets for tropical timber would decrease the value of the forests for governments or private owners, and could well result in even less protection than currently exists as well as further conversion to activities that will produce more of a direct - albeit short-term contribution to the economy.
An option that merits consideration would be to ask consumers not to forego consumption of these wonderful woods but rather to pay more for those that are harvested under situations of good management, including desirable logging methods to safeguard soil and water, and control over the cut forest in view of future crops. Only a very few areas would now qualify, perhaps as little as one-eighth of 1 percent of all tropical forests (Poore, 1988), but the process could be initiated at sites such as those recently established under an ITTO pilot project (Anon., 1990) in Malaysia at Lesong, Sungai, Chrul and Kledang. Since sustainable forestry costs more than exploitation, consumers should be willing to bear the added costs.
Another partial solution would be to give more attention to the development of non-timber products from the tropical forests. In many cases, the sustained harvesting of these kinds of products (and more orderly and better assisted marketing) might be a valuable addition to national economic policy. Moreover, instead of displacing and dispossessing forest dwellers, it could incorporate them into the economic development system by encouraging their traditional forest practices.
However, those who would outlaw timber harvesting in favour of non-timber forest products only should bear in mind that rattan, orchids and other products are also susceptible to overharvesting in the absence of taboos, social contracts, legal enforcement or applied ecological wisdom (a rare situation). Weinstock (1983) and Siebert (1989) in Indonesia show how overharvesting can also impair the sustainable production of non-timber resources
To many people, and to almost all foresters, there is something abhorrent about treeless landscapes. As a result, many areas, predisposed by climate and soils to be natural grasslands or prairies, have been subject to concerted afforestation schemes. Unfortunately, the success record of these efforts is less than exemplary. A classic example is the attempt in the United States, under the Timber Culture Act of 1873, "to encourage the growth of timber on the western prairies" (Hibbard, 1924). Under this law, any person who planted trees on 16 ha of prairie, and maintained them in a healthy growing condition for ten years, would receive free title to 64 ha (including the 16 ha planted). The act was a dismal failure for reasons of climate, fire, insect pests and fraud, and it was finally repealed in 1891. Accounts of this failure also touch on the possibility that the farmer-settlers really did not want the trees and, though they may not deliberately have burned them, did little to prevent their destruction.
This description sounds disturbingly similar to recent afforestation attempts in areas covered by Imperata, Themeda and Saccharum grasslands in the tropics. Fires in grasslands that have been recently planted with young trees have frequently rendered afforestation efforts a failure. It is known that at least some of these fires are deliberately lit by local inhabitants. Could it be that they do not perceive these areas to be useless wastelands?
|
Examples of calls for boycotts of tropical timber 1987. United Kingdom - Friends of the Earth calls for tropical timber boycott. 1988. Germany, Fed. Rep. - 200 cite councils stop using tropical timber. 1988 (July). European Parliament Announcement that all member states will ban imports of Sarawak timber (later rejected by European Commission). 1989 (January). Germany, Fed. Rep. - The Minister for Building announces that the government has stopped using tropical timber. 1989. Germany, Fed. Rep. - The Timber Importers Federation introduces a code of conduct for timber importers. 1989 (February). - European Federation of Tropical Timber Trade Associations proposes a levy on tropical timber imports to the European Community. 1989 (April). Australia - The Federal Government considers banning imports of rain-forest timbers (no decision taken). 1989 (October). Japan - In a speech, made at the Osaka Royal Hotel, former United States President Ronald Reagan raises possibility of a boycott of Japanese products, mentioning tropical logging. 1989 (November). Japan - Malaysia vetoes the ITTO proposal to label tropical logs according to the sustainability of their source. 1990 (February). United Kingdom - Prince Charles calls for boycott of tropical hardwoods from unsustainable sources. 1990 (March). United States - Draft bill introduced in Massachusetts Congress to prohibit state purchases of tropical timber. 1990 (April). United States - Rainforest Action Network calls for ban on tropical timber imports and wood uses. 1990 (July) United States - Sierra Club begins development of a policy for a selective country boycott of tropical woods. 1990 (September). United States- Rainforest Alliance publishes consumer guide for use of tropical woods, emphasizing use of plantationgrown resources. 1990 United Kingdom - Ecological Trading Company attempts to identify and certify "sustainably produced tropical hardwoods". 1990 United States - State of Arizona bans use of tropical timber in public construction. Similar bans under consideration by several United States cities, including Bellingham, San Francisco and Baltimore. 1990 (October). European Parliament passes Resolution banning tropical forest products. ASEAN economic ministers declare strong opposition. Source: Goodland (1990) with additions by the author |
In his analysis of the ecology of Batak (Sumatra) farming, entitled What green desert?, Sherman (1980) explains how, following the harvest of rice or other crops, the land is allowed to revert to Imperata for grazing, with deliberate burning carried out to maintain it in grass. Following the restoration of soil fertility under the grass fallow (which is continuously providing fodder) the area is more easily put into crops than if it had been in secondary forest fallow. Dove (1984) has shown that Sumbawa Muslims in eastern Indonesia greatly value the meat from feral cattle, water-buffaloes and Rusa deer that live in the grasslands. These foods can be accommodated by their faith, while consumption of the wild pig, the primary game animal of the forest, is forbidden. The grasslands are deliberately sustained by these groups, yet the official government attitude, not only in Indonesia but elsewhere in Southeast Asia, is that Imperata is a noxious weed (Dove. 1986). Attempts by the government to plant forests on these lands (with the trees then belonging to the government) will be resisted, especially if the area is a de facto communal grassland resource.
Governments and environmentalists have also castigated Imperata, Themeda and Saccharum as forming an undesirable ground cover for watershed management. Compared with similar slopes under forest cover, Imperata-covered slopes are reputed contributors to floods, lower dry-season flows, declines in the output of springs and wells, and increased erosion and sedimentation. This argument also demands closer scrutiny.
Comparing grassland with forest, the general research experience has been that, under grass, there is decreased water use by plants, higher water-tables, more surface runoff, greater water yield per year, and increased stream flow throughout the year (higher storm flow and higher low-season flow), (Hamilton and King, 1983). Imperata and other rough grasses, which may not be heavily grazed because of low palatability for certain kinds of livestock, may therefore be hydrologically very satisfactory ground covers, giving a greater water yield than forest and causing no erosion. Again, as in the case of agroforestry, crop management is the key to avoiding adverse effects. While light grazing conforming with grassland carrying capacity does not increase on site erosion, most tropical grasslands are probably overgrazed, and this causes erosion. Moreover, grasslands are more susceptible than forested areas to landslips and slumps. Increases in stream sediment can therefore occur, especially if riparian strips are converted to grass and grazed.
Boycotts of tropical timber could increase, rather than decrease destruction of tropical forests
At least some land policy efforts should perhaps go into extension programmes that induce better grassland management rather than automatic afforestation. In some cases, local communities may be very willing to allow or even help in the process of afforestation, if they are brought into the planning process at an early stage and if they feel greater benefits will be achieved from trees than from Imperata or Themeda. In other cases, the grasslands are seen as more useful to the community, and afforestation will only be accomplished (if at all) with considerable difficulty. Even where this is so, it would be better to be forewarned before starting on extensive and expensive afforestation efforts.
This article is by no means the last word on the topic. There are a host of other slogans, claims and misleading statements that have become issues but that are, in fact, examples of the four "m"s: myth, misunderstanding, misinformation and misinterpretation. One that persists in spite of some excellent analyses of the issue (Davidson, 1985; Poore and Fries, 1985; FAO, 1988) is the slogan that "eucalyptus trees are villains" and rob peasants of water, soils and wildlife (Lohman, 1990). Another is the often repeated claim that all shifting cultivation is destructive and is the major cause of loss of tropical forests. Preoccupation with these issues, together with the eight discussed in more detail above, diverts efforts from tackling the long list of real priorities for research, management and policy.
Topics that really should command our attention and resources include: changing patterns of ownership and control of natural forests, particularly in the tropics; improved management and utilization of second-growth forests; standards for, and the documentation of, sustainable forest harvesting as evidence that harvesting and conservation can be compatible; the promotion of institutions and institutional arrangements; the economic contribution of protected forest areas in parks and reserves; increasing the local benefits from timber and non-timber forest products; narrowing the gap between the value of tropical timber in the forest and that of the end-product in the industrialized world; getting more of the returns from timber back to the forest where the wood originated; methods of conflict resolution and the empowering of traditional forest dwellers or users; the intensification of mangrove research; the restoration of natural ecosystems in degraded forests; innovative solutions to land-tenure problems, both within and outside the forest; the development and implementation of sustainable logging practices and the elimination of illegal logging; and (closely related to the latter) the formation of an adequately paid, ethical, motivated and well trained cadre of forest field officers. If tropical forests are to contribute to sustainable development, and to continue to exist as preservers of biological diversity, actions for addressing these issues must be increased dramatically.
Anon. 1990 Malaysia - International Tropical Timber Organization (ITTO) project. ASEAN Institute of Forest Management, Insight, 3(1): 9.
Bowonder, B. 1982. Deforestation in India. Int. J. Environ. Stud., 18(3-4): 223-236.
Colinvaux, P. 1979. Remembrances of rainforests. Nature Conservancy News, 913 (July-August).
Corvera, A. 1981. What caused the great Agusan flood? Weekend (Philippines), 12-13 March.
Davidson, J. 1985. Setting aside the idea that eucalypts are always bad. Working Paper No. 10. Assistance to the forestry sector of Bangladesh. BGD/85/D85. Dhaka, Bangladesh, FAO.
Dove, M.R. 1984. Man, land and game in Sumbawa: some observations on agrarian ecology and development policy in eastern Indonesia. Singapore J. Trop. Geog., 5(2): 112-124.
Dove, M.R. 1986. The practical reason for weeds in Indonesia: peasant versus state views of Imperata and Chromolaena. Human Ecol., 14(2): 163-190.
ESCAP. 1988. ESCAP mission to the flood-affected areas in southern Thailand. ESCAP, Environ. News, 6(4): 10-12.
Goodland, R. 1990. Tropical moist deforestation: ethics and solutions. World Bank Pontificia Academia Scientiarum, Vatican City. (Unpublished ms)
Hamilton, L.S. 1987. What are the impacts of Himalayan deforestation on the Ganges Brahmaputra lowlands and delta? Assumptions and facts. Mountain Res. And Devel., 7(3): 256-263.
Hamilton, L.S. 1988a. Semantics, definitions and deforestation. IUCN, Special Bull., 18(4-6): 8-9.
Hamilton, L.S. 1988b. The recent Bangladesh flood disaster was not caused by deforestation alone. Environ. Conservation, 15(4): 369-370.
Hamilton, L.S. 1990. Timber boycotts and Hawaiian forests. IUCN, Tropical Forest Programme Newsletter, 8: 10.
Hamilton, L.S. & King, P.N. 1983. Tropical forested watersheds: hydrologic and soils response to major uses or conversions. Boulder, Colorado, Westview Press.
Hibbard, B.H. 1924. A history of the public land policies. Madison, University of Wisconsin Press.
Kaufman, M.1988. Bangladesh flood disaster blamed on deforestation. Knight-Ridder Service. In Honolulu Sunday Star Bulletin and Advertiser. (11 September)
Lembaga Ekologi. 1980. Report on study of vegetation and erosion in the Jatiluhur catchment, 1980. Bandung, Institute of Ecology, Padjadjaran University.
Lohman, L. 1990. Thai farmers fight against plantations. Utusan konsumer, 1990: 15.
MacKenzie, D. 1983, Man-made disaster in the Philippines. New Scientist, 13: 6.
Mosley, M.P. 1982. The effect of a New Zealand beech forest canopy on the kinetic energy of water drops and on surface erosion. Earth Surface Processes and Landforms, 7(2): 103-107.
Nation. 1989. Government revokes logging concessions nationwide. Bangkok, Headlines, 14(4241).
O'Loughlin, C.L. 1974. The effect of timber removal on the stability of forest soils. Hydrology, 13: 121-134.
O'Loughlin, C.L. & Ziemer, R.R. 1982. The importance of root strength and deterioration rates upon edaphic stability in steepland forests. In R.H. Waring, ed. Carbon uptake and allocation: a key to management of sub- alpine ecosystems, p. 84-91. Corvallis.
Openshaw, K. 1974. Woodfuels in the developing world. New Scientist, 31: 271-272. (January)
Poore, M.E.D. 1988. Natural forest management for sustained timber production. Yokohama, International Tropical Timber Organization (ITTO), and London, International Institute for Environment and Development.
Poore, M.E.D. & Fries, C. 1985. The ecological effects of eucalypts. FAO Forestry Paper No. 59. Rome, FAO.
Rambo, A.T. & Hamilton, L.S. Social trends affecting natural resources management in upland areas of Asia and the Pacific. In Proc. Symposium on Cooperation in Asia and the Pacific, 1990. Honolulu, Regional Bureau for Asia and the Pacific/UNDP and East West Center. (in press)
Rao, Y.S. 1988. Flash floods in southern Thailand. Tiger Paper, 15(4): 1-2.
Sharp, D. & Sharp, T. 1982. The desertification of Asia. Asia 2000, 1(4): 40-42.
Sherman, G. 1980. What green desert? The ecology of Batak grassland farming. Indonesia, 29: 113-148.
Siebert, S.F. 1989. The dilemma of a dwindling resource: rattan in Kerinei, Sumatra. Principes, 33(2): 79-87.
The Economist. 1989. Score one for the trees. The Economist, 310(7585): 33. (14 January)
UNEP. 1985. Environmental events record, Supp. 1, (November/December). Nairobi, UNEP.
Ussach, I. 1990. Rainforest Alliance. New York. (pers. comm., September)
Westoby, J. 1989. Introduction to world forestry. Oxford, Basil Blackwell Ltd.
Weinstock, J.A. 1983. Rattan: ecological balance in a Borneo rainforest swidden. Econ. Bot., 37(1): 58-68.
Wiersum, K.F. 1984. Surface erosion under various tropical agroforestry systems. In C. O'Loughlin & A. Pearce, eds. Proc. Symposium on Effects of Forest Land Use on Erosion and Slope Stability, p. 231-239. Honolulu, East-West Center.
Wiersum, K.F. 1985. Effects of various vegetation layers in an Acacia auriculiformis forest plantation on surface erosion in Java, Indonesia. In S. El Swaify, W.C. Moldenhauer & A. Lo, eds. Soil erosion and conservation, p. 79-89. Ankeny, Soil Conservation Society of America.
