This section summarises knowledge about the technical feasibility of sustainable forest management in natural and planted forests in the tropical, boreal and temperate regions of the world.1
Natural tropical forests cover some 1,700 million hectares, of which around 900 million hectares are in Central and South America, 500 million hectares are in Africa and about 300 million hectares are in Asia and Oceania. Tropical forests comprise the most biologically diverse ecosystems on earth, containing more than half and possibly as much as 90 percent of the earth's known living species (World Resources Institute, 1989). No tropical forest has been managed for long periods of time and nobody knows for sure whether even the best management practices are truly sustainable. However, experience suggests that there is enough technical knowledge to considerably improve the current management of this type of forest, or at least to avoid the most blatantly unsustainable practices.
Moist tropical forests produce a significant number of global externalities. However, of all the forest types in the world, moist tropical forests probably also present the greatest technical challenges to implementing sustainable forest management. Many experiments to examine sustainable forest management have taken place. Unfortunately, most were marred by non-technical obstacles and events that occurred before conclusive empirical evidence of the technical feasibility of sustainable forest management could emerge.
Most of the obstacles were related to a number of economic, institutional and social factors, including:
· the length of time required for tropical trees to achieve commercial size;
· the use of inappropriate harvesting systems;
· economic pressures to repeatedly log areas in which regenerated trees have not yet matured; and
· encroachment pressures from migratory communities that survive by practising slash and burn agriculture.
In areas with scarce population, there are large reserves of forests that are not threatened. Protected areas in these places have a low opportunity cost and forest plantations are generally not an economically viable option. Furthermore, indigenous peoples frequently utilize forests in a sustainable way. In many cases, there is no need for drastic interventions to ensure sustainable forest management. Circumstances may change rapidly if roads open-up remote areas, if mineral or oil deposits are found under the forests, or if high value species become more accessible.
But in areas of high population density, the proliferation of unsustainable practices is a major problem. In such areas, the total area of moist tropical forests is shrinking and some forest types are extinct. Frequently, the forest has been converted to a mixture of primary and secondary forest. Logging in accessible areas of these moist tropical forests is intense and deforestation and forest degradation prevails. Furthermore, the pressure to convert forestland to farmland to meet expanding agricultural requirements is often intense.
Setting aside forests for protection or for sustained production of wood in areas of high population density is also difficult because the generally high opportunity costs and political costs of such actions. It is also quite likely that wood scarcity may have to become acute before more sustainable forms of forest management become attractive. When this occurs, it is more likely that the establishment of forest plantations and more intensive management of secondary forests will become economically feasible. A brief record of experiences in each one of the tropical regions is given below.
The tropical forests of Asia contain a large proportion of large-sized trees compared with forests in Africa and South America. These forests are often dominated by species from the Dipterocarpaceae family, a large number of which are commercially valuable (e.g. Meranti, Keruing and Kapur). The richness of commercial species in much of this forest allows volumes of up to 70 cubic meters per hectare (and sometimes more) to be obtained at the first-cutting.
In the last few decades, several experiments to examine the sustainability of wood production took place in Asia. One outstanding example is the experiment with the Malaysian Uniform System. The Malaysian Uniform System, developed during fifty years of research, involves felling all commercial species of a diameter at breast height of more than 45 cm, on a cutting cycle of 50-60 years. Each cutting is then followed by silvicultural operations to eliminate all non-commercial species of more than 15 cm diameter at breast height, to reduce competition.
Initially, the Malaysian Uniform System resulted in successful regeneration of lowland dipterocarp forests in Malaysia. Unfortunately however, the forests were converted to agricultural uses, before the long-term sustainability of timber yield from this system could be confirmed. Also, the precarious security conditions in many forest areas prevented the timely application of some treatments specified in the Malaysian Uniform System. However, most analysts generally agree that, had the experiments continued, most of the lowland dipterocarp forests of Peninsular Malaysia would now be sustainably producing second-rotation timber.
The rapid conversion of the lowland forests to agriculture resulted in a movement of forest harvesting into the more complex and fragile hill dipterocarp forests of Malaysia. Forest managers are now attempting to apply the Malaysian Uniform System here, but the system is untested in these types of forest and little research is available to suggest how successful it will be.
As an alternative to the Malaysian Uniform System, its successor, the Selective Management System, is being applied in some parts of Peninsular Malaysia and Sabah, mainly in forests with an abundance of commercial species. Under this system, large trees are felled every 25-30 years, without any silvicultural operations after logging. The production of the next crop relies exclusively on the survival of commercial trees of a medium diameter at breast height (between 30 and 50 cm, depending on the species). The system aims to save these stems for later harvests, by limiting damage to the forest during harvesting.
The system has the advantage that it gives forest managers the flexibility to choose the minimum diameter of stems they wish to exploit. However, it is less reliable than the Malaysian Uniform System and marks a drastic departure from the uniform, monocyclic felling system to a much more complex polycyclic system. Also, the more frequent harvesting may cause substantial damage to the remaining forest and the system requires a strong capacity to monitor and control harvesting. Empirical evidence of the sustainability of this system is also lacking, because large areas managed under this system have yet to be harvested for a second time.
The most recent experiment to look at sustainable forest management in Malaysia is the Model Forest Management Zone, recently established in Sarawak. This experiment aims to demonstrate sustainable management approaches, utilizing knowledge gained from past experiences and modern planning, silvicultural and harvesting techniques that minimize logging damage. It is also too early to assess the success of this experiment.
Other forest management systems tried in Asia include the TPI (Tebang Pilih Indonesia or Indonesian Selective Cutting System) and its successor, the TPTI (Tebang Pilih Tanam Indonesia or Indonesian Selective Cutting and Planting System). These systems involve cutting trees above a certain diameter (depending on forest type) on a monocyclic felling system. Also, in the latter case, regeneration relies on silvicultural operations, on leaving a minimum number of commercial trees after felling or, if this were not possible, on planting a certain number of desirable species.
Experience with these systems suggests that they were complex to organize and monitor. They also require sophisticated technical capacity that often is not available. Because of these obstacles, as in the case of the other experiments reported here, experience with these systems is insufficient to prove their feasibility although their failure was not caused by lack of technical knowledge.
The moist tropical forests of Africa contain a large diversity of species, few of which are commercially valuable. The main commercial species are the so-called "red woods" and forest managers often only harvest these trees, taking between 10 and 40 cubic meters per hectare.
Compared with Asia, the idea of managing forests in a sustainable way is a more recent concept in Africa. Therefore, experience is limited.
The Malaysian Selective Management System was initially tried in Ghana, but the experiment failed because the cutting-cycle used (15 years) was too short and because the forest contained few valuable species. The implementation of this system gradually led to progressive stand impoverishment.
The Tropical Shelterwood System was tried in the moist tropical forests of Nigeria. This system relies on gradually removing the forest cover over a period of 20 years to promote the regeneration and growth of desirable seedlings. However, the complexity of implementing the system on a large scale proved to be too difficult and it was eventually abandoned.
Several other experimental sustainable forest management systems launched in a number of countries, including: Central African Republic; Congo, Cameroon; Côte d'Ivoire; Burkina Faso; and Zimbabwe, relied on a variety of silvicultural treatments to ensure regeneration. Many failed because of non-technical reasons, including: political upheaval; a lack of economic resources to finance operations; and pressure on governments to abandon such methods and exploit forests for more immediate benefits.
Moist tropical forests in South and Central America have a lower species diversity and smaller tree diameters than the moist tropical forests of Africa and Asia. The density of stems is higher, but the lower volume of commercial species in these forests generally results in harvests of only 5 to 30 cubic metres per hectare.
There have been few attempts to implement sustainable forest management techniques in the region and documentation of the few attempts that have been made is poor. Some attempts have been made by private enterprises, but the results of these attempts have not been made public. It appears that none of these experiments have been conducted over long periods of time.
In Trinidad and Tobago, the Periodic Block System was designed but it does not appear to have been fully implemented. Results were never published and much of the data was lost. Similarly, in Surinam, the CELOS Management System was developed on the basis of several years of forest research, but the system was not implemented on a large scale. It was abandoned because of political conflict and insecurity in the area. Other examples of experiments with sustainable forest management systems exist in Mexico (Quintana Roo and Sierra Madre projects), Peru (Palazcu Valley), Brazil (Tapajos, Minas Gerais Cerrado and Caatinga, Mata Atlantica, IMAZON Paragominas and others), Costa Rica (Portico, BOSCOSA and FORESTA projects) Bolivia (Chimanes, MACA-IDB Project) and French Guyana, but these have all suffered from similar problems of implementation or are too recent to derive definitive conclusions (Kirmse, Constantino and Guess, 1993). Therefore, the overall experience with the application of sustainable forest management systems in this region is very limited, too recent or poorly documented.
Dry tropical forests are a mosaic of ecosystems, comprising: dry dense forests; open forests; small woodlands; and forested and shrub savannah. There are some 240 million hectares of dry and very dry forests in the world, nearly two thirds of them in Africa. These arid and semiarid ecosystems (dry forests and other arid land) support the livelihood of some 1 billion people and half of the world's domestic cattle.
Dry tropical and subtropical forests generally receive less international attention than the moist tropical forests. However, dry forests are at least as problematic and are disappearing fast. For example, seventy percent of the world's dry tropical areas are threatened by desertification. Also, because such forests and woodlands tend to occur in more densely populated regions than moist tropical forests, their degradation is likely to have a more severe impact on the poorest members of society. If these forests are not sustainably managed, their disappearance is likely to increase desertification and fuelwood scarcity, leading to increased human suffering.
Although their vegetative density is relatively low, most dry tropical forests support larger numbers of people and domesticated animals per hectare than moist tropical forests. Dry tropical forests are not usually managed for timber production, but for the production of many other goods and services, which they provide to local populations. Therefore, the forest harvesting and processing industry is much less of a dominant force in the management of these forests than in the moist tropical forests.
However, despite the above comments, wood production is still an important output of these forests. For example, one important local use of dry tropical forests is the harvesting of poles and fuelwood from multiple sprouts on coppice stumps. This management system may produce more usable biomass than the traditional timber management systems that are used to produce large logs for the wood processing industry. Other complex management techniques are also used to produce a variety of non-wood forest products, such as frequent light lopping of trees to produce digestible fodder.
While the value of dry tropical forests for commercial timber production is low, dry tropical forests are an essential component of the many complex and interdependent agricultural-forestry-livestock production systems that support large numbers of rural communities. People have learned to live in these harsh ecosystems by living in symbiosis with these woodlands, by relying upon the milk and meat which their tree-browsing animals produce and the replenishment of fertility that the trees bring to the soil.
The scope for implementing sustainable forest management in dry tropical forests is somewhat limited by natural and human factors. Two major natural challenges are soil erosion and the decline in fertility after tree harvesting, which both drastically reduce the scope for sustainable wood production. These forests are also susceptible to bush fires.
Given the intensive use of these forests by many rural people, human considerations are significant in any analysis of how they could be sustainably managed. Indeed, the management of dry tropical forests is so dependent upon the active participation of local communities, that any examination of sustainable forest management in these forests must go beyond purely technical considerations to examine these complex community interactions. Often, however, forest services and donor agencies are unable to develop strategies to cope with many of the dimensions involved in managing these forests, at times concentrating only on silvicultural aspects of forest management. Still some issues related to land and resource tenure are national or constitutional in definition and beyond the purview of forestry authorities.
Comprehensive research into the sustainable management of dry tropical forests is scarce, particularly in America. In Africa, research has concentrated on experiments to examine different participatory approaches to forest management. Also, it has tended to concentrate on the analysis of wood production from different tree species, rather than on the sustainability of the ecosystem as a whole. As a consequence, current understanding of these ecosystems remains inadequate.
Past efforts to meet expanding wood demands in dry tropical forests employed a number of different forest management systems. Initially, forest plantations received great attention. However, these were not managed sustainably. Many were established without the support of local people. Forest management practices then shifted towards the sustainable harvesting of the slow growing, but ecologically robust, indigenous tree species of open savannahs and desert margins. More recent forest management strategies started to recognize the importance of the requirements of pastoral communities living in these areas as components of sustainable forest management.
Some of the most promising examples of sustainable forest management in dry tropical forests come from India, where community-driven Joint Forest Management schemes emerged in the last couple of decades as an influential force in restoring India's degraded forest lands (see Box 3).
Throughout the 1980's, thousands of communities, primarily in eastern India's tribal forestlands, began protecting their degraded forests, often with little or no help from government, NGOs, or donor programmes. In most cases, this process was started by village leaders, when they began to recognize the environmental crisis confronting them as their once densely forested hills were deforested and denuded. Communities then formed hamlet-based forest protection groups and halted cutting and grazing, which often led to the rapid regeneration of the forest.
In response to growing environmental problems around Tangi and the Khurda Forest Division of eastern Orissa, village leaders from five neighbouring communities began holding meetings in Tangi in 1985, to discuss how to preserve and restore their natural forests. In 1987, the communities agreed to form the Five-Village Forest Protection Committee and, by 1996, they had been joined by another 120 villages in the area. These results were replicated elsewhere. For example, at the state level, 4,000 communities started to protect over 250,000 hectares of vigorously regenerating mixed Shorea robusta forests over this period and between 10,000 and 15,000 communities across the whole of India joined the grassroots forest protection movement, with minimal cost to the government.
The results of this grassroots action were immediate and, in many areas, flora and fauna that had been disappearing began to return. In response to the growing political demands of this movement, a national policy breakthrough occurred in 1988, when the Government passed the new National Forest Policy Act. This Act explicitly recognized the legal status of the Joint Forest Management Contracts that were established with these communities.
Key factors that have successfully contributed to the joint management of public forestlands in India include:
· that forest management decisions are taken and implemented by the user group(s), rather than by the village or panchayat as a whole;
· that the user group(s) have been given security of tenure, with the state playing an active role in defining and protecting their boundaries against outside use and encroachment;
· that use regulations have evolved, are enforced locally and have been turned into rules that are understandable and easily adjusted to meet new challenges;
· that the benefits of community management are allocated in a way that reflects both the interests of the people dependent on the resource as well as the elite and the powerful; and
· that the management of the forests has focused on the production of low value products that are locally important.
Source: Arnold and Stewart (1991).
In addition to the tropical forests described above, there are some two billion hectares of degraded tropical forests in the world. Often, these are remnant forests, left after overharvesting of wood and non-wood forest products. The soils in these areas are usually susceptible to erosion and have low fertility. These forest areas are also often susceptible to forest fires. However, some species of trees thrive in these degraded ecosystems and often, due to the poor soils, such sites have few alternative uses (other than to be used as forests).
Large-scale reforestation of degraded tropical forests started during the first half of the century and an impressive body of technical knowledge has been built-up over the years about how to re-establish high-quality forest cover in these areas. For example, reforestation techniques are well developed for a wide variety of tree species and large expanses of degraded forestland have already been replanted, especially in Asia and Latin America. Most of these plantations have been planted with fast growing species for the production of industrial roundwood. However, concerns about the vulnerability of monocultures to pests and fire, recently led to the greater use of species mixtures in forest plantations.
Experience shows that one of the conditions for sustainable forest management in forest plantations, is that appropriate species are selected for planting on each individual site. Another condition is that forest plantations have to be well managed throughout the whole rotation. If the species chosen are not correct, or if forest plantations are not properly managed, then the establishment of forest plantations may lead to undesirable outcomes such as greater soil erosion and, eventually, greater pollution and sedimentation of watercourses. This may also eventually reduce the sustainable wood harvest from such areas.
The boreal forests form a broad belt between latitudes 50º and 70º, across North America, Europe and Asia. At its northern edge, the boreal forest belt stops at the treeless tundra, and its southern fringe merges into the temperate forest region. Boreal forests account for about a third of all forests in the world and contain half of the world's remaining tracts of natural, relatively undisturbed forest (World Resources Institute, 1997). They are also the world's largest store of terrestrial carbon. Seventy percent of the world's boreal forests are located in the Russian Federation.
With few exceptions, present-day boreal forests grow on land formerly covered by ice. Except in mountainous areas or along riverbeds, the glacial soils are largely resistant to erosion. Due to frequent fires, the boreal forest usually consists of a patchwork of tree communities that have regenerated over time after these fires. Frost-hardy conifer species (e.g. spruce, pine, larch and fir) dominate these forests, of which the spruces are the most common. Broadleaf tree species, mainly poplar and birch, also occur in mixed stands with these conifers or occasionally in single species stands.
The Nordic countries have a longer history than anywhere else of sustainable wood production from the boreal forest. In these countries, most of the old-growth forests were replaced long ago by forests managed following sustainable yield principles and many of these forests are now being cut for the second or third time. Management practices are sophisticated and, during the last 40 years, resulted in a 23 percent increase in the growing stock volume and a 36 percent increase in wood increment or yield. These changes are expected to continue for the foreseeable future. For example, forecasts for Sweden's boreal forest suggest that it will be possible to increase the sustainable level of timber harvesting by a further 55 percent over the near-term.
The Nordic countries, the Russian Federation, China and Canada harvest significant quantities of wood valued for sawing and pulping. Canada and the Russian Federation also still have large tracts of virgin boreal forest. In the few areas where boreal forests were converted to other land types, this was mainly been due to logging activities rather than to the deliberate conversion of forestland to agriculture.
In the boreal forests of the Russian Federation and Canada, roughly 75 percent of the total annual removal of industrial roundwood comes from clearfelling in cutting blocks of 25 to 100 hectares or more. Currently, the removals are from forests being harvested on a large-scale for the first time. In the Nordic countries, the forest industry operates in a similar way, but the forests are mostly of second or third generation stands. In comparison, the commercial utilization of the Alaskan boreal forest is relatively limited.
The main reason for the widespread use of clearfelling in the boreal forest, is that this is generally the cheapest way of harvesting the forest. However, all of the commercially important species found there, with the exception of White spruce (Picea glauca), grow best in even-aged stands (Bull et al, 1995). Harvesting operations are predominantly mechanized in the boreal forest and even in forests belonging to small private forest owners (mainly found in the Nordic countries and Eastern Canada) harvesting methods do not differ much from those of the large forest owners. In such cases, large forest harvesting and processing companies usually buy the rights to harvest from small private forest owners and carry-out their own harvesting operations on the land.
Management methods used after clearfelling boreal forests are fairly similar everywhere. Natural regeneration is either spontaneous or is encouraged by leaving seed-trees or by using a shelterwood silvicultural system. In some areas, shade-tolerant fir trees regenerate spontaneously in sufficient numbers without significant intervention.
Natural regeneration usually produces stands with a "natural" appearance, containing species that are well adapted to local conditions. On the other hand, the fact that the stand composition is very similar to the adjacent forest, can be a disadvantage in certain situations. Also, Another disadvantage of natural regeneration, is that forest growth and yield is generally lower than could be achieved if the site were more actively managed. For example, the use of genetically improved tree species could drastically increase timber yields and soil treatment (such as controlled burning) would make it easier for seedlings to establish.
Stands are generally thinned (usually at least twice) in the boreal forests in the Nordic countries. However, thinning is less common elsewhere, either because second-generation forests have yet to reach the thinning stage, or because the markets for small diameter roundwood are more limited. The application of fertilizer to improve tree growth is also common in the Nordic countries, but less common elsewhere. In many areas, seedlings and young stands are often treated with chemicals to increase their resistance to insects and diseases.
The management procedures described above usually result in sustainable wood production, but they are not free from risks. For example, because of the adverse climatic conditions in most boreal forests, timber harvesting along the timberline or in areas at the margin of forest growth, may lead to the complete elimination of these forests if regeneration does not occur.
Moreover, there are other concerns about the wider sustainability of harvesting in such areas. For example, soils are frozen in most of these areas during the winter and may even be frozen permanently in some areas. If harvesting operations take place during these periods (as often happens in northern Russia and eastern and central Canada), damage is minimal but harvesting using heavy machinery when the soils are not frozen, damages soils irreversibly. Furthermore, the boreal wetlands are also extremely fragile ecosystems and the practice of draining them in order to increase forest growth (which used to be fairly common practice) has almost ceased in the Nordic countries and the Russian Federation.
During the last couple of decades, forest managers modified the forest management systems used in the boreal forests, to accommodate concerns about the environment. For example, in some ecologically valuable areas, some stands are left untouched and ecologically valuable trees (e.g. very old, hollow and dead trees) are now left in clearfelled areas to provide niches for species. Also, forest managers moved away from more intensive management of clearfelled areas, back towards more benign management systems, such as re-establishment by natural regeneration. In many cases, the forest industry promotes these more environmentally friendly approaches (See Box 4).
In 1987, a large Swedish forest owning corporation (SCA) published a "Declaration on Nature Conservation" for its forest operations. This was one of the first commitments made by a large forest owner to introduce a modern environmental vision as part of its commercial forestry strategy. The SCA document states that its forestry operations should be conducted in such a way as to:
· avoid permanent adverse effects on soil, surface water and ground water;
· preserve a rich variety of plant and animal life;
· protect all plant and animal species occurring in the part of the country where we operate (although we are aware that this objective cannot always be achieved, this is not an acceptable excuse for failing to pay attention to or take action that has a reasonable chance of succeeding);
· preserve the plants and animals now living in the area in the first instance, with reintroduction of vanished species to take second place; and
· give first priority to species that are unique, with second priority to other species that are locally rare but plentiful elsewhere.
The operational consequences of this commitment, including the reservation of production forest areas, leaving trees that could have been harvested and other measures, resulted in a 10 percent reduction in timber harvest at a cost of about US$ 10 million per year.
While these initiatives may be commendable, the long-term consequences of applying less intensive forest management methods in boreal forests are uncertain, both in terms of their impacts on the volumes and quality of wood produced and their environmental benefits.
The temperate forest zone comprises two bands circling the world in the northern and southern hemispheres, extending from around 30 degrees latitude to around 50 degrees latitude. This definition is only approximate, because local climatic and terrestrial features affect the boundaries of these zones. The climate in the temperate forest zone is characterized by cold winters, when snow may occur and summers that are mild and moist.
The temperate forest zone contains a great variety of ecosystems. It includes humid rainforests such as the rainforests along the West Coast of the United Sates of America and Canada, where conifers (gymnospermae) dominate, and the rainforests of the wet southernmost parts of South America (where the broadleaved Notofagus species dominates). The natural forests of Eastern Canada and the North-eastern United Sates of America (including the Appalachian Mountains) closely resemble the forests of Central and South-eastern Europe, with an abundance of broadleaved species, such as: oak (Quercus spp); ash (Fraxinus spp); beech (Fagus spp); elm (Ulmus spp); and maple (Acer spp), and conifers, such as: pine (Pinus spp); spruce (Picea spp); fir (Abies spp); and larch (Larix spp). Southern Europe, the southern states of the United Sates of America, China, Japan, Chile and New Zealand, also possess other types of temperate forest ecosystems.
The main tree species found in temperate forests are: pine; oak; beech; and eucalypti (eucalyptus spp). Pines tend to dominate in areas of frequent forest fires, such as the southern states of the United States of America. Here, the regeneration process is similar to that of the boreal forest. In areas where fire is less common, oak tends to dominate at first, being later replaced by shade tolerant beech and maple species. However, even where broadleaf species dominate the natural forest, shade tolerant conifers are also generally present.
In many parts of the temperate forest zone, the natural forest contains a large number of trees with an uneven age structure. Natural regeneration occurs in an environment with many seedlings, saplings and mature trees, all coexisting on the same patch of land. However, management of temperate forests of North America and Europe has tended to convert these forests to more even aged stands, with a more simplified composition and structure.
Harvesting in the temperate forest zone produces an amount of industrial roundwood that is somewhat greater than the amount produced in the boreal forest zone. However, these forests are also an important source of other goods and services, including: mushrooms; fruits; and berries and recreational activities such as hunting, walking and fishing.
European countries have the longest experience with temperate forest management. For example, some countries have been managing their forests as even-aged stands for commercial timber production for many decades or even centuries. Many European countries have strict forest legislation, that regulates forest management according to "classical" sustained yield principles and also usually mandates a certain amount of forest management for environmental protection and nature conservation purposes. Many government agencies in Europe also advise private forest owners and often control some of their activities. In contrast, in most other temperate regions, private forest owners have much more freedom to choose how they want to manage their forests.
Western European countries have tried many very different approaches to forest management. For example, France used to manage vast areas of deciduous forests on fairly short rotations for the production of fuelwood (the so-called "low forest" regime), although many of these forests are now being converted back to high forest. The United Kingdom, Ireland, the Netherlands and Denmark established large plantation areas, based mainly on exotic species such as: Sitka spruce (Picea stichensis); Norway spruce (Picea abies); Lodgepole pine (Pinus contorta); and Douglas fir (Pseudotsuga merziesii). Spain and Portugal also planted vast areas with Radiata pine (Pinus radiata) and Eucalypti.
Forest management methods employed in central Europe are more similar between countries. Clearfelling is usually restricted to a few hectares for various reasons, including: the high aesthetic value given to continuous forest cover; biological conservation; and the risk of erosion or avalanches on steep slopes. Instead, many forest areas are often managed on an almost continuous thinning regime. Many central European foresters also prefer to use manual harvesting methods or light harvesting equipment in order to prevent soil damage, but this is often difficult in the case of tall, heavy trees, which often grow in these forests.
One traditional system of forest management, which has a long history in central Europe, is the so-called "Plenterwald" system. This selection forestry system is designed to create, conserve and utilize mixed, often hardwood dominated, forest stands of uneven age, by harvesting single trees as they mature. It also involves harvesting some smaller trees with the mature trees, in order to keep the composition and structure of the forest in a similar state. The system works well biologically in forests containing shade tolerant tree species. It becomes more difficult to use, or even impossible, for forests containing light demanding species such as pines and larches.
The Plenterwald forestry system has attracted attention as seemingly being environmentally-friendly and, therefore, biologically superior to the even-aged forestry system. This is true for some hardwood dominated ecosystems, but is not true in locations where light demanding tree species are growing. It is also regarded as aesthetically more acceptable, which is probably true. In central Europe, particularly in the case of state-owned forests, there is a trend towards the wider application of the Plenterwald forestry system because of these benefits.
In contrast to Europe, harvesting in most of the rest of the temperate forest zone is highly mechanized. The operations are similar to those commonly found in boreal forests and are driven by concerns of profitability and cost-efficiency. Clearfelling is not unusual, but in sensitive areas selective cutting is more common, both in softwood and hardwood forests.
On the West Coast of the United Sates of America and Canada, some forest ecologists have suggested that selection forestry systems may be an ecologically acceptable method for harvesting the humid rainforests found there. To the surprise of many, this advice was accepted by MacMillan Bloedel in 1998, when it announced that it was phasing-out clear-cutting, the standard forest industry practice in British Columbia, to manage its concessions using a selective cutting system.
Forest plantations are mainly established for the production of roundwood, but are also occasionally planted for environmental purposes, such as soil protection. In terms of roundwood production, they have several economic advantages over wood from the natural forest and are expected to become an increasingly important source of industrial roundwood supply in the coming century. (See, for example: Brown (1999), for a more comprehensive discussion of the future prospects for forest plantations). About 10 percent of the world's existing plantations can be classified as "fast growing" (i.e. yielding more, often much more, than 15 cubic meters per hectare per year).
The technical aspects of planting and managing forest plantations for sustainable wood production, are well developed. Particularly in the temperate forest zone, some forest plantations have been producing sustainable yields of wood for many decades or even much longer. For example, in some regions of Japan, there is evidence that forests have been harvested for more than 1,000 years. There is also evidence that forest harvesting has occurred over five or six centuries in some areas of Scandinavia and Central Europe. There is enough technical knowledge to produce sustainable yields of timber in most of the other regions of the world.
To be sustainable, forest plantation development must consider environmental and social impacts. For example, there is evidence of site degradation in a few areas where forest plantations have been established on nutrient-poor sites and unstable soils. Plantations may also reduce the water available for other uses and this can be a problem in areas where water is scarce (e.g. South Africa). However, enough technical knowledge is generally available now, to avoid most of these negative environmental impacts.
When implemented at a broad scale by a single owner, establishment of forest plantations can displace rural populations and result in frictions. Migration of labour into the region can result in a change in social values and behaviour that hurt local people. Where changes lead to social problems, the sustainability of forest plantation is jeopardized. With the present state of knowledge, most of these potential limitations can be quite easily avoided.
Forest plantations can also have an indirect positive impact on the way the natural forests are managed. The most positive impact they are likely to have, is that they provide an alternative source of fibre, which can be used to relieve the pressure to use the world's remaining natural forest as a source of wood supply. For example, by the year 2050, more than half of the world's total demand for wood and wood products is likely to consist of demand for paper and paper products. Much of this demand could be satisfied with wood originating in fast growing forest plantations. Therefore, this trend will provide even greater scope for forest plantations to reduce the pressure on the natural forest. Although, it seems unlikely that plantation grown wood will completely replace wood from the natural forest in the manufacture of pulp, the trend towards increased investment in industrial forest plantations is evident in many countries, such as: New Zealand; Chile; Brazil; Argentina; Uruguay; Indonesia; and South Africa.
A very useful summary of the sustainability (in its narrow sense) of forest plantations established around the world is given in Evans (1999) and this is reproduced in Box 5.
· Measurements of yield in successive rotations of trees suggest that, so far, there is no significant or widespread evidence that plantation forestry is unsustainable in the narrow sense. Where yield decline has been reported, poor silvicultural practices and operations appear to be largely responsible.
· Evidence in several countries suggests that current rates of tree growth including in forest plantations, exceed those of 50 or 100 years ago.
· Plantations and plantation forestry operations do affect the sites on which they occur. Under certain conditions nutrient export may threaten sustainability, but care with harvesting operations, conservation of organic matter and management of the weed environment are usually more important for maintaining site quality. Plantation forestry appears to be entirely sustainable under conditions of good husbandry, but not where wasteful and damaging practices are permitted.
· Plantations are at risk from damaging pests and diseases. New threats will inevitably arise and some plantations may become more susceptible owing to climate-change factors, but the history of plantation forests suggests that these risks are containable with vigilance and the underpinning of sound biological research.
· There are several interventions in plantation silviculture, which point to increasing productivity in the future, providing management is holistic and good standards are maintained Genetic improvement, in particular, offers the prospect of substantial and long-term gains over several rotations.
· Environmental changes will undoubtedly have an impact on plantation forests. Some changes may yield improvement, others damage. Most plantation species are resilient and broadly based genetically and are unlikely to suffer seriously from the kinds of climate change scenarios currently predicted. It will be prudent to maintain genetic diversity and minimize stress to planted trees.
Source: Evans (1999) p57.
A summary of the conclusions drawn from experience with sustainable forest management systems in all moist tropical forests is given in Table 1. Details about the technical features of each of these systems in Asia, Africa, and South and Central America can be found in Annex 4 of Dupuy et al (1998).
The Malaysian Uniform System was successful when abundant natural regeneration was present. In the Philippines, selective logging shows excellent regeneration of preferred species. Successful natural regeneration in Trinidad, Puerto Rico and under the CELOS system in Surinam is promising.
In Malaysia, the Malaysian Uniform System resulted in successful regeneration in lowland dipterocarp forest. Liberation thinnings in selectively logged forests in Sarawak produces new good quality stands quickly and selective logging in the Philippines leaves a commercially valuable residual stand.
Poore et al (1989)
Sustainable management in some small scale projects in Africa has begun. Sustainable management in Malaysia shows promise and sustainable production is carried out in Trinidad and Tobago.
Goodland et al (1990)
Sustainability cannot truly be detected until at least the third cutting-cycle has been completed. Forests managed using sustainable management techniques during colonial regimes in Asia and Africa, the Malaysian Uniform System and other management systems have largely been converted before sustainability could be proved. However, several experiments currently under way in Latin America may turn out to be sustainable.
It is likely that forests managed under the Malaysian Uniform System would be producing second rotation timber if the land had not been converted to agriculture. The strip shelterwood system used in Palcazú shows abundant regeneration and polycyclic systems with liberation thinning show promise in Sarawak and Côte d'Ivoire.
Jonsson and Lindgren (1990)
A forest in Costa Rica, where Carapa guianensis was harvested, is showing abundant regeneration.
Keto et al (1990)
Current forestry regulations in Queensland recognize long-term economic and environmental concerns. However, this study argues that the Queensland model for sustainable forest management is disputable, because it is based on inadequate evidence.
Perl et al (1991)
This study gives thirteen examples of forest management systems in Latin America. None of them are demonstrably successful in every aspect of sustainable forest management and they all require additional time to mature before conclusions can be drawn.
Hartshorn (1990) and Southgate (1998)
In Palcazú, natural regeneration on two demonstration strips has been very good and this suggests that the management methods used in the forest were biologically sound.
Bruenig and Poker (1991)
Positive indications about the feasibility of sustainable forest management have been obtained in Congo. The Selective Management System in Malaysia and the management system used in Quintana Roo have also demonstrated the feasibility of sustainable timber production. Selective logging in dipterocarp forests in the Philippines has successfully left a commercially viable residual stand..
Source: Johnson and Cabarle (1993) and Southgate (1998).
The systems examined all aimed at the sustainable production of wood, with little or no consideration of the many other objectives often associated with sustainable forest management. Most specialists agree that, in these cases, the forest management systems were technically sound, despite the fact that the empirical evidence of sustainable wood production remains incomplete and is mostly limited to evidence of successful regeneration.
The Asian experience shows that forest management of moist tropical forests for sustainable wood production is technically feasible in this region. In Latin America, various researchers believe that sustainable wood production is technically feasible, at least in some ecosystems. For example, Barros and Uhl (1995) contend that sustainable wood production is feasible in the Brazilian Amazon, especially in the floodplains where the diversity of timber species is lower, the volume per hectare of commercial species is relatively high, growth rates are also high and logging does relatively less damage to the remaining vegetation and to the soil. Southgate (1998) reports that the forest management system used in the Palcazú project in Peru is probably biologically sound on the basis of the evidence of abundant regeneration after harvesting. However, the project itself could not be sustained because of security concerns and the poor economic results, which were due to a relative abundance of alternative wood supplies in the area.
In summary, the evidence from Asia suggests that sustainable wood production in moist tropical forests in this region is technically feasible, but that most experiments did not last long enough to eliminate all doubts. In Africa, failure was mainly a result of ineffective public administration. In Latin America, the main problems (with experiments to examine sustainable forest management systems) were the lack of security and insufficient commitment to implement sustainable forest management, on a larger scale.
The evidence generally points to the fact that the forests are either evolving as the researchers expected them to, or that any technical failures could easily be corrected with existing knowledge. The balance of the technical evidence is quite positive and numerous studies and projects provide a solid base for technically sound forest management for sustainable wood production in most of the world's moist tropical forests.
In dry tropical forests the overall experience matches the experience gained in moist tropical forests and suggests that sustainable forest management of dry tropical forests does appear to be technically possible. However, sustainable forest management in this type of forest will only be achieved when forest managers secure the participation of rural people, by integrating their activities with the rural economy and with other activities that sustain the livelihoods of local people. Also, as in the case of other experiences in the tropical region, it is generally too early to judge whether or not the approaches, which currently appear to be successful, will be sustainable in the long-run.
Experience in the boreal forest region is limited to the few attempts to advance from purely timber orientated forest management systems to more ecosystem-orientated sustainable forest management systems. These attempts are all fairly recent and are surrounded by long-term uncertainties. However, despite these caveats, enough technical knowledge is currently available to practice sustainable wood production in the boreal forest, or at the very least, to identify and avoid the most unsustainable practices.
Similar conclusions can be drawn from experience in the temperate forest zone. It is somewhat difficult to generalize from the experience gained in the temperate forest zone because of the many different types of forest ecosystem within this zone. However, in most cases, there is generally enough technical knowledge and experience to manage most of these forests for sustainable wood production and to avoid the most excessive examples of unsustainable practices.
Finally, there is adequate technical knowledge to establish forest plantations that produce a sustainable flow of wood, but there is less certainty about the sustainability of current forest plantation practices in a broader sense. There is also insufficient evidence to report on how successful reforestation projects in degraded tropical forests have been or will be in the future.
1 Large parts of this section have been drawn from the two background papers commissioned by FAO for this study (Dupuy et al, 1998; and Hagner, 1998).