Great efforts have been made in recent years to draft and implement forest management plans. Nevertheless, in only a few cases have management plans been implemented effectively and fully. In 1990, undisturbed natural tropical forests represented only about 155 million ha, or about 30% of world's tropical forest areas used for wood production. The other 70% are constantly being harvested and are thus in more urgent need of being managed in a sustainable manner.
Globally, there are approximately 330 million ha of logged-over tropical forests. In the tropics, more than 148 million m3/year of industrial roundwood is extracted from a potential sustainable production of 134 million m3/year. However, only 18% of total roundwood production is for industrial purposes (see Table 4), 18% of which ends up on international markets. FAO (1997) has estimated that, at a global level, there is a tendency to overharvest timber resources. The ratio of sustained yield production (potential production versus volume actually harvested) provides regional trends of the degree of forest harvesting regimes (see Table 5). It emerges that:
_ the situation in Africa varies by region: in Central Africa, extraction volumes exceed production while in West Africa, the threshold of sustainable forest harvesting has been largely surpassed (and production is now more than 200% of sustainable yield in some cases);
_ in South America, in general, the levels of sustainable yield and current harvesting are in equilibrium, but most forests in Central America are overharvested (with harvesting up to 10 times the sustainable yield in some cases);
_ in Asia and Oceania, forests are generally overharvested, with harvests largely exceeding (by at least 70% and often more) sustainable yield, not taking into account forest clearing and illegal felling.
Table 4: Global consumption of forest products in 1994
Product | |||||
Fuelwood and charcoal |
Industrial roundwood |
Sawnwood |
Wood based panels |
Total | |
Consumption (in million m3) |
1,697 (76%) |
406 (18%) |
112 (5%) |
30 (1%) |
2,245 (100%) |
FAO (1994)
Table 5: Production forest areas in 1990 and current levels of roundwood production compared with sustainable yield
Undisturbed forests (in million ha) |
Disturbed forests (in million ha) |
Average production 1990-95 (in million m3) |
Production as a percentage of sustainable yield | |
Africa |
59.6 |
112.9 |
17.1 |
174% |
Asia and the Pacific |
53.0 |
91.9 |
97.6 |
59% |
South America and the Caribbean |
42.1 |
122.5 |
33.8 |
141% |
TOTAL |
154.7 |
327.3 |
148.5 |
91% |
Source: FAO (1997)
Table 6: Biomass and rates of degradation for natural tropical forests
ECOREGION |
Potential biomass (tonnes/ha) |
Current estimated biomass harvest (tonnes/ha) |
Ratio of degradation (biomass harvest/ potential biomass) |
CONTINENTAL ASIA |
|||
Low-lying humid zones |
449 |
225 |
0.50 |
Low-lying dryland zones |
244 |
76 |
0.31 |
Mountain zones |
306 |
155 |
0.51 |
PENINSULAR ASIA |
|||
Low-lying humid zones |
543 |
273 |
0.50 |
Mountain zones |
504 |
254 |
0.50 |
TROPICAL AFRICA |
|||
Low-lying humid zones |
412 |
299 |
0.73 |
Low-lying dryland zones |
92 |
60 |
0.65 |
Mountain zones |
197 |
105 |
0.53 |
Source: FAO (1997)
Fuelwood consumption accounts for almost 75% of global wood production. However, most of this biomass appears to be harvested outside established forests (in shrublike formations, perennial crops, hedgerows and gardens etc.). In highly populated and deforested areas, especially in Asia, forests still supply around 25% of fuelwood requirements even though many forests are overharvested. Other observations about fuelwood use include the following:
_ the overharvesting of forests increases with the scale of people's needs as is the case in: India and Bangladesh; mountain forests in Burundi and Rwanda; dryland forests in West Africa (Niger, Nigeria, Togo and Benin); and in Southern Africa (Botswana, Somalia, Zimbabwe, Malawi), but current biomass removals represent less than 50% of sustainable biomass production (see Table 6);
_ in the world's humid zones, the situation is more favourable in Africa than in Asia and worrying levels of biomass harvesting occur in: Indonesia; peninsular Asia; the Philippines; and Sri Lanka.
The location of the world's humid tropical forests is shown in Figure 1.
Figure 1: The location of humid tropical forests
Africa. Despite the floristic variety and the abundance of large trees in African humid tropical forests, these forests (covering approximately 340 million ha) contain only a relatively small number of species that can be considered commercially viable. Harvesting is often far below the potential volume that can be removed, in part due to strict market requirements that make concessionaires concentrate on harvesting only the currently highly valued species (the "redwoods") that are mainly located in remote inland areas. Harvesting intensity in these forests is typically between 10 m3/ha and 40 m3/ha.
Asia. In general, humid tropical forests in Asia (covering approximately 220 million ha) are characterised as having an abundance of trees of similar size, with fewer large trees per hectare than are found in African forests. However, tree diameters are generally greater than those found in tropical South and Central America. The dominant family - the dipterocarps - contains most of the high value species. The good technical timber qualities of these species and their abundance on the Asian islands are reflected in large-scale commercial harvesting activities there. Harvesting intensity is generally high at about 70 m3/ha and often more.
America. Humid tropical forests in tropical South and Central America (covering approximately 750 million ha) contain less species diversity and trees tend to be smaller than in other regions. The main species generally lack the good technical timber qualities that have been the source of commercial forestry success in Asia and Africa. As a result, harvesting intensity in the humid tropical forests in tropical South and Central America is generally lower, with rates of between 5 m3/ha and 30 m3/ha.
Historically, Asia has had the most potential for industrial wood processing development on the basis of existing wood processing technologies and the markets for tropical wood. Consequently, numerous humid tropical forest areas in this region have become impoverished where formerly dense forests occupied vast areas. Now, some former net wood products exporters have become net importers (e.g. Thailand and the Philippines). Faced with this impoverishment of the forest resource, many countries in the region have become aware of the need to implement sustainable forest management systems.
Compared to the situation in Asia, attempts to implement sustainable forest management are a more recent phenomenon in Africa and tropical South and Central America. However, there has not, to date, been any integrated implementation of management planning systems in these regions. In fact, the need to properly manage forest resources has only been recognised and enforced in the last few years, following recent international awareness of the threats to forest resources from ranching and agricultural activities.
For a long time, sustainable forest management projects really only examined silvicultural techniques aimed at managing forests for sustainable wood production. Systems examined included:
_ the "Malaysian Uniform System" (MUS) in Southeast Asia;
_ the improvement of natural stands system or "L'Amélioration des Peuplements Naturels" (APN) in Africa; and
_ the "Celos Management System" (CELOS system), tested in Surinam.
A range of silvicultural treatments were developed, tested and implemented in research into these various systems, that emphasised sustainable wood production. However, many of these experiments have failed, in that they have been only partly implemented or have not been maintained over a long enough time period to produce really reliable results.
The technical feasibility of these systems has rarely been a cause of failure in these experiments. For example, despite the fact that Malaysian and Indonesian sustainable forest management systems were only partially implemented (because of a number of problems), the evidence from the Asian experience suggests that it is very likely that tropical forest management for sustainable wood production is technically possible. Similar research programmes were started in South America, but have been interrupted because of socio-economic and political problems there (e.g. controversies over land rights). Application of sustainable forest management systems in Africa has been limited by the limited resources available to forest administrations in most African countries.
Furthermore, political changes have often had the effect of changing the orientation of forestry institutions in many countries, encouraging them to give preference to techniques that promise to produce faster results (e.g. development of forest plantations) rather than develop sustainable supplies of wood from the slower growing natural forest.
In general, the main obstacles to a better understanding of tropical forest management arise from a lack of knowledge about the application and results of various silvicultural treatments and a poor understanding of ecosystem dynamics, particularly techniques for promoting adequate forest regeneration after harvesting. Improved knowledge about these subjects would be useful to strengthen the basis on which sustainable forest management systems are developed. However, it is generally believed that the results obtained to date (from numerous studies and projects) have provided a reasonably solid basis for effective silviculture in humid tropical forests. Difficulties encountered with implementing sustainable forest management have more often been found outside the technical arena, in areas such as: land development policy; socio-economic conditions; and political circumstances.
Technical and scientific issues. Good inventory data is a prerequisite for any sustainable forest management project. However, more often than not, inventory data are unreliable, obsolete and/or inaccessible, due to a lack of resources and/or investment in this area. Information about productivity or growth of valued species and their long-term yield is also scarce. In fact, databases (numerical, cartographic and bibliographic) that group together all available knowledge about climate, soil, topography, flora and fauna, are often lacking at the regional, local and national levels. Improving the flow and storage of management information is an economical and efficient way of continuously improving management and databases containing this information should be created and continuously updated using a permanent flow of field observations.
The choice of forest management techniques in any particular forest area is determined by two factors: management objectives and inherent stand characteristics (e.g. yield potential, fire risk, etc.). A technically sound approach to silviculture can be articulated in terms of three requirements:
_ harvesting at a rate that is compatible with wood production potential or yield;
_ making sure that harvesting and extraction is planned in a correct and timely fashion; and
_ encouraging the growth of highly valued species while maintaining biodiversity.
Management according to these principles (e.g. by assessing growth, harvesting in line with these estimates and choosing the most appropriate harvesting practices) is difficult and, in reality, forest administrations in most countries do not have enough staff to approve and monitor management plans. In other words, adequate knowledge about sustainable forest management techniques is available in most cases, but implementation is poor due to limited resources.
Socio-economic and political issues. During the implementation of any long-term forest management plan, the political and socio-economic context is likely to change. If management plans are not flexible enough to respond to such changes, they can be called into question and finally abandoned therefore, possible future changes in context and circumstance should be taken into account.
Neither stability nor long-term forecasts can be guaranteed in many developing countries because there are numerous factors that can generate unpredictable conditions that are incompatible with sustainable forest management (e.g. pressures to expand agricultural production, infrastructure developments and economic crises such as the recent crisis in Asia). Against this background, negotiation and periodic adaptation of management plans should be guided by the long-term objectives of management. Furthermore, political discussions about overall objectives are often neglected, leading to high-level administrators questioning the plan at the last minute if they are not consulted earlier. Greater attention should be given to the social and institutional framework within which forest management plans are produced and implemented.
In general, local communities are often very dependent on forests. It is therefore, important to promote their participation and to maintain a dialogue with them during the formulation and implementation of forest management plans. Divergent objectives among the various stakeholders can often lead to conflicts of interest, so it is also essential to emphasis the long-term benefits to each of them and describe how they will be affected by the management plan. The major problem here is to extend the "temporal and spatial horizon" of stakeholders so that natural forest resources are not overharvested to meet short-term requirements.
Mangroves cover more than 16 million ha and include a limited number of haliophilic species (e.g. Rhizophora, Avicennia, etc.). These forests are exposed to strong ecological limitations due to cyclical tidal flooding and, consequently, mangroves represent one of the most vulnerable ecosystems on earth. Nevertheless, mangroves can be very productivity and they play important protection and economic roles (e.g. by stabilising coastlines and supporting local fisheries). They supply extremely varied goods and services and numerous communities depend on them for their survival.
Mangroves appear to be well preserved in countries with low population density and adequate wood resources (e.g. Gabon, Guyana and Australia). In contrast, they are in decline in areas with high population pressure (e.g. Senegal, Thailand, Vietnam and Bangladesh). For example, in the Philippines and Ecuador, mangroves have been illegally converted to use for intensive aquaculture operations while, in Indonesia, they have been overharvested for other purposes (e.g. timber production). In East Africa, the main reason for decline in mangroves has been conversion into salt marshes.
It is rare is for mangroves to be sustainably managed for wood production (including wood fuel and industrial roundwood production) except in some Asian countries such as: India; Bangladesh; Thailand; and Malaysia. Australia seems to have the best management systems in place for mangroves, including areas for protection and conservation of these resources (e.g. they have 23 protected national parks and sites) and other areas for sustainable harvesting.
Mangroves play a recognised role in protection against coastal erosion and the conservation of aquatic fauna. This importance has been recognised in much of Asia and Central America, where reforestation and the restoration of degraded mangroves has been carried out with these objectives in mind. Technically, mangroves can be managed for sustained yield of wood and non-wood forest products. However, management depends considerably on other factors, especially variations in the water regime and therefore, the management of inland coastal areas should be integrated into mangrove management systems.
The location of the world's dryland forests is shown in Figure 2.
Figure 2: The location of dryland forests
Dryland tropical forests are composed of a mosaic of different ecosystems, including dense dryland forest, open forest and woodland formations, single trees, and scrublike savannahs. There are 238 million ha of dryland forests in the world and Africa alone has 64% of that amount. These ecosystems provide shelter to nearly 1 billion people and half of the world's domestic livestock, not to mention a large variety of wildlife.
For almost 50 years, these dryland regions have been weakened through repeated drought and human intervention (e.g. the erroneous use of fire as a management tool, conversion to agricultural land, overgrazing and overharvesting of forest resources, etc.). Wood from these ecosystems accounts for between 50% to 90% of energy used in Africa (but far less in Asia and tropical South and Central America). For a long-time (and still today), fuelwood has been considered as a free resource, with the only price being the cost (usually in terms of time) of harvesting it. Open access to resources (land, forest and rangeland) and the absence of land security have contributed to the destruction of this resource. Unrestricted forest clearance and fuelwood collection has far exceeded the ecosystem's capacity to regenerate naturally. Furthermore, the expansion of cultivated land has reduced the land available for traditional livestock breeding, leading to greater use of the forest for seasonal migration, where the forage produced by certain woody species complements grazing.
Table 7: Proportion of total energy needs met by the use of wood fuel in several tropical countries
Year | |||
Country |
1978 |
1982 |
1990 |
Senegal |
60% |
82% |
54% |
Mauritania |
69% |
94% |
na |
Mali |
93% |
90% |
80% |
Burkina Faso |
94% |
94% |
91% |
Niger |
88% |
95% |
80% |
Chad |
89% |
na |
80% |
Côte d'Ivoire |
65% |
60% |
72% |
Thailand |
na |
na |
24% |
Philippines |
na |
na |
43% |
Note: na = not available. Source: FAO (1992)
In dry tropical zones, forest harvesting generally exceeds the sustainable level of supply. Furthermore, dryland forests are rarely managed properly despite the presence of various management planning systems in all three continents. In Asia, several forest management trials have been established in dryland forests, but without any apparent success to date. Very little is known about current systems for dryland forest management in tropical South and Central America. Dryland forest management is considered important in Africa and Madagascar and this is reflected by the substantial number of projects carried out or ongoing in this region. However, at present, most of these projects are mainly pilot projects aimed at analysing participatory approaches to forest management.
Up until 1970, "classical" forest management systems were mainly applied to dryland forests in most regions. However, the forest management plans based on these systems were never really applied effectively, because of a lack of popular participation and insufficient knowledge of an environment that was much more complex and vulnerable than in many of the other countries where these systems had originally been developed.
In the 1980s, numerous projects were initiated in Africa, usually with one main management objective (e.g. industrial timber or fuelwood production, or wildlife management), but again with limited popular participation. In a few cases, local people were consulted and/or formed into forest management groups or local conservation committees. Eventually awareness of the particular problems of dryland forest management (e.g. inherent difficulties of managing dryland areas and the complexities of dealing with many stakeholders seeking many different benefits) led to the reorientation of the objectives of projects towards more decentralised management of natural resources, with particular attention being paid to the benefits sought by local people.
Considerable effort was also made to halt or even reverse desertification, which is the final stage of dryland forest degradation, by implementing programmes such as: afforestation with exotic species; planting "green barriers"; agroforestry development; and other measures. Unfortunately however, despite significant investment in these projects, this problem is far from being resolved and results have fallen far short of expectations. In the case of forest plantations, this was due to excessively high costs of most schemes and rejection of such schemes by the general public in many cases. Many other regreening activities failed because they were not effectively linked to the implementation of other policies (e.g. agricultural and pastoral policies).
A final point to note with respect to dryland forests is that wildlife should be a vital component of forest management plans because they are an important source of meat and other non-wood forest products that are consumed by local people. In addition to this, wildlife resources are also important for the tourism economy in countries such as: Kenya; Tanzania; and Zimbabwe.
Technical and scientific issues. Still not enough is known about the complex biological interactions that exist in dryland forests and the way that they evolve and function. For example most experiments and inventories in dryland forest ecosystems have focused only on wood production, rather than on management for multiple objectives. Sustainable forest management in these areas needs to be integrated with other land uses (i.e. integrated agro-silvo-pastoral management), which makes it necessary to be familiar not only with the forest, pastoral and agricultural resources, but also the with wildlife and various non-wood forest product resources (e.g. honey, gum, etc.) present in the forest. Agro-silvo-pastoral management systems should also encompass management of natural forests, multiple-use tree plantations, windbreaks, shelterbelts and hedgerows.
Faced with growing demand for agricultural and pastoral land, it is important to apply techniques aimed at improving and maintaining the productivity of agricultural land and rangeland in conjunction with forestry programmes, in order to avoid land degradation. Soil erosion and a drop in soil fertility effectively restrict all sustainable management options. Water management is another critical issue in these regions that, by definition, only receive small amounts of rainfall each year with which to grow plants and replenish groundwater supplies. Brush fires also limit sustainable management. They can be managed through the deliberate burning of high-risk areas at the beginning of the dry season, together with appropriate grazing pressure.
Socio-economic and political issues. The main constraints to dryland forest management stem from legal and socio-economic factors. These include: complex relationships between stakeholders and the forest; contradictions between land law and customary law (e.g. with respect to ownership of forest resources and user rights); and difficulties in replacing current agricultural and livestock production methods with new forms of rural land organisation and natural resource use. Nevertheless, given the prevalence of poverty in these regions, the improvement of food security is an absolute prerequisite to sustainable development. In effect, the main constraint to the implementation of sustainable forest management plans is the intensity of land use. Even in heavily degraded areas people still depend, to a great extent, on what remains of the forest to meet their basic needs. In order to eliminate an important source of pressure on dryland forests, it is vital to provide permanent solutions to the population's energy problems. As in other types of tropical forests, management plans in dryland forests have also been abandoned or poorly implemented due to inadequate monitoring by forest administrations and political pressures for change in the longer-term.
In degraded tropical forests, past unsustainable land management practices have led to the replacement, partially or totally, of forest ecosystems by grasses, shrubs and other invasive species. Such degradation can be caused by overharvesting, shortening of shifting agricultural cycles, or excessively high cropping pressure leading to a drop in soil fertility and abandonment of the land. Degraded forests are characterised by a low soil fertility and poor soil structure, considerable soil erosion and high susceptibility to fire.
Degraded tropical forests cover more than 2,000 million ha in total. Depending on the degree of forest degradation, several management actions to restore fertility and/or to promote site productivity, can be undertaken:
_ Secondary forest management. Secondary forests emerge naturally on land where human intervention has destroyed the original vegetation. They have reduced species diversity but, in terms of silviculture, are relatively easy to treat. However, their intrinsic value is also lower than in primary forest, except in some instances such as with Aucoumea klaineana and Cordia alliodora. Global interest in secondary forests has recently increased since it has been estimated that they cover more than 350 million ha (50% of which is in tropical South and Central America), but knowledge about this type of forest and its development is very limited.
_ Conversion to forest or agricultural tree plantations. Conversion of secondary forest to forest plantations or agricultural tree plantations (e.g. rubber trees, fruit trees and palm trees) is an acceptable option to meet protection and production objectives in a technical sense. Furthermore, such plantations generate income, employment and can even help the global environment by storing carbon.
Most large-scale tropical forest plantation establishment (e.g. teak in Asia) has taken place during the last half of this century. The rate of tropical forest plantation establishment world-wide has progressively increased, particularly in South America and Asia (mainly in Brazil and Indonesia, respectively). Experience has shown that the most important factors to consider when establishing a forest plantation are the objectives of management and the vulnerability, in ecological terms, of the site to be planted.
To date, most forest plantations have been established as even-aged monocultures, mainly using exotic rapidly growing species (e.g. eucalypti, acacias and pines). These species appear to be technically easier to manage and control and more profitable (for wood production) in the short-term. The result of this trend has been the restoration of productivity in some forest areas at the cost of a drop in biodiversity and heightened vulnerability to disease, pests and fire. In contrast to single-species plantations, mixed forests have fewer pest control problems, fire is inhibited due to their multi-layered composition, they can restore and maintain soil fertility and they present a more varied range of development possibilities.
Experience shows that wood yield from forest plantations appears sustainable if species are adapted to the site and if effective management methods are used. In fact, most failures in forest plantation projects occur due to bad species selection or mismatching species and site or the absence of forest maintenance and follow-up activities. In such cases, failed forest plantations can actually accelerate soil erosion, water pollution and siltation of watercourses.
Tropical forest plantation establishment and management techniques are currently well known for many species. Measures to improve tropical forest plantations have yielded notable results, but socio-economic and technical constraints (e.g. low manpower availability and difficulties in expanding the result of experiments to large areas) have led to a greater interest in the development of intensive mechanised methods.
Given current forest product prices, forest plantations nearly always turn out to be too costly to be economically viable in the short term. Furthermore, when considering that the revenue from plantation investments arises in the long-term, they are constantly exposed to various risks, such as: collapses in prices; natural disasters; and political instability. Another factor that has to be taken into account in the appraisal of tropical forest plantation programmes, is their impact of on the landless and poor people who are directly competing to use the land. In some cases, tropical forest plantations have led to the eviction of traditional users, upset existing systems of harvesting and extraction for local use and fostered serious social conflict. Thus, it is necessary to consider the wider impacts of such developments, but little concrete information about such issues ids usually available.
Agroforestry encompasses a large number of land use systems ranging from those where trees are planted on farming land to those where agriculture is practised on forest lands without leading to deforestation. In some regions, notably in Southeast Asia, multiple-use trees have been planted in agricultural areas in order to increase productivity and restore soil fertility.
The development of agroforestry systems has seen great progress over the last ten years thanks to new research the testing of new techniques and improvements in extension. However there is still room for progress in the development of sustainable management systems that are biologically and socio-economically robust.
In view of the scale of forest resource degradation, secondary forest management has recently become an important aspect of tropical forest management and represents one of the most important challenges to managers in tropical regions today. Forest cover can be restored naturally through natural plant succession and forest protection. Nevertheless, the development of older trees is necessary before the forest regains its original structure and composition. This process is slow and experience shows that many degraded sites are exposed to periodic disturbances (e.g. fire) that can inhibit natural regeneration and halt recovery. Very often, short fallow tree cycles (of several decades) are used as a means of restoring degraded site fertility prior to reusing the land for agriculture. It is useful to consider this in combination with long-term forest production and conservation options, as an option for the management of secondary forests.
Secondary forests hold considerable production potential for wood and non-wood forest products and provide numerous environmental functions, including: climate modification; soil protection; biodiversity conservation; and amenity. Furthermore, sustainable management of secondary tropical forest can help to restore undegraded forestland.
Projects with objectives to manage secondary forests have generally failed in the past because of economic reasons (e.g. high costs) and conflicts over land uses. Long-term objectives to restore secondary forests should recognise that there will not be any immediate financial returns to such investments. This requires that the indirect benefits of forest cover regenerated in this way are taken into consideration in the decision-making process.
The main problem with sustainable management of secondary forests is that natural succession in such complex systems is not properly understood or known and considerable investment in research is required to provide some answers to important questions. However, from a technical point of view, the long-term results are likely to be unpredictable because of the many different outcomes that may arise from natural ecosystem evolution, which are difficult to model using current knowledge and techniques.
