Crop

Tropical forests and classification of forests types
Trends in tropical forest area
Tropical timber harvesting

Tropical forests and classification of forests types

Consistent with the International Tropical Timber Agreement (ITTA), this section defines tropical forest as forest lying between the tropics of Cancer and Capricorn. The classification of tropical forest types is notoriously difficult and contentious. The forest classification used by the United Nations Environment Programme-World Conservation Monitoring Centre (UNEP-WCMC) is given below. Closed tropical forest is generally taken to include natural tropical forests with a tree canopy cover of greater than 30 per cent.

UNEP-WCMC tropical forest types

Source: UNEP-WCMC's harmonised general forest classification.
Note: "Canopy cover" is defined as the percentage of the ground covered by a vertical projection of the outermost perimeter of the natural spread of the foliage of plants.

Another way to group tropical forests is according to their designated functions (i.e. the function or purpose assigned to a piece of land either by legal prescriptions or by decision of the land owner/manager). In most countries, logging and other extractive activities are only permitted on forest areas designed for production purposes (production forests). Production forests include both natural forest (land of naturally regenerated native species) and planted forest (forest stands established through planting or seeding of both native and introduced species).

Designated functions of forests
in the tropical permanent forest estate (PFE)

Source: ITTO Status of Tropical Forest Management 2005.
Note: Tropical permanent forest estate (PFE) is defined as land, whether public or private, that is to be kept under permanent forest cover.

Trends in tropical forest area

The world's tropical forest area in 2000 was just less than 1,787 million hectares, corresponding to 46 per cent of total forest area (tropical and non-tropical). South America accounted for 43.4 per cent of total tropical forest area, followed by Africa and Asia with 35.1 and 15.3 per cent respectively. Central America and Oceania accounted for the remainder (3.4 and 2.8 per cent). Tropical (rain) forests are mainly found in the Amazon basin of South America, the Congo basin of Central Africa and insular South-East Asia where the climate is hot and humid throughout the year.

Tropical forest area in per cent of country area, 2000 (%)

Source: UNCTAD secretariat, based on ITTO and FAO data.

Twenty-eight countries had more than half their total area covered by tropical forests, and eight of these had more than 75 per cent of their total area covered. Most of these were small island states in the Pacific Ocean, but the list also included three low-lying coastal states and territories in South America (Guyana, Suriname and French Guyana) and one country in the Congo Basin (Gabon).

Ten countries with the largest tropical forest, 2000
(% of total tropical forest)

Source: UNCTAD secretariat, based on ITTO data.

The five countries with the largest tropical forest area accounted for almost half of total tropical forest area (approximately 865 million hectares or 48 per cent). Brazil alone accounted for 27 per cent of the world total, or about 490 million hectares.

Tropical forest continued to decrease steadily over time. The total net change in tropical forest area in the period 1980-1990 is roughly estimated at -12.8 million ha per year, equivalent to a loss of 0.6 per cent of the remaining tropical forest area each year during this period. The total net change in forest area in 1990-2000 is estimated at about -11.5 million ha per year - a loss of 0.6 per cent per year over the period. Compared to 1980, total tropical forest area had decreased by 12 per cent in 2000. Africa and South America continued to have the largest loss of forest, but the most rapid decrease occurred in Central America and Asia.

Trends in tropical forest area by region, 1980-2000 (million ha)

Source: UNCTAD secretariat, based on ITTO data.

Annual tropical forest change by region, 1980-1990 and 1990-2000

Source: UNCTAD secretariat, based on ITTO data.

Five countries with largest negative changes in tropical forest area,
1980-2000

Source: UNCTAD secretariat, based on ITTO data.

In many tropical countries, deforestation is due mainly to the expansion of capital-intensive agriculture (cattle ranching and, more recently, the planting of soybeans, which are generally the most immediately profitable land-uses). Timber extraction from natural forests plays a relatively minor role.

There is no straightforward correlation between a country's forest endowment and its timber production. In nearly all tropical countries, timber comes from areas of forest, whether natural or planted, specifically designated for extractive activities (production forest). Accordingly, much depends on the extent of the natural tropical forest that has been allocated to production (natural production forest), the plantation estate, as well as the character and intensity of timber harvesting.

The forest area designated for production in ITTO producer member countries is estimated to be 353 million hectares, or 29 per cent of the total area of tropical closed forest (estimated by FAO 2001 to be 1.2 billion hectares). Wood from natural production forests is supplemented in many countries by planted forests.

Closed tropical forest, natural production forest and planted forest,
2005 (million ha)*

Source: UNCTAD secretariat based on ITTO data.
*Note: Regional aggregates comprise ITTO producer member countries. In many cases, data for plantation areas are from FAO 2001.

Of the estimated 209 million hectares of closed natural forest in the ITTO producer member countries in Africa, an estimated 70.5 million hectares (34 per cent) are assigned as natural production forest. In the West African countries, all or nearly all the closed tropical forests have already been logged at least once. In the Congo Basin, in contrast, there are still large areas of primary forest. The total area of planted forests (825,000 hectares) is small compared to that in Latin America and the Caribbean and especially in Asia and the Pacific.

Of the estimated 204 million hectares of closed natural tropical forest in ITTO member countries in Asia and the Pacific, an estimated 97.4 million hectares (48 per cent) are allocated to production. By far the largest area of natural production forest is in Indonesia (46 million hectares), followed by India (13.5 million hectares), Malaysia (11.2 million hectares), Myanmar (9.7 million hectares) and Papua New Guinea (8.7 million hectares). Thailand has no natural production forest, since it has banned logging in natural forests. In addition, there are about 38.3 million hectares of plantations (more than 80 per cent in India).

Of the estimated 788 million hectares of closed natural tropical forest in the ITTO producer member countries of Latin America and the Caribbean, an estimated 185 million hectares (23 per cent) are designated for production. The total plantation estate in the tropical part of ITTO producer member countries in Latin America and the Caribbean amounts to about 5.6 million hectares, the majority (68 per cent) in Brazil, where the main use is for wood pulp.

For a complete analysis, please refer to:
International Tropical Timber Organization. Status of Tropical Forest Management 2005. ITTO Technical Series No 24, 2006.
Food and Agriculture Organization of the United Nations. Global Forest Resources Assessment 2005. FAO Forestry Paper 147. Rome: FAO, 2005.

Tropical timber harvesting

In spite of very high biomass levels, tropical forests generally support lower volumes of merchantable timber than temperate forests.

Source: Vanclay, Jerome K. Estimating Sustainable Timber Production from Tropical Forests. A Discussion Paper prepared for the World Bank. Working Paper No. 11. Jakarta: CIFOR, 1996. View pdf (363 KB).

The volume of timber harvested from an average hectare of tropical forest worldwide is less than 30 m3 and usually involves 10 or fewer trees, each of which is a different species (Food and Agriculture Organization of the United Nations. Forest Resources Assessment 1990: Tropical Countries. FAO Forestry Paper No. 112. Rome: FAO, 1993). In Africa, some highly selective operations remove only one tree in 10 ha. By comparison, a typical operation in the coniferous forests of the Pacific Northwest of the United States extracts 500 m3/ha from 200 to 300 trees, most of which are a single species. As a consequence of the relatively low volume of merchantable timber harvested per hectare of tropical forest, logging operations in the tropics are spread over extensive areas and the area disturbed by logging to obtain a given volume of industrial roundwood is substantially larger than in temperate forests.

Current logging practices

Most tropical countries impose regulations on logging activities. Timber harvesting is only permitted to occur in areas of forest designated for production. Current logging practices in the tropics involve the setting of minimum diameter cutting limits (MDCL), annual allowable cuts (AAC) and cutting cycles (i.e. the interval between successive harvest on any particular area - for tropical forests, cutting cycles are typically in the range of 20 to 40 years). For example, according to the MDCL rule applied in the mixed dipterocarp forests of South-East Asia, any tree with a diameter at breast height (dbh) above the specified limit of 60 cm may be felled. In the lowland dipterocarp forests, this rule leads to felling intensities as high as 10-20 trees/hectare or 100-150 m3/hectare. The sustainability of these systems depends mostly on the regeneration capacity of the forest and the harvesting modalities (intensity of extraction and rate of damage).

Reduced impact logging (RIL)

The term "reduced impact logging" (RIL) has become associated with logging technologies that aim to reduce the environmental and social impacts of timber harvesting, while improving the production efficiency of logging operations. Although it varies somewhat with the local situation, RIL in tropical forests generally requires the following:

• a pre-harvest inventory and the mapping of individual crop trees;
• the pre-harvesting planning of roads, skid trails and landings to minimize soil disturbance and protect streams and waterways with appropriate crossings;
• pre-harvest vine-cutting in areas where heavy vines connect tree crowns;
• the construction of roads, landings and skid trails following environmentally friendly design guidelines;
• the use of appropriate felling and bucking techniques including directional felling, cutting stumps low to the ground to avoid waste, and the optimal crosscutting of tree stems into logs in a way that maximizes the recovery of useful wood;
• the winching of logs to planned skid trails and ensuring that skidding machines remain on the trails at all times;
• where feasible, using yarding systems that protect soils and residual vegetation by suspending logs above the ground or by otherwise minimizing soil disturbance; and
• conducting a post-harvest assessment in order to provide feedback to the resource manager and logging crews and to evaluate the degree to which the RIL guidelines were successfully applied.

RIL operations incur costs associated with pre-harvest activities, harvest planning activities and training of personnel that are not incurred by conventional logging (CL) operations. The core issue is whether gains in efficiency attributable to planning operations equal or exceed the incremental RIL costs.

Logging characteristics and financial cost estimates, CL v. RIL

Source: Holmes, Thomas P., Frederick Boltz and Douglas R. Carter. "Financial Indicators of Reduced Impact Logging Performance in Brazil: Case Study Comparisons". In Applying Reduced Impact Logging to Advance Sustainable Forest Management. Bangkok: Food and Agriculture Organization of the United Nations, Regional Office for Asia and the Pacific, 2002.
Note: Research was conducted at three study sites in the Brazilian Amazon during the mid-1990s.

For more information on RIL, browse and download news releases, reports and articles related to reduced impact logging on the ITTO's site.

Complementary rules to RIL

Foresters and ecologists generally agree that RIL operations based only on minimum diameter cutting limits can neither sustain timber yields in the long term nor maintain forest ecological and functional integrity. New harvesting rules complementing RIL have been proposed for mixed dipterocarp forests. Suggested guidelines and practices include: (1) integration of reduced-impact logging practices into normal management operations; (2) limiting the cut to 8 or less trees/ha (with a felling cycle of 40 to 60 years to be determined according to local conditions); (3) defining minimum diameter cutting limits according to the structure, density and diameter at reproduction of target species; (4) avoiding harvesting species with less than 1 adult tree/ha (dbh 50 cm over an area of 50-100 ha); (5) minimizing the size and connectivity of gaps (<600 m2 to the extent possible); (6) refraining from post-logging treatments such as understorey clearing; and (7) providing explicit protection for key forest species.

For a complete analysis, see:
Plinio Sist, "Why RIL won’t work by minimum-diameter cutting alone," ITTO Tropical Forest Update 11/ 2 (2001) View pdf (150 KB) and "Towards sustainable management of tropical forest: moving beyond RIL and Minimum Diameter Cutting Limits," in La forêt, source de vie : XIIè Congrès forestier mondial, Canada, 21-28 September 2003/FAO. View pdf (219 KB).