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Chapter 4. Trees outside the forest


The world has billions of trees that are not included in the FRA 2000 definitions of "forest" and "other wooded land". Trees outside the forest (TOF) include trees in cities, on farms, along roads and in many other locations which are by definition not a forest. All trees make a contribution to the environment and to the social and economic well-being of humankind. This chapter briefly describes the importance of trees outside the forest and some of the issues related to their assessment. FRA 2000 did not attempt a comprehensive global assessment of TOF, nor has such an assessment ever been carried out. However, many studies have been made of TOF for specific countries or land areas, often with an emphasis on their economic contributions. The chapter provides a summary of selected studies and discusses the practical and conceptual difficulties related to a comprehensive global assessment. Suggestions are made for improvements that might be made in future assessments.


The significance of trees outside the forest (TOF) can be observed in several contexts. In countries with low forest cover, TOF resources constitute the main source of wood and non-wood "forest" products, even though trees may be so scattered that the maps produced by FRA 2000 indicate that no forests exist. Trees are found on agricultural lands, in densely populated areas, in fruit-tree plantations and in home gardens, which often cover a large proportion of the land. In urban areas trees provide important aesthetic and environmental services in addition to providing shade and greatly increasing the livability of cities. Communities, farmers and herders who do not have access to forests diversify their production and protect their land by maintaining various tree systems on their farms.

Deforestation has been mapped and quantified, but very little is known about the fate of land formerly under forest; forest clearing is often followed by the establishment of production systems of which trees are an integral part. Not much is known about the dynamics of trees on farmlands and their corresponding contribution to the production of wood and other products and services. Similarly, little is known about changes in tree cover in fields and urban systems. Knowledge of trees outside the forest comes mostly from local studies on agroforestry, sylvipastoralism and urban, social, community or rural forestry.

This widespread and multipurpose resource, familiar to farmers but poorly defined by managers and mostly absent from official statistics and development policies, needs to be better assessed and known. Growing populations, shrinking forests and degraded ecosystems all suggest that trees outside the forest are destined to play a larger local and global role in meeting the challenges of resource sustainability, poverty reduction and food security. Trees outside the forest relieve the pressure on forest resources, conserve farmland, boost agricultural productivity, blunt the harmful impact of urban growth on the environment, increase food supplies, provide income and in general make valuable contributions to food security.

FRA 2000 did not undertake a global assessment of trees outside the forest, mainly because of resource limitations; nor has there ever been a comprehensive global assessment of trees outside the forest and their products. However, a number of studies have been carried out for specific sectors or geographic areas, often with an emphasis on their economic contributions. This chapter provides a summary of selected studies and discusses the practical and conceptual difficulties related to a comprehensive global assessment.

The chapter responds to the concern expressed by the Expert Consultation on Forest Resources Assessment 2000 (Kotka III) regarding the lack of information on TOF (Finnish Forest Research Institute, 1996). For more information, national case studies and working papers can be found on the FRA Web page. An FAO Conservation Guide on trees outside the forest will be published at the end of 2001.


Trees outside the forest are defined by default, as all trees excluded from the definition of forest and other wooded lands (see Appendix 2). Trees outside the forest are located on "other lands",[2] mostly on farmlands and built-up areas, both in rural and urban areas. A large number of TOF consist of planted or domesticated trees. TOF include trees in agroforestry systems, orchards and small woodlots. They may grow in meadows, pastoral areas and on farms, or along rivers, canals and roadsides, or in towns, gardens and parks. Some of the land use systems include alley cropping and shifting cultivation, permanent tree cover crops (e.g. coffee, cocoa), windbreaks, hedgerows, home gardens and fruit-tree plantations.

Classification of trees outside the forest presents certain difficulties. There are existing classifications for agroforestry, but none applicable to all trees outside the forest (Kleinn 2000). For practical reasons, the FRA 2000 definition of "forest" combines aspects of both land cover and land use. This approach creates difficulties not only for classification of forest, but also for classification of TOF.

In a study on data-gathering on TOF in Latin America (Kleinn et al 1999), where classification was primarily based on land use criteria, separating land use and land cover aspects was found to be a main source of misinterpretation. There was a possibility of confounding coffee plantations and trees in pasture with forest, given their high density. This clearly shows some of the problems involved in establishing a simple and reliable a posteriori classification.

In France, the National Forest Inventory (IFN) and Teruti Land Use Study[3] have begun to attempt coordinating classifications of trees outside the forest. The objective is eventually to use the annual Teruti data to update the IFN ten-year data, with a single national nomenclature as a possible end result (IFN 2000).


In industrialized countries, farmers list shade and shelter, soil protection and improvement of the landscape and rural environment as their main reasons for growing trees (Auclair et al. 2000). In the tropics, farmers grow woody species for food security and subsistence. Trees outside the forest are a major source of food (Bergeret and Ribot 1990). Livestock fodder produced by TOF can be a matter of life and death in semi-arid or mountainous areas.

Fuelwood remains the prime source of energy in developing countries, representing up to 81 percent of the wood harvest (FAO 1999). In contrast, in the industrialized countries, fuelwood accounts for less than 10 percent of total fuel consumption (FAO 1998). Very few studies have reported on overall fuelwood output from stands and single trees outside the forest, but agroforestry systems and orchards are known to provide a large part of the resource.

Trees outside the forest are an important source of non-wood forest products,[4] described in more detail in Chapter 11.

Trees outside the forest have an important ecological role. Planted trees and shrubs in fields help to check runoff and erosion and control flooding, as well as helping to purify water and protect against wind. Trees lining rivers and streams help to maintain biodiversity, providing spawning beds for fish and shellfish and shade which reduces eutrophication.

The unique role of trees in soil protection and conservation, checking wind and water erosion and maintaining soil fertility is universally acknowledged. Also important are the cumulative benefits of trees on smallholdings to soil and water conservation, in particular in the larger context of mountain watershed management; their positive impact on climate; and their role in buffering the effects of desertification and drought.


In spite of the limits of data at the regional or global level, a number of local initiatives have been carried out. The approaches of the various studies differ in accordance with the purpose and scale of the analysis. Few studies use methods resembling the conventional forest inventory. Many studies rely on existing literature or estimates drawn from surveys and interviews. The quantification of products is often based on different parameters, such as estimates of global output, marketed output, observed or potential productivity or economic value. Thus the reliability of the results is uncertain.

The following are the results of some national initiatives that have assessed trees outside the forest (FAO 2001).

In Kerala, the most densely inhabited state of India, a study estimated that of the total annual production of 14.6 million cubic metres of wood in the state, about 83 percent was from homesteads (house compounds and farmlands), 10 percent from estates (plantations of rubber, cardamom, coffee and tea) and only about 7 percent from forest areas (26.6 percent of the state area is under forest cover (FSI 1998). Trees outside the forest met about 90 percent of the fuelwood requirements of the state. Fuel from coconut trees alone, including both wood and non-wood materials (pruned and fallen), constituted about 70 percent of the total fuelwood supply (Krishnakutty 1990).

A study in Haryana State in India, an intensively cultivated state with about 3.8 percent of its area classified as forest land but only about 2 percent under actual forest cover (FSI 1998), showed that farm forestry (trees along farm bonds and in small patches up to 0.1 ha) accounted for 41.2 percent of the total growing stock of wood. Multiple tree rows along roads and canals accounted for 13 percent and 9.6 percent, respectively; village woodlots for 24 percent; and block plantations of less than 0.1 ha for 10.6 percent (FSI 2000).

In Morocco, where forest cover is less than 5 percent of the land cover and other wooded lands only 7 percent, nearly 20 percent of the land may be occupied by trees outside the forest, namely as wooded pasture (84 percent) and fruit-tree plantations (12 percent) (Rosaceae, citrus, olives trees, palm trees, walnut trees, fig trees, almond trees). Fruit production has an important place in the national economy (MADRPM 2000). It is noteworthy that even when a forest is largely destroyed, the carob (Ceratonia siliqua) is one of the few species traditionally conserved, as it is highly appreciated by farmers for multiple purposes, providing both fodder and income from the sale of its fruit for export. However, there are no reliable data on the distribution and potential of this "forest" resource, which is of interest for farmers, herders, concessionaires and the government and distributed on agricultural and forest lands.

In the Sudan, the National Forest Inventory has undertaken a national land use inventory to provide area and volume statistics for planning at the subnational and national levels (FAO 1995). The inventory was designed to provide preliminary estimates regarding products other than the traditional fuelwood and timber, such as the amount of gum, fruit or nuts that can be collected and the distribution of non-wood species of interest (Glen 2000).

In Costa Rica, the Tropical Agricultural Research and Higher Education Center (CATIE), in collaboration with Freiburg University, Germany, is developing a regional methodology for Central America to assess tree resources outside the forest. A mix of satellite remote sensing, aerial photos and ground sampling is used to address the complexity of the resource (number of species, distribution and structure) and to allow dynamic monitoring of resources at the national and regional levels (Kleinn et al. 1999). Kleinn et al (1999) studied data-gathering on TOF in eight Latin American countries (Brazil, Costa Rica, Colombia, Guatemala, Haiti, Honduras and Peru). None of these countries had established a database and the search for information was multisectoral. The statistics on land cover and land use gave some idea of the relative importance of trees outside the forest.

In Kenya, extensive tree planting on farmlands was promoted in the 1970s and 1980s, with land tenure security as a major incentive. There is an increasing trend of tree cover and species diversification on privately owned farms (Kiyiapi2000). Assuming that the present rate of increase in tree planting will continue, it was estimated that farms produced about 9.4 million cubic metres of wood in 2000 and will produce about 17.8 million cubic metres in 2020. Their share of the total wood produced in the medium- and high-potential districts was projected to increase to 80 percent in 2020 (FDK 1994). Njenga et al. (1999) indicate that tree crops contributed 18 to 51 percent of the total household income at the farm level. Indeed, while natural stands of trees have declined there has been a corresponding increase in tree planting in much of the densely populated plateaus of Kenya. As natural forests are reduced or become inaccessible, agroforestry systems help people to diversify production and income and to protect themselves from shortages of fuel and wood (FDK 1994).

In Bangladesh, natural forest formations cover less than 6 percent of the country and the population growth rate is extremely high. An inventory of homestead/village forests in the country (FAO 1981; Douglas 1981; Hammermaster 1982, quoted in Singh 2000) indicated that trees outside the forest constitute a vital resource for local populations, providing food, fodder and fuelwood. The sampling method was based on dual village/household sampling with an agro-ecological and administrative sampling base. Rural Bangladesh was divided into six major regions considered as agro-ecological strata, each subdivided into thanas (administrative entities, subdistricts). The households making up the sampling units were chosen at random from a number of villages. The inventory sampled data on palm trees and cane as well as trees, bamboo and thickets. The results, expressed per stratum and per inhabitant, provide volumetric data for fuelwood and sawnwood, and species data for total amounts under and over 20 cm. This inventory was apparently the first to nationwide assessment of trees outside the classified forests in Bangladesh.


A priority challenge of future assessments is to know the state and dynamics of all tree resources both in and outside the forest. A country embarking on a planning exercise cannot confine itself solely to the trees within its forests, especially when its wood resources appear to be insufficient.

The choice of tools and methods used to describe or assess trees outside the forest depends on the scale of analysis, kind of data and degree of exactitude desired. The tools used are not generally specific or new; rather, they are combined and implemented in original ways. The inventory in Bangladesh described above is one of the numerous examples of methods developed for gathering data on TOF. The Bangladesh study gives evidence of the adaptations needed to bring conventional forest inventory procedures in line with the specific nature of this resource.

In some aspects - e.g. structure, spatial distribution and extent of area cover - trees outside the forest are more difficult to assess than forest formations. The assessment of TOF does not lend itself to the potential cost savings associated with expanded uses of remote sensing technology. Remote sensing by satellite presents more difficulties for assessing TOF resources than for assessing attributes such as forest area. However, satellite data do allow a region to be stratified on the basis of ecological criteria and land cover, providing the basis for a good working document for more specific work in the future.

The most commonly used remote sensing technology for TOF resources is aerial photography, which can be used to describe spatial distribution and to distinguish TOF cover classifications, providing the appropriate scale is chosen. However, high costs prohibit widespread use of aerial photography for TOF assessments in most countries. The new 1 m resolution satellite sensors represent a possible future alternative to aerial photography.

Some TOF field inventories are modelled on forest inventory methods and keep to biological and physical criteria; others emphasize social aspects, choosing villages as the sampling units. For measurements on the ground, sampling arrangements designed for forest stands may not be the most effective arrangements for trees. Less traditional sampling plans which would theoretically be better suited to this resource should be tested on various categories of TOF, especially those covering fairly large areas.

Studies of the social and economic benefits or impacts of TOF often rely on household surveys, interviews or standardized appraisals such as rapid or participatory rural appraisal.

The integration of the last two approaches - biophysical inventory and socio-economic analysis - is not simple and calls for caution given the great variety of social situations that are only meaningful in the local context.

Environmental benefits or impacts of TOF might be indirectly assessed by linking measurable indicators, such as the number and type of trees, with environmental variables such as water quality or erosion. In an urban setting, tree cover might have direct impact on the ambient temperature. Measuring the environmental impact of tree management is an issue for all natural resource planning or management operations.

Assessment of trees outside the forest requires geographical, ecological, biophysical, social and economic data. However, this implies that an important amount of information will have to be carefully processed. The diversity of end-uses for this information, including land use planning and analysis based on inventory, will need to be considered in data assembly and processing and in the presentation of results.

It is important to know the status of trees outside the forest at any given moment, but it is even more essential to be able to trace patterns of change over time in the same area. The two most commonly used approaches have been comparison of aerial photos taken at sufficiently long intervals, and surveys among villagers/managers combined with field inventories.

Some countries, such as France and the United Kingdom, have undertaken periodic inventories based on the establishment of permanent plots linked to permanent forest inventories. However, the high cost of this type of operation limits the number of countries able to adopt it. India and Bangladesh are now experimenting with options for the future.

The current trend towards decentralized authority in land use planning suggests the importance of carrying out assessments at the local level, where the geographical, historical and socio-economic context is relatively harmonious. A minimum number of common rules concerning methods and arrangements is necessary, however, if the data are to be comparable at the country level. Certainly, the technical side of assessing trees outside the forest is complex, and more research is needed to better pinpoint the resource.


Trees outside the forest are increasingly recognized by policy-makers, planners and managers as an essential component of sustainable development. This ancient resource has been part of the daily context and culture of rural populations and in many cases TOF resources are critical to food security. However, much work and discussion will be needed before trees growing in non-forest areas can be considered an integral part of planning and development policies.

One important need is a consensus working definition that can be adapted with time and circumstances to fit the rapidly changing economic, ecological, social and cultural context of this resource. This would facilitate the work of framing laws that are neither sectoral nor contradictory, incorporating rights of ownership, use and access for land and trees. In many countries there is a need for more secure land tenure and user rights for trees growing outside forest areas, especially for less empowered sectors of the population, including women.

Databases on trees outside the forest, although fairly substantial in some countries, remain fragmented, diffuse, sometimes empirical and often sectoral. Advances are needed in practical approaches to the use of knowledge to assess the true contribution of TOF resources to economic needs, social demand and ecosystem maintenance. Inventories and assessments of TOF resources based on reliable and accessible methods are essential to effective land use planning. Strategies to promote and support trees outside forest areas need to address the importance of sustainability as they seek to maintain traditional advantages to populations while expanding opportunities for new benefits from this resource.

Moves towards devolution and empowering people in the management of local resources should enhance and promote the conservation and sustainable use of trees outside the forest. FAO is committed to improving the assessment of trees outside the forest in future global assessments, and to assisting member countries in building their capacity to assess TOF resources effectively and to use this knowledge to evolve and implement effective sustainable development policies and programmes.


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[2] “Other lands” include farmlands (including pasture and meadows), built areas (including human settlements and infrastructure), bare lands (including oasis) and snow and ice.
[3] The Teruti survey of the Central Bureau of Statistical Surveys and Studies was initiated by the French Ministry of Agriculture in 1981; it monitors changes in TOF areas and wooded areas.
[4] Non-wood forest products (NWFP) are products of biological origin other than wood derived from forests, wooded lands and trees outside forests.

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