2. Resource assessment and development

Determining tenure and access
The resource inventory
Other factors in resource assessment
Species selection
Sustainable harvest levels
Scope for domestication of species
For further reading

A first step in developing any viable forest enterprise is understanding the capacity of the forest resource. It is impossible to manage the resource wisely or profitably without knowing about its natural growth and production, and the human environment that affects it.

Many people assume that harvests of NWFPs have less impact on a forest than logging. However, this assumption is unfounded. Forest ecosystems have such complex interrelationships that harvests of some non-wood resources can affect plant (and wildlife) populations as negatively as logging. Without a sound knowledge of the resource and regular monitoring, harvests of certain non-wood resources can have a disastrous impact that is not noticed until it is too late to remedy.

For example, overharvesting of fruits or seeds of a tree species can drastically reduce regeneration to the point of local extinction without any visible effect. Large individual trees may remain and the system might appear undisturbed. Only years or decades later, when the large trees die and no individuals replace them, will the damage become evident (Peters, 1994).

This chapter describes the steps required to gain an understanding of an area's non-wood resource. Based on this, a community or enterprise can begin to prepare a plan for management. Chapter 3 describes the equally necessary step of gauging the existing nearby communities' dependence on the resource.

Determining tenure and access

Even before producers can assess the biological components of an ecosystem for management, they must understand the legal situation of the land in question. Legal title and the rights of harvest determine the scope of management options, the management objectives and the possibilities for resource inventory.

The first questions that must be answered in a resource inventory include: Who owns the resource? Who has the right to use the resource? What restrictions (e.g. licensing) apply to management?

Property rights can be divided into four categories:

private property situations are fairly straightforward, although resolving conflicting land-use claims can be complex (see Chapter 8);

common property resources have clearly recognized users who, although they may not own the resource, have recognized access rights and the ability to limit access to others (ATI, 1995). Many traditional communal systems for land use are common property systems;

open-access resources, accessible to all, have no recognized users and are not easily controlled;

state or public property often requires users to negotiate rights or obtain authorization for secure rights or access.

Successful extractive activities using NWFPs often have the features of common property management. Common property resources may often be mistaken for open-access resources, but common property resources are more widespread. If a resource is open-access, the resource manager(s) should seek to change this, because it is very difficult to manage an open-access resource sustainably and equitably (ATI, 1995).

The resource inventory

Advance planning
Inventory methods
Importance of wildlife
Analyzing the results
Reducing inventory costs

Once tenure is clarified, a resource inventory should ask certain key questions: What economic plant and animals species occur in the area? What are their ecological and biological characteristics? What products do they produce? How abundant are they and what is their capacity for regeneration? During which seasons are they harvestable? What local social and cultural values are associated with different parts of the forest? (Reds, 1995)

In tropical forests, one consequence of species diversity is extremely low densities for individuals of any given species. In inventories at two sites (one in Amazonia and one in Southeast Asia), less than 10 percent of the species had more than four trees per ha. Such low density causes difficulties in accurate inventory as well as in harvest management. Of course, there are many exceptions to this generalization. Oligarchic forests (in which one species predominates) exist in almost every region of the wet tropics and offer great promise for relatively easy sustainable harvests (Peters, 1994).

Advance planning

Planning helps to make inventories, which are expensive and labour-intensive, more efficient. Before the inventory, it is useful to answer the following questions, among others, for each major species (Peters, op. cit.):

• Where does the desired species occur in greatest abundance? Its distribution should be mapped as precisely as possible;

• is the species limited to a certain forest type, or is it fairly evenly distributed throughout the area?

• is the desired material produced by only one species or by several species? What is the exact taxonomic identity of these plants?

• has a product already been harvested from the area? For how long and how, and by whom? Heavily exploited areas and areas of selective planting or other management by local people should be noted on the map;

• do any good maps, aerial photos or satellite images of the region exist? Handheld, low-cost global positioning systems (GPS) now permit communities to locate boundaries fairly accurately using satellite data;

• has the area ever been inventoried, perhaps for another resource (timber, minerals, wildlife)? If so, for what kind of resource? Try to obtain copies of any information available.

In this advance work, no available sources of information should be overlooked, including: unpublished reports by local government officials, companies or projects; local export statistics; or specimens at a nearby herbarium (Peters, op. cit.).

Inventory methods

When all the above information has been collected, a professional inventory specialist or team should conduct the inventory. Conventional forestry methods for conducting inventories are geared to wood production and are not well suited to the task of assessing non-wood resources. Still, they provide a starting point for understanding the resource (see "For further reading" regarding inventory methods).

Peters (op. cit.) describes information that an inventory should provide:

• a reliable estimate of the resource density (i.e. total number of harvestable individuals per hectare for that species) in different forest types. For fruit and oil seed species, this means the total number of adult trees. For rattan, medicinal plants and species that produce latex, this may also include juvenile individuals;

• the current size-class distribution of adults. For trees, this means measuring the diameter at breast height (DBH) of all stems. For herbaceous plants and small understorey plants, height measurements are used instead;

• a preliminary assessment of species regeneration. Are there enough small individuals to replace the older adult trees when they die or are removed? Answering this requires that smaller, non-productive individuals also be counted and measured.

The smallest diameter limit of trees to be measured depends on the size distribution of the species and it;, density in the forest. Using a smaller minimum diameter increases the useful information that the inventory will produce, but also makes it more expensive due to the added fieldwork required. For tree species that occur at relatively low densities, a minimum diameter of 10 cm DBH is useful; for more abundant species, a higher minimum might be used.

The overall sampling intensity (or pattern of sample plots used) also depends on the trade-off between inventory precision versus cost, and the species. For example, inventories of bamboo and rattan may measure all stems 3 m and longer in a 10-m radius plot. An inventory of nipa palm (Nipa fruticans) might use different sample plot sizes for different plant sizes: all seedlings shorter than 1.5 m may be measured in plots of 2-m radius; in 5-m radius plots, all plants taller than 1.5 m may be measured (Reds, op. cit.).

An inventory of non-wood resources in southern Ghana focused on a few forest products that were widely traded or otherwise subject to increasing pressure. These included climbers (such as cane), bamboo and some herbaceous plants. The inventory used a uniform 1-ha sample plot size throughout, but sampling methods varied depending on the species. For cane, the inventory recorded the numbers of mature, immature and cut stems. For herbaceous plants, the inventory noted the number of plant groups (clumps) per plot. (Falconer, 1992).

A useful inventory should take advantage of local knowledge. For this, the inventory team should include a knowledgeable local collaborator who can help record each plant's local uses (all plant parts used) and local harvest techniques (Reds, op. cit.).

Some innovative inventory procedures compare natural forest with locally managed forest plots (Salick, 1992). One inventory in Nicaragua compared species regeneration in both situations, using 5 x 2 m subplots within 1-ha plots. This study thus provided a resource inventory along with detailed comparisons with local management. These comparisons permitted a general assessment of the impact of current local harvests and management.

Recently, some new models of arrangements have been developed to carry out comprehensive inventories of biological resources. Examples of this "biological prospecting" are the INbio-Merck agreement in Costa Rica (see Chapters 4 and 10 for more details) and the grants organized by the US National Institutes of Health in Latin America and Africa (Sittenfeld and Lovejoy, 1994 and Grifo, 1994).

Importance of wildlife

Wildlife is often an important non-wood forest resource, particularly in Africa. Wildlife population characteristics should be recorded in a forest inventory. Even where communities do not use the wildlife resource, wildlife activity influences forest dynamics in important ways, for example, as seed dispersal agents.

Analyzing the results

Before analyzing the results of an inventory, it is necessary to divide the information following a suitable classification (e.g. species, size classes, forest types, use types). The data for each forest type can, for example, be translated into charts of size-class structure. Size-class divisions for these charts vary for different types of trees. For large canopy trees, 10-cm diameter classes are adequate. Smaller tree species may need to be divided into 5-cm diameter classes. For shrubs and small palms, Peters (op. cit.) suggests a 50-cm height interval. Each chart could include 8 to 12 size classes.

These charts provide a valuable baseline for assessing the impact of harvesting. They can show when a population presents a healthy distribution of different-aged trees, or in contrast, reveal a worsening situation where species regeneration is severely limited for some reason, with no established seedlings. Peters (1994) explains in more detail how to interpret these charts.

Reducing inventory costs

Inventories are expensive to conduct and most communities or enterprises cannot afford them by themselves. However, several groups interested in a forest's various wood and non-wood resources may work together to conduct an inventory and share the costs.

Alternatively, in some cases, an "indicator" species might be studied as a signal of forest health. An indicator species is one that is more sensitive to changes in forest conditions. Where such a species is recognized locally, a focused inventory could study this species to gauge the impact of harvesting on the ecosystem (FAO, 1995).

Other factors in resource assessment

The previous section summarizes the ecological aspects of resource inventory. At the same time, an overall assessment of prospects should also consider the following (Vantomme, 1995):

socio-economic information on the nearby communities and the costs and benefits of managing the resource. Besides financial factors, economic values need to be assigned to otherwise non-monetized costs and benefits (see Chapter 3);

existing and future demand for preferred species (including preferences on size assortment and quality), site conditions affecting harvesting costs, size and types of cottage industries, location of processing units and transport facilities, and scale of traditional and potential uses (Chapters 3-7);

operational information, or factors that will affect the specific operations, such as protection, harvesting, nursery establishment and other logistics;

institutional information, meaning the legal and policy framework and political forces influencing resource use. This includes local attitudes, existing and proposed policies, legal rights and obligations, and training and research support to communities (Chapters 8-10).

Species selection

With a good knowledge of the forest environment and the socio-economic environment, a community or enterprise can rationally decide on which species to harvest and utilise. This decision involves social and cultural preferences and economic and ecological factors.

For their own subsistence use, communities will likely have already developed social preferences for products through their history of extraction and traditional use. Likewise, certain taboos may have evolved prohibiting the use of other species.

For products intended for market, economic criteria play a larger role. Usually groups will choose to exploit higher-value resources first.

Ecological criteria should reflect the species' biological potential for being managed on a sustained-yield basis. Some species are inherently better suited to continual harvesting than others. For tree species, factors that determine this potential include (Peters, op. cit.):

life cycle characteristics. A species that fruits annually and is pollinated easily is better adapted to regular harvests than one that flowers at unpredictable intervals. In general, the management of primary forest species, which tolerate shade as seedlings, has less ecological impacts than the management of fast-growing, light-demanding pioneer species that require large gaps in the canopy for seedling establishment;

type of non-wood resource harvested. Harvests of vegetative structures (i.e. bark or roots) very often kill a plant.2/ Harvests of fruits, leaves, oil seeds and latex do not necessarily kill the trees but can alter the population structure (in case of overharvesting of fruits and seeds); and although they can have negative impacts, these are relatively easier to address;

2/ This varies with species. For example, cork (Quercus suber) is unusual in that its bark regenerates itself after each peeling. In some areas, bark from certain species is traditionally harvested in longitudinal strips; this can be a sustainable management practice and should even be promoted where appropriate (Ocampo, 1994). In Mali collectors of baobab (Adansonia digitata) fibres harvest only once every two or three years to avoid killing the trees (Montagne, 1985).

density in different forest types. Species that occur locally in high densities are easier to manage sustainably than those that are scattered and involve more travel for harvests. Also, if a species is abundant only in a part of the forest that is seasonally inaccessible (e.g. due to flooding), it can be difficult to obtain a regular supply;

size-class distribution. Even species that are abundant in the area can present problems if, for example, all the individuals are of roughly the same adult age and there is no evidence of regeneration. If compatible with social and economic criteria, species that show good natural regeneration are preferable over other types.

Table 2.1 summarizes major characteristics of tree species and their influence on the species' potential for sustainable harvests.

Table 2.1: Overall potential of non-wood forest resources for sustainable management, based on species characteristics

Low potential

Medium potential

High potential

Type of resource

bark, stem, roots

some resins, seeds, fruits

latex, fruits, leaves





Species characteristics


few, large


small, many


few, large


small, many

Seed germination

low viability

Intermediate viability

high viability

Sprouting capability




Population structure

Size-class distribution

Type III curve

Type II curve

Type I curve

Plant density/ha

0-5 adults

5-10 adults

10+ adults

Spatial distribution




Regeneration guild

early pioneer

late secondary


Flower/fruit phenology


supra- annual


Reproductive biology


biotic, specialized vector

biotic, generalist vector


Pollinator abundance

rare; bats, hummingbirds

intermediate; beetles, moths

common; small insects

Seed dispersal

biotic, specialized vector

biotic, generalized vector


Disperser abundance

rare; large birds, primates

intermediate; small mammals

common; bats, small birds

(Source: Peters, 1994)

In most cases, obtaining all this information requires extensive discussions with local collectors and trips to the areas of production, preferably during the species' flowering or fruiting season.

Sustainable harvest levels

Yield studies
Regeneration studies
Harvest assessments

To determine what harvest level a resource can sustain without destruction, it is important to know the quantity of non-wood material that the species produces naturally. A major problem among non-wood forest enterprises is that most of them do not possess this knowledge.

The type of non-wood harvest helps to determine sustainable harvest levels:

• harvests of vegetative structures (such as roots or bark) would have to be infrequent, if at all;

• sustainable harvest level of fruits and seeds depend on (1) the intensity of collection, (2) the means of plant pollination and dispersal and (3) the species' specific requirements for regeneration and growth (Peters, op. cit.). Harvesting commercial quantities of fruits and seeds can affect not only species regeneration, but genetic composition and quality of the resource, if only "inferior" fruits and seeds are left to regenerate. In harvests of wild fruits, the effect on wildlife populations must also be considered;

• harvests of plant exudates (latex, gums and resins) do not kill the tree or remove its seeds from the site. However, many techniques of tapping create destructive wounds and sometimes involve burning or felling;

Yield studies, regeneration studies and harvest assessments are important tools for evaluating sustainable harvest levels.

Yield studies

Yield studies focus on the total amount produced and the relationship between productivity and plant size. A simple yield study consists of three steps (Peters, op. cit.):

• Select a representative sample of healthy plants of different sizes from each forest type. Individual samples should be marked with paint for permanent field identification.

• Measure each plant's production of the selected product(s). Enlist local collectors to weigh, count or measure the amount they collect from each tree. For fruits and seeds, this must be complemented with estimates of the amount of marketable material left unharvested.

• Plot the data to form a yield curve for each forest type.

Yield studies should be repeated every few years with the same sample plants because annual differences in rainfall and temperature can cause variable yields.

Using the forest inventory and yield studies together, the forest manager can determine (1) the area's total production, (2) the portion produced by each size-class of plant, and (3) which forest types produce most.

Based on this information and the relative abundance of each species, forest managers can determine the boundaries of different management units and how each should be harvested. Marking these on a map is useful. Some indigenous groups manage non-wood resources using this kind of resource division (Reds, op. cit.).

Regeneration studies

Regeneration studies assess, in permanent regeneration plots, the impact of management on seedlings and saplings, the individuals most sensitive to adverse effects. Permanent plots should be re-inventoried at suitable intervals (e.g. every five years) to monitor the long-term impact of harvests on regeneration (Peters, op. cit.).

Harvest assessments

Visual appraisals of adult plants can help detect problems in regeneration before they become serious. Forest managers should periodically inspect the trees marked as sample plants in yield studies and note their vigour, damage from pests and insects, and yield variability (Peters, op. cit.).

The Kenya Indigenous Forest Conservation (KIFCON) project is conducting this kind of assessment in western Kenya indigenous forests. The project, begun in 1989 by the National Museums of Kenya, studies current ecological and socio-economic aspects of grazing, recreation tourism and the effect of bark-peeling for the construction of beehive coverings for local beekeeping.

Harvest assessments in combination with regeneration studies permit forest managers to find a sustainable harvest level in one of two ways (Reds, op. cit.): (1) when studies suggest that collection has brought regeneration below replacement levels, collectors reduce harvest levels; or (2) managers identify a quantitative basis for sustainable yield using computer simulations and matrix models of population growth.

Scope for domestication of species

Advantages and disadvantages

When yield, regeneration and harvest studies reveal that actual harvests exceed a species' ability to regenerate, collectors may have to supplement wild sources with domestication (Haeruman, 1995). Many forest species depend on the interrelationships of a forest ecosystem to survive, but others do lend themselves to domestication or cultivation.

There often is not a clear border between unmanaged and domesticated resources. Evidence suggests that at least 12 percent of Amazonian forests are under indigenous forestry and agroforestry systems for managing dozens of fruit and nut species (Leakey and Newton, 1994). These systems involving guided regeneration, or enrichment planting, practiced by many forest - dwelling groups are a form of domestication in the forest itself (Reds, op. cit.). This has been found true also for wildlife; ranch animals are considered an intermediate step between wild and domesticated stock (Redford et al., 1995).

Domestication is therefore a tool that is flexible to match communities' preferences for managing a species.