A method for the economic valuation of non-timber tropical forest products

A Method for the Economic Valuation of Non-Timber Tropical Forest ProductsAuthor(s): Ricardo Godoy, Ruben Lubowski and Anil MarkandyaSource: Economic Botany, Vol. 47, No. 3 (Jul. - Sep., 1993), pp. 220-233Published by: Springer on behalf of New York Botanical Garden PressStable URL: http://www.jstor.org/stable/4255516 .

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A METHOD FOR THE ECONOMIC VALUATION OF

NON-TIMBER TROPICAL FOREST PRODUCTS'

RICARDO GODOY, RUBEN LUBOWSKI, AND ANIL MARKANDYA

Godoy, Ricardo, Ruben Lubowski, and Anil Markandya (Harvard Institute for International Development, Harvard University, Cambridge, MA 02138, U.S.A.). A METHOD FOR THE ECONOM- IC VALUATION OF NON-TIMBER TROPICAL FOREST PRoDucTs. Economic Botany 47(3):220-233. 1993. By drawing on quantitative studies in social anthropology, zoology, ethnobotany, and economics we present a method for conducting an economic valuation of non-timber forest products. A review of 24 studies suggests that the median value for non-timber forest products is about $50/ha/year. We discuss problems with past studies and suggest ways to get better estimates of output quantities, marginal costs, and prices. Key Words: non-timber forest products; tropical forests; economic valuation; methods; sustainability.

Policy-makers often assume tropical forests have no economic value unless they are logged or farmed (Dove 1983; Hecht, Anderson, and May 1988). Besides timber, tropical forests produce food (Arnold 1991; FAO 1989), construction materials, medicinal plants, fodder, and fire- wood, all of which villagers use daily (Panayotou and Ashton 1992). As a proxy for the opportunity cost of the forest-the maximum value derivable from the forest before it is put to new uses (Go- doy 1992)-the economic value of non-timber tropical forest products is conservative because the forest also produces other benefits, such as biological diversity and environmental services (Panayotou, pers. comm.). Policy-makers and development organizations need an accurate estimate of the opportunity cost of the forest to evaluate proposed projects and filter out eco- nomically disadvantageous ones. Under some conditions, leaving the forest unlogged and using it to get non-timber forest goods and environmental services may be socially and economi- cally optimal (Panayotou, pers. comm.).

In this article we review studies estimating the economic value of non-timber tropical forest products. Drawing on anthropology and economics, we present a method for future valuation

' Received 8 April 1993; accepted 5 May 1993.

studies. We limit our discussion to non-timber forest goods because methods for valuing other goods and services from the tropical forest (e.g., timber, biodiversity) are outlined elsewhere (Go- doy 1992; Panayotou, pers. comm.) and because the valuation of non-timber products is the area of tropical forestry in which we are likely to make the greatest contribution. Ethnographers are fa- miliar with the social uses of many forest goods through their research on hunting and gathering and swidden agriculture. Ethnobotanists have provided detailed inventories of useful forest plants. Social anthropologists have the classic ethnographic fieldwork tools, such as participant observation, time allocation methods, household diaries, direct records of the goods extracted from the forest, and long-term field research, that give them a comparative advantage in studies of forest products.

We focus on tropical forests for brevity, though the valuation method outlined here could be applied to any forest type. Lastly, we focus on valuation at the forest gate, the point at which villagers first sell or consume the goods, rather than assessing the value of forest goods to the regional, national, or world economy. We omit studies that present too little information to permit cal- culation of yearly profits per hectare (e.g., Fearn- side 1989; Hart 1978; Hecht, Anderson, and May 1988; Jessup and Vayda 1989; Peluso and Pof-

Economic Botany 47(3) pp. 220-233. 1993 ? 1993, by The New York Botanical Garden, Bronx, NY 10458 U.S.A.



1993] GODOY ET AL.: METHOD FOR VALUATION 221

fenberger 1989). In assessing the studies and pro- ducing our methods we draw on the anthropological literature on hunters and foragers, surveys of methods in social anthropology (e.g., Bernard et al. 1984, 1986; Borgerhoff and Caro 1985; Gregory and Altman 1989; Gross 1984), con- versations with some of the leading researchers in the study of tropical-forest plant and animal use, and our own fieldwork experience in Asia and Latin America.

Until recently few scholars had studied the economic value of non-timber tropical-forest products (e.g., Dunn 1975). In 1988 the Inter- national Tropical Timber Organization published a report calling for the rigorous study of these products (Panayotou and Ashton 1992). Since then many researchers have done such valuations (e.g., de Beer and McDermott 1989; Go- doy and Feaw 1989; Padoch and de Jong 1989; Peters, Gentry, and Mendelsohn 1989; Plotkin and Famolare 1992; Schwartzman 1989). Table 1 contains a summary of these studies and points up four problems with them: incompatibility of results, a tendency to examine flora (mainly) or fauna but not both, a lack of attention to sustainability, and a disproportionate attention to Latin America.

The net values vary widely, ranging from about $1 to about $420/ha/year. The variation can be explained by the biological and economic diversity of the different study sites sampled, the difference in the methods and assumptions used, and the different products studied. Even when studying the same goods, independent valuations conducted at nearly the same time have produced different results (e.g., Padoch and de Jong 1989; Peters, Gentry, and Mendelsohn 1989). Even a single plot may yield different values de- pending on the valuation technique used (Abey- gunawardena and Wickramasinghe 1992). Fu- ture valuations should use a common method and reporting procedure to facilitate the comparison of results (Borgerhoff and Caro 1985; Johnson 1978; NSF/USAID 1989:12; Redford and Robinson 1987).

Though hunting is reputed to produce benefits comparable to those from converting forest to farmland (Panayotou and Ashton 1988; Paucar and Gardner 1981), few researchers have estimated the economic value of the fauna extracted, and, as far as we know, no one has measured the combined economic value of plants and animals. A complete economic valuation of non-timber

tropical-forest products must include both fauna and flora. Ethnographies of hunting and fishing are of limited use in estimating the value of wildlife per hectare because their authors do not report both the size of the catchment area and the monetary value of the game caught.

Few researchers discuss the extent to which extractive practices are sustainable (Schwartz- man 1989). Lastly, most of the studies come from Latin America, mainly the Amazon basin. We need studies from the tropical forests of Africa and Asia, where different harvesting methods, forest types, societies, and economies may yield different values (Anderson 1990, citing Nair 1985). Besides addressing these issues, researchers must discuss the reasons for their choice of study site, the sample of people studied, and the representativeness of the study period so other researchers can assess the typicality of their find- ings. They will need to measure the quantity, location, price, and marginal cost of the goods brought from the forest to determine their net value.

For non-marginal use or extraction rates, where extraction is sustainable, the value of the non- timber products may be measured as Qi(Pi - Ci), where Qi = the quantity of good extracted, Pi = the forest gate price of the good (which may be equal to its price under competitive market conditions with no externalities), C, = cost of extraction and i = set of non-timber tropical products. If the extraction rates are so large as to change the prices of the products concerned, or supply a significant share of the market, then allowance needs to be made for the intra-marginal values, by measuring the consumer and producer surplus that is created by the supply of the goods. Furthermore, if the extraction rates are non-sustainable, adjustment should be made for the eventual depletion of the products by adding to Ci, a depletion premium based on the expected date of extraction. Markandya and Pearce (1987) discuss how to calculate this premium. In this context, researchers should evaluate directly the sustainability of plant and animal extraction, rather than assume that local people necessarily use the forest in an ecologi- cally sound manner.

Even after allowing for all these corrections, this method of valuation underestimates the value of non-timber tropical forest products because it does not fully capture the benefits of its services in lean years (Arnold 1991; FAO 1989).



222 ECONOMIC BOTANY [VOL. 47

THE CONTEXT

In few of the studies surveyed do the researchers discuss the biological representativeness of their research sites, so it remains unclear to what extent the sites resemble the forest around them. Since tropical forests are heterogeneous, different study sites will yield different information. Un- less researchers discuss the biophysical characteristics of their sites, it is difficult to generalize or to compare the results of different studies. To make sure that the study site represents the sur- rounding forest and to get a measure of variance one should where possible choose a sample of study sites. Researchers may often be unable to select representative forest sites, but they should always discuss the reasons for their choices to enable other scholars to compare and evaluate their results.

Proper sampling of the population is necessary for a study to be generalizable (Gregory and Alt- man 1989; Gross 1984). The main attributes of forest-product extractors which influence harvesting should first be identified. Important attributes may include age, technology, and income: men under 17 years of age or over 50 may hunt less frequently (Hill and Hawkes 1983), teen- age hunters may be less skilled (Yost and Kelley 1983), shotguns are better than blowguns and bows for certain types of kills (Stearman 1990; Yost and Kelley 1983), and richer villagers may rely less on forest goods (FAO 1989). After iden- tifying the major variables, the researcher should conduct a census, noting the distribution of the attributes of interest, and then select a stratified random sample to ensure that the study group mirrors the entire population in these attributes (Borgerhoff and Caro 1985). Most anthropologists working with extractors of forest-products do not use stratified random samples because these often include people who are difficult to reach. Anthropological samples are usually too small for conventional statistical testing (Behrens 1990). Reviewing time-allocation studies, Minge- Klevana (1980) finds a median sample of about 50 households or persons.

Unless the researcher collects information for 12 consecutive months, sampling must cover the seasonal variations in a year. Hurtado and Hill (1990), Henley (1982:47-49), and Nietschmann (1972, 1973) show that the amount of non-timber tropical forest products collected varies with the season because of climatic changes, govern-

ment regulations (Hart 1978), or seasonal work in agriculture. To avoid skewed results, researchers should randomly select for observation the same number of weeks within each month of the year and the same number of days within each week (Gross 1984). Even a continuous yearlong study may not reflect the typical composition of goods removed from the forest because the amounts of game and plants vary from year to year (Ashton 1989; Leighton and Leighton 1982; Vickers 1979). Contraction or expansion of the larger economy or a crisis in the household may also influence the degree to which people depend on forest resources. Redford and Robinson (1987) show that only 3 of the 21 studies they review on hunting in the neotropics lasted more than a year. Researchers can begin to decide whether the natural supply of non-timber tropical forest products during their study period is representative by comparing regional climatic information during the period of the study with information from past years.

QUANTITY

Researchers should distinguish between two types of quantities: the inventory (the stock quantity in the forest) and the flow (the quantity actually used by people). Some researchers value the inventory (e.g., Caballero, Toledo, and Ar- gueta 1978; Peters, Gentry, and Mendelsohn 1989; Prance et al. 1987; Toledo, Caballero, and Argueta 1978), others the flow (e.g., Godoy and Feaw 1989; Schwartzman 1989), and still others value both (e.g., Padoch and de Jong 1989). For most purposes, the value of the inventory is a meaningless concept related neither to present or to sustainable use. The difference in value between the flow and the inventory can be large. Padoch and de Jong (1989) measured the potential and the actual yearly profits of non-timber tropical forest products per hectare in two sep- arate plots in Iquitos, Peru, and found that the value of the goods extracted was only 2.5-3.5% of the value of the inventory. If we assume this relation between flow and inventory, the value reported by Peters and his coworkers for Iquitos would correspond to about $15/ha/year for flow, comparable to the flow value reported by Padoch and de Jong (1989) for a neighboring site.

The most accurate method of valuing the products extracted is to identify, count, weigh, and measure them as they enter the village each day (e.g., Bergman 1986; Dufour 1983; Hill and




Hawkes 1983; Stearman 1990; Vickers 1980; Wilkie and Curran 1991). This technique may be difficult if extractors live scattered in different villages, if they consume goods in the forest (Nietschmann 1973:150), or if they extract goods at night or before dawn. To address the problem of scattered users, researchers must observe a random sample of villages and households. To estimate the type and amount of goods consumed in the forest, they can either ask extractors or randomly follow them and record their consumption. We know of only one scholar who has recorded extraction of products from the forest at night (Scaglione 1986).

In weighing goods, researchers should use scales or balances suited to the different types of goods collected (Hart 1978; Hurtado and Hill 1987, 1990). Weighing the entire daily yield may be time-consuming, but informants can be trained to help. If it is impossible to weigh each animal, the average weight for the species can be deter- mined and used instead. For instance, Yost and Kelley (1983) approximated the weight of adult animals hunted using the average weight for the species but reduced the weight by 60% if hunters classified the animal as young. Redford and Rob- inson (1990) recommended that researchers weigh a sample of at least five adults to establish the average weight of a species. If such a sample is weighed only once, it may not reflect the seasonal variation in the weight of the animals during a year. Again, if the researcher cannot count the entire catch, average weights for aggregate quantities (e.g., a basket of fish) should be estimated (Gregory and Altman 1989:148). If extractors eat part of the animal in the forest, the weight of the animal should only be estimated for the parts brought back to the village. We should not value what is eaten because that is part of the cost of hunting. When researchers do not see the animal, they can estimate its weight from hunters' reports of its size (Gregory and Altman 1989:146).

When counting and weighing extracted goods, researchers must also identify the species in- volved. Redford and Robinson (1987) report that the irregular use of scientific names hinders the comparison of hunting studies in the Amazon. Since species identification may be difficult, they recommended elsewhere (1990) that researchers take photographs and collect skulls from which, in combination with information on the weight and the location of the kill, taxonomists can later identify them. Researchers should also note the

sex and the age of the animals and the number of fetuses of pregnant ones; such information helps in assessing the sustainability of hunting and fishing (Redford and Robinson 1990).

Through direct observations researchers can measure the extraction area. They can map the terrain covered by extractors using aerial photographs (Bergman 1980:32) or pedometers (Stearman 1990). Vickers (1980) calculated distance indirectly by measuring the time hunters were out in the forest; he found that hunters on average traveled 2-3 km per hour. Researchers can also follow extractors as they forage or question them about the location of their activities, preferably at the end of each day (Vickers 1983: 457). They can also ask them to pinpoint the locations of their kills on maps; Vickers found an informant who gave him a detailed map of local hunting trails. A new device for measuring the size of the extraction area is the Global Po- sitioning System (GPS) receiver, which picks up satellite signals to give its users their ground co- ordinates (Baksh 199 1; Behrens and Sever 199 1).

Researchers are limited in the number of persons they can directly observe, but they can increase the amount of information they can gather by questioning extractors about their activities and by training them to help gather information. With literate populations, researchers can train extractors to keep diaries on the results and locations of extractive expeditions and on the allocation of their time in the forest. White (1976), Bergman (1986), Alcorn (1981), Dufour (1983), Padoch and de Jong (1989), and Stephen Beck- erman (pers. comm.) trained informants to keep diaries, and extractors have been taught to weigh and measure the daily catch (Bergman 1986:32; Nietschmann 1973:21; Stocks 1983; Wilkie 1989).

Although extractors may give accurate information, one should avoid relying too heavily on their accounts. Distortions arise because people may be careless in their record keeping, lie to the researcher (Nacham 1984), or forget past events. The accuracy of recall information drops when people are asked to remember events far in the past (Bernard et al. 1984). Besides errors from carelessness, lying, and faulty memory, people bias information by reporting culturally significant events or information they believe inter- viewers want to hear. For instance, Dufour (pers. comm.) says that the Tucano of Colombia do not report all the game and fish caught because they




eat large animals in secrecy to avoid customary food-sharing norms. Several researchers (Ayres and Ayres 1979; Redford and Stearman 1990; Smith 1976) say that hunters under-report kills of smaller animals (e.g., birds) because they con- sider them unimportant. Extractors may also under-report plants or animals for use in the household rather than for sale because the market is seen as more important. Through training and special interviews, researchers can increase the quality ofthe information reported (Vickers 1984; Yost and Kelley 1983).

Incentives to enhance recall information may introduce distortions. Wilkie (1989) paid informants a wage to show him their catch that was "sufficient to encourage reporting of animals killed but not so much as to promote hunting purely for the reward." He checked hunters' reports by questioning other villagers but concluded that having hunters keep records probably produced selective reporting and underreporting of many animals commonly eaten (Wilkie 1989). After reviewing the accuracy of informant recall, Bernard and his coworkers concluded that "on average, about half of what informants report is probably incorrect in some way" (Bernard et al. 1984). Other researchers echo this conclusion (Bernard et al. 1986; Borgerhoff and Caro 1985; Gross 1984).

When using oral or written reports from extractors, researchers should check the information to ensure that it is reliable. Diaries and other written records should be checked regularly (e.g., Bergman 1986:32; Stocks 1983). Besides failures to complete such records, Bergman (1986:32) identified errors in time-allocation diaries from his memory of what he had seen people do. Yost and Kelley (1983) trained assistants to collect information on hunting activities from all villagers and then cross-referenced extractors' reports with each other and with their own report. Researchers can also randomly select informants for observation in the forest and compare their own records with the extractors' diaries or with the information they provide in interviews at the end of the day.

Methods to correct for errors in extractors' reports are less developed, but several deserve attention. Filling diaries throughout the day re- duces misinformation. Engle (pers. comm.) used three techniques to enhance recall from interviews: eliciting the entire story, reviewing it with the informant, and presenting the informant with

stories from other individuals (e.g., "What did you do this morning? Here is what X did"). Re- call enhancement techniques increased the number of activities recalled from 40% to 63% and the amount of time accurately recalled from 58% to 70% (Engle and Lumpkin, pers. comm.). Sim- ilarly, Bernard et al. (1984) describe studies showing that memory enhancement techniques increase accuracy by 5-10%. Their studies also reveal that groups recall details of events better than individuals (pp. 510-51 1). Devices for en- hancing recall might also be used. For example, extractors might be asked at the end of each day to select cards, each stamped with the name or with a photograph of a non-timber product. Pointing to the card, the researcher could prompt the collector: "Do you remember how much of this you took out today?"

Whether researchers get information on quantities of forest products extracted from direct observations or from extractors, they should adjust this information by the losses from spoilage during storage in the village and transport to the market.

PRICE The most difficult part of valuation is assigning

the products a monetary value. Optimal-foraging theorists use expenditures of labor or energy as a measure of value in nonmarket societies (Smith 1983) but these two measures can produce different results (Gregory and Altman 1989:150- 15 1). Moreover, neither is consistent with modern valuation theory as applied in this area.

The best method of valuation is to miake use of the prices that exist of the commodity concerned, or that prevail in related markets. For example, a non-timber product may have no market but may be bartered for a product that does. In that case it is easy to impute a price for the product in which we are interested. Another method could be to use the value of a close substitute with a price. This will require establishing a relative price between the priced and unpriced products, which can be done on the basis of product characteristics. If neither of these methods is feasible, the researcher can resort to a contingent valuation approach where users of the product are asked what is their willingness to pay for the product. Contingent valuation methods have been widely tested in developed countries with strong market traditions and their use in situa- tions where familiarity with, and acceptance of,




markets is much more limited should be carried out with great care (Mitchell and Carson 1989). Fortunately it is rarely necessary to resort to contingent valuation methods for most forest products.

Few researchers have measured the shares of non-timber tropical forest products going to the household and to the market (Behrens 1986; Nietschmann 1973). The distinction is important because goods for the market and for the home should be valued differently. Products consumed at home or exchanged with kin should be valued at their retail purchasing price in the village; goods sold on the market should be valued at their selling price (Chibnik 1978; Painter 1986). If the population is literate, a random sample of households can be selected to keep log books of daily income, expenses, and amounts of non- timber tropical forest products sold and consumed at home. In a Philippine village, Hayami (1978) selected 11 households to keep daily records of income, expenses, and uses of production; the records were checked twice a week.

Since the purpose of the exercise is to make a judgement of the valuation of the tropical forest products from a national viewpoint, the analyst must always try to estimate the total economic value of the products. This means adjusting for any taxes and subsidies that may cause the price to deviate from the opportunity cost of the resource. Such adjustments are referred to as shadow prices. For most standard resources (e.g., minerals, capital, labor) these shadow prices are estimated for most countries, and revised peri- odically. The full set of adjustments that have to be made will depend at which stage of the product cycle the valuation is being carried out. If it is at the forest gate then only those adjustments that are relevant to that stage need to be made (Godoy and Bennett 1991; Godoy and Feaw 1989). If the valuation is being carried out where the product is nationally sold, then a number of additional adjustments may have to be made. As Feamside (1989) says, shadow pricing is important in providing an economic rationale for extractive resources, which may not be financially profitable. For a detailed discussion of shadow pricing in the appraisal of projects see Squire and van der Tak (1975).

Besides correcting for taxes and subsidies, a full exercise in shadow pricing also requires estimating the externalities of extracting non-timber forest products. In no study have researchers

valued the environmental externalities of extracting non-timber tropical forest products. By failing to quantify these factors, conventional valuations, such as those in Table 1, underesti- mate the economic benefits of these products to society.

MARGINAL COSTS To get an accurate measure of the marginal

costs of extracting and processing non-timber tropical forest products, the researcher must calculate the cost of the materials (e.g., bullets, ar- rows) used, the labor time directly associated with finding, extracting, processing, and transporting the goods from the forest to the village or to the market, and the temporal cost of resources-the benefits forgone by delaying the sale or the use of the good.

Researchers have not often calculated the cost of the materials used in extraction, and this cost can be high (Bailey and Aunger 1989; Moran 1991; Nietschmann 1972, 1973:153-154; Ross 1978). In studying the Waorani hunters of Ec- uador, Yost and Kelley (1983) found that the cost of making goods to trade for shotgun shells and travelling to buy them was three hours per shell.

Studies based on optimal-foraging theories give detailed information on the time spent searching for, pursuing, killing, and processing game (Hawkes and O'Connell 1981; Hill and Hawkes 1983; Smith 1983), but students of plant collec- tion have not included comparable information. To calculate the gross time spent in the forest, researchers can log departures from and returns to the village (Beckerman 1980; Hill and Hawkes 1983; Hill and Kaplan 1989; Hurtado and Hill 1990) or train villagers to do this (Hill and Kap- lan 1989; Hurtado and Hill 1990). These methods overestimate the time spent procuring goods because people use part of the time in the forest to farm, eat, or rest (Henley 1982:69; Hill and Hawkes 1983). To gather information on time allocated for extraction and processing, the researcher must either rely on recall information or follow a random sample of villagers in the forest for direct observation.

Researchers can interview extractors at the end of the day to decide how they spent their time in the forest (Gross 1984; O'Connell and Hawkes 1984; Vickers 1980; Yost and Kelley 1983). Ex- tractors can also be taught to record how much time they spent at different activities in the forest,




TABLE 1. SURVEY OF OPPORTUNITY COST OF FOREST FROM FORAGING.

Net value Location ($/ha/year) Comments Source

Venezuela 0.75 Experimental caiman harvest. Thorbjarnarson (1991) Korup National Park, 1.06 Net present value of forgone gross Ruitenbeek (1988) and

Cameroon benefits from hunting = $2.7 m Infield (1988) at a 5% discount rate; area = 126 000 ha; hunting said to be non-sustainable.

Mudumalal Sanctu- 3.0 0.02 elephants/ha at $1500 per ele- Sukumar (1989) and per- ary, South India phant. Excludes costs of domesti- sonal communication

cation and training. Price refers to a domesticated animal. As- sume a 10% discount rate.

Ituri Forest, Zaire 0.50-3.18 318 kg of game/km2 of primary for- Wilkie (1989) and Wilkie est or 50 kg/km2 in climax forest and Curran (1991) at $1/kg. Estimate leaves out costs. Price is for prized meats.

Amazon, Brazil 4.8 Estimate is gross return/ha/year; Schwartzman (1989) only values flora.

Sarawak, East Malay- 8.00 Values wildlife in one square kilo- Caldecott (1987) sia meter.

Maya Biosphere Re- 10.00 550 000 hectares produce about Nations (1992) serve, Guatemala $5.5 million/year in exports of

chicle, xate palm, and allspice; gross value.

Western Amazonia 5-16 Gross value varies by the size of the Hecht (1992) extraction area (150 to 300 hectares).

Cross River National 16.50 Yearly income from hunting gather- Ruitenbeek (1989) Park ing, trapping = $826, Naira/per-

son = $108; population = 38 300; area = 250 000 hectares. Gross value.

Iquitos, Peru 16-22 Based in part on villager's diaries. Padoch and de Jong (1989) Iquitos, Peru 20 Potential value of about six species Pinedo-Vasques, Zarin and

of latex and fruits. Jipp (1992) Belize 36-166 Medicinal plants; 5% discount rate. Balick and Mendelsohn

(1992) Hantana, Sri Lanka 50 50 randomly chosen household sur- Abeygunawardena and

veyed in three villages; used con- Wickramasinghe (1992) tingent valuation and opportunity cost approach; estimate leaves out cost of extraction.

Kalimantan, Indone- 53 Net present value of cultivated rat- Godoy and Feaw (1989) sia tan = $529/ha over 25 years with

a real discount rate of 10%.

Amazon, Brazil 59 Includes kernel, charcoal, and feed Anderson, May and Balick meal of babassu palm. Unclear (1991) whether returns are net or gross.




TABLE 1. CONTINUED.

Net value Location ($/ha/year) Comments Source

Combut Island, Gua- 79 $3171/year/family; average of 5 Anderson and loris (1992) ma River, Brazil families in 1984-1988. Estimate

is gross value and only includes semi-wild cacao, acai, and rubber. We assume one family worked 40 hectares of forest.

Tamilnadu, India 80 Fuel and fodder. Appasamy (1993) Brazil 97 Value of Brazil nuts only ($/hect- Mori (1992)

are): Collector's price = 97; Ex- porter's price = 176; Retail price = 1059.

Para, Brazil 110 Value after selective thinning of Anderson (1990b) competitors and pruning of acai palm.

Veracruz, Mexico 116 Estimate leaves out lumber and cof- Alcom (1989) fee.

Amazon, Ecuador 120 Values wildlife over 500 square ki- Paucar and Gardner (1981) lometers.

India 117-144 Gross benefits; includes fruits, Chopra (1993) herbs, and medicinal plants.

Jenaro Herrera, Peru 167 Values only harvest of wild camu Peters quoted in Vasquez camu; unclear if estimate is gross and Gentry (1989) or net.

Iquitos, Peru 420 Values the inventory in one hectare; Peters, Gentry and Mendel- only includes plants. sohn (1989)

either at the end of the day or in the course of it. In a study of fishing among the Cocamilla, Stocks (1983) gave out watches and trained local people to record each day the time spent travelling and working; he checked and copied the records every day. Bergman (1986:30) gave Shi- pibo men diaries and wristwatches and instruct- ed them to keep track of their time. Never having owned watches, most of these men had to learn to tell time, and some of them had to find some- one else to write for them. Bergman reviewed and copied the diaries twice a week.

To measure the allocation of time directly, researchers generally use instantaneous sampling. Pioneered by Johnson (1975), the method requires visiting randomly chosen subjects at random times of the day and recording their activity at the instant they are first seen. By collecting many spot observations it is possible to gather a great deal of information in a short time and to estimate the proportion of time people devote to different activities. Instantaneous sampling is not as useful for studying time allocation in the for-

est. Hames (1980) used instantaneous sampling to study the Ye'Kwana and Yanomamo of Am- azonian Venezuela but found it impossible to observe individuals who were out of the village; instead he asked relatives who had stayed behind about the activities of those who had left (see also Colfer 1981). Behrens (1986) says he could not observe individuals out of the village and therefore had to rely on recalls, hearsay, and a larger sample.

Rather than using instantaneous sampling to study the uses of time in the forest, researchers can use focal subject sampling. With this method, the researcher spends a full day following one randomly chosen individual, noting the amount of time spent in different activities (Hill and Hawkes 1983; Hill and Kaplan 1989; Hurtado and Hill 1987). Following extractors in the forest also yields information on the amount of forest products consumed in the forest that will allow correction of the estimates of quantities weighed in the village (Hill and Kaplan 1989). Focal subject sampling will allow the researcher to esti-




mate the time spent by the focal individual in different activities, but if an extractor works in a group it will not permit a reliable estimate of total labor cost. In such cases, the unit of observation should be the group, and the researcher should record the activities of everyone in it. If the group is large or if it splits up, the researcher will have to observe as many individuals as possible and learn about the others from diaries or from interviews at the end of the day.

Whether one follows extractors or relies on diaries and interviews, one should decide on the categories for classifying labor activities in the forest to ensure that the results of the study will be comparable to those of others. The following categories may be useful for classifying extractive activities: travelling, resting, searching, harvesting, pursuing, and processing (Hill and Hawkes 1983).

Having measured the extractors' allocation of time in the forest, researchers must also assign a monetary value to the labor time. Some researchers (e.g., Peters, Gentry, and Mendelsohn 1989) use the country's official wage as an estimate of the unprotected rural wage, but this should not be done uncritically. Instead, researchers should use what people actually pay each other. Such payments can take many forms and can be complex, including not only money wage but also gifts of food (Godoy and Feaw 1989; Godoy and Bennett 1991). Although rural wages vary by season, age, sex, and type of work, most of the studies in Table 1 use only one wage. In future valuation studies, the flow of goods from the forest over time should be matched to the wage pre- vailing at the time the good is extracted.

In calculating the marginal costs of non-timber tropical-forest products extraction, the cost of capital is seldom measured. Discounting is important when extraction and consumption or sale occur at very different times (Timmer, Falcon, and Pearson 1983). Though private time pref- erences vary by age, length of waiting period, size of reward, and income (Thaler 1981; Rogers, pers. comm.; Lawrence 1991), the most appropriate practice at the present time is to use an estimate of the social discount rate. The literature on how to estimate this rate is complex (Markandya and Pearce 1991), but the consensus is that the social discount rate is much lower than the market rate of discount in developing countries. The latter can be as high as 15-20%, whereas the social rate of discount is more likely to be around 3-6%.

For many countries some estimates of the social discount rate have been made. Where no such estimates exist, the researcher can take a value of 4-5% as representative of the range of num- bers that have been established.

SUSTAINABILITY

Estimating the economic value of non-timber tropical forest products at one point in time leaves unanswered the question of to what extent the estimated value is sustainable. Scholars are di- vided into at least three camps on this issue. Some say that indigenous people manage non- timber tropical forest products sustainably; others say that they do not, and a third camp says that sustainability is the result of special conditions that must be identified in each case.

Anthropologists who say that indigenous people manage the forest sustainably (e.g., Dufour 1990; Posey, Frechione, and Edding 1984; Vick- ers 1984) point to practices reportedly designed to enhance production, such as manipulating forest fallow to speed the growth of desirable plants (Irvine 1989; Padoch et al. 1985; Posey 1985, 1989) and animals (Stocks 1987), establishing corridors and scattered gardens and spacing human settlements to stimulate reproduction of wildlife (Linares 1976; Lovejoy and Schubart 1980; Nations and Nigh 1980; Redford and Rob- inson 1987), mandating the hunting of one animal species to relieve hunting pressure on others (Balee 1985), tabooing the killing of threatened animals, and forbidding hunting and fishing in depleted zones (Ross 1978; McDonald 1977). Other researchers (e.g., Hart 1978; Henley 1982: 50-52; Jessup and Peluso 1986; Johnson 1989; Redford and Robinson 1985, 1987) argue that depletion of forest resources may have started before contact and continues to increase as markets envelop indigenous societies (Gross et al. 1979; Nietschmann 1972,1973; Roosevelt 1980; Smith 1983). Johnson (1989), Winterhalder (1983), and Hames (19-87) suggest that low population density, localized resources, effective social sanctions, and limited possibilities for expansion encourage conservation or intensification of resource use. Redford and Robinson (1985) say that sustainability must be assessed directly by counting animals and plants in the forest.

Hall and Bawa (1993) discuss methods for assessing the biological sustainability of plant extraction. To measure the sustainability of hunting, anthropologists have used indirect measures,




such as increases in the distance, frequency, and duration of hunts, increases in the capture of smaller, less desirable animals, movement of human settlements, and people's recall of yields over time (e.g., Stearman 1990; Stocks 1983). The only way to get direct measures of hunting sustainability is to compare rates of game killed in hunting with rates of natural reproduction and mortality from censuses of animal populations in the wild (Redford and Robinson 1985, 1990). As far as we know, researchers have not yet done this analysis.

Where use patterns are not sustainable, the valuation of current extraction rates should allow for that by lowering the value of the non-forest products. The appropriate adjustment is a depletion premium, which will depend on how long the present extraction can continue, and on the discount rate.

CONCLUSIONS Valuation of non-timber tropical forest prod-

ucts is plagued by inadequate measurement of costs, quantities extracted, and prices. Although researchers have produced important case studies, the results of different studies cannot be directly compared because different methods have been used. Most such valuations seem to have been an afterthought. Researchers must pay more attention to problems of method if future valuation studies are to produce generalizable results.

Although there is no substitute for direct observation over several years, the best method for an economic valuation study will depend on the cultural background of the people studied, the level of literacy, and the settlement pattern. The resources and the time available to undertake the study also influence the choice of method. Mind- ful that diaries and interviews can produce in- accurate information, researchers must use them because they can save time and money. Diaries, if feasible, are potentially more accurate than interviews, but interviews are still important to check on them as well as to give researchers great- er flexibility in questioning extractors.

Few scholars have directly measured the sustainability of non-timber tropical forest product extraction (e.g., Hall and Bawa 1993; Reining et al. 1991). Future valuations should include censuses of the plants and animals removed by hu- mans to assess the effects of harvesting on the availability of these goods. Scholars should not

assume or infer from direct information that local people manage the forest sustainably.

Most valuation studies have been done by researchers interested in the flora rather than in the fauna of the forest. Ethnobotanists have calculated returns per hectare; students of hunting have calculated returns per unit of labor. Flora and fauna per unit of area must be valued together, by a single method. Valuation of non- timber tropical forest products should begin to pull together scholars from different disciplines. Future valuations will need to combine the skills of, at least, a natural-resource economist or economic anthropologist to price the goods and to measure the flow of goods removed from the forest and a zoologist and a botanist to determine the sustainability of extraction. Indigenous people and local scholars must be recruited to assist in the assessment.

ACKNOWLEDGMENTS

This research was partially financed by grants to Harvard University from the Rockefeller Foundation, the John Merck Fund, and the W. Alton Jones Foundation. We thank the following for providing information on their research methods: Paul Appasamy, Stephen Beckerman, Kanchan Chopra, Wade Davis, Patrice Engle, Daniel Gross, Kristen Hawkes, Kim Hill, Stephen Hubbell, Allen Johnson, and William Vick- ers.

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