Year : 2004 | Volume
| Issue : 2 | Page : 315-346
Acai Palm Management in the Amazon Estuary: Course for Conservation or Passage to Plantations?
Stephanie Weinstein1, Susan Moegenburg2
1 Nature Conservancy, 1510 East Fort Lowell Road, Tucson, Arizona 85719, USA
2 Tetratech, 15 State Street, Montpelier, VT 05602, USA
Nature Conservancy, 1510 East Fort Lowell Road, Tucson, Arizona 85719
Source of Support: None, Conflict of Interest: None
|Date of Web Publication||18-Jul-2009|
| Abstract|| |
In the lalate 1980s, the acai (Euterpe oleracea) fruit and palmito extraction system of eastern Amazonia was heralded as a promising alternative to deforestation that could simultaneously provide income to rural producers and protect forest integrity. We e tested these claims in ffive communities located along a distance gradient from the lalargest regional market in Belem, Brazil. We e evaluated the market accessibility and management strategies of acai producers, and assessed the impacts of management on forest characteristics. In contrast to other NTFP systems, we found that distance to the major market is not a limiting factor for acai sales because throughout the region intermediaries are readily available to transport acai from producer to market. Demand for acai fruit is increasing, leading to intensification of palm management, which results in the conversion of native flfloodplain forests into acai-dominated forests that closely resemble plantations. We e conclude that the acai system is not typical of other NTFP and should not be regarded as a model for merging forest conservation with rural development. However, the increased demand for acai, especially from educated consumers, together with the ease of production and marketing, present an opportunity to develop the acai system into one in which both rural livelihoods and forest integrity are supported.
|How to cite this article:|
Weinstein S, Moegenburg S. Acai Palm Management in the Amazon Estuary: Course for Conservation or Passage to Plantations?. Conservat Soc 2004;2:315-46
| Introduction|| |
Non TTimber Forest Products as a Strateegy ffor the Conservation of Biodiversity
OVER THE PAST fififteen years, enthusiasm over the conservation and development potential of non-timber forest products (NFTP) has waxed and waned. Early reports suggested that NTFP might support rural livelihoods while simultaneously protecting forest cover and biodiversity ty (Arnrnold and Perez 1998; Fearnside 1989; Panayotou and Ashton 1992; Peters et al. 1989a, 1989b; Plotkin and Famolare 1992). Moreover, it was proposed that as markets for NTFP developed and grew, the forests that provide these products would be increasingly valued intact and be less subject to deforestation for timber or agricultural production. As researchers have delved into studies of the social, economic and ecological aspects of the NTFP harvest, however, it has become increasingly clear that these lofty goals may be more difficult to achieve than initially envisioned. In some cases there is inadequate demand for the NTFP; in others markets are inaccessible to rural communities and the forests from which they harvest (Browder 1992; Godoy and Bawa 1993; Guimaraes and Uhl 1997; Padoch 1992; Pendleton 1992; Shanley et al. 2002; Wallace 1999). A signifificant hindrance to marketing NTFP is the distance harvesters must travel to markets to sell their products. The cost of getting a product to market increases with distance, because fuel for transport is expensive. In some regions intermediariries, or middlemen, buy NTFP from harvesters and transport them to markets, but reliability of intermediary ry transport decreases with distance. If intermediariries fail to show up, or if harvested areas are too far frfrom markets (that is, requiriring several travel days), then perishable NTFP such as fruit may spoil before ever reaching markets. If markets are reached with viable products, the income earnrned may be too low to offset the costs of production and transport. Finally, market pririces of NTFP can flfluctuate greatly, and this can affect the ability of NTFP producers to effectively manage and harvest their products. The importance of these `access to markets' issues suggests they may play a pivotal role in the future of NTFP development.
In addition to economic difficulties, NTFP enterprises have also faced challenges on ecological grounds. Some NTFP are harvested in destructive ways, such as collecting fruits by cutting down the tree (Pefia Claros 1996; Peters 1996; Vasquez and Gentry ry 1989), or are harvested at intervals or intensities that have a negative impact on the health or recruitment of the resource (Anderson 1999; Gould et al. 1998; Hall and Bawa 1993; Peters 1994, 1996; Robinson and Redford 1994). Increased household income obtained in NTFP sales does not necessarily guarantee the maintenance of forest resources, as it is sometimes invested in technology that facilitates deforestation (Godoy 1995). Also, when an NTFP becomes economically important, the nature of its utilisation often changes. As an NTFP increases in value, the forest may be increasingly enriched with NTFP species to augment their production (Anderson et al. 1995; Ricker et al. 1999; Schulze et al. 1994) or the resource may be planted in home gardens and agriricultural plots (Smith et al. 1992), and eventually in plantations where the yield and harvest is more efficient (Homma 1992, 1994).
Thus, there exists a tension between the socio-economic and ecological aspects of NTFP development (Lawrence 2003). On the one hand, overcoming obstacles to market access (for example, distance to market) can boost rural incomes, but may lead to intensification of forest management, destructive harvesting and the creation of plantations (Arnrnold and Perez 2001; Struhsaker 1998). On the other hand, pririoriritising forest integririty ty can help ensure the long-term conservation of biodiversityty, but may do little to alleviate rural poverty ty (Browder 1992). Resolving this tension is a necessary ry step to achieving the multiple goals of NTFP development.
In the late 1980s data began to emerge on a so-called model for conservation in the Amazon basin: the acai palm, Euterpe oleracea. Research suggested that forests managed for Euterpe oleracea (hereafter `acai'; pronounced ah-sigh-EE) closely resembled native forests yet provided substantial income for rural people (Anderson 1988; Anderson and loris 1992). More recently, acai has been a focal species in extractive reserves (areas designated specifically for the long-term sustainable harvest of forest resources) and other rural communities (Allegretti 1990), where people actively manage forests for production. Markets for NTFP from acai (primarily fruit and palm heart) have greatly expanded, as have strategies for its production. One proposal calls for the planting of 5 billion acai plants in the next ten years (0 Liberal 2000). These recent developments beg the question of whether the acai system truly strikes a balance between conservation and development.
In this article, we present results of detailed socio-economic and ecological studies of the acai system across a range of sites in the Amazon estuaryry. Our research addressed two main questions: (a) How does household distance from a major market centre inflfluence acai palm management decisions? and (b) What are the ecological effects of acai palm management? To address the former, we collected information on acai palm management strategies and household production, sales and transportation of acai NTFP in interviews with acai-producing households at sites along a distance gradient from the major centre of acai commerce. We evaluated the ecological effects of acai palm management at two levels: (a) acai populations; and (b) forest composition and structure. We analysed acai density and demography from forest areas managed for acai to address how management affects acai populations at sites throughout the Amazon estuaryry. We evaluated the effects of acai management on forest vegetation composition and structure by comparing canopy height, vegetation density ty and stem diameters of vegetation in forest stands managed for acai production with stands not managed for acai production. By understanding the factors that inflfluence management decisions and the ecological effects of that management, a more comprehensive strategy to promote forest conservation and rural incomes can be developed.
The Afai Palm: A Model NTFP ffor Conservation in the Amazon?
The quotations at the opening of our article offer a glimpse into the importance of acai in the eastern rn Amazon. Archaeological evidence indicates that the fruit of the acai palm has been a component of the diet of estuarine inhabitants since ancient times (McCann 1999; Roosevelt et al. 1996), and today acai is venerated in popular songs and festivals, which are held in its honour in scattered villages duriring the fruit harvesting season. As traditional forest management systems have attracted increased attention from scholars and conservationists, research has documented the various current and potential uses of acai (Pollak et al. 1995; Strudwick and Sobel 1988); the ways in which it is managed and harvested (Anderson 1988, 1990; Anderson et al. 1995); its role in household, local and regional economies (Anderson and loris 1992; Hiraoka 1995; Mufiiz-Miret et al. 1996; Warren 1992), and the potential for increased production and more efficient management (Anderson and Jardim 1989; Jardim and Rombold 1994). In many ways, acai is considered a model NTFP for conservation of flfloodplain forests of the Amazon delta because it overcomes many of the challenges often attributed to other NTFP systems: (a) unlike many tropical forest trees, acai occurs at high densities along accessible river margins; (b) local inhabitants have a long history ry of extractivism and the palm has traditionally provided products that are a major part of their subsistence; (c) the extensive network of ririvers and streams throughout the region provide access to markets and towns, including Belem, the largest city in the Amazon basin; (d) the acai palm has two commercially valuable products, its fruit and palm heart; and (e) other land uses, such as timber extraction or agricultural production, are considered less profitable than NTFP extraction in the flflooded estuary ry environment (Anderson and loris 1992).
While the acai palm provides many useful products to local inhabitants (called ribeirinhos or caboclos), it is most known for its commercially valuable products: its fruit (acai fruit) and palm heart (palmito). Acai fruit is harvested by climbing the tree and cutting off the ripe bundles of fruit (the infructescence; [Figure 1]).
The rind (mesocarp) of the acai fruit is ground and mixed with water to form the thick, purple vinho, which forms a staple part of the ribeirinho diet. In towns and cities, acai is processed into vinho at small stands or shops and sold by the litre, or it is made into ice cream or other desserts. Palmito is generally not eaten in the estuary ry but is exported principally to southern rn Brazil, France and the United States.
Ecologically, E. oleracea is considered to be an ideal source of NTFP because an individual palm grows as a multi-stemmed clump [Figure 1]. In biological terms, these clumps are called `genets', and they consist of genetically identical stems, each of which is called a 'ramet' (hereafter we will refer to a genet as a clump and a ramet as a stem). Although stems of the palm are felled in order to harvest palmito, the entire palm is not killed because of its growth form, whereby other stems and sprouts remain in the clump. Not only does the palm survive the palmito harvest, but the selective harvest of stems has been shown to increase fruit production in the remaining stems (Anderson and Jardim 1989). Thus, riribeiririnhos can benefit economically from management strategies that allow them to harvest both palmito and acai (Anderson 1988; Anderson and loris 1992). Ribeirinhos actively manage acai for fruit and palmito production in forests that have been described as being `almost indistinguishable from the native flfloodplain forests' (Anderson 1990: 70).
Despite the potential for sustainable use of acai for both palmito and fruit, over-harvesting of palmito has been reported in parts of the estuaryry, resulting in the demise of some palm populations and threatening the subsistence needs of locals (Clay 1997; Pollak et al. 1995). One factor that may inflfluence harvest and management decisions is the distance that ribeirinhos are frfrom markets. Although most ribeirinhos are fairly accessible to towns and cities via waterways, acai fruit is highly perishable and must reach market and be processed within twentyty-four to forty-eight hours of harvest to retain its unique flflavour (Smith 1999). In contrast, palmito is the apical bud of the palm and is protected by leaf sheathes. Palmito remains fresh for four to five days and is processed in factoriries in towns and cities as well as in small backyard processing facilities scattered along river margins. Thus, ribeirinhos living close to cities might be expected to focus on acai fruit production, while those at greater distances might be predicted to focus on palmito production.
| Study Area|| |
Ecology of the Amazon Estuary
The Amazon estuary ry extends frfrom the mouth of the Xingu river to the mouths of the Amazon and Para rivers, which merge on the eastern rn side of Marajo, a 50,000 sq. km island [Figure 2]. Most of the Amazon estuary ry is within the Marajo vkrzea ecoregion, which is distinct from surrounding areas by its seasonal and tidal flflooding and poorly-drained clay soils consisting of Holocene (less than 10,000 years old), and slightly older and higher tertiary ry deposits (WWF 2001). The region receives an average of 2,300 mm of annual rainfall, three quarters of which falls duriring the rainy season from December to June (Calzavara 1972). Tides inundate the estuary ry twice daily, pushing a large volume of river discharge onto the landscape and raising the water level an average of 1.2 m. The tides and seasonal flflooding create an interconnected network of rivers, streams and channels surrounding abundant sedimentary ry islands. These waterways and landforms are dynamic landscapes, with constantly changing stream margins, vegetation and drainage. There are over 25,000 sq. km of flfloodplain forests (also called vkrzea) in the estuaryry, including 10,000 sq. km that are dominated by Euterpe oleracea (Lima 1956). The vegetation of the ecoregion is characterirised by low plant diversity and dominance by plant species that are adapted to extreme flflooding, shallow soils, low soil oxygen levels and frequent disturbance. Species that are well-adapted to these conditions include aninga (Montrichardia sp.; Araceae), the miriti palm (Mauritia flflexuosa) and the acai palm, which are considered important in colonising and stabilising ririverbanks and island margins (Strudwick and Sobel 1988). The vkrzea forests perform important ecological functions such as nutrient cycling, and the ecoregion has a high diversity of birds, freshwater fish and aquatic mammals (WWF 2001).
All of our study plots were located within flfloodplain forests in the Amazon estuary. From prehistoric times to the present, these forested areas have been shaped to varyrying degrees by human activities, including NTFP extraction, logging, and agriculture (for example, Anderson et al. 1999; Dean 1987; Roosevelt et al. 1996). None of the forest areas where data collection took place could be considered `pristine'. However, aside from differences in management, our study plots were located in ecologically similar environments on tidally inundated lands where the acai palm is a native and conspicuous component of the forest systems.
The lives of ribeiririnhos are intricately linked to the ebb and flflow of the river. They live in scattered settlements in towns or along rivers and island margins where their homes are built on stilts to avoid the twice-daily tidal inundations [Figure 3]. The existing pattern rn of riribeirinho settlement heralds back to at least as early as the nineteenth-century ry rubber boom, when ribeirinhos were the pririmary labour force for European landholders (Brondizio and Siqueira 1997). Today the majority ty of ribeirinhos live on small areas of land (1-50 ha). Although most do not have legal title to their land, these smallholders are free to decide how to manage their lands, including how and where NTFP and/or agricultural products are managed, when they are harvested, and where and to whom they are sold (ibid.). Owners of medium to large landholdings (50-200 ha) are primarily urban entrepreneurs who do not live in the flfloodplain forests and instead rely on riribeirinho sharecroppers or lessees (ibid.). Ribeirinhos who are sharecroppers on these larger properties have little control over natural resource management, and in particular over the harvest and marketing decisions for acai and palmito (ibid.). We limited our study (and the description of ribeirinho land uses, below) to include only those households that have full control over forest management decisions.
Every ry ribeirinho household has some form of watercraft, whether a dugout canoe or motorboat, which is used for transportation to school, markets and to access NTFP in the surrounding forests. The vkrzea environment is rich with aquatic and terrestrial resources used by ribeirinhos. Ribeiririnhos catch fish and shrimp from the ririvers and streams, and are able to cultivate some crops, including beans and manioc on higher ground. Forest gardens surrounding ribeiririnho homes (homegardens) include a diverse assortment of exotic, native and semidomesticated plants, which are important sources of food, medicine and construction materials (Smith 1999). In the Amazon estuaryry, homegardens also include an intensively managed area of the acai palm, called an a (aizal. Floodplain forests are farther from ribeirinho homes and are managed to varyrying degrees. Areas closest to the home are often managed to increase production of acai; in this study we refer to these areas as `acai-enriched' forests. Other forest areas, usually more distant from the home, may be used by ribeirinhos for hunting, selective logging, fishing, and gathering of wild fruits and other NTFP as a source of food, medicine or construction materials. These areas have sometimes been called `mature flfloodplain forests' (for example, Anderson et a].1995) because they are late-successional forests that are less intensively used than other forest areas. In our study we refer to these forest types as 'non-enriched' to emphasise that they are not enriched for acai production, although they may be used by ribeirinhos for other purposes. Because the majority of ribeirinhos rely on NTFP for some of their income, ribeirinho activities are seasonal and depend on market demands (Anderson et al. 1995; Hiraoka 1999; Jardim 1996).
Ribeirinhos in the estuary ry are integrated at various levels into the market economy. Villages with markets, shops, churches, hospitals and other institutions are scattered throughout the estuary ry and ribeirinhos have links to these populated centres. The largest city in the Amazon basin is Belem, located at the mouth of the Para river, with almost 2 million inhabitants. The largest market in Belem is the Ver-o-Peso ('see the weight'), where boats from all over the Amazon converge every ry mornrning before dawn and unload a diverse array of products including fish, cultivated fruits and vegetables, and numerous NTFP gathered by ribeirinhos from the surrounding flfloodplain forests. The Ver-o-Peso has an enormous market for acai fruit, the Feira do Acai, where an estimated 70 to 120 vendors sell approximately 204,000 kg of fruit per day during the peak harvest season from July to December (Warren 1992). Belem also has numerous other smaller markets for agricultural products and NTFP, including four smaller-scale acai fruit markets (ibid.). Some of the scattered towns throughout the Amazon estuary ry have small markets where NTFP and agricultural products are sold. Although these markets may also serve as the fifinal destination for ribeirinhos' NTFP, demand is substantially lower in these areas than in Belem, particularly in the case of acai. For example, although Abaetetuba is one of the largest towns in the estuaryry, its population of approximately 64,000 (FIBGE 1997) is signifficantly smaller than that of Belem. Consequently, the demand for acai in Abaetetuba is substantially less than in Belem, with ten to twenty ty vendors selling approximately 45,000 kg of fruit per day during the peak harvest season (Stephanie Weinstein and Susan Moegenburg, personal observations).
Palmito factories are scattered throughout the estuaryry. They range in size frfrom simple makeshift structures on ribeirinhos' properties that are used as seasonal operations, to larger factories that are registered with IBAMA, the Brazilian environmental protection agency. Palmito is processed at these factoriries and then transported to Belem where it is exported to regions outside the Amazon.
| Methods|| |
Afai Palm Management Strategies
Semi-structured interviews were conducted with twentyty-five ribeiririnho households from May to August 1999. Interviews took place in riribeirinho homes, homegardens and managed forest areas. The purpose of the interviews was to gather information on the types of acai palm management strategies used by ribeirinhos, and the frequency and intensity ty of their use at sites throughout the estuaryry. We also wanted to determine if ribeirinhos focused acai palm management on palmito or acai fruit production, and if this focus varied among study sites.
Households were located on islands or in rural areas surrounding five main sites: Combo Island (n = 5 households), Igarape Miri (n = 5), Abaetetuba (n = 6), Oeiras do Para (n = 5) and Breves (n = 4). These sites were chosen in order to have a sample of households found along a distance gradient from Belem; sites are located 1.5, 52, 70, 150 and 250 km from Belem respectively [Figure 2]. Within each study area, households were selected using a snowball sampling method in which a key consultant is located and this person then leads the researcher to other appropriate consultants (Bernrnard 1995). Study households were limited to those possessing the right to make all decisions regarding the harvest, marketing and transport of acai fruit and palmito from the property (that is, not sharecroppers), and to those that produced acai fruit to sell (that is, in addition to household consumption).
Market Influences on Afai Palm Management and Sales
In each of the twenty-fifive households sampled using the methods described in the previous section, we also conducted interviews to determine if a household's distance to Belem inflfluenced acai management decisions and the annual sales of acai fruit and palmito. As the largest population centre and the site of the largest NTFP markets in the Amazon basin, we hypothesised that Belem exerts a disproportionate inflfluence on ribeirinho forest management decisions throughout the Amazon estuary ry and that this inflfluence varies along a distance gradient from Belem. We expected that acai palm management decisions would depend largely upon the household production of acai fruit and palmito, transportation opportunities to bring acai NTFP to markets, and the pririces received for these products. Because acai fruit is highly perishable and its greatest demand is in Belem, we expected that households located closer to Belem would focus acai palm management on fruit production and sales whereas those farther from Belem would concentrate on palmito production. Additional informal interviews were conducted at each site with palmito factory ry workers, acai fruit vendors and middlemen in acai markets to develop a better understanding of the palmito and acai fruit industry throughout the estuaryry.
Ecological impacts of Acai Palm Managgement
Acai Palm Density and Recruitment Differences in household management activities might be reflflected in differences in acai population structure, including acai clump density and acai stem demography. Acai clump density ty is an important measurement because it gives an indication of acai enrichment planting activities. Acai stem demography data allow us to assess if suffficient recruitment is occurring from each life stage of the acai palm, from seedling to adult. It is important to evaluate recruitment in studies of NTFP systems because the harvest of the NTFP could impact particular life stages of the plant. For example, areas with intensive acai fruit harvesting might have fewer seedlings, whereas areas with intensive palmito harvesting might have a high number of younger stems of acai but fewer larger, reproductively active stems.
Data on acai populations were collected along transects in the flfloodplain forests at each of the twentyty-fifive households where interviews took place. Transects began at a point in any area of the forest where the harvest of NTFP frfrom acai occurred, outside of the homegarden. The direction of the transect was selected such that the length of the transect could be walked without crossing the household land boundary ry or fording any rivers. Density ty of acai clumps was estimated using the point-centred quarter method (Greig-Smith 1983). Starting at the chosen point within the acai-managed forest area, a quadrant was formed in a random orientation by tossing a stick in the air and laying another stick perpendicular to the ffirst. In each of the four quadrants, the distance (r) from the sticks' intersection point to the centre of the nearest clump of acai was measured. In each quadrant we recorded the number and height of each seedling and adult stem of acai and categorised each into one of six size class categoriries: (a) seedlings without stems; (b) seedlings with stems up to 2.5 m in height; (c) juveniles 2.5-6.0 m; (d) adults 6.0-10.0 m; (e) adults 10.0-15.0 m; and (f) adults greater than 15.0 m. Size categories are based on personal observations of heights at first fruiting in managed flfloodplain forests (usually over 6 m) and the recorded height limits for this species (Henderson 1995). At each quadrant we also recorded data on the amount of vegetation cleared around a clump of acai. A second point-centre was laid 20 m directly ahead in the predetermined direction. Between six and eight quadrants were laid on a transect (transect length 120-160 m, n = 24-32), depending on household land area or land constraints, such as rivers cutting across landholdings.
The density ty of acai clumps at each household forest area was determined by measuring r, the distance in metres from the point-centre to the clump, and n, the number of quadrants sampled on a transect. Acai clump density ty was calculated using the following equation: density = 1/(Zr/n)' 1/(Zr/n)' 1/(Zr/n)' 1/(Zr/n)' 1/(Zr/n)' 1/(Zr/n)' 1/(Zr/n)' 1/(Zr/n)' 1/(Zr/n)' (Greig-Smith 1983). We calculated the density ty of acai stems in each size class by multiplying the result of the equation above by the mean number of stems in a size class per clump on a transect.
Vegetation ClearingAroundAfai Palms We estimated the amount of clearing of mid- and overstorey vegetation around the acai clumps using the point-centred quarter method described above. Within each quadrant, we measured the distance between the acai clump and the closest tree (not acai) with diameter at breast height (DBH) greater than or equal to 5 cm. Distances were grouped into four categories: (a) 0-3 m; (b) >3 and <5 m; (c) >5 and <10 m; and (d) >10 m. For each transect, the number of measurements in each of the four categories was converted to a percentage. These percentages were then averaged for all transects within a site (that is, Combn, Abaetetuba, Igarape-Miri, Oeiras do Para and Breves) to give an estimate of clearing.
Vegetation Composition and Structure in Afai-enriched and Non-enriched Forest Areas In addition to affecting acai palm populations, management might also affect overall structure and composition of the forest. To evaluate this, a detailed analysis was done of vegetation structure and composition in forest stands on islands near the town of Abaetetuba. Data were collected from September to November 1997 in ten forest stands: five enriched with acai (hereafter `enriched') and five not enriched with acai (hereafter 'non-enriched'). These forests were identified through conversations with local people. Enriched stands had been so managed for at least twenty ty years and were approximately 4-5 ha in size. The sizes of the non-enriched stands ranged from 10 to 100 ha. Although some of the enriched and non-enriched stands were adjacent to each other, the locations at which data were collected within the stands were all greater than 500 m apart. Aside frfrom differing in management activities, the ten forests were in close proximity ty and were similar in soils, topography and vegetation. Non-enririched forests have long been subject to subtle management, in which people selectively remove trees for timber and remove other products, such as palm leaves for thatch, bark for medicines and fruits for food. Nevertheless, they differ from enriched forests by not being managed specifically for acai production.
Vegetation variables, including canopy height, canopy cover, and the number and diameter at breast height of all plant stems were evaluated in each of the ten sites along a 50×1 m transect. Fifty ty metres was chosen as the minimum transect length that allowed a characterisation of the vegetation while remaining within a homogeneous stand of each forest tytype. Within such stands, transect starting points and orientations were located randomly. Along each transect canopy height and cover were estimated at 5 m intervals for a total of ten points per transect. Canopy cover was measured using a spherical densiometer, an instrument for measuring forest overstorey density (Lemmon 1957). Canopy height was visually estimated after practising with a clinometer at known distances from trees. All stems within each transect were counted and recorded as belonging to one of the following categories: E. oleracea, other palms (for example, Mauritia flflexuosa, Raphia taedigera), aninga (Montrichardia linifera non-woody vine, woody liana or hardwood tree. DBH of all stems was measured using either a DBH tape or dial calipers.
| Result and Discussion|| |
Acai Palm Management Strategies
A summary of ribeirinho management strategies for acai is found in [Table 1]. Data were pooled for all households because of small sample sizes at each individual study site. Sample sizes less than twenty-five signify that ribeirinhos at one or more households were not certain if a particular management strategy was used.
Ribeirinhos generally divided management activities into three main categories: enrichment, cleaning and stem cutting. These three general categories of acai management are described in more detail later. In addition to these commonly employed management strategies, we also describe two other practices that were infrequently used by ribeirinhos: cutting off the inflflorescence, and tying the leaves of juvenile stems into knots.
Enrichment Enrichment strategies include planting acai palm seeds and/or seedlings and relocating seedlings to areas of the forest where more acai palms are desired. Fifteen of the twenty-five households interviewed, representing households from all study sites, regularly engaged in enrichment activities. Those that did not plant acai seeds and seedlings stated that the palms were already at suffificient densities, indicating that enrichment activities had likely occurred at sometime in the past. After making vinho, the staple food from acai, households are left with a tall mound of discarded seeds, which serves as food for domestic animals as well as a source of acai seeds and seedlings (Strudwick and Sobel 1988). Seedlings are transplanted to areas with more available sunlight, or farther from other acai clumps where they do not compete for light or nutririents and are sufficiently spaced such that they are easier to climb. Some households plant seeds of rare varieties of acai, such as `white acai' (acai branco), which sells at higher prices in markets (approximately US$ 0.60 more per 15 kg in 1999). Nine of the ten households that planted significant number of acai seeds and seedlings were from areas surrounding Abaetetuba and Igarape Miri. This region has recently undergone a transition from sugarcane production and swidden-fallow agriculture to acai-managed flfloodplain forests (Brondizio et al. 1994; Brondizio et al. 1996; Brondizio and Siqueira 1997; Hiraoka 1995).
Cleaning A second group of management activities is termed `limpeza' (literally meaning `cleaning') by ribeirinhos. The most commonly practised cleaning activities were weeding understorey vegetation, such as various species of grasses, seedlings and tree saplings, and cutting or girdling vines, woody lianas and trees from the area surrounding an acai clump [Figure 4]. Households from all sites took part in cleaning activities, which generally begin at the end of the rainy season in May before the fruit has riripened, and continue throughout the duration of the acai harvest. Ribeirinhos stated that cleaning activities encourage acai to grow faster, improve access to the palms, make the palms easier to climb, and make them safer to climb (for example, by removing poisonous snake habitats).
Those households that refrained from weeding did so because they claimed they lacked the time or labour required. Only two households did not cut trees frfrom the forest; these households already had a mature and well-established acai-enriched forest, and one explained that cutting other trees would cause increased light penetration and the spread of unwanted understorey vegetation. To this person, lower fruit production was offset by lower labour needs. Of the twentyty-three ribeirinhos that removed trees, fourteen were selective about the trees that they cut, leaving certain species that are economically important, such as virola (ViVirola la surinamensis) and andiroba (Carapa guianensis), both valuable timber species. Nine of twentyty-fifive households, representing all sites except for Combti and Breves, aimed to turn rn as much of their forest as possible into a virtual monocrop of acai, and only refrained from cutting or girdling those trees that might fall on the palms.
Stem Cutting Ribeirinhos distinguished between the above-mentioned activities and stem cutttting (called `manejo' by ribeirinhos, literally meaning 'management'), which was reserved to describe cutting adult stems of acai from clumps. Ribeirinhos remove stems from acai clumps to harvest palmito, particularly during the winter (January ry to May) when acai production is scarce (Anderson and loris 1992). In addition to providing needed seasonal income, ribeirinhos gave other reasons for removing acai stems, including: to stimulate younger stems to develop faster; to increase fruit production, especially during the winter (rainy season) when acai fruit is tytypically scarce; to clear an area of the forest that will be used for another purpose, such as agricultural production or cultivation of other fruit trees; and to prevent neighbours frfrom stealing fruit and/or palmito. In experimental forest plots, Jardim and Rombold (1994) corroborated ribeirinhos' assertions that removing stems from a clump of acai does indeed serve to increase fruit production in the remaining stems. Twentyty-three out of twenty-ffive households interviewed removed acai stems, and all but one sold the palmito from the cut stems. Those that did not harvest palmito were only found at Combu and Oeiras do Para, and stated that it was not worth the time and effort to do so for the low wages received. However, all households had harvested palmito at some point in the past, and most spoke of indiscriminate harvesting of palmito on their properties when the industry first arrived in the estuary in the late 1960s. Today, households are divided on how frequently they harvest palmito. Ten out of twenty-three households cut many stems from portions of their landholdings every ry one to two years, whereas seven out of twenty-three harvested less frequently, usually every ry fifive to seven years. However, because of the importance of acai fruit in household subsistence and economics, seventeen out of twenty-three households cut only those acai stems that no longer serve in acai fruit production because they are too tall to climb safely or they are older and have diminished fruit yield.
In sum, although twentyty-two out of twenty-fifive households harvest palmito, all households balanced the palmito harvest with management to maintain suffificient acai production for subsistence needs and income. This ffinding did not support our hypothesis that households farther from Belem would concentrate acai management on palmito production. Many households admitted that they once cleared their forests of acai to sell the palmito and that, as a result, they suffered from a lack of acai fruit for consumption. Today it appears that, at least at the household level, ribeirinhos generally do not engage in indiscriminate palmito harvest on their own properties due to their negative experiences with overharvesting in the past. Nonetheless, ribeiririnhos complained of theft of both acai fruit and palmito from their properties, and one motivation for some households to harvest palmito was to attempt to pre-empt theft of either palmito or acai. Because households in the estuary ry are in relative proximity ty to one another and are easily accessible by boat, theft of NTFP is a common occurrence and is diffficult to control. Predatory ry palmito harvesting from large landholdings, especially with absentee landowners, is also likely to still occur in parts of the estuary ry (0 Liberal 2002).
Other Management Strateegies In addition to the commonly used strategies noted above, some ribeirinhos described other acai management practices, including climbing trees to cut off the inflflorescence before the fruits develop and tying the leaves of juvenile stems into knots. The technique of cutting the inflflorescence was described by households in the vicinity of Oeiras do Para. Cutting off the inflflorescence when it fifirst emerges in the summer apparently causes the tree to produce a new inflflorescence that will produce fruit by winter, when acai is normally scarce and expensive. This management practice was experimentally tested by Jardim and Rombold (1998). The authors found that cutting early inflflorescences resulted in an extended fruititing season (that is, into the winter), but did not result in increased fruit yield. Tying knots in the leaves purportedly produces a shorter and stouter adult tree that has a fatter palm heart and fruits that grow lower to the ground. Many ribeirinhos had heard of this technique, but only one household encountered actually practised it. We never observed this management practice, nor do we know if or how tytying knots in leaves produces the described effects.
Market Influences on Acai Palm Managemenent and Sales
Because there is such great demand for acai fruit in Belem and it is highly perishable, we expected that there would be signifificant differences in household sales of acai fruit and palmito, market values and household income from acai NTFP among sites across the distance gradient to Belem. However, this hypothesis was not supported by data gathered in household interviews.
The Palmito Indusrty As discussed in the previous section, twentyty-three of the twentyty-fifive households harvest palmito and there was no relationship between the frequency of harvest or number of stems harvested and the distance of a household to Belem. Palmito prices vary ry primarily depending on the size and texture of the palmito. Prices are slightly higher in the summer, when most ribeirinhos are harvesting acai fruit rather than palmito. Palmito prices are lower and flfluctuate less than acai fruit. For example, in Igarape Miri in 1999, fifty first-quality tems of palmito were sold for US$ 7.50, which is approximately as much as one to two baskets of acai fruit (about three to ten infructescences; 15-30 kg). Although palmito provides a valuable source of income for acai producers when acai fruit is scarce, the future of the palm heart industry ry in the estuary ry is uncertain. One household in this study cut stems from acai to promote increased fruit production, but did not harvest the palmito frfrom cut stems. This may signal a decrease in the importance of palmito production from the Amazon estuary ry and other households may follow suit, particularly if acai production during the winter increases. French and United States imports of palmito extracted from plantatition-grown Bactris gasipaes (called pupunha in Brazil, chonta in Ecuador and pejibaye in Costa Rica) from Costa Rica and Ecuador have been increasing steadily since the 1990s and will likely overtake imports of Brazilian palmito (Library ry of Internrnational Trade Resources 2000; SICA 2003). Heart of palm from plantation-grown B. gasipaes offers what the industry ry considers to be a higher quality product than the palmito produced from E. oleracea in forest stands. In 1999 three palmito factories visited near Breves were struggling to stay in business. Numerous makeshift factories in ribeirinhos' homes that were once common sights around Igarape Miri had disappeared by 2001, allegedly because of a crackdown by IBAMA. Recent deaths in southern rn Brazil frfrom botulism from canned palmito also brirings into question the health standards of the largely unregulated industry in the estuary.
Household Pvxluction and Sales of Acai Fruits In the acai fruit trade, a standard unit of measurement of acai fruit quantity ty is the `lata'. A lata is a large can that holds approximately 15 kg of fruit. The estimated number of latas of acai sold per harvest season by a household ranged widely, from a low of twentyty-six (on Combu) to a high of 5,000 (in Igarape Miri), with a mean ± standard error of 1,300 ± 252 latas for all households. The volume of acai fruit sold during the main summer harvest season for acai from June to December was not significantly different among sites or with distance from Belem (ANOVA F 4,19 = 1.50, p > 0.2). The price received per kilogram during the summer harvest season was also not significantly different among sites (ANOVA F4,19= 1.27, p > 0.2) with a mean ± standard error of $2.0 ± 0.1 and a range of $1.2 to $2.7 per lata. 
The data presented above are for household production and sales of acai limited to the summer harvest season, when the fruit is most abundant and all households have surplus acai fruit to sell once household consumptive demands are met. However, during the winter (rainy) season few households have sufficient quantities of acai fruit to sell and during this season most must dilute vinho with water to stretch their supplies to meet consumptive needs. Because of its relative scarcity duriring the winter, the market demand for acai fruit is greater and prices increasedoubling or increasing up to almost ten-fold that of the summer prices, ranging from $5.40 to $11.10 per lalata. In years of notable scarcityty, a lata of acai fruit regularly sold for as much as $15 in the winter. Only twelve out of twenty-five households were able to sell acai fruit during the winter, but those that did derived a significant portion of their yearly income from acai fruit sold at this time (a mean of 18.2 per cent up to a maximum of 57.2 per cent of their yearly income). Households from Combu sold significantly more acai fruit during the winter harvest (ANOVA F 4.19 = 4.23, p<0.02; means =107+ 39 latas) than households from all other sites except Igarape Miri. Households from Combu did not seem to manage acai differently or more intensively than households from other sites and did not have significantly higher densities of acai palms. However, the commercialisation of acai fruit in the Amazon estuary ry began in the region around Belem in the early 1970s, so it is possible that households frfrom Combu have more experirience with E. oleracea management and marketing than in other localities and have managed to increase winter production in ways that were not detected in this study. Alternrnatively, the higher volume of acai fruit sold in the winter from Combu might be attributable to natural variation in acai fruit ripening periods throughout the estuaryry.
Based on estimates of volume sold during the harvest and price received per lata, we calculated a rough estimate of income derived from the sale of acai in each household. Household income frfrom acai during the acai harvest season ranged from $70 to $8,100, which was equivalent to $1.70 to $702 (mean ± SE = 135 ±40) per ha of household land. In contrast, when acai fruit sales from the winter harvest are included in calculations of annual income, it increased to a maximum of $951 per ha (mean ± SE = $159 ± 50), with a range from $16.60 to $951 per ha of household land, when including only those households with winter income (n = 12). Although data represent riribeirinhos' estimates of their production and income rather than direct measures of these variables, interviews with acai vendors and middlemen on acai prices were used to confirm the accuracy of household estimates. Also, the range in acai fruit production and income frfrom acaienriched forests are comparable to that described in other studies [Table 2]. Because there was no signifificant difference between the volume of acai fruit sold and prices by site, factors other than the household distance from Belem account for the range in household sales of acai fruit. Although we found that households practised many of the same management strategies [Table 1], there may be differences in the intensity of management between households that account for the variation in household production of acai. Other factors that might inflfluence acai production are the number of years since acai palm enrichment (as seen in [Table 2]) and household labour availabilityty, which is required to engage in management activities and to climb palms to harvest acai fruit. It is clear that ribeirinhos can benefit from sales of acai fruit when demand and prices are high during the winter season, but the factors that contribute to increased winter productivity ty of acai are not known. Although cutting the inflflorescence of the acai palm in the summer is a means to have winter fruit production, few households engaged in this activity.
Market Distance and the Role of the Middleman As we have shown, acai fruit prices were not significantly different between sites and did not vary across a distance gradient from Belem. Despite the large size of the Feira do Acai in Belem, smaller local markets scattered throughout the estuary ry were more commonly the destinatition of ribeirinhos' acai fruit. The time required for ribeirinhos in this study to arrive at the local market (defifined as the market closest to the household) variried from fifive minutes to three hours (one-way) (mean = 51 minutes; n = 25). No differences in household acai management were apparent based on the amount of time to reach local markets. [Table 3] presents information on where ribeirinhos sell acai and how they transport it to the market. Fifteen out of twentyty-three households sold surplus acai fruit at a local market, and all of these households used their own source of transportation (canoe or motorboat) for acai transport. Only three out of twenty-three households sold acai fruit at a market more distant than the local market ('regional markets'), and five additional households sold acai to both local and regional markets, depending on the time of year or quantity of fruit harvested. Seven out of twentyty-three households relied on middlemen to transport acai fruit to regional markets at least at some times of the year. As a result, households that are distant from the Feira do Acai in Belem or from local acai fruit markets still have numerous opportunities to transport and sell acai fruit because of the availability ty of middlemen.
Although the Feira do Acai is clearly the largest acai market in the Amazon, other smaller markets are signifificant in local trade. A web of trade networks exists between the many small and medium-sized towns throughout the estuary ry and middlemen transport acai fruit between these markets in addition to Belem's Feira do Acai. Despite the reputation that middlemen have in the Amazon for exploiting local producers (for example, Gray 1990), they perform a valuable service for ribeirinhos who are unable or reluctant to transport acai fruit to market themselves. Furthermore, intermediaries often struggle to earn rn a meager living. Interviews with middlemen revealed that they try ry to gain a profit of $0.60 per lata, but they usually pay ribeirinhos beforehand and market prices are notably unpredictable. Acai fruit pririces flfluctuate not only between years and seasons based on overall fruit availabilityty, but also between days or even the time of day, based on the number of vendors in the markets or the quality ty of the fruit. Consequently, middlemen often lose money. Several middlemen claimed that they often lost more than they gained, and one energetically characterised his career as an adventure because of the unpredictability ty of the financial rewards and losses. Any delay in the middleman's journrney to regional markets increases the amount of time between the harvest and sale of acai, which jeopardises acai quality ty and price received for the fruit. Where an intermediary ry buys and sells acai fruit depends on his or her social connections in the estuary ry and on the differences in the timing of fruiting at different sites. Local peaks in fruit ripening times throughout the year encourage trade between communities and regions within the estuaryry. Middlemen transport acai fruit between these regions with different acai fruit ripening times in order to meet market demands.
Because household interviews were limited to those that had surplus acai to sell after meeting consumptive needs, it is possible that our small sample size was biased to those with market access. However, households represented a large range in the distance from the home to Belem and the time that it took to arrive at the local market, minimising this possibilityty. The market situation for acai described above is atypical for many NTFP systems where transportation to markets and/or market demand is at a premium (Marshall et al. 2003). Even in the Amazon estuaryry, where river travel and transportation is available, there is a lack of market demand for numerous other NTFP, limiting the ability ty of riribeirinhos to derive economic benefits frfrom forest products (Shanley et al. 2002).
Ecological Impacts of Acai Palm Managemenent
Afai Palm Density and Recruitment The management strategies employed by ribeirinhos result in a wide range of acai clump densities with no differences among sites (ANOVA F 4 ~ 20 = 0.89, p > 0.48). Clump densities ranged frfrom 220 to 2,080 per ha, with a median density ty of 1,250 per ha. Although household interviews revealed that similar management strategies were used to promote the acai palm, future studies could be designed to look more closely at whether management intensity, land use history ry or the time since acai palm enririchment accounts for differences in acai clump density. In comparison to other studies, the low density of acai clumps is comparable to vkrzea that is not managed or is managed at low intensities for acai and the highest clump densities are comparable to acai agroforests that have been managed for close to twenty ty years [Table 2]. Among all households, the mean number of stems of acai in a clump was 6.28 and the mean number of adult stems in a clump was 2.76 (n = 586).
The distribution of acai stem densities in all samples by size class resembles an inverse J-shape, with high densities of seedlings and lower densities of adult stems [Figure 5]. Size class distribution data were pooled for all samples because the pattern rn was similar among all households. This size class distribution pattern rn is common for many species of tropical trees that produce many seedlings, with few surviving to adult sizes due to competition for resources (Peters 1996). The high density ty of acai seedlings and saplings (size classes 1 and 2) indicates that at this point in time, the palm is readily regenerating in forest areas managed by ribeirinhos for acai fruit and palmito production. Unlike many other NTFP systems where there is concern rn that extraction threatens the future production of the NTFP itself, regeneration of acai is not threatened by the palmito and acai harvest. Acai is fast-growing, so areas where overharvesting for palmito occurred in the past may have since regenerated naturally or via enririchment planting. The relative significance of acai fruit in household consumption and the recent increases in market demand likely inflfluence management strategies at the household scale such that the palm is not overharvested.
Vegetation Clearing Around Acai Palms Ribeiririnhos revealed in interviews that they clear vegetation from around acai clumps to facilitate movement through the forest for NTFP collection, and they cut and girdle trees from around the clumps to encourage acai growth and increased fruit production. These management strategies were apparent in measures of the distance between the palm clumps and the closest tree ('clearing' values). Only a small proportion of any transect had less than 3 m cleared around a palm clump, and households from different sites had different clearing measures [Figure 6]. In particular, transects in Igarape Miriri had more than 10 m cleared around 50 per cent of all palm clumps. Some ribeirinhos stated that their goal was to remove all other tree species and convert as much of their property as possible into a plantation of acai. The clearing data show that this is actually happening in parts of the estuaryry. Unlike what had been described for the acai NTFP system in the early 1990s (for example, Anderson 1990), acai management does not seem to be a subtle alteration of forest composition and structure. Instead, the clearing data demonstrate that some areas are being converted to plantation-like stands of the acai palm. Hence, in the case of acai, the dual goals of NTFP harvesting to promote biodiversity conservation and to support local livelihoods do not seem to be met.
Veg Composition and Structure in Acai-enriched and Non-enriched Forest Areas In addition to increasing acai clump densities, management activities also alter overall forest composition and structure, especially in forest stands where acai palm enrichment was actively practised ('enriched' forest), compared with forest stands where acai palm enririchment was not practised ('non-enriched' forest). Vegetation structure differed substantially between enriched and non-enriched forest [Figure 7]. On average, the forest canopy was 6 m higher (F1 ~90 = 111.50, p < 0.01) and 9 per cent more closed (F1,(F1,(F1,(F1, 9o = 96.70, p < 0.01) in non-enriched than in enriched forest. Similarly, stem density of all species was 2.8 times higher (t = 3.91, df = 8, p < 0.01) and basal area 4.8 times higher (t = 3.72, df = 8, p < 0.01) in non-enriched than in enriched forest stands.
These changes in overall vegetation structure were accompanied by much higher densities of acai in the enriched forests [Figure 8]. Acai-enriched forest stands contained six times the number of acai adults (t = 3.86, df = 8, p < 0.01), eleven times the number of juveniles (t = 2.97, df = 8, p < 0.02), and seven times as many saplings as did non-enriched forest stands (t = 3.96, df = 8, p < 0.01). The density of adult-sized acai stems in enriched forests was similar to that found in other studies, whereas the density ty of adult-sized acai stems in non-enriched forests was much lower [Table 2].
Enriched and non-enriched forest stands also differed in their densities of nonpalm stems. Non-enriched forests contained four times more small trees (<10 cm DBH; t = 3.84, df = 8, p < 0.01), five times more vines (t = 2.95, df = 8, p < 0.02), and eighty-four times more lianas (t = 4.51, df = 8,p < 0.01). Non-enririched forests also tended to have more large-diameter (>10 cm DBH) trees and Montrichardia linifera. In general, acai stems and lianas tended to be larger in the enriched forest, while hardwood stems, vines, and M. linifera stems were larger in non-enriched forest.
The differences in vegetation composition and structure between acai-enriched and non-enriched forest stands signify that ribeirinho forest management strategies are not only increasing acai density ty across the Amazon estuaryry, but also that these activities are fundamentally changing the structure and composition of vkrzea forests. With a nearly complete loss of vines, lianas and large woody trees, and an accompanying opening and lowering of the canopy, heavily managed forests no longer resemble native vkrzea. In fact, the differences between non-enririched and acai-enriched forest are comparable to differences between non-enriched forests and agroforests (Thiollay 1992), coffee and cacao plantations (Alves 1990; Greenberg et al. 1997), and logged forests (Johns 1988; Mason 1996). Nevertheless, forest enrichment is a popular and recommended strategy for increasing the economic value of forests in many regions (for example, Ricker et al. 1999).
| Conclusions and Recommendations|| |
Our study has shown that a variety ty of management activities are used throughout the Amazon estuary ry to promote acai palm density, growth and production. Aside from the threat of theft, which caused some ribeirinhos to extract more palmito than they would ideally harvest, there was no evidence of conflflict between palmito and acai production or management on household landholdings. Management for acai NTFP does not have a negative impact on the regeneration of the palm itself. The demand for acai in household consumption and in local and regional markets serves to limit overharvesting of stems for palmito extraction. Although the fruit is highly perishable, household distance to Belem did not inflfluence management activities because many households have boats and transport their own production of acai to local markets and because middlemen facilitate trade to numerous other acai markets throughout the estuary ry in addition to Belem. Acai, and the estuary ry in general, is probably not tytypical of other NTFP systems where transportation is often unavailable or insufficient, and markets for the products are lacking (Browder 1992; Crook and Clapp 1998; Shanley et al. 2002).
The demand for acai fruit continues to grow throughout the estuary ry and beyond. Although ribeirinhos appear to be benefiting financially from the industryry, there are seririous consequences for the ecological integrity and biodiversity ty of the vkrzea. Acai is now available in cities and small towns throughout Brazil where it is marketed as a nutritious energy drink. A growing portion of the production from the estuary ry is exported internrnationally to Japan, Europe and the United States in the form of powder or frfrozen or pasteurirised pulp (Brondizio, forthcoming; 0 Liberal 1999; Melo et al. 1988). As the demand for acai continues to increase, the `acaization' of the estuary ry (Hiraoka 1995) intensifies and expands. Acai-enriched flfloodplain forests once described as a subtle alteration of mature flfloodplain forests (Anderson 1988, 1990; Anderson et al. 1995) increasingly resemble acai plantations. Not only are vkrzea forests being cleared to make room for acai, but in some areas acai plantations are being established in the terra firme uplands of the estuary ry (0 Liberal 2003). Recent analysis has revealed that rates of deforestation in the Amazon flfloodplains is comparable to that occurring in the uplands, due in part to the expansion of acai-managed forest areas (Zarin et al. 2001). Not only does vegetation structure and composition differ in enriched versus non-enriched forests, but the composition of the bird community also differs, as does the relative abundance of fruit-eating birds and native vkrzea bird species (Moegenburg and Levey 2002). Furthermore, within enriched forest stands, higher-intensity ty acai harvests reduces the diversity ty of fruit-eating birds due to reduced fruit availability (Moegenburg and Levey 2003).
Given our findings, we question whether the acai system is a 'win-win' system (see also, Uma Shaanker et al., this issue) for local development and flfloodplain forest conservation, as had been described in the past (Anderson 1990; Fearnrnside 1989; Peters et al. 1989a). However, our study offers some insights into how the acai NTFP system could be improved upon such that local producers realise economic benefits and ecological impacts of management are minimised. Perhaps the most dramatic effect of acai enrichment is the altered vegetation composition and structure due to `cleaning' management strategies (including the removal of understorey vegetation, canopy trees, vines and lianas). Although the acai palm typically responds to these treatments with increased growth rates and greater fruit output, cleaning activities could be used more selectively such that a better balance is achieved between acai production and maintenance of characteriristic vkrzea composition and structure. Some riribeirinhos interviewed in this study chose to minimise cleaning activities in acai-enriched forests because they preferred to have a more diverse forest that offered numerous NTFP for subsistence use or supplemental income. More diverse forests may serve as `insurance' in the face of rapidly changing market demands, which are characteristic of many Amazonian NTFP 'boom-bust' cycles. Selective cleaning strategies can also benefit acai production itself. We encountered some ribeirinhos who had participated in an acai management course where extension agents advised against transforming the forests into a monoculture of acai, but recommended leaving numerous other species of trees to prevent erosion and maintain soil moisture and nutrients. There is a need to support similar efforts in other areas of the estuary ry to encourage sound management that also benefits ribeirinhos.
Another way in which ecological impacts of acai enrichment could be minimised is to find ways to intensify production such that ribeirinhos can gain greater economic returnrns from a smaller area of land, thereby preventing enririched forest areas from spreading throughout the vkrzea. Rare varieties of acai fruit have a potential niche market that could become profitable for ribeiririnhos in some regions. Other households could realise financial gains from a smaller forest area by increasing production during the winter harvest season when prices for acai fruit are much higher. Factors that inflfluence seasonal variation in acai fruit ripening times throughout the estuary ry should be investigated to determine the role of ecological conditions and/or management practices. We encountered few households that cut the inflflorescence off acai palms to increase off-season fruit production and this could be one means by which intensification could be achieved. Strategies to increase acai production during the off season could become increasingly important if the palmito industry ry continues to suffer in the estuary ry and riribeirinhos lose this important source of winter income.
The growing interest in acai internrnationally also presents opportunities to improve the acai system to benefit riribeirinhos and flfloodplain forests. Acai is being touted as a product that helps protect the Amazon rainforest-not one that contributes to flfloodplain forest conversion into acai plantations. Certification of selected acai production areas could be a tool to increase consumer awareness and promote acai management systems that are more ecologically sustainable. Certification of acai fruit and palmito harvesting exists in at least one area in the estuary ry (FSC 2003).  However, our results reveal that one must consider the ecological effect of acai management on flfloodplain forest composition and structure instead of only evaluating the effect of the harvest on acai palm recruitment.
Although the ecological impacts of acai management may be less severe than other threats to biodiversity in the Amazon such as cattle ranching or logging (for example, Fearnrnside 1988; Uhl et al. 1993) it is clear from our study that acai management will be insufficient to protect the biodiversity of the flfloodplain forests in the Amazon estuary ry over the long term. Fully protected areas do not exist in the Marajo vkrzea ecoregion (WWF 2001), but they may be necessary ry if biodiversity conservation is a goal. Insofar that acai management protects major ecological processes and provides habitat for selected native species, this land use would be appropriate in regions surrounding protected areas. By understanding the markets for acai and the ecology of the vkrzea, we can continue to work towards finding the balance between rural development and conservation.
Acknowledgements: This research would not have been possible without the kind generosity and insight shared by numerous ribeirinhos in the Amazon estuary. Special thanks go to Nena and Orivaldo Quaresma, Joao, Agosta, Marcelo and Raimundo Pantoja, and Domingos Deniz for opening their homes and assisting with ffieldwork (SW), and to Zusa Ferreira and Batista Sabito for generous help (SM). Drs Nigel Smith, Marianne Schmink and Doug Levey (University of Florida) helped guide many aspects of this work. Dr Mario Hiraoka availed his property to SM for fifieldwork, and Drs Chris Uhl and Mark Cochrane provided invaluable advice. Drs Louis Forline and Mario Jardim (Universidade Federal do Para and Museu Paraense Emilio Goeldi), and Dr Luiz Afonso Sefer provided logistical supported in Brazil. This research was as generously supported by grants from the University of Florida (Tropical Conservation and Development Program, Department of Geography, Dickinson Award in Tropical Agriculture, and the Charles Wagley Research Award), the Foreign Language Area Studies Award, the Lincoln Park Zoo Scott Neotropic Fund and the National Geographic Society. Comments from two anonymous reviewers greatly helped improve the manuscript.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]
[Table 1], [Table 2], [Table 3]