Forest Management Patterns in the Floodplain of the Amazon Estuary

Anthony B. Anderson; Pennie Magee; Anne Gely; Mario Augusto Goncalves Jardim

Conservation Biology, Vol. 9, No. 1. (Feb., 1995), pp. 47-61.

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Forest Management Patterns in the Floodplain of the Amazon Estuary

*Ford Foundation, Praia do Flamengo 100, Rio de Janeiro - RJ - 22.210 Brazil t918 University Avenue, Boulder, CO 80302, U.S.A. $Part Pheonix, 405 Promendade des Anglais, Nice, 06200 France §Departamento de Botkica, Museu Paraense Emilio Goeldi, Caixa Postal 399, Belem - PA - 69.000 Brazil

Abstract: In the Amazon basin, few studies have focused on environmentally sound land-use alternatives that are linked to markets. This paper analyzes land uses cawied out by traditional inhabitants (ribeirinhos) on three islands in the Amazon estuary. Management of the native floodplain forest is the most extensive form of land use on these islands. Such management varies in response to local economic and ecological conditions but invariably targets key nontimber forest resources destined for local markets, requires minimal input of labor and capital, and maintains a considerable stock of biotic resources. While restricted to a specific forest type, this form of land use is associated with relatively high population densities and if supported by appropriate developmentpolicies, could provide an environmentally sound land-use alterna- tive for hundreds of thousands of rural inhabitants of Amazonia

Patrones de manejo del bosque en la llanura de inundacion del estuario del Amazonas

Resumen: En la cuenca del Amazonas, pocos estudios se ban centrado en las llamadas alternativas ambien- tales de uso de la tierra que esten ligadas a mercados. Este trabajo analiza usos de la t i m a llevados a cabo por habitantes tradicionales (ribeirinhos) en tres islas del estuario del Amazonas. El manejo del bosque nativo de la llanura de inundacidn, es la forma mks extensiva de uso de la tierra en estas islm Este manejo varia en respuesta a las condiciones de la economia local y a las condiciones ecoldgicas, pero invariable- mente apunta a recursos no-maderables claves del bosque destinados a mercados locales, requiere una inversidn minima de trabajo y capital y mantiene u n considerable stock de recursos bioticos. Si bien esta restringida a u n tipo particular de bosque, esta forma de uso de la t i m a esta asociada con una densidad poblacional relativamente alta y si es apoyada por medidas de desawollo apropiadas, puede proveer una alternativa ambientalmente viable de uso de la t i m a para cientos de miles de habitantes rurales del Amazonas.

Introduction ticed by local inhabitants. A growing body of research reveals the intricacy of resource-use strategies em-

Concern over the effects of deforestation in the Amazon ployed by traditional Amerindian groups (see Hames &basin has led to increasing interest in land-use alterna- Vickers 1983; Posey & Balee 1989; Redford & Padochtives that maintain forest cover and are currently prac- 1992). Likewise, Japanese immigrants in the Brazilian

Amazon have established intensive agroforestry systems

Paper submitted October 20, 1993;revised manuscript accepted that provide extraordinarily high economic returns April 2, 1994. (Subler & Uhl 1990). Although these alternatives appear

Conservation Biology, Pages 47-61 Volume 7, No. 1, February 1775

48 Forest Management in the Amazon Floodplain

to be environmentally sound, land-use systems of tradi- tional Amerindians are rarely linked to markets, while those of Japanese immigrants require enormous capital and labor investments. Both systems reflect highly spe- c5c cultural heritages that are distant from the main- stream contemporary Amazonian society and, as a re- sult, may not be not readily applicable to the resource destruction occurring over much of the Amazon basin today.

For centuries the traditional rural inhabitants of the Amazon basin's extensive floodplain areas-known as river dwellers (ribeirinhos or r iberenosthave pro- vided numerous market and subsistence products de- rived from a mixture of farming, hunting and fishing, and forest extraction (Meggers 1950; Wagley 1976; Parker 1985). In contrast to traditional Amerindian groups, river dwellers are tightly linked to local, regional, and even (in some cases) international markets. Formerly overlooked because of their dispersed settlement and "nonexotic" lifestyles (Ross 1978; Parker 1985), they have recently attracted increasing attention of research- ers interested in alternative forms of resource manage- ment in the region (see literature review by Hiraoka 1992).

Research on resource management among ribeirin- hos in the Peruvian Amazon, for example, has revealed that traditional farming systems incorporate not only annual and perennial crops but forest resources, many of which are sold in local markets (Padoch et al. 1985). In the Brazilian Amazon, native floodplain forests pro- vide the major source of income among ribeirinho fam- ilies and are subject to subtle yet pervasive forms of management (Anderson & Jardim 1989; Anderson 1990).

The studies cited above represent the few docu- mented cases of market-based forest management in the Amazon basin and, as such, illustrate how regional for- ests can be utilized without being destroyed. These studies were carried out at specific sites adjacent to major urban markets (Iquitos and Belem). To determine the effects of varying economic and ecological condi- tions on such management, this paper examines the land uses of traditional ribeirinho populations at three loca- tions in the Amazon estuary.

Methods and Materials

In August-September 1986 three islands were selected for comparative analysis: Ilha das Onqas, adjacent to Belem; Ilha Jubinha, on the Tocantins River about 65 km from its mouth; and Ilha Saraca, at the mouth of the Tocantins River (Fig. 1). These islands were selected because they exhibited floodplain forest management under varying economic and ecological conditions.

Economic conditions are strongly affected by the is-

Anderson et al.

lands' distance to markets. The largest market in the Amazon region is Belem, with a 1991 population of 1,244,688 (IBGE 1992). By boat, Ilha das Onqas is 4 km, Ilha Saraca 106 km, and Ilha Jubinha 158 km from Belem. However, most market products from the latter two islands are sold in nearby Cameta, with a 1989 pop- ulation of 39,529 (IDESP 1990). Ilha Jubinha is 18 km from Cameta, whereas Ilha Saraca is 41 km away. Based on travel time to market, then, we consider Ilha das Onqas to be the most accessible of the three islands and Ilha Saraca the least.

Ecological conditions on the three islands also vary. Ilha das Onqas and Ilha Jubinha are covered with topo- graphically intermediate floodplain forest, characterized by a moderate diversity of tree species and high domi- nance of the a ~ a ipalm (Euterpe oleracea). In contrast, Ilha Saraca is covered with topographically low flood- plain forest, characterized by low tree-species diversity and high dominance of the miriti palm (Mauritiaflex- uosa). All islands have low-humic gley soils with high clay content (Vieira et al. 1971). Like flood-prone areas elsewhere in the Amazon estuary, these islands- especially the low-lying Saraca-are subject to tidal floods that peak when the rainy season coincides with the March-April equinox.

Using 1:25,000 base maps provided by the Brazilian Institute of Geography and Statistics (IBGE), the area of each island was determined with a planimeter. Data on demography and land use were obtained by question- naire in selected households on each island. The loca- tions of all households were mapped, and a proportion was randomly sampled for application of the question- naire. We sampled approximately 40% of the house- holds on Ilhas Jubinha and Saraca. On Ilha das Onqas, which had a much larger population, we restricted our survey to one canal, along which we surveyed approx- imately 40% of the households. Based on previous field- work on Ilha das Onqas (Anderson et al. 1985), we be- lieve this sample was representative of the island as a whole.

Data on the size of each household's landholding and the percentage of land allocated to different land uses were obtained through the questionnaire. Among a smaller subset of sampled households, questionnaire re- sponses were verified by measuring the area of each land-use unit with a 50-meter tape and compass in the presence of household representatives.

On each island, we selected two sites with similar topography and soil type for detailed study: one covered by late-successional floodplain forest with no apparent signs of anthropogenic disturbance (mature floodplain forest), and the other by forest subject to obvious ma- nipulation (managed floodplain forest). At each site we established a 50-by-50-meter (0.25 ha) plot in which all terrestrial vegetation with diameter at breast height (dbh) of at least 5 cm was inventoried. Following meth-

Conservation Biology Volume 9, No. 1, February 1995

Anderson et al. Forest Management in the Amazon Floodplain 49

Figure 1. Map of the southeastern portion of the Amazon estuay. Squares indicate study sites.

odology described in Halle et al. (1978), we prepared profiles and crown projections of the terrestrial vegeta- tion with dbh 2 cm or more within a 60-by-10-meter plot. Botanical specimens of all species encountered in our sample plots were collected, identified, and depos- ited in the herbarium of the Emilio Goeldi Museum of Para in Belem, Brazil.

Results Demography The demographic characteristics of the three islands varied considerably (Table 1). Ilha das Onqas is the larg- est of the islands, with a total area of 44 km2, and it also had the largest total population (1919). Despite its proximity to Belem, the population density of Ilha das Onqas (37 inhabitants per km2) was intermediate

among the three islands. At the other extreme, Ilha Sa- raca had the lowest population density of the three is- lands (11 inhabitants per km2), probably reflecting its relatively low topography and high frequency of flood- ing. Ilha Jubinha is the smallest of the three islands, with a total area of only 9 km2, yet had the highest population density (50 inhabitants per km2).

Land Uses

Most of the five land-use units identified in this study have been described in detail elsewhere (Anderson et al. 1985; Anderson 1990). A summary description of each land-use unit and- a comparison of its relative ex- tent on the three islands (Table 2) follow:

(1) The house garden is a small (generally less than 1 ha), intensively managed land-use unit surrounding the

Conservation Biology Volume 9, No. 1, February 1995

50 Forest Management in the Amazon Floodplain

Table 1. Area and population data of three islands in the Amazon estuary.

Island

Variable Oncas Juhinha Saraca

Area (km2) 44 9 29 Estimated Number

of Households 176 48 42 Mean Number of

Individuals per Household 9.2 9.4 7.3

Total Population 1,619 45 1 307 Population Density

( n o . h 2 ) 3 7 50 11

household dwelling that is used primarily for raising domesticated animals and cultivating a wide range of plants destined for both domestic consumption and markets. House gardens occupy a relatively larger per- centage of land on Ilha das Onqas (3%) than on Ilha Jubinha (2% ) or Ilha Saraca (1% ). The additional area allocated to house gardens on Ilha das Onqas is used primarily for cultivation of perennial fruits and orna- mental plants destined for the nearby market of Belem.

(2) Swidden plots are scattered within the floodplain forest and are usually established for cultivation of short-cycle crops such as corn, rice, beans, manioc (on elevated sites), and sugarcane. On low sites, this form of land use is severely limited due to tidal flooding, which leaves the soil waterlogged during most of the year. In areas where staples can be readily purchased or ex-changed, local inhabitants are increasingly abandoning swidden cultivation. We found swidden plots only on Ilha das Onqas, although they were formerly more wide- spread on all three islands according to local residents. On Ilha das Onqas, swidden plots cover only 2% of the land area and are used primarily for production of veg- etables bound for the Belem market.

(3) Perennial cash-crop plantations usually consist of 1-3 crops planted in plots of 1-10 ha in which the

Table 2. Percentage of land area allocated to diierent land uses on three islands in the Amazon estuary.

Area (%)a

Zlha das Zlha Zlha Onqas Jubinha Saraca ~ e a n ~

Land Use (18) (16) (44)

House Garden 3 2 1 2 Swidden plot 2 0 0 1 Perennial

Cash Crop Plantation 0 6 0 1

Managed Forest 29 81 86 5 5

Mature Forest 66 11 13 41

aNumba of households sampled in parenthesis. b ~ e a nvalues weighted according to total area of each island

Anderson et al.

original floodplain forest has been completely cleared. We observed perennial cash crop plantations only on Ilha Jubinha, where they cover 6% of the land area and are dedicated exclusively to production of cacao (Theo- broma cacao). The small area allocated to this land-use unit on the three islands is probably due to the fact that, although relatively productive, cacao requires substan- tial inputs of labor and capital, which are usually limited among ribeirinho families.

(4) Managed forests consist primarily of floodplain forest subject to manipulation by local inhabitants. (We define manipulation as a discernible modification of for- est structure to increase the productivity of selected biotic resources. Management is a more general term that includes both manipulation of forest structure and nondiscernible practices, such as the decision not to eliminate a specific forest resource or to maintain a mix of land-use units-including those not subject to manip- ulation.) On the islands studied, examples of manipula- tion include weeding of competitors to enhance fruit production in the a ~ a ipalm and establishment of un- derstory plantations of cacao. In contrast to the rela- tively open house gardens or swidden plots, managed floodplain forests typically contain a more or less con- tinuous tree cover and are less intensively managed. This land-use unit produces an impressive variety of subsistence and market products. Managed forests cov- ers an estimated 55% of the total area of the three is- lands surveyed, occupying a far greater percentage of land on Ilhas Jubinha (82% ) and Saraca (86% ) than on Ilha das Onqas (29% ).

(5) Mature forests provide a wide variety of products, including fruits, palm heart, latex, wood, fertilizer, or- namental plants, fibers, honey, oilseeds, medicine, uten- sils, and game such as pacas, agoutis, porcupines, sloths, and feral pigs. While present on all islands, we found a much greater proportion of land covered by mature for- ests on Ilha das Onqas (66%) than on Ilha Jubinha (11%) or Ilha Saraca (13%).

Forest Management

On Ilha das Onqas, mature floodplain forest exhibited relatively high species diversity, canopy cover, and basal area, which declined substantially in forest subject to manipulation (Figs. 2 and 3; see Table 3 for following data). For example, we found the number of species per 0.25-ha plot was 53 in mature forest and 28 in managed forest. The Shannon-Weaver diversity index-which as-signs a weighted value for each species according to its ecological importance within the community (Shannon &Weaver 1963)-was 2.63 in mature forest and 2.25 in managed forest. In mature forest, canopy cover was 98% and basal area was 39.9 m2ka; in managed forest, the corresponding figures were 85% and 31.3 m2ka, respectively.

Conservation Biology Volume 9, No. 1, Febmaiy 1995

Anderson et al. Forest Management in the Amazon Floodplain 51

Figure 2. Profile and crown projections of all plants with dbh 2 cm or more in a 60 X 10 m area of mature floodplain forest on Ilha d m O n ~ m , following methodology of Halle et al. (1978). Euterpe oleracea is not numbered, 1 = Pterocarpus officinalis, 2 = Spondias mombin, 3 = Pithecellobium latifolium, 4 = Carapa guia- nensis, 5 = Astrocaryum murumuru, 6 = Hevea brasiliensis, 7 = Cyrometra marginata, 8 = Macrolobium angus- tifolium, 9 = Inga cJ alba, 10 = Pentaclethra macroloba, 11 = Quararibea guianensis, 12 = Crudia sp,, 13 =

Mora paraensis, 14 = Virola surinamensis, 15 = Symphonia globulifera, 16 = Pithecellobium glomeratum, 17 =

Rheedia macrophylla, 18 = Virola cJ michelli, 19 = Eschweilera alba, 20 = Posoqueria sp., 21 = Parinari ex- celsa, 22 = Ocotea caudata, 23 = Richardella glomerata, 24 = Licania sp., 25 = Swartzia racemosa, 26 = Ae-giphila sp,, 27 = Socratea exhorrhiza, 28 = Herrania mariae, 29 = Swartzia polyphyla, 30 = Couepia sp., and 31 = Inga sp.

Floodplain forest management on Ilha das Onqas fo- mercial production is limited to locales such as Ilha das cused on the economically important a ~ a ipalm, the Onqas that are easily accessible to markets. In addition fruits of which are used to make a beverage that is to thinning undesirable competitors, residents selec- widely consumed as a staple food in the eastern Amazon tively prune the multiple stems of this species for har- (Strudwick & Sobel 1988).Because acai fruits begin to vesting of palm heart, which is sold to local industries. spoil within 24 hours at ambient temperatures, com- On Ilha das Onqas, various species had greater repre-

Conservation Biology Volume 9, No. 1 , February 1995

52 Forest Management in the Amazon Floodplain Anderson et al.

Figure 3. Profile and crown projections of all plants with dbb 2 cm or more in a 60 X 10 m area of managed floodplain forest on Zlba d m Onps, following methodology of Halle et al. (19 78). Euterpe oleracea is not numbered, 1 = Hevea brasiliesis, 2 = Theobroma cacao, 3 = Inga edulis, 4 = Spondias mombin, 5 = Inga cf alba, and 6 = Genipa americana.

sentation under management (Appendix), including rubber (Hevea brmiliensis) and a popular fruit tree known locally as inga cipo (Inga edulis). These species were not planted, but local residents dispersed the latter and deliberately refrained from weeding both. Four other species were planted in managed forest: cacao, cupuacu (Tbeobromagrandzflorum),genipap (Genipa americana), and mango (Mangifera indica). On the other islands, economically important species that in- creased under management included tapereba (Spon- dim mombin), which produces tasty fruit, and two fast-growing timber species, virola or ucuuba (Virola

Conservation Biology Volume 9, No. 1, February 1995

surinamensis) and andiroba (Carapa guiansensis) (Appendix).

On all three islands, numerous floodplain forest spe- cies were reduced or eliminated under management, such as the leguminous trees mututi (Pterocarpus offi- cinalis) and pracuuba (Mora paraensis) and the spiny murumuru palm (Astrocayum murumuru). In addi- tion, woody vines such as Dalbergia monetaria and Macbaerium leiopbyllum represented a high propor- tion of the basal area in the mature floodplain forest on Ilha das On~as. This proportion declined considerably in managed floodplain forest (Table 3).

Anderson et al. Forest Management in the Amazon Floodplain 53

Table 3. Comparison of vegetational attributes in 0.25-ha plots of mature and managed floodplain forest on three islands in the Amazon estuarv.

Attribute

Species Richness (no.spp/0.2 5 ha)

Diversity Indexa Canopy Cover (% )b Absolute Dominance

(mZ/0.25 ha) Relative Dominance (% ) Dicot. Trees and

Shrubs Monocot. Trees

and Shrubs Woody Vines

Zlha dm Onqm Zlha Jubinha Ilha Saraca

Mature

53 2.63

98

10.0

82.7

16.2 1.1

Managed Mature Managed Mature Managed

28 34 15 13 14 2.25 2.34 2.16 1.19 1.2

85 89 79 99 92

7.8 12.4 9.7 7.4 10.1

82.4 82.2 89.7 14.8 38.9

17.4 17.7 10.3 85.2 61.1 0.2 0.1 0 0 0

= relative dominance of each species. Adapted from Shannon and Weaver (1963). aDiversity index calculated as - pilog Pi, where P , Canopy cover calculated as percentage of 50-by-10-meter sampling area covered in crown projection maps (Figs. 2-7) using a planimeter

Species diversity, canopy cover, and basal area were also considerably higher in mature than in managed for- est on Ilha Jubinha (Figs. 4 and 5; see Table 3). For example, the number of species per 0.25-ha plot was 34 in mature forest and 15 in managed forest, and the Shan- non-Weaver diversity index was 2.34 and 2.16, respec- tively. Canopy cover was 89% and basal area was 49.6 m2/ha in mature forest on Ilha Jubinha. In managed for- est, the corresponding figures were 79% and 38.7 m2/ ha, respectively. In contrast to Ilha das Onqas, woody vines on Ilha Jubinha showed greater abundance in man- aged forest (Appendix), suggesting that their elimina- tion was not a management objective (Table 3).

Two salient features distinguish managed from ma- ture forest on Ilha Jubinha: the a ~ a ipalm practically disappeared, and cacao on managed sites increased sub- stantially (Figs. 4 and 5; Appendix). These features prob- ably reflect islanders' responses to different market op- portunities. In the case of a~a6the local market in Cameta is limited, the Belem market is excessively dis- tant, and residents report that the dense root system of this species inhibits the growth of cacao. In processing for chocolate production, cacao seeds are removed from the fruits and dried, thus reducing spoilage and permitting commercial production in areas distant from markets. Furthermore, in contrast to the other is- lands, cacao was already abundant in mature floodplain forest on Ilha Jubinha. Floodplain forest management on this island consequently reduced a ~ a iand favored cacao.

On Ilha Saraca, ecological as well as economic factors strongly influenced forest management. The mature floodplain forest was a successional community charac- teristic of recent sediments and almost completely dom- inated by two species of palms: miriti in the canopy and a ~ a iin the understory. As a result, the species diversity and basal area were considerably lower than those of mature forests on Ilha das O n ~ a s and Ilha Jubinha (Figs.

6 and 7). For example, in a 0.25-ha plot of mature forest on Ilha Saraca, we found only 13 species and a diversity index of 1.19; at 29.5 m2/ha, the basal area was also relatively low (Table 3). Due to these factors, only a few species characteristic of floodplain forest were actively eliminated on Saraca, including a ~ a i(Figs. 6 and 7), Pterocarpzrs officinalis, and red mangrove (Rhizophora mangle) (Appendix). As on Ilha Jubinha, the choice of eliminating acaiand favoring cacao was dictated by dis- tance to markets.

In contrast to a~a6the other dominant palm on Sa- raca, miriti, increased under management and, together with cacao, was largely responsible for the higher basal area of managed forest (Appendix, Table 3). Miriti pro- duces edible fruits, fibers, wine, and construction mate- rials that are used in both market and subsistence econ- omies (see Wilbert 1976). Yet local residents on Saraca valued this species primarily as a food source for a va- riety of game animals, including fish. In addition, this species' prolific litterfall generates mounds of organic material that provide critical sites for establishing un- derstory plantations of cacao (see Fig. 7). Residents re- ported that such plantations were far more successful on elevated mounds of well-aerated organic material than on the topographically low sites between palm trees, which are subject to frequent inundation by tidal floods.

Discussion

General Patterns

This study shows that floodplain forest management is not limited to sites adjacent to major markets but rep- resents a widespread form of land use among the ribei- rinho population of the Amazon estuary. In fact, forest management appears to have supplanted swidden agri- culture as the most extensive form of land use on the

Conservation Biology Volume 9, No. 1, February 1995

54 Forest Management in the Amazon Floodplain Anderson et al.

Figure 4. Profile and crown projections of all plants with dbh 2 cm or more in a 60 X 10 m area of mature floodplain forest on Ilha Jubinha, following methodology of Halle et al. (1978). Euterpe oleracea is not num- bered, 1 = Theobroma cacao, 2 = Hevea brasiliensis, 3 = Virola surinarnensis, 4 = Carapa guianensis, 5 = Ceiba pentandra, 6 = Swartzia acuminata, 7 = Guarea cJ guidonia, 8 = Mora paraensis, 9 = Socratea exorrhiza, 10 =

Licaria mahuba, 11 = Inga cinnamonea, 12 = Unonopsis guatterioides, 13 = Vatairea guianensis, 14 = Inga cJ nobilis, 15 = Caryocar microcarpum, and 16 = Genipa arnericana.

three islands surveyed (Table 2). In contrast to flood- trocayum murumuru), and trees that are used primar- plain areas in the middle and upper portions of the Am- ily as firewood (including Pterocarpus officinalis and azon, agriculture in the estuarine floodplain is limited by Moraparaensis). To minimize damage to the surround- relatively nutrient-poor sediments and a high frequency ing forest, large trees are frequently girdled rather than of tidal flooding (Lima 1956;Gibbs 1967;Falesi 1974). felled.

The forest management carried out by ribeirinhos The second strategy is to favor a few selected forest in the Amazon estuary involves three strategies. The species by actively promoting their productivity. In first is to eliminate undesirable competitors such as floodplain forests of the Amazon estuary, this strategy woody vines (including Dalbergia monetaria and invariably involves nontirnber resources and is imple- Machaerium leiophyllum), spiny palms (including As- mented by establishing plantations or, alternatively, dis-

Conservation Biology Volume 9, No. 1, February 1995

55 Anderson et al. Forest Management in the Amazon Floodplain

Figure 5. Profile and crown projections of all plants with dbh 2 cm or more in a 60 X 10 m area of managed floodplain forest on Ilha Jubinha, following methodology of Halle et al. (1978). Euterpe oleracea is not num- bered, I = Theobroma cacao, 2 = Virola surinarnensis, 3 = Hevea brasiliensis, 4 = Carapa guianensis, 5 = Spon-dias mombin, 6 = Terminalia dichotoma, and 7 = Homalium guianense.

persing propagules. On the three islands surveyed in this study, species planted in managed forests included cacao, mango, genipap, cupuaGu (Theobroma grandi- florum), and avocado (Persea americana). Highly val- ued species such as acaz; cacao, and miriti were actively managed by concentrating organic material at their bases and weeding competitors; both acai and cacao were also regularly pruned. In the case of the multi- stemmed a ~ a 4experimental thinning of competitors and selective pruning caused substantial increases in fruit production (Anderson & Jardim 1989).

Finally, the third strategy associated with floodplain forest management involves tolerance of numerous re- sources, such as rubber, Spondias mombin, Inga edulis, and Virola surinamensis. In some cases, tolerating such

species while weeding their competitors appeared to result in increased basal area under management (Ap- pendix). Tolerance also maintains a repository of forest resources that can be more intensively utilized and man- aged should new market opportunities arise.

Local Variations

While the broad strategies of forest management were similar on the three islands, its specific characteristics varied from place to place. One of the most striking variations involved the principal species targeted for management. On Ilha das Ongas, acai was strongly fa- vored in managed forest, while on the other islands it was actively eliminated. In contrast, cacao was a minor

Conservation Biology Volume 9, No. 1,February 1995

56 Forest Management in the Amazon Floodplain Anderson et al.

Figure 6 Profile and crown projections of all plants with dbh 2 cm or more in a 60 X 10 m area of mature floodplain forest on Ilha Saraca, following methodology of Hall6 et al. (1978). Euterpe oleracea is not num- bered, 1 = Mauritia flexuosa, 2 = Pterocarpus off~cinalis, 3 = Macrolobium angustifolium, 4 = Montrichardia arborescens, 5 = Pithecellobium latifolium, 6 = Batesia floribunda, 7 = Mora paraensis, 8 = Hevea brasiliensis, and 9 = Palicourea sp.

component of managed forest on Ilha das Ongas and a major component on the other islands. These choices probably reflect varying accessibility to the Belem mar- ket: the high accessibility of Ilha das Ongas favored pro- duction of the perishable fruits of a ~ a (while the rela- tive inaccessibility of Ilhas Jubinha and Saraca favored production of cacao, the seeds of which can be trans- ported over greater distances.

Access to markets also appeared to influence the overall land-use patterns on the islands. For example, over 80% of the area of Ilhas Jubinha and Saraca was covered by managed forest, where cacao is cultivated in the understory. In contrast, managed forest covered un-

Conservation Biology Volume 9, No. 1, February 1995

der 30% of Ilha das Ongas. Here accessibility of the market permits production of a wide range of special- ized products from house gardens and swidden plots, both of which were more extensive on this island (Ta- ble 2). The relatively high intensity of these land uses probably reduced the availability of labor for forest man- agement.

Of the three islands surveyed in this study, only Ilha Jubinha contained populations of cacao in mature flood- plain forest. This species is a native component of non- inundated, upland forests in the Amazon and was prob- ably introduced into the floodplain during colonial times, when cacao plantations were widespread in the

57 Anderson et al. Forest Management in the Amazon Floodplain

Figure 7. Profile and crown projections of all plants with dbh more than 2 cm in a 60 X 10 m area of man- aged floodplain forest on Ilha Saraca, following methodology of Hall6 et al. (1978). Euterpe oleracea is not numbered, 1 = Theobroma cacao, 2 = Mauritia flexuosa, 3 = Hevea brasiliensis, 4 = Virola surinamensis, 5 =

Carapa guianensis, and 6 = Ficus insipida.

Tocantins river basin (Sweet 1974). These consider- ations indicate that the forest management practices ev- ident on Ilha Jubinha today may, in fact, be centuries old.

In contrast to the other two islands, managed forest on Ilha Saraca had slightly higher biological diversity and substantially higher basal area than mature forest (Table 3). These differences stem from ecological char- acteristics of the native floodplain forest on Saraca, which contained relatively low basal area and was dom- inated by the economically important miriti palm-a

species not only maintained by actively favored in man- aged forest. Together with cacao, miriti constituted a major target for management due to its role in ecolog- ical processes. In short, floodplain forest management exhibited striking variations on the three islands, prob- ably in response to changing economic and ecological conditions.

Forest Management Rationale Managed floodplain forests have a number of tangible advantages over mature forests. In the case of a~ai -

Conservation Biology Volume 9, No. 1, February 1995

58 Forest Management in the Amazon Floodplain

which provides over 80% of the annual income among ribeirinho families near Belem (Anderson & Ioris 1992)-increased yields under management can pro- vide substantial economic returns. In addition to boost- ing the productivity of targeted species, management facilitates access to forest resources and, according to local residents, reduces the likelihood of snakebites-a common occurrence in floodplain areas (Anderson 1990).

Another advantage is that, compared with more in- tensive forms of land use, forest management requires minimal input of labor or capital. Because a high degree of forest cover is maintained (see Figs. 3, 5, and 7; Table 3), weeding is much easier in managed forests than in other land-use units such as house gardens, swidden plots, or perennial cash crop plantations. Furthermore, residents on the three islands manage floodplain forests without applications of fertilizers or pesticides. The need for such applications-in addition to vastly in- creased labor requirements-probably explains the scarcity of perennial cash crop plantations on the islands surveyed in this study. The minimal material and labor requirements of floodplain forest management make this land use especially appropriate for low-income pro- ducers.

Forest management also maintains an extraordinary variety of biotic resources that are either actively fa- vored or tolerated. In addition to manipulated resources such as a~a4miriti, and cacao, managed floodplain for- ests contain high concentrations of tolerated species such as rubber and numerous fruit and timber trees, and they also provide palm heart, firewood, fibers, fertilizer, ornamental plants, honey, and game. By maintaining a wide range of forest resources, managed forests repre- sent an important hedge against changing economic conditions.

Finally, managed forests are tightly linked to other land uses commonly practiced in the floodplain of the Amazon estuary (Anderson 1990). Thus, through selec- tive control of regeneration, a house garden, swidden plot, or perennial cash crop plantation can be trans- formed into managed forest; likewise, when regenera- tion ceases to be controlled, a managed forest gradually reverts to mature forest. The maintenance of extensive areas of managed forest thus represents an intermediate land-use option, from which more or less intensive land uses can be readily derived in response to changing needs.

Implications for Regional Development

While apparently successful as a land-use strategy, man- agement of floodplain forests is limited to highly specific ecological conditions. Compared to upland (terra firme) forests elsewhere in the Amazon basin, estuarine floodplain forests exhibit low biological diversity and

Anderson et al.

high dominance by one or a few species that are often of economic value (Anderson 1990). As in other so-called oligarchic forests (Peters et al. 1989), these character- istics facilitate harvesting and management of forest re- sources and are probably indispensable for the success of the land-use practices described in this paper. Yet a~ai-dominatedforests cover an estimated 10,000 kmz in the Amazon estuary (Calzavara 1972-r a mere 0.3% of the total forest cover in the Brazilian Amazon (3.374 million km2, see Pires 1974).

The land uses described in this paper consequently apply to a tiny portion of the Amazon region. From a demographic perspective, however, they assume greater significance. There are no data available on the size of the ribeirinho population in the Amazon estuary, but our population density estimates from the three is- lands range from 11 to 50 inhabitants per km2. Even if the lower figure is considered more representative of current population densities in the estuary, a ~ a i -dominated forests support an estimated population of 110,000 inhabi tantwr 2.5% of the Brazilian Amazon's total rural population (4,325,699 in 199 1, according to IBGE 1992). We believe that the population density of Ilha Jubinha-at 50 inhabitants per km2-is representa-tive of the potential carrying capacity of this ecosystem. Using this figure, estuarine floodplain forest manage- ment could partially support up to 550,000 inhabitants, or 12.7% of the Brazilian Amazon's total rural popula- tion. Although hypothetical, this calculation illustrates the significance of floodplain forest management as a land-use alternative in the Amazon region.

Utilizing the high carrying capacity of the floodplain is a sound development option for the Amazon. Because of its constant renewal of soils through sedimentation and relative ease of access, the floodplain has long been ad- vocated as a more viable site for settlement than inter- fluvial zones (Falesi 1974; Junk 1982; Sternberg 1982; Sioli 1984). In the case of the estuarine floodplain, car- rying capacity would be enhanced by expanding mar- kets for local forest products. For example, diffusion of simple food-preservation technologies could permit the transport and sale of acai fruits over much of the estu- arine region. Likewise, developing new Brazilian and in- ternational markets for floodplain forest products-such as the edible fruits of a ~ a iand cupuaCu or natural oils produced by andiroba and miriti-could provide promising economic opportunities for local producers. And rather than opening new highways for expanding markets, improvement of existing fluvial transport would be an inexpensive and ecologically sound devel- opment option.

Management of estuarine floodplain forests is a local- ized form of land use that nevertheless could have a significant impact on development in the Amazon re- gion. In contrast to other land-use alternatives, such management is already practiced by rural inhabitants, is

Conservation Biology Volume 9, No. 1, February 1995

59 Anderson et al.

tightly linked to markets, and requires minimal input of labor and capital. Furthermore, it maintains continuous forest cover, supports high population densities, and- under favorable conditions-can provide substantial economic returns (Anderson & Ioris 1992). If sup- ported by appropriate development policies, manage- ment of estuarine floodplain forests could provide a vi- able land-use alternative for a substantial proportion of the rural population of Amazonia.

Acknowledgments

This study was supported by grants from the Ford Foun- dation, the Brazilian Council of Scientific and Techno- logical Development, and the British Overseas Develop- ment Administration. The authors gratefully acknowledge the institutional support of the Emilio Goeldi Museum of Para. We also express our gratitude to the late Charles Wagley, who provided travel support for Pennie Magee; Susanna Hecht and Peter May, who assisted in the re- search design; Nelson Rosa, Carlos Rodrio, and Cristina Arnoroso, who participated in the fieldwork and in iden- tlfying botanical specimens; Pamela Richards and Mari- anne Schmink, who helped with the data analysis; and Sandoval and AntBnio Martins, who prepared the draw- ings. Finally, we wish to thank Mario Hiraoka, Miguel Pinedo-Vasquez, John Rombold, Gary Hartshorn, and Ellen Main for their constructive comments on the manuscript.

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60 Forest Management in the Amazon Floodplain Anderson et al.

Appendix Dominance of Plant Species in 0.25-ha Sample Plots of Mature and Managed Floodplain Forest on ilha das Onqas, Ilha Jubinha, and Ilha Saraca.

Dominance (cm2)

Ilha das Onqas Ilha Jubinha Ilha Saraca

Species Family* Mature Managed Mature Managed Mature Managed Mean

Mauritia flexuosa PAL 0 95 1 1017 1837 4240 58580 Hevea brasiliensis EUP 4844 23746 26507 19310 50 20 146 Euterpe oleracea PAL 13814 11919 19645 8104 19998 2996 Virola surinamensis MYS 612 129 18907 24558 267 462 Spondias mombin ANA 16770 9526 0 10713 0 0 Pterocarpus officinalis LEG 21408 0 7333 0 3249 38 1 Theobroma cacao STR 0 2359 5963 7097 0 13952 Carapa guianensis MEL 6357 269 9402 4737 78 1170 Ceiba pentandra BOM 0 0 17671 0 0 0 Tminal ia dichotoma CMB 3740 0 0 6362 0 0 Mora paraensis LEG 2463 0 5763 0 530 0 Ficus cf.paraensis MOR 0 851 1 0 0 0 0 Urbanella excelsa SPT 0 0 0 8332 0 0 Inga edulis LEG 0 8009 0 0 0 0 Macrolobium angustifolium LEG 4343 0 0 0 1745 0 Cynometra marginata LEG 5430 0 0 0 0 0 Vatairea guianensis LEG 0 0 1734 3318 0 0 Inga alba LEG 2143 2724 123 0 0 0 Rhizophora mangle RHI 0 0 0 0 4760 0 Pentaclethra macroloba LEG 3259 1035 264 0 0 0 Guarea cf. guidona MEL 0 1324 2848 0 0 0 Astrocayum murumuru PAL 2223 721 644 0 0 0 Matisia paraensis LEG 2333 0 113 0 0 0 Cecropia cf. obtusa MOR 0 2229 0 0 0 0 Bombax aquaticum BOM 0 0 0 0 0 2009 Crudia sp. LEG 1955 0 0 0 0 0 Pithecellobium latifolium LEG 1587 102 0 0 117 0 Clinostemon mahuba LAU 0 0 1156 0 0 321 Swartzia acuminata LEG 0 0 0 1324 0 0 Theobroma grandaporum STR 0 1215 0 97 0 0 Quararibea guianensis BOM 1155 0 113 0 0 0 Genipa americana RUB 0 1176 2 3 0 0 0 C d i a oblonga LEG 1176 0 0 0 0 0 Cordia cf. bicolor BOR 0 1064 0 0 0 0 Inga cinnamonea LEG 0 0 1013 0 0 0 Protium cf.polybotrium BRS 989 0 0 0 0 0 Trichanthera gigan tea ACA 0 0 860 0 0 0 Socratea exhrrohiza PAL 102 0 613 0 0 0 Sapium hippomane EUP 0 0 0 695 0 0 Sterculia cf. elata STR 693 0 0 0 0 0 Mangifera indica ANA 0 487 0 0 0 0 Ocotea sp. LAU 0 0 380 0 0 0 Montrichardia linifera ARA 0 0 0 0 369 0 Unonopsis guatterioides A N 0 0 0 302 0 0 0 Ca yocar microcarpum CAR 0 0 294 0 0 0 Swartzia polyphylla LEG 293 0 0 0 0 0 Phyllanthus nobilis EUP 0 0 0 0 0 283 Gustavia hexapetala LCY 0 0 250 0 0 0 Persea americana L A U 0 0 0 0 0 248 Clitoria arborea LEG 0 0 247 0 0 0 Allopbyllus mollis SAP 0 236 0 0 0 0 Dalbergia monetaria LEG 235 0 0 0 0 0 Symphona globulifera GUT 186 0 38 0 0 0 Machaerium leiophyllum LEG 162 0 48 0 0 0 Sarcaulus brasiliensis SPT 0 0 209 0 0 0 Pithecellobium glomeratum LEG 0 0 184 0 0 0 Hernandia guianensis HER 0 0 0 183 0 0 Aegiphila cf. arborescens VER 0 146 0 0 0 0

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Anderson et al. Forest Management in the Amazon Floodplain 61

Appendix Continued.

Dominance (cm2)

Ilha das Onqas Ilha Jubinha Ilha Saraca

Species Family* Mature Managed Mature Managed Mature Managed Mean

Derris cf. negrensis LEG 126 0 0 0 0 0 2 1 Psidium Guajava MYR 0 121 0 0 0 0 20 Cedrela odorata MEL 0 119 0 0 0 0 20 Inga cf. nobilis LEG 0 0 115 0 0 0 19 Carazpa grandzyolia GUT 108 0 0 0 0 0 18 Pouteria sp. SFT 0 0 0 0 0 103 17 Cydista sp. BIG 102 0 0 0 0 0 17 Eschweilera alba LCY 99 0 0 0 0 0 17 Unidentified vine 1 ? 99 0 0 0 0 0 17 Uncaria guianensis RUB 9 3 0 0 0 0 0 16 Batesia jloribunda LEG 0 0 0 0 91 0 15 Ficus citrzyolia MOR 0 0 0 0 0 89 15 Rheedia macrophylla GUT 88 0 0 0 0 0 15 Adenocalymma cf.

inundatum BIG 82 0 0 0 0 0 14 Couepia sp. CHB 71 0 0 0 0 0 12 L icania macrophy lla CHB 0 0 7 1 0 0 0 12 Macuna altissima LEG 0 0 69 0 0 0 12 Cecropia concolor MOR 64 0 0 0 0 0 11 Guarea kunthiana MEL 64 0 0 0 0 0 11 Paragonia cf.pyramidata BIG 61 0 0 0 0 0 10 Miconia sp. MLT 0 5 5 0 0 0 0 9 Allantoma cf. lineata LCY 5 2 0 0 0 0 0 9 Sterculia pruriens STR 52 0 0 0 0 0 9 Cecropia ficzyolia MOR 0 0 0 0 0 47 8 Guarea trichilioides MEL 0 35 0 0 0 0 6 Richardella glomerata SPT 34 0 0 0 0 0 6 Coussapoa sp. MOR 0 0 3 3 0 0 0 6 Machaerium macrophylla LEG 28 0 0 0 0 0 5 Bauhinia guianensis LEG 26 0 0 0 0 0 4 Cynometra cf. martiana LEG 26 0 0 0 0 0 4 Eugenia sp. MYR 0 26 0 0 0 0 4 Unidentified Vine 4 ? 2 5 0 0 0 0 0 4 Palicourea sp. RUB 0 0 0 0 25 0 4 Virola cf. michellii MYS 24 0 0 0 0 0 4 Tetrapteys sp. MPH 0 24 0 0 0 0 4 Licania heteromorpha CHB 2 1 0 0 0 0 0 4 Unidentified Vine 2 ? 2 1 0 0 0 0 0 4 Hura crepitans EUP 0 0 0 19 0 0 3 Arrabidea sp. BIG 18 0 0 0 0 0 3 Ocotea caudata LAU 17 0 0 0 0 0 3 Unidentified Vine 3 ? 17 0 0 0 0 0 3 Ficus trigona MOR 16 0 0 0 0 0 3 Lophostoma sp. THI 15 0 0 0 0 0 3

Total 9972 1 78258 123952 96686 73685 100787 95515

'Acronyms for family names after Weber (1982)

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