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10. Traditional uses of south american mangrove resources and the socio-economic effect of ecosystem changes

Samuel C. Snedaker

Up until the late 1960s, coastal mangrove forest ecosystems were considered wasteland in most parts of the world (Lugo and Snedaker 1974) and were either ignored or abused. However, in a few countries in Asia (e.g. Bangladesh, Pakistan, Malaysia, Thailand, Viet Nam) mangrove forests were viewed as natural resources that could be managed for economic gain. In contrast, the mangrove forests on the Atlantic, Pacific, and Caribbean coasts of South America were, with certain exceptions, never managed or utilized except to provide subsistence needs for local populations. Part of the reason for the benign neglect of the South American mangrove forests was the fact that most of the major population centres were located in high-altitude mountain environments (e.g. Bogota, Colombia, and Quito, Ecuador) or in areas distant from any mangrove forest (e.g. Caracas, Venezuela, and Lima, Peru). To a large extent, this preference for high, inland elevations was due to the cooler, more favourable climate (Hoidridge 1967) and a relatively lower incidence of diseases such as yellow fever and malaria.

A number of authors began to document the ecological and economic values of mangroves in the 1960s and early 1970s (see Golley, Odum, and Wilson 1962; Odum 1969, 1971, Heald 1971; Snedaker and Lugo 1973). Among the cited values are the roles of mangrove forests in coastal protection (e.g. against storms and erosion), in the perpetuation of coastal water quality, and in the maintenance and the production of coastal and marine fin-fish and shellfish populations. On the basis of this new perspective, various international organizations such as Unesco, FAO, UNEP, USAID, and IUCN initiated a variety of programmes with scientific, conservation, and management objectives that resulted in widely communicated results (Rollet 1981; FAO 1982; Saenger, Hegerl, and Davie 1983; Snedaker and Snedaker 1984; Hamilton and Snedaker 1984; Snedaker and Getter 1985). In part because of a decade of international publicity, and for a variety of other reasons, most of the countries of South America now have an expanding interest in the mangrove-forest-dominated coastal zone as a resource for national economic development. In many respects, the situation in Ecuador represents a microcosm of the changes that are rapidly taking place in the traditional uses of mangroves and the socio-economic consequences of the current coastal development. In this paper, a review of the general situation in South America is followed by a more detailed examination of a specific aspect of the situation in Educador.

The Mangrove Forests of South America

Geographic Distribution

The mangrove forests of South America extend from northern Peru on the Pacific coast to Brazil's southern state of Rio Grande do Sul on the Atlantic coast. The cold Humboldt current limits the southern extension on the Pacific coast to about 6°S latitude, whereas warm currents along the southern coast of Brazil permit limited mangrove growth to about 28°S latitude. Throughout the continent, the structural development of mangrove forests is best in areas that receive relatively high rainfall and/or abundant fresh-water runoff; a similar pattern has been documented for Central America and the Caribbean (Pool, Snedaker, and Lugo 1977). The only major exception is the delta region of the Amazon River, where there is no significant influence of salinity in the coastal zone. In the absence of salinity, mangroves cannot compete with fresh-water species which form the dominant vegetation (West 1956). In contrast, the delta of the Orinoco has extensive mangrove forests because of the seasonal periodicity in fresh-water discharge and the dry-season rise in the ambient salinity.

Mangrove Forest Area

The total area of mangrove forest land in South America, including Panama, has been estimated at some 4.6 million ha (see appendix), which represents about 22 per cent of the world's 21 million ha (Snedaker and Brown, in preparation) The national areas range from 2.5 million ha in Brazil to 2,500 ha in northern Peru:

Most of the largest single areas of undisturbed forest are found in remote areas that are largely inaccessible -for example, the Orinoco delta in eastern Venezuela (495,200 ha) and the Pacific coast of Colombia (451,300 ha). Similar expanses also occur in northern Brazil.

Species Composition

South American mangrove forests are limited to some 15 species distributed among the genera Rhizophora, Avicennia, Laguncularia, Conocarpus, and Pelliciera. This contrasts with the larger number and greater diversity of species (and genera) found in Old World mangrove forests. The diversity of associated animals is also significantly higher in the Old World, which supports the hypothesis that the centre of origin of the mangroves in the broad sense lies in the Old World.

Historical and Traditional Uses

The uses that have been made of mangroves and mangrove products are very poorly documented historically, and much of the extant information is based on conventional widom and anecdote. The earliest recorded use of mangroves is inferred from a law promulgated by King Jose of Portugal in 1706. The law, imposed on Brazil, made it illegal to fell mangrove trees without simultaneously utilizing the bark. It was feared that the extensive felling of trees for firewood would limit the availability of bark for the tanneries. In addition to a financial penalty the law also imposed a three-month jail term (Hamilton and Snedaker 1984).

There is little evidence in the ethnographic and archaeological literature concerning direct uses of mangroves by pre-Columbian Indians, although they are known to have inhabited coastal areas characterized by extensive mangrove forests (Meggers, Evans, and Estrada 1965). In general, pre-Columbian and historical uses are presumed to have been the same as the traditional uses that are observed today. The dominant traditional uses include the cutting of trees for firewood, charcoal, and small-diameter poles for light construction and domestic use. Each of these uses involves a small-scale operation undertaken by single families or several adults from one village. This is unlike similar activities in parts of Asia, where the harvesting and sale of poles and the production of charcoal are small to medium-size industries. In South America, and Latin America in general, the small-scale production of charcoal is inefficient and yields a product of variable quality. There is a relatively high demand for charcoal by the Panamanian middle class, and it commands a fairly high price. In Panama, the production technique is based on constructing a densely packed cone (4 m in diameter and 2-3 m high) of small logs and branch wood (25-50 cm long), covered with earth and fired from the centre. In the Panama City charcoal market, the buyers demand smokeless charcoal, which the small producers can supply only by allowing the wood to burn for an excessive period. The technique does not permit the control of the kiln temperature, and the resulting smokeless charcoal has a very low caloric value (Snedaker 1981).

Another small-scale use of mangroves has been the stripping of bark from felled Rhizophora trees for the production of tannin. However, the collapse of the world market for tannin has almost eliminated tannin production activities on all but a very small scale in South America. One of the larger producers is located in south-west Costa Rica and uses bark stripped from Rhizophora trees in Panama and illegally exported. Other than this one activity, tannin production elsewhere is presumed to be minimal and performed at the family level.

Summaries of the traditional uses of mangroves are given in Saenger, Hegerl, and Davie 1983 (by region and country) and in Hamilton and Snedaker 1984 {by species). A more detailed review of the uses of mangroves was prepared by Walsh (1977). In general, these publications confirm that much more has been reported about the traditional uses and socioeconomic values of Asian than of South American mangroves. This appears to be due in part to the differences in the distribution of human populations in the two regions.

Uses and Economic Value

The use of mangrove forests for economic purposes has had a long and mostly successful history in Asia. In fact, the only complete forest-management plans that exist as models for sustained forest yield are from the Asian region (e.g. Curtis 1933; Dixon 1959; Khan 1966; Choudhury 1968). No such plans exist in South America. However, there are schemes for large-scale forest utilization, albeit not on a sustainable basis.

Use of South American mangrove forests on a large, commercial scale has begun only recently, and most government-inspired efforts remain in the planning stage. At present the governments of Brazil, Panama, and Venezuela are working toward the development of forest-management plans. However, their implementation and the subsequent development of mangrove-forest-based industries is extremely slow because of the widespread opinion that mangrove wood and wood products have minimal value compared to those of other tropical forest species. One notable exception is the commercial harvesting of large Rhizophora trees in the Orinoco delta for use elsewhere in Venezuela as power utility poles (Hamilton and Snedaker 1984). In addition to the environmental impact (Pannier 1979), other knowledgeable observers claim that the Orinoco harvesting is exploitive and not likely to lead to an industrial base that offers permanent job opportunities in a region that is only minimally developed. Plans to use mangrove trees for timber in other countries in South America all tend to be highly exploitive rather than being based on sustained yield. In part, this is due to the short-term economics which favour the clear felling of all commercial timber at one time for sale to international wood-chip buyers. In addition to the economic situation that does not favour sustainedyield management, there is also the problem that mangrove wood and wood products are perceived as inferior to available substitutes.

Other forms of utilization of the mangrove ecosystem involve clearing the forest (with or without use of the wood) for conversion of the land to salt-evaporation ponds or maricultural ponds. Conversion to rice agriculture is not seen as an option in South America as it is in parts of Asia and Africa. Salt-evaporation ponds are limited to arid and semi-arid climates and only infrequently require the conversion of mangrove forests. Investors and developers of maricultural ponds for the production of shrimp (mostly penaeids) also prefer semi-arid climates and seek out salt flats, barren coastal areas, and former mangrove areas for the construction of ponds. This preference is due to the fact that the land is devoid of trees, essentially flat, and close to salt water, which translates into low landpreparation and pond-construction costs. However, the extremely rapid development of the mariculture industry in South America is forcing the developers of new pond systems to convert productive mangrove forest areas as well as productive farmland (Snedaker and Dickinson, in preparation). Before 1980, only Ecuador had made a significant investment in shrimp mariculture, but the perceived financial success has inspired other countries to follow suit, sometimes with the assistance of international development organizations. As a result, most other countries have either begun encouraging mariculture or have announced plans to do so. Colombia, for example, has announced its desire to develop maricultural industries on its Caribbean and Pacific coasts.

The socio-economic impact of the widespread development of maricultural industries is only now beginning to be recognized and understood. In the following section, the experience in Ecuador is examined in greater detail because it illustrates many of the ecological, economic, and political problems of this rapidly developing industry.

Shrimp Mariculture in Ecuador: An Overview

Of the three most important Ecuadorean export crops (oil, bananas, and fishery products) shrimp from the trawler fleet and from maricultural ponds represent the top export item. In terms of foreign earnings, the shrimp industry is second only to oil. Over 70 per cent of the shrimp yield comes from managed ponds, primarily in the southern provinces of Guayas, Manabí, and El Oro, which have the greatest concentration of ponds in Ecuador. Cintron (1981a) notes that shrimp-pond yields tend to be greatest in climatic environments where the potential evapo-transpiration exceeds rainfall, which is a characteristic of southern coastal Ecuador. In 1975, shrimp production in Ecuador amounted to less than 6,000 metric tons (all sources), but by 1983 it had risen to 36,000 tons, of which some 29,000 tons were from shrimp farms (Snedaker and Dickinson, in preparation; see also Mock 1981). The rapid increase in the harvest of wild stock and the culture of shrimp in ponds throughout the world is driven by the relatively high prices that can be obtained on the world market. Ecuadorean shrimp, however, are purchased by a relatiely few large buyers for export to, and consumption in, the United States. In Ecuador, shrimp exports are said to represent an important source of foreign-currency earnings and employment opportunities along the Pacific coast.

The shrimp trawler industry had its beginnings in the 1940s, following the popularization of the Gulf of Mexico pink shrimp. The development of a shrimp fishery formed a focal industry in the Guayaquil area of Ecuador. The trawler fleet consists of day boats, which ice their catch and return to port within 24 to 36 hours, and larger vessels that refrigerate their catch and remain longer at sea. The vessels range in size from 10 to 30 m, displacing 15 to 60 tons, and are locally constructed of wood. About 20 new vessels are constructed each year. Until the mid-1970s, the trawler fleet was the dominant source of shrimp for both local consumption and the lucrative export market, and a source of local employment. The shrimp fleet still operates out of coastal Ecuador, but it is now secondary in production to the shrimp-pond industry.

Ponds for shrimp production or grow-out are intentionally located in the near-shore coastal zone, primarily for access to sea water. In Ecuador, the shrimp farms range in size from a few to several hundred hectares, with individual ponds ranging from a few hundred square meters to several hundred hectares; depths average 0.7-1.5 m (Snedaker and Dickinson, in preparation). The ponds are flooded with moderate-strength sea water, which is renewed at 10-30 per cent of volume per day. When the industry was first developing in the 1970s, the ponds were constructed on salt flats inland from the mangrove forests. However, when these habitats were no longer available, new ponds were constructed in area dominated by mangroves. In addition to expansion toward the mangrove-dominated shoreline, pond development in Ecuador is now moving to the more northern (and more humid) provinces closer to the Colombian border. As of 1985 about 60,000 ha of coastal inter-tidal and supratidal land has been converted to shrimp ponds. This contrasts with the 300 ha that were in production in 1970 (Snedaker and Dickinson, in preparation).

In shrimp mariculture, the ponds are stocked with postlarval (PL) shrimp for grow-out to a mature size over a period of several months. The preferred species are Penaeus vannamei and, to a lesser extent, P. stylirostris (sun 1982a), which are stocked at rates of 50,000-250,000 PLs per hectare and higher (sun 1982b). Following a five-to seven-month grow-out period, the pond yields range from 180 to 360 kg/ha/yr, although feed and other subsidies can double or triple the yields (Mock 1981). Few pond owners use feed supplements, believing that the marginal gain does not justify the cost. Penaeid PLs are obtained by netting wild shrimp populations that are present in local estuarine waters. The gathering or harvesting of PLs is itself a substantial industry that provides much significant employment. The netting of PLs is done by individuals, who are each able to collect 20,000-50,000 PLs during an outgoing tide. The individual harvests are sold to on-site brokers, who in turn supply the pond-owners/managers (Snedaker and Dickinson, in preparation).

In the late 1970s and early 1980s, numerous complaints began to be sounded over the decline or scarcity of PLs. Complaints reached a peak prior to the 1982/83 "El Niño" event. The problem has continued, as can be seen from the fact that the area in production ponds has increased by 60 per cent just since 1982, while the annual harvest of PLs has remained more or less constant at less than 10 million animals (Snedaker and Dickinson, in preparation). The common opinion in Ecuador is that the destruction of coastal mangrove forests, the nursery grounds for many species of shrimp (as well as fin fish and shellfish), is the cause of the decline in PLs (Fundacion Natura 1981). The concern appears to be valid, based on the results of quantitative studies (Turner 1977; Martosubroto and Naamin 1977} which independently showed that harvested yields of commercial shrimp are proportional to the total area in coastal mangroves and marshes. Turner's data (1977) show an average yield of 767 kg of shrimp per hecatare of mangrove forest per year (about twice the annual yield from minimally managed grow-out ponds). Thus, the loss of mangrove and associated inter-tidal area can be presumed to have a significant effect on local shrimp populations. Other possible causes for the decline include abnormal sea-surface temperatures and salinity, and near-shore water pollution (Snedaker and Dickinson, in preparation).

As a result of the unpredictable availability of PLs, there is now considerable interest in Ecuador in establishing one or more hatcheries for their production (Instituto Nacional de Pesca 1982). Ostensibly, this would relieve the pressure on the wild stocks and guarantee continuing supplies of seed shrimp to the pond producers. However, this approach would favour the large producers who can provide the capital investment and operating funds for a hatchery while forcing small and marginal producers to continue to rely on wild PLs, stocks. Should hatchery production techniques succeed in supplying the entire demand for PLs, the economic incentive to the industry for preserving the mangrove source of PLs would be lost.

Because of the interest in promoting the pond culture of shrimp while preserving the mangrove habitat both for the perpetuation of shrimp and for other reasons, significant technical research has been undertaken in Ecuador, particularly in the Guayaquil area. There are many useful papers on techniques relating to pond production (e.g. Cun 1982a, 1982b; Cun and Marin 1982; Cun and Regalado 1982; Yoong and Reinoso 1982). The interest in pond production is also matched by a widespread interest in the mangrove ecosystem as an important natural resource (e.g. Cintron 1981a, 1981 b; Cintron and Schaeffer-Novelli 1981 a; Horna, Medina, and Macias 1980; Valverde 1980), mainly because of the relationship with shrimp. In addition, there are a variety of published recommendations offering alternatives to general problems that affect the industry {cf. Barniol n.d.; Hallberg 1977; Primer Congreso Nacional de Productores de Camaron 1982). However, with the exception of a US Agency for International Development research study currently being completed by Snedaker and Dickinson (in preparation), there has been no socio-economic analysis of the shrimp industry per se, nor has there been an evaluation of the effect that the development of the industry has had on the life-styles and wellbeing of the local people.

Many problems affecting the shrimp industry came into focus during the massive flooding in the coastal zone that was associated with the 1982/83 El Niño phenomenon, whose severity brought world-wide disaster relief to Ecuador. The significance of its recurrence resulted in pressures on the government to undertake major infrastructural investments in flood control and drainage. These actions, coupled with hydro-electric and irrigation projects being implemented or contemplated, added more pressures on coastal ecosystems, natural and artificial, that depend on seasonal pulses of fresh water and sediment. Erosion is already a serious problem in the Machala area, where there is a high density of producing ponds. In spite of the 1982/83 El Niño event and the focus of attention on the coastal zone, there are still no effective plans for managing the shrimpfarm industry for its own benefit and the economic benefit of the region.

The expansion of the area in shrimp grow-out ponds in Ecuador, in the absence of a guiding policy and management protocol, has resulted in a number of development problems. Some of the more significant or well-publicized problems include (1) a significant reduction in mangrove area and interruption in drainage patterns, which affect the availability of shellfish and fin fish in off-shore and estuarine waters for local and national consumption, (2) the loss of the mangrove forest as a source of wood products, (3) the loss of mangrove nursery area for the postlarval shrimp used in grow-out ponds, (4) highly variable and generally low shrimp-pond production because of a lack of technical know-how, (5) salinization of valuable irrigated farmland in many provinces caused by shrimp ponds located on farmland, (6) leaching and drainage of pesticides and herbicides from active farmlands into the near-shore waters, and (7) potential reduction in shrimp-pond and mangrove production alike due to upstream infrastructures causing freshwater and sediment starvation.

Among scientists who have studied the Ecuadorean shrimp-pond industry, there is a pervasive feeling that the socio-economic problems may far outweigh the technical and/or management problems (Snedaker and Dickinson, in preparation). It is also felt that any solutions to the latter problems cannot be effectively implemented without a prior resolution of the socioeconomic problems. Among the foremost issues are (1) the concentration of shrimp-pond wealth and knowledge in the hands of a relatively few entrepreneurs coupled with a perceptible shift to foreign ownership, (2) the inevitable decline in job opportunities as pond contruction peaks out and hatcheries substitute for the extensive harvesting of wild PLs, (3) the "flight" of maricultural earnings to foreign banks, and (4) smuggling across the Colombian and Peruvian borders to acquire PLs, to avoid Ecuadorean export taxes, and to make profits on discrepancies in currency exchange rates.

Acknowledgements

This paper was developed from my experiences in Latin American dating back to the mid-1960s. Some of the specific data and information on shrimp mariculture in Ecuador were taken from in-country research supported by the US Agency for International Development, Program in Science and Technology Cooperation, Grant No. DPE 5542-G-SS-4022-00. The paper was typed and assembled by Tropic House International, Inc., of Miami, Florida, USA.

Appendix: Mangrove Forest Area in South America, by Country and Locality

Note: This appendix has been modified from Snedaker and Brown (in preparation!.

Brazil
a. Data obtained from FAO/PNUMA 1981, cited in Cintron and SchaefferNovelli 1981b. Although there are a number of estimates of the mangrove forest area in Brazil, the FAO/PNUMA report is reported to be the best estimate (Gilberto Cintron and Yara Schaeffer-Novelli, personal communication).
b. Data obtained from Hueck 1966, cited in Weishaupl 1981.
c. Data obtained from Ruschi 1950, cited in Weishaupl 1981.
d. Data obtained from Brazil 1974a and 1974b, cited in Weishaupl 1981.
e. Data obtained from Instituto de Recursos Naturais do Estado do Maranhao 1975,

Colombia
f. Data provided by Jorge Hernan Torres Romero (personal communication); they are in general agreement with the majority of other estimates obtained from Colombia, including Colombia 1967. FAO/PNUMA 1981 gives a total area of 450,000 ha, of which 287,000 ha are located on the Pacific coast. There is an extensive area of tropical lowland forest on the Pacific coast which grades into the mangrove forest. It is possible that the higher estimates are the result of an inadequate differentiation between the two forest types. However, l believe that the 287,000 ha estimate for the Pacific coast may be too conservative.

Ecuador
g.. Total area estimate obtained by summarizing the individual areas. FAO/PNUMA 1981 estimates the total area at 235,000 ha.
h. There are various estimates for Esmeraldas, including 8,000 ha (Berthon 1959), 29,600 ha (Acosta-Solls 1957), 40,300 ha (Dixon et al., n.d.) and 180,800 ha (Rafael R. Horna Zapata, Francisco Yoong Basurto, and Blanca Reinoso de Ayeiga, personal communication). The estimate from Dixon et al. is considered to be a reasonable provisional value and is used in the summary.
i. Data provided by Rafaei R. Horna Zapata, Francisco Yoong Basurto, and Blanca Reinoso de Ayeiga (personal communication). Ministerio de Agricultura y Ganaderia 1980 gives an estimate of 14,700 ha, but this is believed to be too high (Gilberto Cintron, personal communication).
j. Data obtained from Cintron 11981a, 1981c). In addition to the mangrove areas, there are salt flats comprising 42,712 ha in Guayas and 13,024 in El Oro. These areas are not in cluded in the estimate used.

A large variety of estimates for the mangrove area in Ecuador were obtained, and the more conservative alternatives are used in the report. For example, Dixon et se. (n.d.) state that there are 403 km² of mangrove forest in the San Lorenzo-Limones area, of which 290 km² are in regenerating forest and an additional 113 km² in "degraded" forest (Gilberto Cintron, personal communication). Other estimates for Ecuador, provided by Rafael R. Horna Zapata, Francisco Yoong Basurto, and Blanca Reinoso de Ayeiga (personal communication), may be unrealistically high, particularly for Esmeraldas:

French Guiana
k. Data obtained from FAO/PNUMA 1981.

Guyana
l. Data provided by C. A. Persaud and Reuben Charles (personal communication!. FAO/PNUMA 1981 gives an estimate of 150,000 ha, but the more conservative value is probably the best estimate.

Panama
m. Data obtained from FAO/PNUMA 1981, cited by G. Cintron (personal communication). Cintron also cites FAO/PNUD 1972 as giving a total mangrove area for Panama of 409,210 ha. One possible reason for the large variation in estimates may be a difference in whether or not contiguous lowland forests, such as those dominated by cativo (Prioria copaifera) and orey (Campnosperma panamensis), are included in the estimates. The range of estimates for Panama include the following: 104,000 ha (Donaldson et al. 1963), 199,000 ha (Falla 1978a), 505,600 ha (Falla 1978b).
n. Data (in acres) from Donaldson et al. 1963 obtained by G. Cintron.

The actual distribution of mangrove areas among the other provinces of Panama is also questionable. l obtained data from the offices of the Ministerio de Desarrollo Agropecuario, Dirección Nacional de Recursos Naturales Renovables, which are probably representative of the relative distribution among the provinces:

Peru
o. Data (in square meters) provided by Miguel A. Checa L. (personal communication). This estimate is an order of magnitude lower than the 28,000 ha estimated by FAO/PNUMA 1981.

Suriname
p. Data obtained from FAO/PNUMA 1981.

Venezuela
q. Data provided by F. Pannier (personal communication). FAO/PNUMA 1981 gives a total area for Venezuela of 260,000 ha, but it is believed that this reflects only the extensive areas of potentially commercial forest.

References

In addition to literature cited, the following list includes the sources of personal communications.

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Berthon, P. F. 1959. Informe al gobierno del Ecuador sobre el desarrollo de las industrias forestales en las regiones de Guayaquil y San Lorenzo. Report no. 1125. Food and Agriculture Organization/ETAP, Rome.

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