4 Social and Environmental Impact of Rapid Change in the Coastal Zone of Vietnam: an Assessment of Sustainability Issues J.W. Gowing,1 T.P. Tuong,2 C.T. Hoanh3 and N.T. Khiem4 1School of Agriculture, Food & Rural Development, University of Newcastle, Newcastle upon Tyne, United Kingdom, e-mail: j.w.gowing@ncl.ac.uk 2International Rice Research Institute, Metro Manila, Philippines 3International Water Management Institute, Regional Office for South-east Asia, Penang, Malaysia 4Faculty of Agricultural Economics, An Giang University, An Giang, Vietnam © CAB International 2006. Environment and Livelihoods in Tropical 48 Coastal Zones (eds C.T. Hoanh, T.P. Tuong, J.W. Gowing and B. Hardy) Abstract Ca Mau Peninsula, which lies at the extreme southern tip of the Mekong Delta in Vietnam, has experi- enced rapid environmental and socio-economic change, particularly since the 1990s when the doi moi (renovation) policy introduced an agenda of agriculture-led growth. The peninsula lies entirely within the zone of saline intrusion, which previously extended up to 50 km inland during the dry season, thus limiting traditional rice production to only one rainy-season crop. To promote the intensification of rice production, a plan was devised to build a series of coastal embankments and tidal sluices to control salinity intrusion. The protected area lying within Bac Lieu Province, which covers approximately 160,000 ha, is the focus for this discussion. Data collected on environmental and socio-economic conditions within the protected area during the study period reflect a complex spatial and temporal pattern of impacts. However, the pattern can be seen as a transition between a freshwater environment supporting rice production and a brackish environ- ment supporting shrimp production. The impacts of these changes in environmental management strate- gies are discussed. A strategy favouring rice production depends on the operation of sluices in such a way that a freshwater environment is maintained. Intensification of the rice production system involves relatively low risk for farmers, but results in relatively low income. On the other hand, shrimp produc- tion requires that a brackish environment be maintained and is seen to offer the potential for increased wealth, but at high levels of risk and indebtedness. Currently available evidence of impact cannot easily be extrapolated to assess long-term sustainability. Introduction Ca Mau Peninsula, which lies at the extreme southern tip of the Mekong Delta in Vietnam (Fig. 4.1), has experienced rapid environ- mental and socio-economic change, particu- larly since the 1990s when the doi moi1 policy introduced an agenda of agriculture-led growth. The peninsula lies entirely within the zone of saline intrusion, which previ- ously extended up to 50 km inland during the dry season, thus limiting traditional rice production to only one rainy-season crop (June–November). To promote the intensifi- cation of rice production, a plan was devised to build a series of coastal embankments and tidal sluices to control salinity intrusion (Tuong et al., 2003). The first sluice in this area became operational in 1994 and the zone protected from saltwater intrusion gradually expanded westward as successive sluices were completed (Fig. 4.1). Within the protected area, the duration of freshwater conditions was extended in line with the pol- icy to promote double or triple cropping of rice. However, as the freshwater zone spread gradually westward, the local economy was undergoing rapid change. Profitability of the rice crop was falling and at the same time aquaculture was experiencing a dramatic boom, fuelled by technical innovations and the high local and export prices of tiger shrimp (Penaeus monodon). Traditional exten- sive systems of shrimp production based on natural recruitment of shrimp larvae were being replaced by semi-intensive monocul- ture production systems (Hoanh et al., 2003). By 1998, tiger shrimp culture was wide- spread in the western part of the project area (Fig. 4.2). The expansion of tiger shrimp culture was consistent with the official policy2 of the central government adopted in 1998, which explicitly encouraged production for export. But shrimp farming in the protected area contradicted the land-use policy of rice intensification in the area. Despite the appar- ent success and popularity of shrimp farm- ing, tidal sluices continued to be built and the freshwater zone continued to spread westward up to 2000 (Fig. 4.1). When the supply of brackish water required for shrimp production was cut off, many farmers were forced to abandon aquaculture and to con- vert to less profitable rice farming. Some shrimp farmers resisted and attempted to maintain favourable conditions by blocking secondary canals and pumping brackish water into their fields, but this created con- flict with rice farmers, who depended on fresh water to irrigate their fields. Eventually, in 2001, the original policy emphasizing rice production was revised to accommodate extensive shrimp cultivation in the west while maintaining areas of inten- sive rice production in the east. Land use adjusted rapidly to this new policy and by 2002 areas of intensive rice production had shrunk back to the freshwater zone in the non-acid soils to the east (Fig. 4.2). The background to this policy shift within the highly dynamic environmental and socio-economic circumstances of the project area is discussed by Hoanh et al. (2003). This shift is significant because it represents a relaxation of centralized planning in order to allow more freedom for private-sector deci- sions on land use. The pressure that brought about this change can be seen as the rational response by farmers to economic incentives. However, several emerging issues point to the need for continuing scrutiny and regula- tion of land use (and in particular shrimp farming) to ensure that short-term gain does not result in failure to achieve long-term sus- tainable development. The essential requirements for sustainable development can be defined as poverty erad- ication, changing unsustainable patterns of production and consumption, and protecting and managing the natural resource base Social and Environmental Impact of Rapid Change 49 1 Doi moi can be translated as ‘renovation’ and is commonly used to describe the move from a centrally planned command economy to a market economy with accompanying democratization of social relations. 2 Decision on the ratification of the programme of developing the export of aquatic products up to 2006; Government Decision no. 21, 1998. (UN, 2002). These objectives need to be understood as mutually supportive and the importance of poverty–environment link- ages should be seen as the core of sustain- able development strategies. Poor people are predominantly rural and predominantly dependent on natural resources for their livelihoods. They are therefore particularly vulnerable to environmental problems. They need economic growth to escape poverty, but this must be based on the sustainable use of environmental resources. Concern for envi- ronmental protection is therefore not seen as being in conflict with concern for human development. The enhancement and mainte- nance of environmental capital allow for the prudent use of natural resources in the short term while providing for effective protection of the environment in the long term. The notion of vulnerability is critical to understanding the impacts of change. Vulnerability occurs because livelihoods are exposed to stress and are unable to cope with that stress (Adger and Kelly, 2001). Shocks (such as floods and storms) may pro- duce stress when people lose their assets or are forced to dispose of them as a short-term survival strategy. Longer-term adverse trends (such as soil erosion, siltation or acidi- fication) may gradually degrade assets and also create stress. The inherent fragility of poor people’s livelihoods limits their adap- tive options and makes them generally more vulnerable. Vulnerability therefore relates to both: (i) exposure to risk likely to affect livelihood; and (ii) weakness of the existing state that limits capacity to cope with the resulting stress. The rapid expansion of brackish-water shrimp farming in the study area indicated farmers’ preference for this production over rice. However, brackish-water shrimp farm- ing elsewhere has been characterized by recurrent boom-and-bust cycles that cast 50 J.W. Gowing et al. Fig. 4.1. Study area showing extent of saline intrusion at different stages of project development. doubts on its sustainability (Primavera, 1998). Adverse environmental and socio-eco- nomic impacts have been widely reported over the past decade (Phillips et al., 1993; Beveridge et al., 1997; Primavera, 1998; Lebel et al., 2002; Shanahan et al., 2003). It is impor- tant to examine the sustainability of shrimp farming in the study area. One of the characteristics of the study area is the presence of extensive deposits of acid sulphate soils (ASS), particularly in the western part. These soils develop as a result of the drainage of parent materials that are rich in pyrite (FeS2), as occurs with the recla- mation of brackish-water intertidal swamps. ASS are characterized by low pH (< 4), which results from the oxidation of reduced S- and Fe-bearing compounds producing acid via a number of possible chemical and biochemical pathways (Dent, 1986). The acid released in this way reacts with clay minerals to produce soil–water solutions containing high concentrations of aluminium and iron. Reclamation of ASS for agricultural use depends on leaching these toxic substances out of the root zone and has been reported to create severe acidification of the aquatic environment in Indonesia (Klepper et al., 1990) and Australia (Wilson et al., 1999) as well as in Vietnam (Minh et al., 1997b). The acid pollution and associated changes in water chemistry can have severe impacts on fish populations (Callinan et al., 1993), which are not confined to the reclaimed area. The impact on estuarine ecosystems has been reported by Sammut et al. (1996) and Wilson et al. (1999) for Australia, where mass mortal- ities of fish have been recorded as a result of episodic acidification, and there is also evi- dence of chronic long-term effects on estuar- ine and coastal ecosystems. The conflict between agricultural produc- tion and environmental protection poses a question of the sustainability of development of ASS within the study area. Leachate from reclaimed ASS in the Mekong Delta shows Social and Environmental Impact of Rapid Change 51 Fig. 4.2. Land-use change in the study area. marked peak acidity and Al concentration at the start of the rainy season (Minh et al., 1997a; Tuong et al., 1998), which may create shocks for the aquatic resources and vulnera- bility for the landless poor who depend a great deal on fisheries for their livelihood. Objectives of This Study Given the nature of the deltaic environment, strategies for both land use and water man- agement have been equally influential in determining the nature and extent of recent environmental changes in Ca Mau Peninsula. The pre-2000 strategies, favouring rice monoculture, can be criticized (with the benefit of hindsight) for suffering from the same faults identified by Hori (2000) in a review of development planning throughout the lower Mekong basin. They failed to rec- ognize the diversity of livelihoods of the population and did not give adequate con- sideration to environmental impact. The study reported here was therefore conducted between 1999 and 2003 to investigate the likely sustainability of development as it affects that part of the newly protected area lying within Bac Lieu Province (approxi- mately 160,000 ha). Sustainability is a multidimensional con- cept that is measured by reference to multi- ple indicators selected to represent environmental, social and economic aspects. However, it is clear that two critical issues against which recent change in Bac Lieu Province should be judged are: ● environmental sustainability, which is achieved when the productivity of the natural resource base (i.e. environmental capital) is conserved or enhanced; and ● livelihood sustainability, which is achieved when households respond and adapt to change without becoming more vulnerable. The objective of this chapter is therefore to present an assessment of the sustainability of the development, with a particular focus on: ● the state of the environment and natural resources within the project area, and ● socio-economic conditions and the rela- tionship between livelihoods and natural resources within the project area. Short-term Assessment of Project Impact Social impact: method of assessment In recognition of the importance of liveli- hood sustainability, one of the work pack- ages within the study focused on social impact assessment, that is, assessing changes in farmers’ livelihoods and farmers’ resource-use strategies in coping with changes brought about by salinity intrusion protection. The initial activity under this work pack- age was to establish a framework for social differentiation so that the poor could be identified as a distinct stakeholder group in order to permit an appraisal of environ- ment–poverty linkages and any differential impact of environmental change on them. The framework adopted was based on par- ticipatory wealth-ranking exercises. At an early stage in the project (in 2000), a quantitative survey was conducted in 14 hamlets representing different hydrological, soil and land-use regimes (Tuong et al., 2003). This survey provided data required to char- acterize the baseline condition in terms of asset and production profiles for 350 repre- sentative households across four wealth cate- gories. This was followed by an in-depth qualitative survey that used standard partici- patory rural appraisal (PRA) tools in inter- views with key informants to improve understanding of livelihood strategies and to help identify the key issues affecting poor people (Chambers, 1997). Follow-up surveys were conducted toward the end of the project (in 2003) to pro- vide data for an assessment of short-term livelihood impacts. A combination of quanti- tative and qualitative surveys was again adopted within seven of the original 14 ham- lets, where all households previously included in the baseline study were resur- veyed. The key indicators used to measure changes in livelihoods are summarized in Table 4.1. These indicators provide some 52 J.W. Gowing et al. insight into the short-term impact of environ- mental change within the project area based on quantitative data for 1999 to 2003, which can be extended back to 1994 on the basis of insights derived from the PRA. However, the prediction of future livelihood trajectories of different stakeholders is more problematic. Environmental impact: method of assessment In recognition of the importance of environ- mental sustainability, another of the work packages within the study focused on envi- ronmental impact analysis, that is, character- izing the changes in soil and water quality and resource use brought about by salinity protection interventions. The initial activity under this work pack- age was the collection and compilation of data from existing soil and land-use maps and the water quality monitoring network in the area. Subsequently, the activities involved the actual soil and water quality monitoring carried out by the study team. By bringing these data into a GIS for spatial data management, integration and visualiza- tion, it was possible to establish an idea of the baseline condition (Kam et al., Chapter 15, this volume). It also provided a means of linking the monitoring activity to modelling work based on the VRSAP3 hydraulic model (Hoanh et al., 2001, 2003). The soil map published by IRMC4 in 1999 at a scale of 1:50,000 provided a baseline for monitoring soil changes. Initial fieldwork was undertaken (in 2000) to verify the pre- dictive value of the soil map at selected loca- tions based on the previously defined sampling zones. It was found to be satisfac- tory, but some areas mapped in 1998 as potential acid sulphate soils had already developed into actual acid sulphate soils. A soil monitoring programme was established as part of this work package, which included intensive surveys of acidity release. Data on water quality are subject to much more temporal variability than are soil data, and therefore presented a greater sampling problem. Data on salinity, pH and Al3+ from 26 locations throughout the study area were collected from 1993 to 2000, but the fre- quency of observations was inconsistent. A follow-up water monitoring programme was established in 2001, which included more intensive roving surveys. The aim of these activities was to provide data on short-term changes and a basis for predicting longer- term impact on soil and water quality. Particular concerns were: ● the presence of extensive deposits of acid sulphate soils (ASS) that provide a source of acidity likely to affect water quality, and ● the impact of water quality change (acid- ity and/or salinity) on the productivity of fisheries. Social and Environmental Impact of Rapid Change 53 3 VRSAP, Vietnam River System and Plains model. 4 IRMC, Integrated Resource Mapping Center. Table 4.1. Key indicators of livelihood impact. Livelihood asset Investigate changes in Natural Land ownership; total size of landholding; number of land parcels; cropping patterns; rice production; non-rice crop production; aquaculture production (shrimp and other); capture fisheries catch and seasonality, including destina- tion of catch (home consumption or sale) Financial Total net HH income; contribution to total HH income from rice, shrimp, other aquaculture, livestock, employment, capture fisheries; remittances from relatives and other funds Physical Access to TV, radio, rowing boat, motorboat, tiller/pump/thresher Human Workers available per HH; age of HH head; % of female-headed HH; main occupation of HH heads HH, household. Use of the VRSAP model allowed for spa- tial analysis across the whole of the pro- tected area for the period 1993–2003, but downstream impacts in the surrounding coastal zone may also be significant and these were not monitored. To analyse envi- ronmental sustainability, it is necessary to consider both wider and longer-term impacts. Evidence of short-term impact Data collected on environmental and socio- economic conditions within the protected area during the study period should be seen in the context of rapid change occurring at that time, which resulted in a complex spa- tial and temporal pattern of impacts. However, the key characteristic is the transi- tion between a freshwater environment sup- porting rice production and a brackish environment supporting shrimp production, as summarized in Fig. 4.3. A strategy favouring rice production depends on the operation of sluices in such a way that a freshwater environment is main- tained. Intensification of the rice production system involves relatively low risk for farm- ers, but results in relatively low income. On the other hand, shrimp production requires that a brackish environment be maintained and is seen to offer the potential for increased wealth, but at high levels of risk and indebtedness. Within the extensive areas of ASS, rice production is seriously constrained by soil conditions, but low profitability precludes the adoption of measures to ameliorate the problem. However, there is evidence that more land is brought into use after conver- sion to shrimp production. Inputs of lime are widely used to ameliorate acidity within the shrimp ponds, although release of acidity into the wider environment still occurs. Other impacts on natural resources and consequently on livelihoods can also be identified. The freshwater environment favours higher production of fruits and veg- etables from home gardens, and of livestock for sale and consumption, than is possible in the brackish environment. On the other hand, by sustaining freshwater conditions, the catch of wild fish from open-access canals is seen to decline. These impacts on productivity of the nat- ural resource base result in knock-on effects on livelihoods, but the nature of these sec- ondary impacts varies depending on the livelihood strategy adopted by a particular 54 J.W. Gowing et al. Rice ShrimpAcid release to aquatic environment Freshwater environment Brackish environment + Low risk + Less indebtedness + Increased opportunity for wage labour + More productive home gardens + More productive livestock – Less productive fishery – Low income – Low production on ASS – Increased use of agrochemicals + Increased wealth + Increased trading opportunity + Productive use of acid sulphate soils + More productive fishery – Less productive livestock – Less productive home gardens – Increased levels of debt – Increased inequality – High risk of failure Fig. 4.3. Impacts of alternative environmental management strategies within the protected area. Social and Environmental Impact of Rapid Change 55 household (Table 4.2). Households classified as ‘very poor’ were identified in five of the 14 hamlets and represent 7% of all house- holds. They exhibit a very high proportion of functionally landless and depend on selling labour. They find more employment oppor- tunities in rice areas than in shrimp areas. Households classified as ‘poor’ exist in all hamlets and represent 34% of the total popu- lation. They have some land and may benefit from conversion to shrimp production, but their asset base is low and the associated risk makes them very vulnerable to indebted- ness. ‘Average’ and ‘rich’ households repre- sent, respectively, 37% and 21% of the total. Long-term Assessment of Sustainability Shrimp production Probably the most frequently voiced concern over shrimp farming is the degradation of coastal wetland ecosystems and in particular the loss of mangrove forests. Over the last 50 years, Vietnam has lost a large proportion of its original mangrove cover through various pressures, but during the last decade the principal threat was reported as shrimp aquaculture (Shanahan et al., 2003). Critics have pointed to the adverse consequences of conversion of mangroves to shrimp ponds on aquatic resources and habitat and forest products, and the increased vulnerability to storms and typhoons in Thailand, the Philippines, Indonesia and Bangladesh, as well as in Vietnam. However, this criticism does not apply to the particular circum- stances of the study area, where the expan- sion of shrimp aquaculture has occurred on land previously cleared for agriculture. Salinization of soil and water is another major concern associated with shrimp aqua- culture, particularly where shrimp ponds have expanded into rice land (Flaherty et al., 1999). Shrimp production requires brackish water and its import into non-saline areas affects neighbouring rice fields and degrades water used for both agricultural and domes- tic needs. Again, when applied to the partic- ular circumstances of the study area, this criticism is not valid. Salinity intrusion is a natural seasonal phenomenon within the area, which can now be managed using the recently constructed tidal sluices, and soil salinity cannot be attributed to shrimp pro- duction. There is evidence (Tran et al., 1999) that salt leaching from shrimp ponds into adjacent rice fields can be significant, but no long-term buildup of salts is apparent in sequential shrimp–rice production systems (Brennan et al., 2002; Phong et al., 2003). This problem can be managed by appropriate zoning and the adoption of appropriate pro- duction systems. Other environmental impacts are closely linked to the level of intensity of the shrimp production system. In this respect, there is a marked contrast between Vietnam and other major producer countries, such as Thailand, where the ‘industrialization’ of shrimp aqua- culture has resulted in much higher intensi- ties (Lebel et al., 2002), as reflected in Table 4.3. As production becomes more intensive, economic viability becomes dependent on high levels of feed, pesticides and antibiotics Table 4.2. Livelihood strategies. Wealth category Landholding (ha)a Landless (%) Livelihood strategy Very poor 0.6 21 Mainly off-farm employment; capture fishery (n = 24) important; no home garden Poor 1.3 18 50% income from own farm; also off-farm (n = 120) employment and fishing Average 2.0 9 80% income from own farm (n = 131) Rich 2.9 3 90% income from own farm (n = 75) aLandholding is mean area per household available for productive use. in order to achieve high postlarval survival rates and high growth rates. Water exchange then releases contaminated pond effluents into the wider environment. The same receiving waters generally serve as intake water for neighbouring shrimp farms and water-borne disease agents spread rapidly from farm to farm, thus encouraging the greater use of antibiotics. Within the study area, production sys- tems are at relatively low intensity (as also reported by Lebel et al., 2002), with lime and seed (postlarvae) as the main purchased inputs. The low quality of hatchery-reared seed is a major constraint contributing to the spread of disease, high risk of failure and pressure to increase the use of antibiotics. Under present circumstances, pollution is not a major concern and the release of acidity is a more significant impact; however, there is clear evidence from elsewhere that highly intensive systems are not sustainable. Shrimp aquaculture has been encouraged by the government of Vietnam to help raise the standard of living of rural communities. Perceived benefits include job creation dur- ing pond construction, income generation for shrimp farmers, increased trading opportu- nities and employment in aquaculture ser- vices (seed supply, other inputs, processing, marketing) and increased foreign exchange earnings. The potential to generate wealth undoubtedly exists, yet shrimp aquaculture has been responsible for the deterioration of livelihoods and promotion of poverty in many countries. Drawing on a series of case studies undertaken in Vietnam, Adger and Kelly (2001) concluded that poorer house- holds are most vulnerable because: (i) they are likely to depend on a narrower range of resources and income sources; and (ii) the loss of common property management rights represents a serious erosion of their ability to cope. They found evidence of benefits from an increase in overall wealth, but increased inequality. The high risk associated with the enter- prise exposes poor people to financial ruin and landlessness. The vast majority of shrimp farmers must borrow money to pay for pond construction and purchase inputs. When the enterprise is successful, profits can be high, allowing them to pay off their debts quickly. However, the risk of failure is also high; Lebel et al. (2002) report a 70% rate, Shanahan et al. (2003) report a 70–80% rate and a survey in the study area indicates a similar risk of failure. Failure leads to spi- ralling indebtedness and eventually to land- lessness (as reported also by Luttrell, Chapter 2, this volume), although there is as yet no direct evidence that this has occurred within the study area. Relatively poor farm- ers are more likely to fail, but, if their neigh- bours have converted from rice to shrimp farming, they have no alternative. Landless households depend on selling labour, but evidence from elsewhere (Lebel et al., 2002; Shanahan et al., 2003) supports findings within the study area that shrimp farming creates fewer employment opportu- nities than rice farming. Environmental 56 J.W. Gowing et al. Table 4.3. Comparative characteristics of typical shrimp farms (adapted from Lebel et al., 2002). Item Study area Ca Mau/Bac Lieu Western Thailand Eastern Thailand Mean pond size (ha) 2.0 2.6 0.6 0.5 Stocking rate (per m2) 2–3 4.8 55 66 Survival rate (%) naa 11 59 51 Use of feed (% farms) 0 14 100 99 Mean production (kg/crop/ha) 150 185 4760 4460 ana, not available. degradation combined with enclosure of open-access areas affects the livelihoods of poor people (particularly landless house- holds) and adversely affects food security. Where shrimp ponds are developed on land reclaimed from open-access mangrove forest there is a particular concern, but within the study area this is not the case. However, an indirect impact on common property resources still exists because of the change in water quality and its effect on the productiv- ity of the fishery in the canals. Reclamation of acid sulphate soils The conflict between agricultural production and environmental protection is the core problem and assessment of the sustainability of development of ASS within the study area leads to the question: Can the land be man- aged to maintain agricultural productivity while minimizing downstream impacts, or should it be returned to wetlands (Tuong et al., 1998)? This requires considering processes that generate acidity (i.e. pollution source) and processes that spread acidity (i.e. pollution transport). Figure 4.4 presents a schematic compari- son of acid pollution processes in rice fields and shrimp ponds. During the dry season, the availability of brackish water allows for the filling of shrimp ponds that are limed to ameliorate the effects of acidity, but rice fields on ASS are likely to remain fallow. Shrimp ponds may lose some water to the surrounding canals via seepage (Fig. 4.4a). During the wet season, rice cropping depends on collecting direct rainfall, but can continue after the end of the monsoon by irrigating. In addition to leaching and flush- ing of rice fields, leaching of acidity from embankments also occurred (Fig. 4.4b). Data collected from the study showed that the pH of the canal water in the ASS area of the study site was as low as 3 at the end of May and beginning of June, depend- ing on the rainfall (Tuong et al., 2003), but was approximately 7 in the dry season. High pH in the dry season suggests that shrimp ponds do not generate high acid pollution loads. This could also be attributed to the salinity of the brackish water in the dry sea- son, which has high buffering capacity. Very low pH at the beginning of the rainy season indicates that leaching and flushing of rice fields and leaching of embankments represent an environmental hazard. Evidence collected during the study indi- cates that the embankments of the shrimp ponds were a major source of acidity, which flushes directly into the wider environment at the start of the monsoon. This was sup- ported by Minh et al. (1997a,b), who reported that acidic loading from raised beds in ASS (for growing upland crops such as sugarcane and yam) was eight times higher than that from rice fields. The formation of embank- ments is similar to that of raised beds and involves the excavation of acidic materials and putting them on the embankments/ raised beds. The materials oxidize during the dry season. The acidity is mobilized by rain- fall. The pollution is most problematic at the beginning of the rainy season because the high loading coincides with low river dis- charge for dilution. Though the study did not quantify the impact of acidic pollution on fishery resources, farmers in our surveys confirmed that the diversity of fishery resources declined during the period of high acidity. Those poor farmers who relied on capture fishery also reported low catches during this period. Acid generation from rice fields is more controllable in that it depends largely on managed flushing prior to planting and therefore depends on the timing of the crop- ping season. An integrated rice–shrimp sys- tem – rice cropping in the rainy season and shrimp raising in the dry season – would allow good prospects for control over acid pollution from rice fields. However, acidity release from the embankments and conse- quential impact on water chemistry are likely to remain a problem for many years and it is important that the operation of tidal sluices does not exacerbate the problem. These sluices may reduce neutralization by tidal inflows of estuarine water, which would otherwise occur naturally. Estimated rates of acid production and export from ASS in Australia have been reported as 100–300 kg H2SO4/ha/year (Sammut et al., Social and Environmental Impact of Rapid Change 57 1996; Wilson et al., 1999). Accumulation behind sluices during sluice closure, fol- lowed by sudden release as slug flow into the downstream receiving water, can be cata- strophic. Conclusions It is clear that conditions are highly dynamic and livelihood strategies have adapted to economic, technological and policy change. But are they sustainable? The concept of sus- tainability requires a long-term perspective, but currently available evidence is short- term and inconclusive. The concept is also multidimensional and demands considera- tion of trade-offs among environmental, social and economic impacts, but informa- tion is incomplete. The analysis presented here is therefore a tentative attempt to extrapolate from what has been learned dur- ing the study by drawing upon experience elsewhere. The analysis has focused on envi- ronmental sustainability and livelihood sus- tainability. In making this assessment, particular consideration has been given to two critical issues that are likely to have a 58 J.W. Gowing et al. (a) Shrimp pond Shrimp pond (b) Fallow rice field Rice field ET Liming Pumping ET Acidification Brackish water Seepage Rain Rain Rain Flushing Leaching Fresh water Leaching Fig. 4.4. Acid pollution processes in reclaimed acid sulphate soils in the dry season (a) and wet season (b). ET, evapotranspiration. dominant impact on sustainability: shrimp aquaculture and the reclamation of acid sul- phate soils. Within the study area, systems of shrimp production are currently at relatively low intensity. Consequently, the environmental impact from shrimp production is not a major concern and the release of acidity from the reclamation of ASS is more significant. However, social impact is still an issue because of concern for the high risk of mass mortality from diseases and increased inequality. Effective dissemination of good practice, together with improved quality control of hatchery-reared postlarvae, can be expected to reduce the high risk associated with shrimp production. However, long- term sustainability will depend on limiting intensification and concerted action among all stakeholders to adopt integrated manage- ment of the environment. The original development strategy, which promoted intensive rice production through- out the protected area, was rejected by many local stakeholders. Intensification of the rice production system involves relatively low risk for farmers, but results in relatively low income. Within the extensive areas of ASS, rice production is seriously constrained by soil conditions, and low profitability pre- cludes the adoption of measures to amelio- rate the problem. Consequently, there is a clear preference among many landholders to produce shrimp in this environment. Inputs of lime are widely used to ameliorate acidity within shrimp ponds and the acid pollution problem consequently decreases, but some release of acidity into the wider environment still occurs. Within the designated freshwater zone on non-acid soils, the current strategy of double-cropped rice appears to be favoured by local stakeholders and no major sustainability concerns have been identified. Elsewhere, an integrated rice–shrimp system offers the best prospects for balanced and sustainable development. Fish have always been abundant and are considered as a commodity, like water and air, that will always be there, but there is evi- dence that changes within the protected area have had an impact on fishery resources. The tidal sluices have a direct impact by acting as a barrier to fish migration and an important indirect impact by controlling upstream tidal influence and salinity levels. Their impact on water quality is exacerbated by the accumu- lation of acid water leached from reclaimed ASS. The acid pollution and associated changes in water chemistry (e.g. high con- centration of dissolved aluminium) can be expected to affect the aquatic ecosystem both within the protected area and in the down- stream estuarine receiving waters. Evidence from Australia of chronic long-term effects of acid pollution on estuarine and coastal ecosystems provoked White et al. (1996) to raise concerns about likely adverse impacts of constructing tidal sluices. 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