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4 Social and Environmental Impact of RapidChange 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. Khiem41School of Agriculture, Food & Rural Development, University of Newcastle,

Newcastle upon Tyne, United Kingdom, e-mail: [email protected] 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 Tropical48 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 withinthe zone of saline intrusion, which previously extended up to 50 km inland during the dry season, thuslimiting traditional rice production to only one rainy-season crop. To promote the intensification of riceproduction, a plan was devised to build a series of coastal embankments and tidal sluices to controlsalinity intrusion. The protected area lying within Bac Lieu Province, which covers approximately160,000 ha, is the focus for this discussion.

Data collected on environmental and socio-economic conditions within the protected area during thestudy period reflect a complex spatial and temporal pattern of impacts. However, the pattern can be seenas 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 away that a freshwater environment is maintained. Intensification of the rice production system involvesrelatively 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 increasedwealth, but at high levels of risk and indebtedness. Currently available evidence of impact cannot easilybe extrapolated to assess long-term sustainability.

Introduction

Ca Mau Peninsula, which lies at the extremesouthern 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 policyintroduced an agenda of agriculture-ledgrowth. The peninsula lies entirely withinthe zone of saline intrusion, which previ-ously extended up to 50 km inland duringthe dry season, thus limiting traditional riceproduction to only one rainy-season crop(June–November). To promote the intensifi-cation of rice production, a plan was devisedto build a series of coastal embankments andtidal sluices to control salinity intrusion(Tuong et al., 2003). The first sluice in thisarea became operational in 1994 and thezone protected from saltwater intrusiongradually expanded westward as successivesluices were completed (Fig. 4.1). Within theprotected area, the duration of freshwaterconditions was extended in line with the pol-icy to promote double or triple cropping ofrice.

However, as the freshwater zone spreadgradually westward, the local economy wasundergoing rapid change. Profitability of therice crop was falling and at the same timeaquaculture was experiencing a dramaticboom, fuelled by technical innovations andthe high local and export prices of tigershrimp (Penaeus monodon). Traditional exten-sive systems of shrimp production based onnatural recruitment of shrimp larvae werebeing 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 culturewas consistent with the official policy2 of thecentral government adopted in 1998, whichexplicitly encouraged production for export.But shrimp farming in the protected area

contradicted the land-use policy of riceintensification in the area. Despite the appar-ent success and popularity of shrimp farm-ing, tidal sluices continued to be built andthe freshwater zone continued to spreadwestward up to 2000 (Fig. 4.1). When thesupply of brackish water required for shrimpproduction was cut off, many farmers wereforced to abandon aquaculture and to con-vert to less profitable rice farming. Someshrimp farmers resisted and attempted tomaintain favourable conditions by blockingsecondary canals and pumping brackishwater into their fields, but this created con-flict with rice farmers, who depended onfresh water to irrigate their fields.Eventually, in 2001, the original policyemphasizing rice production was revised toaccommodate extensive shrimp cultivationin the west while maintaining areas of inten-sive rice production in the east. Land useadjusted rapidly to this new policy and by2002 areas of intensive rice production hadshrunk back to the freshwater zone in thenon-acid soils to the east (Fig. 4.2).

The background to this policy shift withinthe highly dynamic environmental andsocio-economic circumstances of the projectarea is discussed by Hoanh et al. (2003). Thisshift is significant because it represents arelaxation of centralized planning in order toallow more freedom for private-sector deci-sions on land use. The pressure that broughtabout this change can be seen as the rationalresponse by farmers to economic incentives.However, several emerging issues point tothe need for continuing scrutiny and regula-tion of land use (and in particular shrimpfarming) to ensure that short-term gain doesnot result in failure to achieve long-term sus-tainable development.

The essential requirements for sustainabledevelopment can be defined as poverty erad-ication, changing unsustainable patterns ofproduction and consumption, and protectingand 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 centrallyplanned command economy to a market economy with accompanying democratization of socialrelations.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 beunderstood as mutually supportive and theimportance of poverty–environment link-ages should be seen as the core of sustain-able development strategies. Poor people arepredominantly rural and predominantlydependent on natural resources for theirlivelihoods. They are therefore particularlyvulnerable to environmental problems. Theyneed economic growth to escape poverty, butthis must be based on the sustainable use ofenvironmental resources. Concern for envi-ronmental protection is therefore not seen asbeing in conflict with concern for humandevelopment. The enhancement and mainte-nance of environmental capital allow for theprudent use of natural resources in the shortterm while providing for effective protectionof the environment in the long term.

The notion of vulnerability is critical tounderstanding the impacts of change.Vulnerability occurs because livelihoods are

exposed to stress and are unable to copewith that stress (Adger and Kelly, 2001).Shocks (such as floods and storms) may pro-duce stress when people lose their assets orare forced to dispose of them as a short-termsurvival strategy. Longer-term adversetrends (such as soil erosion, siltation or acidi-fication) may gradually degrade assets andalso create stress. The inherent fragility ofpoor people’s livelihoods limits their adap-tive options and makes them generally morevulnerable. Vulnerability therefore relates toboth: (i) exposure to risk likely to affectlivelihood; and (ii) weakness of the existingstate that limits capacity to cope with theresulting stress.

The rapid expansion of brackish-watershrimp farming in the study area indicatedfarmers’ preference for this production overrice. However, brackish-water shrimp farm-ing elsewhere has been characterized byrecurrent 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 reportedover the past decade (Phillips et al., 1993;Beveridge et al., 1997; Primavera, 1998; Lebelet al., 2002; Shanahan et al., 2003). It is impor-tant to examine the sustainability of shrimpfarming in the study area.

One of the characteristics of the studyarea is the presence of extensive deposits ofacid sulphate soils (ASS), particularly in thewestern part. These soils develop as a resultof the drainage of parent materials that arerich 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 reducedS- and Fe-bearing compounds producingacid via a number of possible chemical andbiochemical pathways (Dent, 1986). The acidreleased in this way reacts with clay mineralsto produce soil–water solutions containinghigh concentrations of aluminium and iron.

Reclamation of ASS for agricultural usedepends on leaching these toxic substancesout of the root zone and has been reported tocreate severe acidification of the aquaticenvironment in Indonesia (Klepper et al.,1990) and Australia (Wilson et al., 1999) aswell as in Vietnam (Minh et al., 1997b). Theacid pollution and associated changes inwater chemistry can have severe impacts onfish populations (Callinan et al., 1993), whichare not confined to the reclaimed area. Theimpact on estuarine ecosystems has beenreported by Sammut et al. (1996) and Wilsonet al. (1999) for Australia, where mass mortal-ities of fish have been recorded as a result ofepisodic 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 aquestion of the sustainability of developmentof ASS within the study area. Leachate fromreclaimed ASS in the Mekong Delta shows


Fig. 4.2. Land-use change in the study area.

marked peak acidity and Al concentration atthe start of the rainy season (Minh et al.,1997a; Tuong et al., 1998), which may createshocks for the aquatic resources and vulnera-bility for the landless poor who depend agreat 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 indetermining the nature and extent of recentenvironmental changes in Ca MauPeninsula. The pre-2000 strategies, favouringrice monoculture, can be criticized (with thebenefit of hindsight) for suffering from thesame faults identified by Hori (2000) in areview of development planning throughoutthe lower Mekong basin. They failed to rec-ognize the diversity of livelihoods of thepopulation and did not give adequate con-sideration to environmental impact. Thestudy reported here was therefore conductedbetween 1999 and 2003 to investigate thelikely sustainability of development as itaffects that part of the newly protected arealying 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 representenvironmental, social and economic aspects.However, it is clear that two critical issuesagainst which recent change in Bac LieuProvince should be judged are:

● environmental sustainability, which isachieved when the productivity of thenatural resource base (i.e. environmentalcapital) is conserved or enhanced; and

● livelihood sustainability, which is achievedwhen households respond and adapt tochange without becoming more vulnerable.

The objective of this chapter is therefore topresent an assessment of the sustainability ofthe development, with a particular focus on:

● the state of the environment and naturalresources within the project area, and

● socio-economic conditions and the rela-tionship between livelihoods and naturalresources 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 socialimpact assessment, that is, assessing changesin farmers’ livelihoods and farmers’ resource-usestrategies in coping with changes brought aboutby salinity intrusion protection.

The initial activity under this work pack-age was to establish a framework for socialdifferentiation so that the poor could beidentified as a distinct stakeholder group inorder to permit an appraisal of environ-ment–poverty linkages and any differentialimpact 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), aquantitative survey was conducted in 14hamlets 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 ofasset and production profiles for 350 repre-sentative households across four wealth cate-gories. This was followed by an in-depthqualitative survey that used standard partici-patory rural appraisal (PRA) tools in inter-views with key informants to improveunderstanding of livelihood strategies and tohelp identify the key issues affecting poorpeople (Chambers, 1997).

Follow-up surveys were conductedtoward the end of the project (in 2003) to pro-vide data for an assessment of short-termlivelihood impacts. A combination of quanti-tative and qualitative surveys was againadopted within seven of the original 14 ham-lets, where all households previouslyincluded in the baseline study were resur-veyed. The key indicators used to measurechanges in livelihoods are summarized inTable 4.1. These indicators provide some


insight into the short-term impact of environ-mental change within the project area basedon quantitative data for 1999 to 2003, whichcan be extended back to 1994 on the basis ofinsights derived from the PRA. However, theprediction of future livelihood trajectories ofdifferent stakeholders is more problematic.

Environmental impact: method of assessment

In recognition of the importance of environ-mental sustainability, another of the workpackages within the study focused on envi-ronmental impact analysis, that is, character-izing the changes in soil and water quality andresource use brought about by salinity protectioninterventions.

The initial activity under this work pack-age was the collection and compilation ofdata from existing soil and land-use mapsand the water quality monitoring network inthe area. Subsequently, the activitiesinvolved the actual soil and water qualitymonitoring carried out by the study team. Bybringing these data into a GIS for spatialdata management, integration and visualiza-tion, it was possible to establish an idea ofthe baseline condition (Kam et al., Chapter15, this volume). It also provided a means oflinking the monitoring activity to modellingwork based on the VRSAP3 hydraulic model(Hoanh et al., 2001, 2003).

The soil map published by IRMC4 in 1999at a scale of 1:50,000 provided a baseline formonitoring soil changes. Initial fieldworkwas undertaken (in 2000) to verify the pre-dictive value of the soil map at selected loca-tions based on the previously definedsampling zones. It was found to be satisfac-tory, but some areas mapped in 1998 aspotential acid sulphate soils had alreadydeveloped into actual acid sulphate soils. Asoil monitoring programme was establishedas part of this work package, which includedintensive surveys of acidity release.

Data on water quality are subject to muchmore temporal variability than are soil data,and therefore presented a greater samplingproblem. Data on salinity, pH and Al3+ from26 locations throughout the study area werecollected from 1993 to 2000, but the fre-quency of observations was inconsistent. Afollow-up water monitoring programme wasestablished in 2001, which included moreintensive roving surveys. The aim of theseactivities was to provide data on short-termchanges and a basis for predicting longer-term impact on soil and water quality.Particular concerns were:

● the presence of extensive deposits of acidsulphate soils (ASS) that provide a sourceof acidity likely to affect water quality, and

● the impact of water quality change (acid-ity and/or salinity) on the productivity offisheries.


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; croppingpatterns; 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, otheraquaculture, livestock, employment, capture fisheries; remittances fromrelatives and other funds

Physical Access to TV, radio, rowing boat, motorboat, tiller/pump/thresherHuman 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, butdownstream impacts in the surroundingcoastal zone may also be significant andthese were not monitored. To analyse envi-ronmental sustainability, it is necessary toconsider both wider and longer-termimpacts.

Evidence of short-term impact

Data collected on environmental and socio-economic conditions within the protectedarea during the study period should be seenin the context of rapid change occurring atthat 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 brackishenvironment supporting shrimp production,as summarized in Fig. 4.3.

A strategy favouring rice productiondepends on the operation of sluices in such away that a freshwater environment is main-tained. Intensification of the rice productionsystem involves relatively low risk for farm-ers, but results in relatively low income. On

the other hand, shrimp production requiresthat a brackish environment be maintainedand is seen to offer the potential forincreased wealth, but at high levels of riskand indebtedness.

Within the extensive areas of ASS, riceproduction is seriously constrained by soilconditions, but low profitability precludesthe adoption of measures to ameliorate theproblem. However, there is evidence thatmore land is brought into use after conver-sion to shrimp production. Inputs of lime arewidely used to ameliorate acidity within theshrimp ponds, although release of acidityinto the wider environment still occurs.

Other impacts on natural resources andconsequently on livelihoods can also beidentified. The freshwater environmentfavours higher production of fruits and veg-etables from home gardens, and of livestockfor sale and consumption, than is possible inthe brackish environment. On the otherhand, by sustaining freshwater conditions,the catch of wild fish from open-accesscanals is seen to decline.

These impacts on productivity of the nat-ural resource base result in knock-on effectson livelihoods, but the nature of these sec-ondary impacts varies depending on thelivelihood strategy adopted by a particular


Rice ShrimpAcid releaseto aquaticenvironment

Freshwater environment Brackish environment

+ Low risk+ Less indebtedness+ Increased opportunity

for wage labour

+ More productivehome gardens

+ More productivelivestock

– Less productivefishery

– Low income– Low production on ASS– Increased use of agrochemicals

+ Increased wealth+ Increased trading opportunity+ Productive use of acid sulphate

soils

+ More productivefishery

– Less productivelivestock

– Less productivehome gardens

– Increased levels of debt– Increased inequality– High risk of failure

Fig. 4.3. Impacts of alternative environmental management strategies within the protected area.


household (Table 4.2). Households classifiedas ‘very poor’ were identified in five of the14 hamlets and represent 7% of all house-holds. They exhibit a very high proportion offunctionally landless and depend on sellinglabour. They find more employment oppor-tunities in rice areas than in shrimp areas.Households classified as ‘poor’ exist in allhamlets and represent 34% of the total popu-lation. They have some land and may benefitfrom conversion to shrimp production, buttheir asset base is low and the associated riskmakes 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 concernover shrimp farming is the degradation ofcoastal wetland ecosystems and in particularthe loss of mangrove forests. Over the last 50years, Vietnam has lost a large proportion ofits original mangrove cover through variouspressures, but during the last decade theprincipal threat was reported as shrimpaquaculture (Shanahan et al., 2003). Criticshave pointed to the adverse consequences ofconversion of mangroves to shrimp pondson aquatic resources and habitat and forestproducts, and the increased vulnerability tostorms and typhoons in Thailand, thePhilippines, Indonesia and Bangladesh, aswell as in Vietnam. However, this criticismdoes not apply to the particular circum-

stances of the study area, where the expan-sion of shrimp aquaculture has occurred onland previously cleared for agriculture.

Salinization of soil and water is anothermajor concern associated with shrimp aqua-culture, particularly where shrimp pondshave expanded into rice land (Flaherty et al.,1999). Shrimp production requires brackishwater and its import into non-saline areasaffects neighbouring rice fields and degradeswater used for both agricultural and domes-tic needs. Again, when applied to the partic-ular circumstances of the study area, thiscriticism is not valid. Salinity intrusion is anatural seasonal phenomenon within thearea, which can now be managed using therecently constructed tidal sluices, and soilsalinity cannot be attributed to shrimp pro-duction. There is evidence (Tran et al., 1999)that salt leaching from shrimp ponds intoadjacent rice fields can be significant, but nolong-term buildup of salts is apparent insequential shrimp–rice production systems(Brennan et al., 2002; Phong et al., 2003). Thisproblem can be managed by appropriatezoning and the adoption of appropriate pro-duction systems.

Other environmental impacts are closelylinked to the level of intensity of the shrimpproduction system. In this respect, there is amarked contrast between Vietnam and othermajor 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 Table4.3. As production becomes more intensive,economic viability becomes dependent onhigh 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 survivalrates and high growth rates. Water exchangethen releases contaminated pond effluentsinto the wider environment. The samereceiving waters generally serve as intakewater for neighbouring shrimp farms andwater-borne disease agents spread rapidlyfrom farm to farm, thus encouraging thegreater use of antibiotics.

Within the study area, production sys-tems are at relatively low intensity (as alsoreported by Lebel et al., 2002), with lime andseed (postlarvae) as the main purchasedinputs. The low quality of hatchery-rearedseed is a major constraint contributing to thespread of disease, high risk of failure andpressure to increase the use of antibiotics.Under present circumstances, pollution isnot a major concern and the release of acidityis a more significant impact; however, thereis clear evidence from elsewhere that highlyintensive systems are not sustainable.

Shrimp aquaculture has been encouragedby the government of Vietnam to help raisethe standard of living of rural communities.Perceived benefits include job creation dur-ing pond construction, income generation forshrimp farmers, increased trading opportu-nities and employment in aquaculture ser-vices (seed supply, other inputs, processing,marketing) and increased foreign exchangeearnings. The potential to generate wealthundoubtedly exists, yet shrimp aquaculturehas been responsible for the deterioration oflivelihoods and promotion of poverty inmany countries. Drawing on a series of case

studies undertaken in Vietnam, Adger andKelly (2001) concluded that poorer house-holds are most vulnerable because: (i) theyare likely to depend on a narrower range ofresources and income sources; and (ii) theloss of common property management rightsrepresents a serious erosion of their ability tocope. They found evidence of benefits froman increase in overall wealth, but increasedinequality.

The high risk associated with the enter-prise exposes poor people to financial ruinand landlessness. The vast majority ofshrimp farmers must borrow money to payfor pond construction and purchase inputs.When the enterprise is successful, profits canbe high, allowing them to pay off their debtsquickly. However, the risk of failure is alsohigh; Lebel et al. (2002) report a 70% rate,Shanahan et al. (2003) report a 70–80% rateand a survey in the study area indicates asimilar 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 asyet no direct evidence that this has occurredwithin the study area. Relatively poor farm-ers are more likely to fail, but, if their neigh-bours have converted from rice to shrimpfarming, they have no alternative.

Landless households depend on sellinglabour, but evidence from elsewhere (Lebelet al., 2002; Shanahan et al., 2003) supportsfindings within the study area that shrimpfarming creates fewer employment opportu-nities than rice farming. Environmental


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 ofopen-access areas affects the livelihoods ofpoor people (particularly landless house-holds) and adversely affects food security.Where shrimp ponds are developed on landreclaimed from open-access mangrove forestthere is a particular concern, but within thestudy area this is not the case. However, anindirect impact on common propertyresources still exists because of the change inwater quality and its effect on the productiv-ity of the fishery in the canals.

Reclamation of acid sulphate soils

The conflict between agricultural productionand environmental protection is the coreproblem and assessment of the sustainabilityof development of ASS within the study arealeads to the question: Can the land be man-aged to maintain agricultural productivitywhile minimizing downstream impacts, orshould it be returned to wetlands (Tuong etal., 1998)? This requires consideringprocesses that generate acidity (i.e. pollutionsource) and processes that spread acidity (i.e.pollution transport).

Figure 4.4 presents a schematic compari-son of acid pollution processes in rice fieldsand shrimp ponds. During the dry season,the availability of brackish water allows forthe filling of shrimp ponds that are limed toameliorate the effects of acidity, but ricefields on ASS are likely to remain fallow.Shrimp ponds may lose some water to thesurrounding canals via seepage (Fig. 4.4a).During the wet season, rice croppingdepends on collecting direct rainfall, but cancontinue after the end of the monsoon byirrigating. In addition to leaching and flush-ing of rice fields, leaching of acidity fromembankments also occurred (Fig. 4.4b).

Data collected from the study showedthat the pH of the canal water in the ASSarea of the study site was as low as 3 at theend of May and beginning of June, depend-ing on the rainfall (Tuong et al., 2003), butwas approximately 7 in the dry season. HighpH in the dry season suggests that shrimpponds do not generate high acid pollutionloads. 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 rainyseason indicates that leaching and flushingof rice fields and leaching of embankmentsrepresent an environmental hazard.Evidence collected during the study indi-cates that the embankments of the shrimpponds were a major source of acidity, whichflushes directly into the wider environmentat the start of the monsoon. This was sup-ported by Minh et al. (1997a,b), who reportedthat acidic loading from raised beds in ASS(for growing upland crops such as sugarcaneand yam) was eight times higher than thatfrom rice fields. The formation of embank-ments is similar to that of raised beds andinvolves the excavation of acidic materialsand putting them on the embankments/raised beds. The materials oxidize during thedry season. The acidity is mobilized by rain-fall. The pollution is most problematic at thebeginning of the rainy season because thehigh loading coincides with low river dis-charge for dilution. Though the study didnot quantify the impact of acidic pollutionon fishery resources, farmers in our surveysconfirmed that the diversity of fisheryresources declined during the period of highacidity. Those poor farmers who relied oncapture fishery also reported low catchesduring this period.

Acid generation from rice fields is morecontrollable in that it depends largely onmanaged flushing prior to planting andtherefore depends on the timing of the crop-ping season. An integrated rice–shrimp sys-tem – rice cropping in the rainy season andshrimp raising in the dry season – wouldallow good prospects for control over acidpollution from rice fields. However, acidityrelease from the embankments and conse-quential impact on water chemistry arelikely to remain a problem for many yearsand it is important that the operation of tidalsluices does not exacerbate the problem.These sluices may reduce neutralization bytidal inflows of estuarine water, whichwould otherwise occur naturally. Estimatedrates of acid production and export fromASS in Australia have been reported as100–300 kg H2SO4/ha/year (Sammut et al.,


1996; Wilson et al., 1999). Accumulationbehind sluices during sluice closure, fol-lowed by sudden release as slug flow intothe downstream receiving water, can be cata-strophic.

Conclusions

It is clear that conditions are highly dynamicand livelihood strategies have adapted toeconomic, 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 alsomultidimensional and demands considera-tion of trade-offs among environmental,social and economic impacts, but informa-tion is incomplete. The analysis presentedhere is therefore a tentative attempt toextrapolate from what has been learned dur-ing the study by drawing upon experienceelsewhere. The analysis has focused on envi-ronmental sustainability and livelihood sus-tainability. In making this assessment,particular consideration has been given totwo critical issues that are likely to have a


(a)Shrimppond

Shrimppond

(b)

Fallow rice field

Rice field

ET

Liming

Pumping ET

Acidification

Brackish water

Seepage

RainRain

Rain

FlushingLeaching

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: shrimpaquaculture and the reclamation of acid sul-phate soils.

Within the study area, systems of shrimpproduction are currently at relatively lowintensity. Consequently, the environmentalimpact from shrimp production is not amajor concern and the release of acidity fromthe reclamation of ASS is more significant.However, social impact is still an issuebecause of concern for the high risk of massmortality from diseases and increasedinequality. Effective dissemination of goodpractice, together with improved qualitycontrol of hatchery-reared postlarvae, can beexpected to reduce the high risk associatedwith shrimp production. However, long-term sustainability will depend on limitingintensification and concerted action amongall stakeholders to adopt integrated manage-ment of the environment.

The original development strategy, whichpromoted intensive rice production through-out the protected area, was rejected by manylocal stakeholders. Intensification of the riceproduction system involves relatively lowrisk for farmers, but results in relatively lowincome. Within the extensive areas of ASS,rice production is seriously constrained bysoil conditions, and low profitability pre-cludes the adoption of measures to amelio-rate the problem. Consequently, there is aclear preference among many landholders toproduce shrimp in this environment. Inputsof lime are widely used to ameliorate aciditywithin shrimp ponds and the acid pollution

problem consequently decreases, but somerelease of acidity into the wider environmentstill occurs. Within the designated freshwaterzone on non-acid soils, the current strategyof double-cropped rice appears to befavoured by local stakeholders and no majorsustainability concerns have been identified.Elsewhere, an integrated rice–shrimp systemoffers the best prospects for balanced andsustainable development.

Fish have always been abundant and areconsidered as a commodity, like water andair, that will always be there, but there is evi-dence that changes within the protected areahave had an impact on fishery resources. Thetidal sluices have a direct impact by acting asa barrier to fish migration and an importantindirect impact by controlling upstream tidalinfluence and salinity levels. Their impact onwater quality is exacerbated by the accumu-lation of acid water leached from reclaimedASS. The acid pollution and associatedchanges in water chemistry (e.g. high con-centration of dissolved aluminium) can beexpected to affect the aquatic ecosystem bothwithin the protected area and in the down-stream estuarine receiving waters. Evidencefrom Australia of chronic long-term effects ofacid pollution on estuarine and coastalecosystems provoked White et al. (1996) toraise concerns about likely adverse impactsof constructing tidal sluices. This study con-firms their analysis and highlights theimportant connection between environmen-tal and social impacts.


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