Threatening “white gold”: Impacts of climate change on shrimp farming in coastal Bangladesh

Ocean & Coastal Management 114 (2015) 42e52

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Ocean & Coastal Management journal homepage: www.elsevier.com/locate/ocecoaman

Threatening “white gold”: Impacts of climate change on shrimp farming in coastal Bangladesh Nesar Ahmed*, James S. Diana School of Natural Resources and Environment, University of Michigan, Ann Arbor, MI 48109, USA

a r t i c l e i n f o

a b s t r a c t

Article history: Received 23 January 2015 Received in revised form 15 June 2015 Accepted 15 June 2015 Available online xxx

In Bangladesh, tiger shrimp (Penaeus monodon) is commercially known as “white gold”, because of its export value. However, the production of “white gold” under shrimp alternate rice and shrimp-only farming systems in coastal Bangladesh has been accompanied by recent concerns over climate change. Field survey reveals that different climatic variables including coastal flooding, cyclone, sea-level rise, salinity, drought, rainfall, and sea surface temperature have had adverse effects on shrimp culture as well as socioeconomic conditions of farming households. There is also overwhelming evidence that changes in climatic variables has detrimental effects on the ecosystem of shrimp farms, and thus, severe effects on survival, growth, and production of shrimp. Considering extreme vulnerability to the effects of climate change on shrimp farming, we propose that community based adaptation strategies and integrated coastal zone management are needed to cope with the challenges. © 2015 Elsevier Ltd. All rights reserved.

Keywords: Shrimp farming Climatic variables Adaptation Coastal Bangladesh

1. Introduction Bangladesh is one of the most suitable countries in the world for tiger shrimp (Penaeus monodon) farming. The practice of shrimp farming is widespread in coastal Bangladesh, because of favorable biophysical resources and agro-climatic conditions, including the availability of wild postlarvae1 (Ahmed, 2013a). A sub-tropical climate and a considerable area of brackish water provide a unique opportunity for shrimp production. The total shrimp farming area in Bangladesh was estimated at 210,053 ha. About three-quarters of shrimp farms are located in southwest Bangladesh, with the remainder in the southeast. The total shrimp culture production in Bangladesh was estimated to be 68,948 tons in 2012e20132 (FRSS, 2014). Shrimp is commercially known as “white gold” in Bangladesh, because of its export value (Islam, 2009). The sector has become a multimillion dollar industry in Bangladesh due to huge demand for shrimp in global market, particularly the European Union and the United States of America. In 2012e2013, Bangladesh exported

* Corresponding author. E-mail addresses: [email protected], [email protected] (N. Ahmed). 1 The term “postlarvae” usually applies to animals from the time of metamorphosis up to about 60 days later. Postlarvae and fry are interchangeably used in this paper. 2 Bangladesh fiscal year: 1 Julye30 June. http://dx.doi.org/10.1016/j.ocecoaman.2015.06.008 0964-5691/© 2015 Elsevier Ltd. All rights reserved.

43,953 tons of prawn and shrimp valued at US$396 million, of which US$304 million (77%) was shrimp (FRSS, 2014). The shrimp culture sector is the second largest export industry in Bangladesh after ready-made garments, and earnings from shrimp make a significant contribution to the economic growth of the country. The sector has also brought about livelihood opportunities for 833,000 farmers in coastal areas (DoF, 2014). Moreover, a significant number of coastal poor are associated with shrimp harvesting, marketing, processing, and exporting. Overall, shrimp production plays an important role in the economy of Bangladesh, earning valuable foreign exchange, contributing to increased food production, diversifying the economy, and increasing livelihood opportunities (Ahmed, 2013a). However, while shrimp production provides a wide range of economic benefits, the culture of shrimp in coastal Bangladesh has recently been threatened by climate change. Bangladesh is a global hotspot for climate change as the country is already subject to climate extremes and prone to natural hazards. According to the Global Climate Risk Index 2015, Bangladesh is ranked 6th among countries vulnerable to climate change, while it was ranked 1st in 2012 (Harmeling and Eckstein, 2012; Kreft et al., 2014). The potential impacts of climate change on shrimp farming could have dramatic consequences for the economy of Bangladesh. Considering extreme vulnerability of shrimp farming to the effects of climate change, adaptation strategies must be developed to cope with the challenges.

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Fig. 1. Geographical position of Bangladesh with map of the southwest region showing the study area of Mongla.

The aim of this paper is to assess the impacts of climate change on shrimp farming in coastal Bangladesh. It also examines socioeconomic effects to farming households and ecological consequences on shrimp production by climate change. Finally, this paper sets out some preliminary conclusions about the adaptation of shrimp farming to climate change. 2. Study area and field survey 2.1. Study area The study was conducted in the Mongla sub-district under Bagerhat district3 of southwest Bangladesh, a coastal area of the Bay of Bengal (Fig. 1). A total of 760 shrimp farms are located in Mongla (Islam, 2013). However, shrimp culture is traditional and extensive in nature which is practiced in low-lying tidal flats

3 Bagerhat district is divided into 9 sub-districts, among them northern subdistricts are important for freshwater prawn farming while southern sub-districts are promising for saltwater shrimp farming.

(locally known as gher). Farmers usually cut a small portion of dikes to allow tidal water to trap wild shrimp fry. Farmers also prefer to stock wild caught and hatchery fry. There are two types of shrimp farming systems in the study area: (1) shrimp alternate rice, and (2) shrimp-only4 (Table 1). In the shrimp alternate rice farming system, shrimp is grown during the monsoon when farms are inundated by tidal water, while rice is produced during the dry season. Farmers also practice shrimp-only culture where water salinity remains high for 6e9 months annually and rice cultivation is not possible because of salinity. Although shrimp-only farming produces a slightly higher yield of shrimp, the total productivity is higher in shrimp alternate rice farming because of rice production. In spite of promising conditions for shrimp farming, Mongla is one of the most disaster-prone areas in Bangladesh due to climate change. Mongla is located 78 km up-estuary and nearby to the

4 A number of wild fish species (bass, catfish, jawfish, pomfret, and ribbonfish) are often found in both farming systems.

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Table 1 Shrimp farming systems in Mongla of southwest Bangladesh. Farming information

Shrimp culture period Rice culture period Farm size (ha) Water depth (cm) Water salinity (ppt) Stocking rate (postlarvae/ha/yr) Feeding rate (kg/ha/yr) Production (kg/ha/yr) Shrimp Rice

Farming system Shrimp alternate rice

Shrimp

AprileOctober DecembereMarch 0.4e2 75e120 4e12 12,000e18,000 500e1200

MarcheOctober e 0.5e2.5 90e150 8e25 15,000e24,000 600e1400

250e450 2000e3500

300e600 e

Source: Field survey (2013).

Sundarbans mangrove forest.5 During 1998e2010, mean high tidal water level has increased 14.5 mm per year in Mongla (Pethick and Orford, 2013). 2.2. Climate change and coastal Bangladesh Bangladesh is subject to seasonal changes in climatic conditions. The increasing risk to a combination of climatic variables, including: (1) rainfall, (2) flood, (3) drought, (4) cyclone, (5) sealevel rise, (6) salinity, and (7) sea surface temperature. Bangladesh falls in a region of huge rainfall as the country is situated in the monsoon belt with the Himalayas in the north and the Bay of Bengal in the south. Heavy rainfall has made Bangladesh as one of the world's wettest countries. Annual rainfall in Bangladesh varies from 1400 mm in the west to 4300 mm in the east, with 80% occurring between May and September (Shahid, 2010). Climate change has profound impacts on rainfall intensity and variability in Bangladesh, and it is predicted that monsoon rainfall will increase about 10e15% by 2030 (Jakobsen et al., 2005). There is a direct influence of global warming on changes in rainfall patterns as the water holding capacity of air increases 6e7% for every 1
C increase in temperature (Trenberth, 2008). Increased surface temperature of the Bay of Bengal might also change wind patterns leading to increased rainfall in Bangladesh (Shahid, 2010). Bangladesh is flood prone and 20% of the country is normally flooded each year. Even in drought years, 10% of the country experiences floods during the monsoon. Since independence (1971), there have been seven extreme floods when over 35% of the country was submerged (Ahasan et al., 2010; Banerjee, 2010). Siltation and erosion of the major river systems (the GangesBrahmaputra-Meghna) can exacerbate the effects of flood, and Bangladesh has no control over river flooding because the country is called a “land of rivers” that has over 700 rivers including 57 trans-boundary rivers (IUCN, 2012). About 1.7 million ha of floodplains are prone to river bank erosion (Alam and Ahmed, 2010). Higher discharge, low drainage capacity, and backwater effects with tidal surges from the Bay of Bengal increase coastal flooding. Around 14.6 million people in coastal Bangladesh are vulnerable to inundation due to cyclonic surges, and this number will increase to 18.5 million by 2050 (World Bank, 2012). About 5690 km2 coastal area in Bangladesh has identified as a high-risk zone where coastal flooding of depth over 1 m might occur (Karim and Mimura, 2008). The climatic conditions of Bangladesh are characterized by drought in the dry season. During the last 50 years, Bangladesh experienced 19 droughts (Habiba et al., 2012). Seasonal droughts

5 The Sundarbans is the largest mangrove forest in the world, located along the mouth of the Bay of Bengal between Bangladesh and India.

are common in coastal Bangladesh and the frequency of droughts has recently increased due to climate change. Drought is associated with a lack of precipitation and high temperatures (Trenberth, 2008). According to Dai et al. (2004), global warming accelerates the drying of land-surface as heat goes into evaporation of mois~ o6 event with ture, which increases the risk of drought. An El Nin strong warming can cause the monsoon to switch into a dry mode, resulting significant reductions in rainfall leading to severe droughts (Conway and Waage, 2010). The entire coastal zone in Bangladesh is prone to violent storms and tropical cyclones which originate in the Indian Ocean and track through the Bay of Bengal. Between 1877 and 1995, Bangladesh was hit by 154 cyclones, including 43 severe cyclones (Dasgupta et al., 2011). On average, a severe cyclone hits the country every three years (GoB, 2009), and the frequency of 7 m height cyclonic surge occurs once every five years (Dasgupta et al., 2011). Cyclones pose a great threat to lives and properties in coastal Bangladesh. On average, 6000 people die each year in floods from storms and cyclones (Schiermeier, 2014). A cyclone in 1970 resulted in the death of around 300,000 people, and another in 1991 caused 138,000 deaths (World Bank, 2000). In November 2007, the coastal region of Bangladesh was affected by tropical cyclone Sidr and 3406 people died with economic losses estimated at US$1.67 billion (GoB, 2008). In recent years, cyclone Nargis (May 2008), Bijli (April 2009), Aila (May 2009), and Mahasen (May 2013) devastated coastal life in Bangladesh. Bangladesh includes one of the largest deltas in the world which lies just less than 2 m above sea-level (Schiermeier, 2014). The coastal region of Bangladesh is an ideal zone for sea-level rise due to global warming and glacier melting in the Himalayas (Singh, 2001). Sea-level may be rising by 15.9e17.2 mm each year in southwest Bangladesh (Schiermeier, 2014), while global sea-level rises only 2e3 mm each year (Pethick and Orford, 2013). Lives and properties along the Bay of Bengal are highly vulnerable to sealevel rise as the country has a 710 km long coastline (DoF, 2014). An intensification of 10% sea-level rise would increase the inundation zone from today's 19.5e27.5% of coastal Bangladesh (Dasgupta et al., 2010). Sea-level could rise 1 m by 2100 (Rahmstorf, 2007). A 1 m sea-level rise will affect the vast majority of coastal Bangladesh and the Sundarbans mangrove forest would be totally lost (Agrawala et al., 2003). Sea-level rise could cause millions of people to become homeless in coastal Bangladesh. Saline water intrusion is an increasing problem in coastal Bangladesh, which consists of 19 districts out of 64 (about onethird of the country). Saline water from the Bay of Bengal has entered in coastal Bangladesh over 100 km upstream through estuaries and rivers (Allison et al., 2003). The concentration of water salinity has recently increased in coastal rivers to 4 ppt in the monsoon and 13 ppt in the dry season (Khan et al., 2011). About 1.05 million ha of land in coastal Bangladesh are affected by soil salinity (Sikder, 2013). Soil and groundwater salinity in coastal Bangladesh is predicted to affect two million ha of land by 2050 (Conway and Waage, 2010). Sea-level rise and cyclones with tidal surges are likely to play a critical role in increasing salinity of coastal Bangladesh. Cyclones push fully saline seawater from the deepwater layers onto the shelf and then to coastal areas (Dasgupta et al., 2011). Sea surface temperature in the Bay of Bengal has increased from 0.20 to 0.46
C at day and 0.30e0.48
C at night between 1985 and

6 ~ o is the warm phase of the El Nin ~ o Southern Oscillation (also called El Nin ENSO), refers to the cycle of warm temperatures that occurs across the Tropical Pacific Ocean. It is characterized by prolonged warming in the Pacific Ocean sea surface temperatures.

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Fig. 2. Multi-method approaches for field survey where different methods were used for validation of data to get consistent information about the impacts of climate change on shrimp farming as well as adaptation strategies; parentheses indicate sample size of participants.

2009. It is predicted that sea surface temperature in the Bay of Bengal will increase from 0.35 to 0.72
C at day and 0.50e0.80
C at night by 2050 (Chowdhury et al., 2012). Sea surface temperature in the Bay of Bengal is increasing more rapidly than in the global oceans. Global sea surface temperature is about 1
C higher now than 140 years ago (Dailidiene et al., 2011). Global warming as well as greenhouse effect leads to higher sea surface temperature that is likely to intensify cyclones (Dasgupta et al., 2011). A sea surface temperature of 28
C is considered an important factor for development of hurricane categories 3, 4, and 5 (Knutson and Tuleya, 2004). Because of increased sea surface temperature, the coastal region of Bangladesh will heat up faster as there is a greater contrast between the land and the sea (Conway and Waage, 2010).

45

shrimp-only). A total of 100 shrimp farmers, 50 in each farming system, were interviewed at their houses and farm sites. Several visits were made to selected farms to observe farming practices. The interviews lasted about an hour on average, focused on perceived impacts of climate change on shrimp culture. In order to assess farmers views on the impacts of climate change on shrimp production, relative rank was applied for different climatic variables. The ranking scale was between 1 and 5, where 1 ¼ not vulnerable, 2 ¼ less vulnerable, 3 ¼ moderate vulnerable, 4 ¼ highly vulnerable, and 5 ¼ extremely vulnerable. Focus group discussions (FGD) were conducted with shrimp farmers to obtain their views regarding the impacts of climate change on shrimp production with its socioeconomic and ecological effects. The advantage of FGD over other methods is that it allows wider participation of the community, and therefore the information that is collected is likely to be more reliable. A total of 15 FGD sessions were conducted with each group consisted of 6e14 farmers, thereby including a total of 152 people. There were spontaneous gatherings in FGD, as shrimp farmers were supportive owing to their interest in learning. The FGD sessions, which lasted up to 2 h, were held in front of village shops, under large trees, and in farmers' houses. Validation of the information collected was undertaken through cross-check interviews with key informants. A key informant is someone with special knowledge on the impacts of climate change on shrimp farming. Cross-check interviews were conducted with government fisheries officers, researchers, policymakers, community leaders, school teachers, and non-governmental organization (NGO) workers. A total of 25 key informants were interviewed in their offices and work locations in the coastal region. Key informants were also provided suggestions regarding adaptation strategies in relation to climate change, based on their knowledge, skills, and experience. 2.4. Data analysis

2.3. Data collection methods This study employed a combination of participatory, qualitative, and quantitative methods for data collection, including: (1) transect walk, (2) questionnaire interviews, (2) focus group discussions, and (4) key informant interviews (Fig. 2). Multi-method approaches were used for triangulation7 in data collection. Data were collected for a period of six months from July to December 2013. The transect walk method involves developing an understanding of a village and its associated farming and natural resource areas by, as far as is practicable, walking the area in a line. The transect walk is not passively observational; investigators discuss related topics with villagers who accompany them on the walk. As it was difficult to cover the entire study area by walking due to the large distances involved, a motorcycle was often used to cover a cross section along passable roads. The motorcycle stopped every 1e2 km then the investigators proceeded on foot for 20e30 min. At each stop 7e15 people, including shrimp farmers and other community members gathered spontaneously. Approximately 25 discussions were conducted in this stage, involving over 250 people. These discussions provided a broad overview of shrimp farming with potential impacts by climate change. Questionnaire interviews with shrimp farmers were preceded by preparation of a survey and pilot testing of the interview schedule. Shrimp farmers were selected through stratified random sampling based on farming systems (i.e., shrimp alternate rice and

7 Triangulation is a technique that facilitates validation of data by using two or more data collection methods.

Data from questionnaire interviews were coded and entered into a spreadsheet using Microsoft Excel to produce descriptive statistics. The distribution of ranks to evaluate the impacts of climate change on shrimp production were assessed using Kendall's coefficient of concordance, also known as Kendall's W. The measure of Kendall's W range from 0 to 1 and guidelines for interpreting Kendall's W values are: (1) W ¼ 0.1, agreement: very weak, confidence: none; (2) W ¼ 0.3, agreement: weak, confidence: low; (3) W ¼ 0.5, agreement: moderate, confidence: fair; (4) W ¼ 0.7, agreement: strong, confidence: high; and (5) W ¼ 0.9, agreement: usually strong, confidence: very high (Schmidt, 1997). Results from the data analysis, in combination with qualitative information collected by different methods, were used to describe the impacts of climate change on shrimp farming with its socioeconomic effects and ecological consequences. 3. Vulnerability of “white gold” farming All surveyed farmers expressed concern about the effects of different climatic variables on shrimp culture. Based on farmers' opinions, mean ordinal rank indicated that coastal flooding was the most significant climatic variable that affected shrimp farming, followed by cyclone, sea-level rise, salinity, drought, rainfall, and sea surface temperature (Table 2). Farmers believed that all of these climatic variables could severely affect future shrimp production. Kendall's W value was slightly higher for shrimp alternate rice farming (0.56) than for shrimp-only farming (0.51). Survey results suggest that shrimp alternate rice farming is more susceptible to climate change than shrimp-only farming, because of severe effects

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Table 2 Ranking of farmers' opinions for the effects of different climatic variables on shrimp farming. Climatic variable

Shrimp alternate rice (n ¼ 50)a Score

Flood Cyclone Sea-level rise Salinity Drought Rainfall Sea surface temperature a b c

Kendall's W value

Shrimp (n ¼ 50)a Chi-square (c2) value

Score

Kendall's W Value

Mean

SDb

Mean

SDb

4.62 4.54 3.94 3.80 3.40 3.18 2.02

0.60 0.84 0.68 0.57 0.97 0.52 0.62

4.80 4.70 4.16 2.96 2.42 2.30 2.24

0.64 0.71 0.91 0.88 1.01 0.68 0.82

0.56

190.55 (P < 0.0001)

0.51

Chi-square (c2) value

175.16 (P < 0.0001)

Mean ordinal rankc

1 2 3 4 5 6 7

n: sample size of farmers. SD: standard deviation. Based on mean scores of both farming systems.

on both shrimp and rice production. Based on ranking for the effects of different climatic variables, shrimp alternate rice farming faces considerably more risk due to salinity, drought, and rainfall than shrimp-only farming (Fig. 3). Recent changes in these climatic variables have already affected rice production in shrimp farms. Conversely, shrimp-only farming is slightly more susceptible to coastal flooding, cyclone, sea-level rise, and sea surface temperature than shrimp alternate rice farming. The effects of different climatic variables on both farming systems depend on farm locations as well as proximity to the sea. During field visits, it was found that most shrimp-only farms were located near the coast whereas shrimp alternate rice farms were located further inland. 4. Impacts of climatic variables on shrimp farming The impacts of climate change on shrimp farming have been attributed by different climatic variables. The effects of climatic variables on shrimp culture also affect socioeconomic conditions of farming households as their livelihood, income, and food supply mainly depend on shrimp and rice production. Similarly, the effects of climatic variables on farming households also affect shrimp production (Fig. 4). The following sections describe how different climatic variables affect shrimp culture and farming households. 4.1. Flood Shrimp production in the study area is extremely vulnerable to coastal flooding due to the low-lying topography and poor

Fig. 3. Comparative effects of different climatic variables on shrimp alternate rice and shrimp-only farming systems.

protection against tidal surges. All surveyed farmers perceived that coastal flooding is one of the key threats to loss of total or partial harvest, since sudden or prolonged floods often cause physical damage to shrimp farms. Preventing escape of shrimp is very difficult during floods, and farmers are unable to raise their low and narrow dikes. Floods also allow predatory and wild fish entry to shrimp farms, and these fish may also carry diseases and parasites. Water quality of shrimp farms is also affected by coastal flooding due to contamination with land-based pollutants. During field visits, water in shrimp farms was often observed gray or black color with a putrid odor. Poor water quality and presence of toxins often result in shrimp disease (De Silva and Soto, 2009). Farmers reported that black spot, soft shell, tail rot, and white spot to be common shrimp diseases. Coastal flooding often inundates households of shrimp farmers, and thus, they cannot remain involved in shrimp culture. Inundation of farming households may have an impact on health conditions. Climate change has already affected human health in prawn farming communities in southwest Bangladesh (Ahmed, 2013b). According to the survey, family members of shrimp farmers are often exposed to various health diseases, including cholera, diarrhea, dysentery, hepatitis, pneumonia, skin diseases, and mosquitoborne diseases such as dengue fever and malaria. Waterlogged conditions due to coastal flooding boost the population of mosquitoes. Coastal flooding is likely to reduce food consumption by farming households as a result of damaging agricultural crops. Overall, the shrimp farming effort is greatly reduced due to illness and hunger of farming households. 4.2. Cyclone Most surveyed farmers (88%) reported that cyclones with tidal surges often devastated shrimp farms. According to key informants, most cyclones in recent years hit over 80% of shrimp farms in southwest Bangladesh. Cyclones also caused a short-term decline in the abundance of wild postlarvae (Ahmed et al., 2013), and thus, stocking rate. Cyclones destroy roads, communications, and electricity transmission for a period lasting from a week to few weeks. All of these affect shrimp marketing, processing, and exporting. The loss of the shrimp sector in Bangladesh was US$36 million by cyclone Sidr in 2007 (IRIN, 2008). In 2013, cyclone Phailin caused an estimated damage of US$57 million to shrimp farms in the state of Odisha, India (Business Standard, 2013). Shrimp farming communities in Mongla are vulnerable to cyclones because of unaware about weather forecasting and inadequate cyclone shelters. Community people reported that injury, death, damage of crops, and economic loss are the common consequences of cyclones. Cyclones have a devastating effect on

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Fig. 4. Impacts of climatic variables on shrimp culture as well as farming households; dotted lines show the effects of climatic variables on shrimp culture also affect socioeconomic conditions of farming households and vice versa.

housing structure and leave many farmers' homeless every year. Surviving is difficult without houses as women and children are more likely to be exposed to unsafe conditions. The repair of houses is costly as farmers experienced decreasing housing materials, including wood. Thus, farmers increasingly have to collect wood from the Sundarbans, resulting in severe degradation of the mangroves. A number of farmers (32%) are heavily in debt due to lose of household assets as a result of cyclones, and thus, face an uncertain situation for shrimp production. 4.3. Sea-level rise Sea-level rise is likely to have a dramatic impact on low-lying shrimp farms in the study area. Sea-level rise has already increased water depth of a number of shrimp farms. Most farmers (78%) suggested that sea-level rise has affected their ability to trap wild shrimp fry due to reduced abundance in the coastal area. Sealevel rise is likely to have effects on postlarvae fishing by diminishing catch rate (Ahmed et al., 2013). The majority of farmers (72%) reported that total harvesting of shrimp is also a problem due to sea-level rise as they prefer to empty farm water to harvest shrimp. Complete drying of shrimp farms may not be possible due to sealevel rise. Failure to dry shrimp farms results in increase toxicity level and pathogenic bacteria that affect shrimp, and makes them more susceptible to disease (Avnimelech and Ritvo, 2003). Shrimp farming communities in Mongla are subject to sea-level rise that puts them at risk of submerging household resources. Sealevel rise has already submerged agricultural crops as well as grazing land for livestock rearing, and thus, affected food consumption in farming households. A considerable number of farmers (36%) reported that sea-level rise had already reduced their household premises. According to key informants, sea-level rise poses a great threat to human settlement in shrimp farming communities due to displacement from houses. Coastal communities including shrimp farming households will be forced to migrate to inland areas as a result of sea-level rise and they will become

“climate refugees”. However, migration to inland areas is impossible as Bangladesh is one of the most densely populated countries in the world. 4.4. Salinity Although salinity is not a problem for shrimp culture which is a euryhaline species that is able to tolerate 5e40 ppt, increased salinity can lead to change in the physical environment of shrimp farms. The majority of farmers (67%) reported that increased water salinity has increased the prevalence of shrimp disease. The occurrence of shrimp diseases has been linked to fluctuations in salinity and temperature (Kautsky et al., 2000). Salinity could also pose a great threat to rice production. Shrimp alternate rice farmers reported that salinity has decreased rice production by 30%. In spite of environmental constraints, saline water intrusion into rice fields could provide the opportunity for high-value shrimp farming in low saltwater conditions. Low salinity for shrimp culture is commonly practiced in many countries (Flaherty et al., 2000; Roy et al., 2010). Shrimp farming households are sensitive to salinity that may lead to potentially catastrophic difficulties. Homes of shrimp farmers became unstable as a result of saline water intrusion. Food production was significantly reduced because of salinization. Most farming households (82%) suffer from chronic drinking water shortages, because of groundwater salinity. Inadequate access to safe drinking water is considered one of the main reasons for the outbreak of diseases. The effect of drinking water crisis has had particular consequence for women as they have to walk long distances (3e6 km) to procure drinking water. A severe shortage of safe drinking water has resulted in widespread social constraints. 4.5. Drought Drought is one of the foremost environmental limits to shrimp culture as drought events have recently increased in the study area

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due to successive seasons with very low to no rainfall. Most shrimp alternate rice farmers (72%) reported that drought constituted a common threat to rice production. Severe or prolonged droughts often resulted in short culture periods for shrimp and they became more crowded and stressed in low volume of water. Seasonal drought may increase water temperature and salinity that have an adverse effect on shrimp production (DeLorenzo et al., 2009). In April 2014, shrimp farmers in southwest Bangladesh faced extreme drought which destroyed US$25 million worth of shrimp and fish fry (Financial Express, 2014). Drought is one of the most common causes of food shortages in shrimp farming communities. Most farmers (77%) reported that drought reduced the amount of staple food consumption, including rice, fish, vegetables, and fruits. According to key informants, droughts have reduced the coping mechanisms of food insecurity by farming households. The great majority of farmers (84%) reported that drought has adverse impacts on income from shrimp production which in turn affected their ability to purchase food in markets. Moreover, food prices increase as drought has an impact on food supply to coastal markets. Surviving drought has always been hard as severe droughts often cause famine in shrimp farming communities. 4.6. Rainfall Increased rainfall can cause havoc on shrimp culture as it has an adverse effect on stocking of wild postlarvae. The availability of wild postlarvae in coastal Bangladesh is extremely low with heavy rainfall because of the lower concentration of water salinity (Ahmed et al., 2013). The majority of farmers (53%) suggested that water salinity and temperature levels declined due to heavy rainfall, and thus, affected shrimp growth and productivity. Low water salinity with fluctuations of 3e4
C water temperature causes the outbreak of white spot syndrome virus in shrimp (Tendencia and Verreth, 2011). Extreme rainfall often causes physical damage to shrimp farms and farmers lose their crops as shrimp crawl over dikes during huge rain. Shrimp marketing is also a problem during rainy days because of poor road and transportation. Remote coastal areas in shrimp farming communities still face accessibility problems, which in turn affect the quality of shrimp during transportation. Heavy rainfall often reduces working days in shrimp culture by farming households. Farmers also suggested that other household work obligations on rainy days cannot permit them to engage in shrimp production. A few farmers (12%) reported that intense rainfall often lead to mudslides and destroy their household assets. Human mobility in shrimp farming communities was severely affected by huge rainfall as farming households could not move during rainy days. Social interactions and economic activities in shrimp farming communities have also been severely affected by extreme rainfall. 4.7. Sea surface temperature Tidal water temperatures in shrimp farms have increased in recent years as a result of increased sea surface temperature. Changes in water temperature can alter survival, growth, and production of shrimp. Most farmers (63%) reported that shrimp stopped feeding with increased water temperature, and thus, shrimp mortality increased during summer months. According to the survey, seasonal increase in sea water temperature often causes death of shrimp and postlarvae. The availability of wild postlarvae in coastal Bangladesh is lower as a result of increased sea water temperature (Ahmed et al., 2013). Increased water temperature may also increase the possibility of shrimp diseases (Alborali,

2006). Because of increased weather temperatures and heat waves, farmers often feel more dehydrated while working in shrimp farms. Most farmers (71%) reported that dangerously hot weather already occurred more frequently in summer months. According to key informants, global warming is bringing more severe heat waves to coastal communities in southwest Bangladesh. Shrimp farming households, especially women and children could not bear the health risk associated with heat waves. Community people reported that hot weather as well as heat waves cause serious health risks, including heat exhaustion, dehydration, and heat strokes. 5. Ecological effects There is overwhelming evidence that recent climate change has adverse ecological impacts on shrimp farming in the study area. Different climatic variables have profound effects on the ecosystem of shrimp farms. Shrimp is highly sensitive to ecological conditions and changes in ecosystem have severe effects on their growth and production (Table 3). Coastal flooding increases soil erosion that leads to water turbidity in shrimp farms. Turbid floodwater with pollutants decreases light penetration which in turn hinders photosynthesis and reduces dissolved oxygen. According to key informants, the reduction of oxygen below 5 ppm is likely to increase shrimp mortality. Rapid oxygen depletion can results in declining plankton species richness. Ultimately, turbid water with pollutants poses an additional threat to ecological interactions among biotic and abiotic components (Yamanaka et al., 2013). Overall, coastal flooding has severe consequences for the ecosystem of shrimp farms, resulting in an overall loss of shrimp production. The ecosystem of shrimp farms may be irreversibly altered due to cyclones. A huge volume of debris, trash, and dead organisms washes into shrimp farms by cyclones with tidal surges. Farmers reported that dissolved oxygen of shrimp farms sharply declines as a result of decomposition of dead organisms and shrimp become surface layer for gulping due to stress with low oxygen. According to key informants, oil spillage from ships due to cyclones is also a great threat to the ecosystem of shrimp farms. Deteriorating water quality of shrimp farms has detrimental effects on aquatic ecosystems. Changes in sedimentation of shrimp farms by tidal surges may have effects on ecosystem process (Collinge, 2010). Ecological changes in shrimp farms by cyclones ultimately affect growth and production of shrimp. Sea-level rise causes fragile ecosystem of shrimp farms because of accelerating coastal erosion and waterlogged conditions. Ecosystem functions of shrimp farms may be severely affected by sea-level rise that increase carbon dioxide emissions (Harley et al., 2006). Benthic organisms in shrimp farms could be affected by sealevel rise that may have significant impacts on ecosystem functions (Yamanaka et al., 2013). According to key informants, sea-level rise has already affected the ecosystem of the Sundarbans mangrove forest which is an important breeding habitat for shrimp. Changes in mangrove ecosystem may shift breeding season and success of breeding for shrimp, thus reducing availability of wild postlarvae (Ahmed et al., 2013). Increased salinity has an adverse impact on the ecosystem of shrimp farms. Farmers reported that increased salinity has reduced the availability of aquatic flora and fauna in shrimp farms, including birds, crabs, fish, frogs, mollusks, snails, and turtles. Reducing frogs has an adverse impact on shrimp alternate rice farming ecosystems as frogs consume insects and pests in rice fields (Castellano et al., 2007). According to key informants, increased salinity is a slow poisoning aquatic organism. The ecosystem of shrimp farms is becoming increasingly threatened by the loss of aquatic

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Table 3 Ecological effects and consequences of shrimp farming by climatic variables. Climatic variable (in order to rank) Flood

Cyclone

Sea-level rise

Salinity

Drought

Rainfall

Water temperature

Effect on ecosystem                     

Soil erosion, turbidity, poor water quality Hinder photosynthesis, reduce dissolved O2, and decline plankton availability Destruction of ecological interactions Sedimentation, decomposition of dead organisms, and oil spill Decline dissolved O2 Affect ecosystem processes Erosion and waterlogged conditions of shrimp farms Affect benthic organisms, increase CO2 Reduce ecosystem functions Loss of aquatic biodiversity Imbalance ecosystem in shrimp farms Reduce ecosystem services Reduce water level and plankton availability Decline photosynthesis, temperate ecosystems with carbon source Reduce ecosystem functions Water turbidity, reduce photosynthesis, limits primary productivity Low water pH Adverse ecological effects Stratification of water, less primary productivity, reduce dissolved O2 Less nutrient enrichment, increase toxicity Reduce ecosystem functions

Impact on shrimp

      

Reduce availability of wild postlarvae Mortality of shrimp fry Stress in shrimp Affect feeding of shrimp Concern of shrimp health Growth failure of shrimp Affect shrimp production

Source: Field survey (2013).

biodiversity which plays an important role in maintaining ecosystem services and resilience to climate change (Brander, 2007). Drought has severe consequences for the ecosystem of shrimp farms as drought reduces water levels, and thus, reduces plankton availability. Farmers reported that droughts reduced water levels in shrimp farms along with reduced the growth of aquatic plants. A major drought effect is the reduction of photosynthesis that can have impacts on carbon balance in ecosystem (Rocha and Goulden, 2010). Reduction in primary productivity caused by drought could turn temperate ecosystems into carbon sources (Ciais et al., 2005). According to key informants, drought increased the concentration of waste metabolites (ammonia, carbon dioxide, and nitrites) that can irreversibly alter the ecosystem of shrimp farms, and thus, affect growth and production of shrimp. The impacts of rainfall variation in the ecosystem of shrimp farms are becoming increasingly apparent. Heavy rainfall can cause water turbidity that may have detrimental effects on the ecosystem of shrimp farms. Water turbidity reduces sunlight penetration into water that inhibits oxygen production by reducing photosynthesis and limits primary productivity (Short and Neckles, 1999). According to key informants, intense rainfall can cause lower water pH in shrimp farms that may have adverse ecological effects as water with pH ranging from 7.5 to 9 (alkaline) is suitable for shrimp farming. Changes in water temperature may provoke multiple effects which evolve ecosystem functioning of shrimp farms. According to the survey, increased water temperature may reduce dissolved oxygen level and increase toxicity of shrimp farms that could affect ecosystem functions and lead to growth failure of shrimp. Changes in water temperature often cause stratification and less nutrient enrichment to surface waters, thus less primary productivity (Harley et al., 2006). Global warming and increased stratification of water likely lead to declines in dissolved oxygen with changes in biogeochemical cycle (Keeling et al., 2010), and thus, affect the ecosystem of shrimp farms. In summary, climate change has severe impacts on ecosystem functions in shrimp farms. Environmental parameters in shrimp farming ecosystems alter greatly due to changes in climatic variables (Fig. 5). Overall, changes in ecosystem functions of shrimp farms have severe impacts on ecosystem services (i.e., growth,

production). 6. Adaptation strategies With regard to climate change, there is a challenge to the sustainability of shrimp farming. A holistic adaptation planning may help to reduce the impacts of climate change on shrimp production. Considering extreme vulnerability to the effects of climate change on shrimp culture, community based adaptation strategies and integrated coastal zone management can be implemented (Table 4). 6.1. Community based adaptation (CBA) strategies Various CBA strategies have been suggested by our field survey for shrimp farming in changing climate. The construction of earthen dams may help to protect shrimp farms. Moreover, embankments could help to protect inundation in shrimp farming communities. Fencing and netting around shrimp farms may also keep shrimp from escaping as well as predator and wild fish from entering during flood. The construction of higher dikes around shrimp farms is also a key strategy for flood management. Community based irrigation facilities with proper drainage systems may also help for rice and shrimp cultivation in the dry season. A community based integrated system for culture of prawn, shrimp, and fish could be incorporated to cope with saltwater intrusion into rice fields (Ahmed, 2013a). CBA strategies have been suggested for integrated prawn-fish-rice farming in southwest Bangladesh to promote social-ecological resilience (Ahmed et al., 2014). Moreover, the introduction of salt-tolerant and drought-resistant rice varieties may substantially increase rice production. Dike cropping including fruits (e.g., banana, coconut, guava, lemon, and papaya) and vegetables (e.g., bean, cucumber, and gourd) plantation can help to protect shrimp farms from soil erosion. Moreover, community based social forestry through plantation of trees in shrimp farming communities may help to reduce cyclonic effects. Community awareness and preparedness for disaster management is also important, including broadcasting of weather forecast by radios, human mobility, and their shelters may help to protect lives and properties in shrimp farming communities. In order to effective CBA strategies, capacity building of local

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Fig. 5. Impacts of climate change on the ecosystem of a shrimp farm.

Table 4 Adaptation and management strategies to climate change for shrimp culture. Strategies

Elements

Community based adaptation

           

Integrated coastal zone management

Construction of earthen dams to protect shrimp farms Netting, fencing, and higher dikes around shrimp farms Develop water irrigation facilities with proper drainage systems Culture of prawn, shrimp, and fish with salt-tolerant and drought-resistant rice varieties Dike cropping (fruits and vegetables) and social forestation Community awareness and preparedness for disaster management (weather forecast, shelters) Construction of coastal embankments Afforestation of greenbelt in shrimp farming communities Mangrove plantation and conservation of the Sundarbans Maintaining ecosystems of the Sundarbans for breeding grounds of shrimp Protection from water pollution, sedimentation, erosion, and oil spill by precautions Preparedness for disaster management (disaster warning, cyclone shelters)

Source: Field survey (2013).

people with their empowerment is needed (Fig. 6). Active involvement of local institutions with relevant stakeholders, including community members, NGOs, government agencies, and community based organizations may help capacity development to implement CBA strategies. Strong collaboration among these stakeholders will provide empowerment of local communities for accomplishment of CBA strategies. 6.2. Integrated coastal zone management (ICZM) Field survey reveals an ICZM is needed for sustainable shrimp farming in the context of climate change. The construction of large coastal embankments would help to reduce the effects of cyclones

and sea-level rise in shrimp farming communities. Afforestation of greenbelt and mangrove plantation would also help to increase resilience to climate change. Mangroves are significant in protecting coastal flooding, cyclones, and shoreline erosion (Alongi, 2008; Duarte et al., 2013). Moreover, mangrove plantation has been instrumental in maintaining ecosystems of the Sundarbans as well as breeding grounds of shrimp. Mangrove rehabilitation would also help to reduce environmental degradation as shrimp culture has criticized for devastating effects on mangrove forest. It is also necessary to protect from water pollution, sedimentation, erosion, and oil spillage from ships. The construction of adequate cyclone shelters with comprehensive disaster management plan may reduce the vulnerability of climate change in shrimp farming

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Fig. 6. A conceptual framework to implement CBA strategies and ICZM for sustainable shrimp farming in the context of climate change where interactions among CBA strategies, ICZM, and institutional support are highlighted towards empowerment of local communities, capacity building, and disaster management.

communities. In order to effective ICZM, however, institutional support including coordination among government organizations, NGOs, community based organizations, and local communities are essential for disaster management (Fig. 6). 7. Conclusions The evidence of this study confirmed that climate change has severe impacts on “white gold” farming under shrimp alternate rice and shrimp-only farming systems in the Mongla area of southwest Bangladesh. Both farming systems have been threatened by different climatic variables, including coastal flooding, cyclone, sealevel rise, salinity, drought, rainfall, and sea surface temperature. All of these climatic variables have devastating effects on shrimp and rice farming although shrimp alternate rice farming is more susceptible to climate change than shrimp-only farming, because of severe effects on rice production. Different climatic variables have severely affected socioeconomic conditions of farming households. There is also overwhelming evidence that different climatic variables has profound effects on the ecosystem of shrimp farms, and thus, affect survival, growth, and production of shrimp. Future climate change would have severe consequences for shrimp farming in southwest Bangladesh. In order to sustain shrimp farming with climate change, an integrated approach needs to be introduced to cope with the challenges. It has been suggested that CBA strategies and ICZM can be formulated to cope with the effects of climate change on shrimp farming. In order to implement CBA strategies and ICZM, however, institutional support from government is needed for capacity building and empowerment of local communities towards disaster management. Strong collaboration among stakeholders, including government, NGOs, community based organizations, and shrimp farming communities would help to implement CBA strategies as well as ICZM. Overall, institutional support, training facilities, technical assistance, and collaboration among stakeholders would greatly help to reduce the effects of climate change on shrimp farming communities. Further research is also needed to understand better adaptation strategies in respect to technical, environmental, and socio-cultural dimensions of shrimp farming in coastal Bangladesh.

Acknowledgments The study was supported through the Fulbright Fellowship by the J. William Fulbright Foreign Scholarship Board of the U.S. Government. The study was a part of the first author's research work under the Fulbright Fellowship Program at the School of Natural Resources and Environment (SNRE), University of Michigan, USA. Earlier draft of this paper was presented in Fall 2014 at the SNRE Hooper Aquatic Seminar Series, University of Michigan. We thank audience for their encouragement. Thanks to two anonymous reviewers for their helpful comments. The views and opinions expressed herein are solely those of the authors.

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