Journal of Food Quality
Volume 2017 (2017), Article ID 2045157, 23 pages
https://doi.org/10.1155/2017/2045157

Research Article

Effect of Salinity Intrusion on Food Crops, Livestock, and Fish Species at Kalapara Coastal Belt in Bangladesh

Mohammad Zahangeer Alam,¹ Lynne Carpenter-Boggs,² Shishir Mitra,¹ Md. Manjurul Haque,¹ Joan Halsey,³ M. Rokonuzzaman,⁴ Badhan Saha,⁵ and M. Moniruzzaman⁵

¹Department of Environmental Science, Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU), Gazipur 1706, Bangladesh
²Department of Crop and Soil Sciences, Washington State University, Pullman, WA 99164-6420, USA
³Washington State University, Pullman, WA 99164-3615, USA
⁴Department of Agricultural Extension and Rural Development, BSMRAU, Gazipur 1706, Bangladesh
⁵Soil and Environment Section, Biological Research Division, Bangladesh Council of Scientific and Industrial Research (BCSIR) Laboratories, Dhaka, Bangladesh

Correspondence should be addressed to Mohammad Zahangeer Alam; mohammad.alam@wsu.edu

Received 8 April 2017; Revised 11 July 2017; Accepted 7 August 2017; Published 27 September 2017

Academic Editor: Jesús Lozano

Copyright © 2017 Mohammad Zahangeer Alam et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

Salinity has caused significant negative effects on agricultural production. This research is focused on the vulnerabilities of soil and water salinities on crop, fish, and livestock production across the Kalapara coastal belt of Bangladesh. Several parameters were measured as indicators of salinity. The electrical conductivity of water was found to be significant with TDS, F⁻, Cl⁻, , Na⁺, K⁺, Ca²⁺, Mg²⁺, , and . Chloride was found to be identical with , Na⁺, K⁺, Ca²⁺, Mg²⁺, Br⁻, and . Electrical conductivity, F⁻, Cl⁻, , Na⁺, K⁺, and Mg²⁺ were all found to be higher than the recommended values. Similarly, soil conductivity was found significant with TDS, Cl⁻, , Na⁺, F⁻, , , and . Chloride in soil samples was found statistically identical with , Na⁺, , and . About 200 ha fodder crops areas are affected each year due to salinity. Ninety-two percent of the areas were found to be salinity affected in the 36 current cropping patterns. Twelve percent of marine fish and 25 percent of shrimp species have disappeared as a result of salinity. The negative impact of soil and water salinity on crops, fish, and livestock has been increasing in this coastal belt.

1. Introduction

Salinity intrusion is one of the major environmental issues throughout the world [1]. Bangladesh is a growing and developing country. This development is dependent on an agricultural production system which in turn brings economic visibility throughout the world. Salinity issues constrain both the agricultural and economic development. Salinity causes a hostile environment for the normal crop production throughout the year in the coastal belt of Bangladesh. The organic matter content of the coastal soils is pretty low (1.0–1.5%). Nutrient deficiencies of N and P are quite common in saline soils. Micronutrients such as Cu and Zn are both widespread. As a result, the reduction of food crop production in the coastal region has significant impact on the national economy of Bangladesh [2]. This threat is elevated because of the reduction of fresh water flow from upstream tidal flow and groundwater discharge [3]. The coastal belt of Bangladesh consists of 19 districts, which cover 32% of the country and accommodate more than 35 million people [4]. During 1973, salinity affected 83.3 million hectares of land; this was increased to 102 million hectares by the year 2000. After that, salinity affected a recorded 105.6 million hectares during 2009 [5]. Among these affected areas, around 2.5 million hectares of low-lying coastal lands represents 0.9 to 2.1 salinity level (SL) in Bangladesh [2, 6]. Over the last 35 years, salinity has increased around 26 percent in the coastal region of Bangladesh [7].

The Kalapara coastal belt is one of the nearest areas to the Bay of Bengal in Bangladesh. This bay is one of the greatest sources of saline water. The electrical conductivity is an indicator of this saline water [8]. This conductivity increases the salt in soil and water across the coastal belt in Bangladesh. This salt water from the Bay of Bengal increases many ions in the soil and water in this coastal region such as chloride (Cl⁻), sulfate (), sodium (Na⁺), potassium (K⁺), calcium (Ca²⁺), magnesium (Mg²⁺), bromide (Br⁻), phosphate (), nitrite (), nitrate (), and sulfate (). More than 99% of these ions are found in the sea water throughout the world [8]. The adverse impact of this saltwater intrusion is higher in this coastal belt than in any other part of Bangladesh. As a consequence of tropical cyclones, salinity intrusion has been gradually extended toward the inland water and soil [7]. Due to increasing soil and water salinity, people in the communities of the Kalapara coastal regions have been suffering from a scarcity of safe water for the production of crops, fish, and livestock [9]. As a result, soil and water salinity are considered a major constraint to agricultural production and diversity of fish in the coastal areas of this country [9, 10].

Agricultural production has contributed 21% of the national GDP of Bangladesh [14]. The majority of people living in the coastal community are dependent on the agricultural production of crops, fish, and livestock. Several climatic factors such as temperature, wind speed, and rainfall in the coastal zone are favorable for a wide range of food crops [15]. For example, cereals, pulses, vegetables, fruits, and cash crops have been cultivated successfully for many decades [16]. For this reason, planning for cropping patterns with the selection of appropriate varieties that have salinity tolerance is necessary for the local environment [17]. For instance, monsoon season (June to October) is favorable for the cultivation of crops due to the low salinity intrusion [18]. However, as soil salinity increases each year, dry season (November and May) is only favorable for the cultivation of Rabi (December–February) crops. In fact, dry-season agriculture is particularly difficult in Bangladesh due to high salt stress across the coastal belt. For this reason, crop production has been negatively affected each year for many decades across the coastal belt of Bangladesh [19].

Surface water and groundwater are both connected to major rivers along the coastal belt through various estuaries and water inlets [20, 21]. These sources of water are contaminated by salinity which is influenced by rainfall, river flows, upstream withdrawal of water, and sea level rising [22]. Since 1948, salinity of rivers in the southern districts of Patuakhali, Pirojpur, Barguna, Satkhira, Bagerhat, and Khulna has risen by 45% [23]. However, coastal people of Bangladesh rely heavily on rivers for fish, tube wells (groundwater), and ponds for washing, bathing, and drinking [24]. Also, domestic ponds cover 10% of the total land area which is mixed with saline water from rivers, soil runoff, and shallow groundwater [22]. Approximately 20 million people are affected by unpredictable degrees of salinity in the water along the coastal region of Bangladesh [25].

Due to increased salinity there is a shortage of grazing land and fodder crops for livestock production. Because of this, communities must utilize other natural resources to make up for the lack of protein from livestock. This shortage of milk and cattle in the coastal areas is also documented in other studies [26]. The reduced ability for cattle-raising in Bangladesh has had serious economic and nutritional consequences, especially for the children [27]. However, people have also converted fresh water areas through intrusion of saline water for shrimp culture, increasing the salinity in the surrounding areas and damaging the grazing areas of livestock. These kinds of agrobiodiversity changes have caused reduced frequency of consumption of livestock, crops, and fish across the coastal belt in Bangladesh. These changes in food habits might also lead to considerable negative consequences for agricultural production systems for the rural populations across the coastal belt of Bangladesh [28].

In addition, saline water has been increasing across the coastal belt due to the intensity of cyclones in Bangladesh. This saline water has many connections with fresh water bodies across the coastal belt. It leads to changes in the trophic structure and diversity of shallow fresh water bodies such as increased strength of trophic interactions. As a result, saline water fish are mixed with fresh water species. Because of this, the intrusion of saline water in different fresh water bodies has played a significant role in the disappearance of some fish species [29].

There are not currently any established guidelines for salinity levels in agricultural production systems in Bangladesh [30]. High salinity levels might have numerous direct and indirect impacts on crops, livestock, and fish. Due to the connectivity of agricultural products with human livelihood, greater levels of gestational hypertension were found in pregnant women in the southwestern coast of Bangladesh, compared with noncoastal pregnant women. This was hypothesized to be caused by saline water and agricultural crops [31, 32]. In this situation, management of salinity intrusion is the vital issue for Bangladesh. However, salinity in the water and soil may be reduced in ways such as coastal embankment projects, construction of dam and sluices, zoning of coastal salinity areas, a plantation program, selection of salinity tolerance cultivars, and public awareness programs that can contribute to the mission toward sustainable livelihood in the coastal region of Bangladesh [10]. This study documents the current status of soil and water salinities across the coastal belt and their possible impacts on agriculture. It is hypothesized that regular monitoring of soil and water salinity levels will be of significant help in the protection of crops, fisheries, and livestock along the coastal belt of Bangladesh.

2. Materials and Methods

2.1. Description of Study Areas

Kalapara Upazila is the most salinity prone area in the southwestern part of Bangladesh. It is adjacent to the Amtali Upazila of Barguna district on the north, the Bay of Bengal on the south, and Rabnabad channel and Galachipa Upazila on the east. The total area of Kalapara Upazila is 491 square kilometers and the population is 238,000 [33]. Water samples were collected from 12 locations of the Kalapara coastal belt. These areas are Ander manik river, Shibbaria river, Badurtoli Canal, Char Gangamoti (Beach area), Kuakata beach (left), Kuakata beach (right), Char Gangamoti Mangrove, Sonatula River, ShantiBagh Canal, Paira river, Kalapara town pond, and Kalapara town tube well water. Soil samples were also collected from Mustafapur nilgonj, Char Gangamoti (Beach area), Kuakata beach (left), Kuakata beach (right), Char Gangamoti Mangrove, and Niamatpur areas of Kalapara coastal belt of Bangladesh. Geographical Positioning System (GPS) of study areas is shown in Table 1. The study area on a Bangladesh map and sampling locations of these study areas are highlighted in Figures 1 and 2, respectively.

Table 1: Geographical position for water and soil sampling study areas across the coastal belt.

Samples
Locations
Latitude
Longitude

Water
Ander manik river
21°53.67933′
90°8.36508′

Shibbaria river
21°51.26377′
90°7.52335′

Badurtoli Canal
21°54.66933′
90°8.36548′

Char Gangamoti (beach area)
21°48.24381′
90°12.23918′

Kuakata beach (left)
21°48.81624′
90°7.30991′

Kuakata beach (right)
21°48.81645′
90°7.30976′

Char Gangamoti Mangrove
21°49.24878′
90°12.7492′

Sonatula River
21°53.67948′
90°8.36345′

ShantiBagh Canal
21°53.3578′
90°8.4617′

Paira river
22°27.79685′
90°20.47599′

Kalapara town pond
21°53.3569′
90°8.8653′

Kalapara town tube well water
21°53.4689′
90°8.8952′

Soil
Mustafapur Nilgonj
21°56.07547′
90°9.912′

Char Gangamoti (beach area)
21°48.43599′
90°12.3969′

Kuakata beach (left)
21°48.81624′
90°7.30991′

Kuakata beach (right)
21°48.81645′
90°7.30976′

Char Gangamoti Mangrove
21°49.24878′
90°12.7492′

Niamatpur
21°57.92477′
90°11.97595′

Figure 1: Study area on a Bangladesh map.

Figure 2: Sampling locations in the study area.

2.2. Inception Meeting

An inception meeting was arranged at the Department of Agricultural Extension (DAE) in the Kalapara Upazila area of the coastal belt for 3 days. This meeting was conducted with government officials, fishermen, visitors, and farmers who have been living in the Kalapara Upazila area. This meeting was conducted to discuss the soil and water salinities and their possible effects on crops, fish, and livestock. During this meeting, participants contributed their unique perspectives regarding soil and water salinity and the possible impacts upon crops, livestock, and fish. Based on this meeting, we were able to identify the major areas affected by salinity at Kalapara coastal belt for the collection of soil and water samples.

2.3. Collection of Water Samples

Water samples were collected randomly with different salinities along the coastal belt at Kalapara Upazila for analysis of salinity indicators in 2016. Distance of each collected water sample for a location was 50 meters; three collected water samples were mixed together for making a sample for each location. Samples were collected in 100–500 ml polyethylene plastic bottles. Each bottle was cleaned thoroughly by rinsing with diluted HCl followed by washing with distilled water [34]. The water samples were filtered with Whatman 42 to remove suspended solids. Prepared sample solutions were sealed immediately to minimize exposure to air, and collected samples were carried to the Laboratory of Environmental Science of BSMRAU and Bangladesh Council of Scientific and Industrial Research (BCSIR) in Dhaka for analysis of dissolved ions and other water quality constituents. All of the collected water samples were kept at 4°C refrigerator temperature before the analysis of the chemical parameters was completed.

2.4. Collection of Soil Samples

Soil samples were collected from different areas affected by salinity on the coastal belt at Kalapara Upazila for the analysis of chemical properties. Soil samples were collected by Auger from different locations randomly. Distance of each collected soil sample was about 15 meters for a location; four collected soil samples were mixed together for making a sample for each location. All collected samples were kept in polyethylene zip lock bags through proper marking. Then samples were carried into the Laboratory of Environmental Science at Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU) and Bangladesh Council of Scientific and Industrial Research (BCSIR) in Dhaka for analysis of chemical properties. All soil samples were preserved at room temperature in the laboratory before the analysis of the chemical parameters was completed.

2.5. Determination of Water Chemical Properties

Water pH was determined with a glass electrode pH meter (Model: Metrohm 906 Titrande) [35]. The electrical conductivity (EC) was analyzed during sample collection with a conductivity meter (Model: HANNA HI-8633) [35]. Total dissolved solids (TDS) were determined with a TDS meter (Model: HACH SensION 156) [36]. The salinity was measured with a salinity meter (Model: HACH SensION 156) [36].

Anions like fluoride (F⁻), chloride (Cl⁻), nitrite (), bromide (Br⁻), nitrate (), phosphate (), and sulfate () were determined by ion chromatography (Model: Dionex ICS-1600) followed by APHA 4110 method [37]. Sodium (Na⁺) and potassium (K⁺) of water samples were determined by flame emission spectrophotometry (Model: Jenway, PFP7) at 589 nm and 769 nm wavelength, respectively [35]. Calcium (Ca²⁺) and magnesium (Mg²⁺) in water samples were determined with an atomic absorption spectrophotometer (AAS) (Model: AA-7000, Shimadzu) followed by APHA 3111, which was calibrated using certified reference materials (CRMs) [37] (Table 2).

Table 2: Methods for the determination of salinity indicators in soil and water samples across the Kalapara coastal belt in Bangladesh.

Samples
Chemical properties
Methods/instrument for chemical analysis

Water
Salinity %
Salinity meter (Model: HACH SensION 156)

Conductivity (µS/cm)
Conductivity meter (Model: HANNA HI-8633)

TDS, mg/l
TDS meter (Model: HACH SensION 156)

pH
Glass electrode pH meter (Model: Metrohm 906 Titrande)

Fluoride (F⁻), mg/l
Ion chromatography (Model: Dionex ICS-1600)

Chloride (Cl⁻), mg/l
Ion chromatography (Model: Dionex ICS-1600)

Nitrite (), mg/l
Ion chromatography (Model: Dionex ICS-1600)

Bromide (Br⁻), mg/l
Ion chromatography (Model: Dionex ICS-1600)

Nitrate (), mg/l
Ion chromatography (Model: Dionex ICS-1600)

Phosphate (), mg/l
Ion chromatography (Model: Dionex ICS-1600)

Sulfate (), mg/l
Ion chromatography (Model: Dionex ICS-1600)

Sodium (Na⁺), mg/l
Flame emission spectrophotometry (Model: Jenway, PFP7)

Potassium (K⁺), mg/l
Flame emission spectrophotometry (Model: Jenway, PFP7)

Calcium (Ca²⁺), mg/l
Atomic Absorption Spectrophotometer (AAS) (Model: AA-7000, Shimadzu)

Magnesium (Mg²⁺), mg/l
Atomic Absorption Spectrophotometer (AAS) (Model: AA-7000, Shimadzu)

Soil
pH
Glass electrode pH meter

TDS, g/kg
TDS meter

Conductivity (mS/cm)
Conductivity meter (Model: HACH SensION 156)

Salinity %
Salinity meter (Model: DDSJ-308A)

Fluoride (F⁻), mg/kg
Ion chromatography (Model: Dionex ICS-1600)

Chloride (Cl⁻), mg/kg
Ion chromatography (Model: Dionex ICS-1600)

Nitrite (), mg/kg
Ion chromatography (Model: Dionex ICS-1600)

Bromide (Br⁻), mg/kg
Ion chromatography (Model: Dionex ICS-1600)

Nitrate (), mg/kg
Ion chromatography (Model: Dionex ICS-1600)

Phosphate (), mg/kg
Vanadomolybdophosphoric yellow color method

Sulfate (), mg/kg
Turbidimetric method

Sodium (Na⁺), mg/kg
Flame emission spectrophotometer (Model: Jenway, PFP7)

Potassium (K⁺), mg/kg
Flame emission spectrophotometer (Model: Jenway, PFP7)

Calcium (Ca²⁺), mg/kg
Atomic Absorption Spectrophotometer (Model: AA-7000, Shimadzu)

Magnesium (mg²⁺), mg/kg
Atomic Absorption Spectrophotometer (Model: AA-7000, Shimadzu)

2.6. Detection of Soil Chemical Properties

Soil pH was analyzed with a glass electrode pH meter [35]. The electrical conductivity (EC) was examined with a conductivity meter (Model: HACH SensION 156) [38]. Total dissolved solids (TDS) were detected with a TDS meter [38]. The salinity was measured with a salinity meter (Model: DDSJ-308A) [36]. The chloride (Cl⁻), bromide (Br⁻), fluoride (F⁻), nitrite (), and nitrate () were determined by ion chromatography (Model: Dionex ICS-1600) followed by APHA 4110 method [37]. Sodium (Na⁺) and potassium (K⁺) of soil samples were determined with the flame emission spectrophotometer (Model: Jenway, PFP7) at 589 nm and 769 nm wavelength, respectively [35]. The sulfate () content of soil samples was determined by turbidimetric method [39]. Phosphate () content of the soil samples was determined by vanadomolybdophosphoric yellow color method [35]. Calcium (Ca²⁺) and magnesium (Mg²⁺) in soil samples were determined by an atomic absorption spectrophotometer using certified reference material (CRMs) [38] (Table 2).

2.7. Quality Control

Quality control (QC) monitors reagent quality, apparatus cleaning, and accuracy and precision of methods and instrumentation and reliability were implemented daily in the laboratory. Under this QC, blank analysis, replication, internal standard, and certified reference materials were followed properly for each collected soil and water sample for the measurement of salinity indicators. During ion analysis, standard curve was prepared for each single anion at three points of concentration using certified reference material. For every five samples, a reference sample and spiked sample were included to ensure the QC. Ion chromatography, flame photometer, and atomic absorption spectrophotometer were calibrated for every six months and methods of analysis were validated by Bangladesh Accreditation Board (BAB) as per ISO/IEC 17025. All quality assurance was maintained according to the proposed guidelines of American Public Health Association (APHA) [40], National Association of Testing Authorities (NATA) [41], and National Environment Protection Measure (NEPM) [42]. According to their guidelines, several QC parameters are highlighted in Tables 3 and 4.

Table 3: Description of quality control (QC) for the determination of salinity indicators in water samples across the Kalapara coastal belt in Bangladesh.

Salinity indicators in water
Container
Volume (ml)
Sampling and transport
Preservation
Maximum holding time
Storage
Remarks

Salinity %
Polyethylene plastic bottle
500 ml
Filled bottle to exclude air
—
Determined on the sampling locations
Analyzed immediately
The meter was calibrated on the day of use

Conductivity (µS/cm)
Polyethylene plastic bottle
500 ml
Filled bottle to exclude air
—
Determined on the sampling locations
Analyzed immediately
The meter was calibrated on the day of use

TDS, mg/l
Polyethylene plastic bottle
500 ml
Transported under ice and filled container to exclude air
—
Held for 7 days before analysis
Stored in refrigerator at 4°C
Total dissolved solids (TDS) also known as “filterable residues”

pH
Polyethylene plastic bottle
100 ml
Filled bottle to exclude air
—
Determined on the sampling locations
There was no storage in refrigerator
The meter was calibrated on the day of use

Fluoride (F⁻), mg/l
Polyethylene plastic bottle
500 ml
Not maintained
—
7 days
—
—

Chloride (Cl⁻), mg/l
Polyethylene plastic bottle
500 ml
Transported under ice and filled container to exclude air
—
Analyzed on that day
Stored in ice box at 4°C
—

Nitrite (), mg/l
Polyethylene plastic bottle
200 ml
Transported under ice
—
2 days
Stored in refrigerator at 4°C
—

Bromide (Br⁻), mg/l
Polyethylene plastic bottle
500 ml
Transported under ice
—
Analyzed within 7 days
Stored in refrigerator at 4°C
—

Nitrate (), mg/l
Polyethylene plastic bottle
500 ml
Transported under ice
Acidified with HCl to pH < 2
7 days with acidification
Stored in refrigerator at 4°C

Phosphate (), mg/l
Polyethylene plastic bottle
300 ml
Filled bottle to exclude air. Filtered on site (0.45 μm cellulose acetate membrane filter). Transported under ice
—
2 days
Freezed (−20°C) after filtration
—

Sulfate (), mg/l
Polyethylene plastic bottle
100 ml
Filled bottle to exclude air. Transported under ice
—
7 days
Stored in refrigerator at 4°C
—

Sodium (Na⁺), mg/l
Polyethylene plastic bottle
500 ml
Filled container completely to exclude air. Transported under ice
Acidified with nitric acid to pH < 2
Analyzed within 1 month
Stored in refrigerator at 4°C
Acidified for the determination of other metals in the sample

Potassium (K⁺), mg/l
Polyethylene plastic bottle
500 ml
Filled container completely to exclude air. Transported under ice
Acidified with nitric acid to pH < 2
Analyzed within 1 month
Stored in refrigerator at 4°C
Acidified for the determination of other metals in the sample

Calcium (Ca²⁺), mg/l
Polyethylene plastic bottle
500 ml
Filled container completely to exclude air. Transported under ice
Acidified with nitric acid to pH < 2
Analyzed within 1 month
Stored in refrigerator at 4°C
Acidified for the determination of other metals in the sample

Magnesium (Mg²⁺), mg/l
Polyethylene plastic bottle
500 ml
Filled container completely to exclude air. Transported under ice
Acidified with nitric acid to pH < 2
Analyzed within 1 month
Stored in refrigerator at 4°C
Acidified

Table 4: Description of quality control (QC) for the determination of salinity indicators in soil samples across the Kalapara coastal belt in Bangladesh.

Chemical properties
Container
Sampling & transport
Maximum holding time
Storage
Comments

Salinity %
Conductivity (mS/cm)
TDS, g/kg
pH
Fluoride (F⁻), mg/kg
Chloride (Cl⁻), mg/kg
Nitrite (), mg/kg
Bromide (Br⁻), mg/kg
Nitrate (), mg/kg
Phosphate (), mg/kg
Sulfate (), mg/kg
Sodium (Na⁺), mg/kg
Potassium (K⁺), mg/kg
Calcium (Ca²⁺), mg/kg
Magnesium (Mg²⁺), mg/kg
Polyethylene zip lock bag
Transported under ice box
7 days
Stored in refrigerator at 4°C
Field moist or air dried soil

2.8. Data Collection regarding Salinity Affected Cropping and Livestock’s Grazing Areas

Based on the inception meeting, data on salinity affected cropping areas was collected from the Department of Agricultural Extension (DAE) at Kalapara Upazila. Information regarding salinity intrusion on cropping patterns was also gathered from these studies. This data was verified in the discussion with a group of 25 farmers from different cropping areas at Kalapara Upazila with the help of DAE personnel. On the other hand, data pertaining to salinity affected fodder crops for livestock production was collected from the Department of Livestock Services (DLS) at Kalapara Upazila. Similarly, this information was also justified by discussions with the affected livestock farmers from the coastal belt of Kalapara (Tables 8 and 9).

2.9. Information regarding Fish Biodiversity

Based on the inception meeting, information regarding the number of salinity affected fresh water bodies was noted from the Department of Fisheries (DOF) at Kalapara Upazila. Based on the primary information from DoF, we interviewed a group of people who have been living in the surrounding areas of each of the affected water bodies to get data regarding visible, threatened, endangered, and extinct fish species. We interviewed 50 people from each location; among these, an average of 10–12 were women and the rest were men. They were on average 40–60 years old. The interviewees were involved in diverse professions such as fishing, boating, farming, government officials, and researchers. All recorded information regarding the current status of biological diversity of fish is presented in Tables 10 and 11.

2.10. Statistical Analysis

Soil and water quality constituents were analyzed through Pearson correlation coefficient using “R” Software, version 3.2.2 (R Foundation for Statistical Computing, Vienna, Austria). Significant levels of correlation between soil and water quality parameters were analyzed for the validation of the data using “R” Software, version 3.2.2 (R Foundation for Statistical Computing, Vienna, Austria).

3. Results

3.1. Chemical Properties of Water

The percentage of salinity in water was significantly correlated with conductivity, total dissolved solid (TDS), chloride (Cl⁻), sulfate (), sodium (Na⁺), potassium (K⁺), calcium (Ca²⁺), magnesium (Mg²⁺) (), bromide (Br⁻) (), and phosphate () (). The conductivity was found statistically significant with TDS, F⁻, Cl⁻, , Na⁺, K⁺, Ca²⁺, Mg²⁺ (), (), and (). Water pH was correlated with F⁻ (). Similarly, chloride was found statistically identical with , Na⁺, K⁺, Ca²⁺, Mg²⁺ (), Br⁻ (), and (). The bromide (Br⁻) was positively correlated with , Na⁺, Ca²⁺ (), and Mg²⁺ (). The phosphate () was found to have significant correlation with , Na⁺, K⁺, Ca²⁺, and Mg²⁺ (). The sulfate was found to have a significant relationship with Na⁺, K⁺, Ca²⁺, and Mg²⁺ (). Sodium was also significantly different from K⁺, Ca²⁺, and Mg²⁺ (). Potassium was positively correlated with Ca²⁺ and Mg²⁺ (). Calcium was found significantly different from Mg²⁺ (). Several chemical properties of water samples such as conductivity (322.9 μS/cm), F⁻ (3.65), Cl⁻ (5037.60), (557.34), Na⁺ (5184.94), Mg⁺ (38.50), and K⁺ (78.89) (mg/l) were found to be higher than the recommended values of conductivity (300 μS/cm), F⁻ (1-2), Cl⁻ (150–600), (250–400), Na⁺ (200), Mg⁺ (30–35), and K⁺ (12) mg/l (Tables 5 and 7).

Table 5: Correlation coefficient and level of significance between salinity indicators of water samples at Kalapara coastal belt.

Parameters
Salinity
Conductivity
TDS
pH
Fluoride (F⁻)
Chloride (Cl⁻)
Nitrite ()
Bromide (Br⁻)
Nitrate ()
Phosphate ()
Sulfate ()
Sodium (Na⁺)
Potassium (K⁺)
Calcium (Ca²⁺)
Magnesium (Mg²⁺)

Salinity %
1

Conductivity (µS/cm)
0.989
1

TDS, mg/l
0.988
0.999
1

pH
−0.045
−0.013
−0.010
1

Fluoride (F⁻), mg/l
0.282
0.262
0.251
−0.576
1

Chloride (Cl⁻), mg/l
0.982
0.995
0.992
−0.027
0.242
1

Nitrite (), mg/l
−0.181
−0.256
−0.265
−0.311
0.392
−0.257
1

Bromide (Br⁻), mg/l
0.524
0.524
0.515
0.385
−0.025
0.509
−0.129
1

Nitrate (), mg/l
0.052
−0.047
−0.034
−0.286
0.275
−0.084
0.490
−0.097
1

Phosphate (), mg/l
0.702
0.671
0.675
−0.245
0.380
0.665
0.401
0.330
0.306
1

Sulfate (), mg/l
0.977
0.988
0.983
−0.022
0.243
0.993
−0.307
0.535
−0.135
0.602
1

Sodium (Na⁺), mg/l
0.981
0.994
0.990
−0.044
0.252
0.999
−0.252
0.509
−0.088
0.658
0.994
1

Potassium (K⁺), mg/l
0.931
0.947
0.949
0.022
0.127
0.958
−0.220
0.403
0.015
0.683
0.924
0.953
1

Calcium (Ca²⁺), mg/l
0.899
0.905
0.906
0.161
−0.032
0.921
−0.256
0.532
0.020
0.604
0.896
0.916
0.968
1

Magnesium (Mg²⁺), mg/l
0.827
0.820
0.808
0.214
0.002
0.847
−0.154
0.727
−0.085
0.584
0.843
0.843
0.830
0.909
1

indicates significant correlation at 1% level of significance, indicates significant correlation at 5% level of significance, and indicates significant correlation at 10% level of significance.

3.2. Chemical Properties of Soils

The soil salinity was significantly correlated with conductivity, Cl⁻, , Na⁺ (), F⁻, , , and (). The conductivity was found to be statistically significant with TDS, Cl⁻, , Na⁺, (), F⁻, , (), and (). The soil pH was correlated with F⁻ (). The fluoride was found statistically different from , Br⁻ (), and Cl⁻ (). Similarly, chloride was found statistically identical with , Na⁺ (), , and (). Nitrite was significantly correlated with Na⁺ (). The bromide was positively correlated with (). and Na⁺ both were positively correlated with (). and Ca²⁺ both were found statistically significant with Na⁺ () and Mg²⁺ (). The soil conductivity was found to be 6.88 mS/cm, while the recommended value was 0.75–4 for a sustainable environment (Tables 6 and 7).

Table 6: Correlation coefficient and level of significance between salinity indicators of soil samples at Kalapara coastal belt.

Parameters
Salinity
Conductivity
TDS
pH
Fluoride
(F⁻)
Chloride
(Cl⁻)
Nitrite
()
Bromide
(Br⁻)
Nitrate
()
Phosphate
()
Sulfate
()
Sodium
(Na⁺)
Potassium
(K⁺)
Calcium
(Ca²⁺)
Magnesium
(Mg²⁺)

Salinity %
1

Conductivity
(mS/cm)
0.999
1

TDS, g/kg
0.999
0.999
1

pH
0.506
0.503
0.504
1

Fluoride (F⁻), mg/kg
0.782
0.782
0.780
0.790
1

Chloride (Cl⁻), mg/kg
0.993
0.992
0.994
0.490
0.732
1

Nitrite
(), mg/kg
0.738
0.735
0.735
0.495
0.497
0.775
1

Bromide
(Br⁻), mg/kg
0.618
0.618
0.622
0.707
0.877
0.587
0.227
1

Nitrate
(), mg/kg
0.752
0.754
0.753
0.616
0.914
0.691
0.226
0.883
1

Phosphate
(), mg/kg
0.816
0.818
0.814
0.058
0.587
0.785
0.557
0.357
0.577
1

Sulfate
(), mg/kg
0.958
0.958
0.959
0.325
0.578
0.971
0.717
0.432
0.597
0.779
1

Sodium
(Na⁺), mg/kg
0.988
0.988
0.990
0.436
0.695
0.996
0.733
0.566
0.688
0.7887
0.985
1

Potassium
(K⁺), mg/kg
−0.136
−0.14242
−0.134
0.572
2.040
−0.071
0.281
0.098
−0.223
−0.596
−0.167
−0.119
1

Calcium
(Ca²⁺), mg/kg
−0.287
−0.288
−0.295
0.507
0.279
−0.354
−0.148
0.128
0.120
−0.343
−0.501
−0.412
0.284
1

Magnesium
(Mg²⁺), mg/kg
0.547
0.547
0.556
−0.047
0.115
0.591
0.155
0.309
0.345
0.3314
0.695
0.649
−0.136
−0.813
1

indicates significant correlation at 1% level of significance, indicates significant correlation at 5% level of significance, and indicates significant correlation at 10% level of significance.

Table 7: Existing and recommended values of salinity indicators in soil and water samples.

Samples
Chemical properties
Existing average values
Recommended values

DoE, 1997 [11]
USEPA, 1994 [12]
Horneck et al., 2007 [13]

Water
Salinity %
1.88
—
—
—

Electrical conductivity (EC) (µS/cm)
322.9
300
—
—

TDS, mg/l
161.56
1000
500–1000
—

pH
7.89
6.5–8.5
6.5–8.5
—

Fluoride (F⁻), mg/l
3.65
1
2
—

Chloride (Cl⁻), mg/l
5307.60
150–600
250
—

Nitrite (), mg/l
0.85
<1
1
—

Bromide (Br⁻), mg/l
12.94
—
—
—

Nitrate (), mg/l
4.17
10
10
—

Phosphate (), mg/l
1.05
6
—
—

Sulfate (), mg/l
557.34
400
250
—

Sodium (Na⁺), mg/l
5186.94
200
—
—

Potassium (K⁺), mg/l
78.89
12
—
—

Calcium (Ca²⁺), mg/l
49.45
75
—
—

Magnesium (Mg²⁺), mg/l
38.50
30–35
—
—

Soil
pH
1.23
—
—
6.5–7.5

Electrical conductivity (EC) (mS/cm)
6.688
—
—
0.75–4

Note. DoE stands for Department of Environment, USEPA (United States Environmental Protection Agency).

Table 8: Effects of salinity on crops, fisheries, and livestock at Kalapara coastal belt of Bangladesh.

Crops
Fisheries
Livestock

Total cropping areas are 39102 hectare (ha). During Aman season (June to September), 90% of areas are covered by rice. Salinity intrusion is highly visible during dry season (October–May). Cultivation of crops is at an extreme risk as a result of high salinity intrusion.
The number of fresh water bodies recorded at Kalapara coastal area is 18300 with total area of 857 ha. Out of these areas, 2-3% are converted into shrimp culture. Other areas are replaced by saline water fish. Several occurrences of adaptation are ongoing such as introduction of crab fish and Koral and salinity tolerance tilapia fish.
About 200 ha grazing/fodder crop areas have been affected each year due to salinity intrusion. For this reason, food shortage is one of the crucial issues for livestock production in this coastal region. Due to intake of salinity affected fodder crops by livestock, several diseases were found such as diarrhea, skin diseases, liver fluke, loss of body weight, and breakdown of immune system.

Data were collected from the office of Department of Agriculture and Extension (DAE), Department of Fisheries (DOF), and Department of Livestock Office (DLO) at Kalapar Upazila.

Table 9: Effect of soil and water salinity on cropping patterns at Kalapara coastal belt.

Description of cropping pattern
Total cultivable land (ha)
Net cultivated land in percentage (2014-15)
Causes

Fallow-fallow-T. Aman
21310
54.5
Soil and water salinity

Felon-fallow-T. Aman
6251
15.99
Soil and water salinity

Pulse-fallow-T. Aman
5160
13.2
Soil and water salinity

Watermelon-fallow-T. Aman
2300
5.88
Soil and water salinity

Vegetables-fallow-T. Aman
1200
3.07
Drought

Pulse-fallow-T. Aman
381
0.97
Soil and water salinity

Felon-Aus-T. Aman
356
0.91
Soil and water salinity

Boro-fallow-T. Aman
275
0.70
Soil and water salinity

Vegetable-vegetable-vegetable
257
0.66
Drought

Watermelon-Aus-T. Aman
200
0.51
Soil and water salinity

Almond-fallow-T. Aman
150
0.38
Soil and water salinity

Green chili-T. Aus-T. Aman
120
0.31
Soil and water salinity

Pulse-Aus-T. Aman
100
0.26
Soil and water salinity

Wheat-fallow-T. Aman
100
0.26
Salinity and drought

Maize-fallow-T. Aman
100
0.26
Soil and water salinity

Sweet potato-fallow-T. Aman
100
0.26
Soil and water salinity

Pulse-fallow-T. Aman
90
0.23
Soil and water salinity

Sunflower-fallow-T. Aman
80
0.20
Soil and water salinity

Green chili-Aus-T. Aman
80
0.20
Soil and water salinity

Almond-T. Aus-T. Aman
50
0.13
Soil and water salinity

Sweet potato-T. Aus-T. Aman
50
0.13
Soil and water salinity

Pulse-T. Aus-T. Aman
50
0.13
Soil and water salinity

Sesame-fallow-T. Aman
50
0.13
Soil and water salinity

Sunflower-Bona Aus-T. Aman
40
0.10
Soil and water salinity

Wheat-T. Aus-T. Aman
35
0.09
Soil and water salinity

Pulse-T. Aus-T. Aman
31
0.08
Salinity and drought

Sweet potato-T. Aus-T. Aman
30
0.08
Soil and water salinity

Fresh potato-T. Aus-T. Aman
30
0.08
Soil and water salinity

Sugarcane-sugarcane-sugarcane
21
0.05
Drought

Garlic-T. Aus-T. Aman
20
0.05
Soil and water salinity

Wheat-T. Aus-T. Aman
20
0.05
Soil and water salinity

Maize-T. Aus-T. Aman
18
0.04
Soil and water salinity

Garlic-T. Aus-T. Aman
16
0.04
Soil and water salinity

Vegetable-T. Aus-T. Aman
15
0.04
Salinity and drought

Pulse-T. Aus-T. Aman
15
0.04
Salinity and drought

Cucumber-T. Aus-T. Aman
11
0.03
Soil and water salinity

Total number of cropping patterns is 36
Total cropping area 39,102 ha
Total cultivated areas in percentages (100%)
92% of areas are affected by salinity

Note. T. Aman stands for Transplanted Aman Rice; T. Aus stands for Transplanted Aus Rice.

Table 10: Recorded species of fish at Kalapara coastal belt.

Category
Local name
English name
Scientific name

Inland fishes
Bhetki/Koral
Barramundi/Seabass
Lates calcarifer

Kalo bujuri
Tengra mystus
Mystus tengara

Tengra
Striped dwarf catfish
Mystus vittatus

Golsha tengra
Gangetic tengra
Mystus cavasius

Rui
Indian Major carp
Labeo rohita

Catla
Calta
Catla catla

Mrigal
Mrigal
Cirrhinus cirrhosus

Tara baim
One-striped spiny eel
Macrognathus aculeatus

Baim/Guchi
Striped spiny eel
Macrognathus pancalus

Bele
Tank goby
Glossogobius giuris

Magur
Air breathing catfish
Clarias batrachus

Boal
Freshwater shark
Wallago attu

Pabda
Pabdah catfish
Ompok pabda

Koi
Climbing perch
Anabas testudineus

Shol
Banded snakehead
Channa striata

Gazar
Giant snakehead
Channa marulius

Taki
Spotted snakehead
Channa punctate

Cheng
Asiatic snakehead
Channa orientalis

Bheda/Meni
Mud perch
Nandus nandus

Aor
Long-whiskered catfish
Sperata aor

Foli
Grey featherback
Notopterus notopterus

Chital
Humped featherback
Chitala chitala

Ilish
Hilsha
Tenualosa ilisha

Chandana ilish
Toli Hilsha
Tenualosa toil

Tit punti
Ticto barb
Puntius ticto

Jat punti
Spotfin swamp barb
Puntius sophore

Sarpunti
Olive barb
Puntius sarana

Shing
Stinging cat fish
Heteropneustes fossilis

Chapila
Indian river shad
Gudusia chapra

Khalisha
Striprd gourami
Colisa fasciatus

Mola
Indian carplet
Amblypharyngodon mola

Dhela
Cotio
Osteobrama cotio

Kalibaus
Black rohu
Labeo calbasu

Darkina
Rasbora
Rasbora rasbora

Kakila
Needle fish
Xenentodon cancila

Chanda
Elongate glass perch
Chanda nama

Pangus
River pungus
Pangasius pangasius

Ek thota
Halfback
Hyporhamphus limbatus

Potka
Gangaetic puffer fish
Tetraodon patoca

Churi
—
Trichiurus muticus

Kuli
Dusky sleeper
Elotris fusca

Tapasi/muni
Paradise threadfin
Polynemus paradiseus

Lakhua
Indian threadfin
Polydactylus indicus

Parsia
Goldspot mullet
Liza parsia

Poa
Pama
Otolithoides pama

Somudra koi
Tripletail
Labotes surinamensis

Rup chanda
Chinese pomfret
Pampus chinensis

Tular dandi
Gangetic sillago
Silloginopsis panijus

Kuicha
Gangetic mud eel
Monopterus cuchia

Kani magur
Canine catfish eel
Plotosus canius

Rita
Rita
Rita rita

Bata
Bata labeo
Labeo bata

Phasa
Gangetic hairfin anchovy
Setipinna phasa

Choukka
Indian pellona
Pellona ditchela

Kachki
Ganga river sprat
Corica soborna

Bagha air
Gangetic goonch
Bagarius bagarius

Silong
Silond catfish
Silonia silondia

Salbaim
Zig Zag eel
Mastacembelus armatus

Chaka
Squarehead catfish
Chaca chaca

Exotic fishes
Grass carp
Asian carp
Ctenopharyngodon idella

Common carp
European carp
Cyprinus carpio

Silver carp
Asian carp
Hypophthalmichthys molitrix

Thai sarpunti/Raj puti
Firefine barb
Barbonymus gonionotus

Tilapia
Cichlid fish
Oreochromis mossambica

Thai pungus
—
Pangasianodon hypophthalmus

Nilotica
—
Oreochromis niloticus

Bighead carp
—
Aristichthys nobilis

Mirror carp
—
Cyprinus carpio var. specularis

Black carp
—
Mylopharyngodon piceus

Marine fishes
Chitra/Bistara
Spotted butterfish
Scatophagus argus

Java
—
Siganus javus

Tular dandi
Lady fish
Sillago domina

Med
Gaint sea cat fish
Katengus typus

Lal poa/Vola
Silver jew
Johnius argentatus

Konkon
—
Pelamys chiliensis

Churi
Ribbon fish
Trichiurus haumela

Phasa
Anchovies
Thryssa mystax

Datina/Sada datina
Silver bream
Pomadasys hasta

Kani magur
Canine eeltail catfish
Plotosus lineatus

Tular dandi
Gangetic sillago
Silloginopsis panijus

Kuicha
Gangetic mud eel
Monopterus cuchia

Kani magur
Canine catfish eel
Plotosus canius

Rup chanda
Chinese pomfret
Pampus chinensis

Cheowa
Torpedo trevally
Taenoides anguillaris

Shaplapata/Haush
String ray
Himantura uarnak

Bhangan
Mullet
Mugil cephalus

Rekha
Four barred finger fish
Corius quadrifasciatus

Loitta
Bombay duck
Harpadon nehereus

Foli chanda
Silver pomfret
Pampus argenteus

Rup chanda
Chinese pomfret
Pampus chinensis

Cheowa
Torpedo trevally
Taenoides anguillaris

Maitya
Jack and pompanos
Cybium guttatum

Lakhua
Indian salmon
Polynemus indicus

Sada poa
Silver jew
Otolithes argentatus

Gongonia
Grunting toadfish
Allenbatrachus grunniens

Amadi
Pointed tail anchovy
Coilia dussumieri

Kukurjiv
Sole
Cynoglossus macrostomus

Kamot hangor
Requiem shark
Carcharhinus gangetica

Bom maitta
Tuna
Euthynnus affinis

Bata
—
Mugil cephalus

Ghagra bele
—
Gobius personatus

Ghagra
Gagora catfish
Arius gagora

Somudra koi
Tripletail
Labotus surinamensis

Bhut bele
—
Paragobiodon echinocephalus

Somudra chela
—
Thryssa purava

Potka
—
Chelonodon patoca

Lambu/Bara poa
Long jewfish
Sciaenoides brunneus

Foton maach
King mackerel
Scomberomorus guttatus

Ruppan
Thread fun bream
Nemipterus japonicas

Moori
—
Caranyx speciosus

Choukha
Indian pellona
Pellona indica

Kawa
Hard tail
Megalapsis cordyla

Shankhachil
Banded eagle ray
Aetomylaeus nichofii

Katabukha
Beardless sea catfish
Batrachocephalus mino

Kuli
Duckbill sleeper
Butis butis

Kamila
Indian pike conger
Congresox talabonoidis

Haturi hangor
Hammerhead shark
Eusphyra blochii

Tak chanda
Common pony fish
Leiognathus equulus

Dahuk
Walking goby
Scarteloas histophorus

Ilish
Hilsa shad
Tenualosa ilisha

Chandan ilish
Toli shad
Tenualosa toli

Tuna
Yellowfin tuna
Thunnus albacores

Ramchosh/Taposi
Paradise threadfin
Polynemus paradiseus

Khorsula
Corsula
Rhinomugil corsula

Bhetki/Koral
Seabass
Lates calcarifer

Barguni
Jarbua terapon
Terapon jarbua

Rupsha
Skipjack tuna
Katsuwonus pelamis

Prawns
Golda chingri
Fresh water prawn
Macrobrachium rosenbergii

Chatka chingri
—
Macrobrachium malcolmsonii

Gura chingri
Spider prawn
Macrobrachium tenuipes

Shrimps
Bagda chingri
Giant tiger shrimp
Penaeus monodon

Chaka chingri
Indian white shrimp
Penaeus indicus

Chapra chingri
Oriental shrimp
Penaeus orientalis

Horina chingri
Brown shrimp
Metapenaeus monoceros

Chali chingri
Yellow shrimp
Metapenaeus brevicornis

Crabs
Shela kakra
Mud crab
Scylla serrata

Zaji kakra
Blue swimmer crab
Neptunus pelagicus

Sataru kakra
Swimmer crab
Neptunus sanguinolenta

Shela kakra
Mud crab
Scylla serrata

Note. Visible (without asterisk) indicates that species are available and are not considered in any remarkable risk; threatened () indicates that species are likely to become endangered within the foreseeable future; endangered () indicates that species are becoming at risk of becoming extinct; extinct () indicates that there is no doubt that the last individual has died.

Table 11: Present status of recorded visible, threatened, endangered, and extinct fish species at Kalapara coastal belt.

Category
% visible
% threatened
% endangered
% extinct
Causes

Inland fishes (59)
45
24
19
12
Salinity

Marine fishes (57)
43
21
24
12
Cyclone/salinity

Exotic fishes (10)
70
30
—
—
—

Prawns (3)
67
—
33
—
—

Shrimps (4)
50
—
25
25
Cyclone/salinity

Crabs (4)
75
—
25
—
—

3.3. Effect of Salinity on Crops and Livestock Production

We know that farmers are reliant on crop and livestock production across the coastal belt of Kalapara Upazila. Through interviews with community members in the study areas we determined threats that included decreases in crop and livestock production. During Aman season (June to September), 100% of the areas are covered by crops. About 200 ha fodder crop areas are affected each year due to salinity. For this reason, food shortage is one of the crucial issues for livestock and other animals. Due to the high dependence on the salinity affected fodder crops, livestock are affected by many negative consequences such as diarrhea, skin diseases, liver fluke, loss of body weight, and breakdown of the immune system (Table 8). In addition, we found 36 cropping patterns in the 39102 ha cropping area at the Kalapara coastal belt. Among these cropping patterns, 92 percent of these were identified as salinity affected areas (Table 9).

3.4. Effect of Salinity on Fish Species Production

Out of 857 ha water bodies, 2-3% are occupied by shrimp culture which has contributed to the salinity of inland and fresh water bodies across the coastal belt. Other areas have also been replaced by saline water on the Kalapara coastal belt (Table 8). We found the number of fish species to be 59 inland, 57 marine, 10 exotic, 3 prawns, 4 shrimp, and 4 crab across the Kalapara coastal belt in Bangladesh. Among these fish species, the percentages that were identified as visible, threatened, endangered, and extinct under the category of inland fish species were 45, 24, 19, and 12, respectively. On the other hand, between the marine fish species, the percentages of visible, threatened, endangered, and extinct species were found to be 43, 21, 24, and 12, respectively. None of the exotic, prawn, and crab species were identified in the extinct category. However, 25 percent of the shrimp species were recorded in the extinct category. Natural disasters such as salinity and cyclones were both determined to be critical causes for the extinction of fish species across the coastal belt of Kalapara Upazila (Tables 10 and 11).

3.5. Discussion of the Findings

3.5.1. Vulnerabilities of Salinity

Different cations and anions are inconsistent in saline soil and water. The degree of salinity effects on crops, livestock, and water bodies in fish may not have the same level of effects on the environment [43]. Specific ion toxicity occurs most commonly due to excessive boron, Cl–, , Na⁺, and other ions [44, 45]. Similarly, cations, anions, and conductivity in soil and water in the Kalapara coastal belt were recorded at an extremely toxic level. For instance, the soil conductivity was found to be 6.88 mS/cm, while recommended values were 0.75–4 for sustainable crop production. Moreover, several chemical properties of water samples such as conductivity (322.9 μS/cm), F⁻ (3.65), Cl⁻ (5037.60), (557.34), Na⁺ (5184.94), and K⁺ (78.89) were found at a more toxic level, whereas recommended values of conductivity, F⁻, Cl⁻, , Na⁺, and K⁺ were found to be 300 (μS/cm), 1-2, 150–600, 250–400, 200, and 12 mg/l, respectively (Table 7). According to Dusgupta et al. [1] thirty-nine (39) percent of salinity will be increased across the coastal belt in Bangladesh by 2050. The intensity and spread of this salinity across the coastal belt in Bangladesh were connected with the changes of sea level rise, temperature, and rainfall and altered riverine flows from the Himalayas [46]. Agricultural production of crops, fish, and livestock has been negatively affected due to this extreme level of soil and water salinity trends across the coastal belt in Bangladesh.

Coastal agriculture is based on farmlands, which provide livelihood support for the community [47]. Several groups of people often suffer a shortage of freshwater in different areas of the coastal belt [48]. Many regions in the world along with the coastal belt of Bangladesh have used saline water for food crop cultivation, fodder crop production, drinking, and bathing [49]. These practices have contributed to the enormous negative effects on agricultural production systems as well as human health [50, 51]. Coastal agriculture is predominantly affected by unequal water distribution over the last decades. This system causes an increase in salt levels in the crop fields as well as reduced yield [52]. Also, soil salinity has negatively affected rice yield, spikelet sterility, and 1000-grain weight in the coastal belt of Thailand as well as Bangladesh. In this regard, salinity is responsible for a 20% yield reduction of coastal region agriculture. In fact, the soil nutrient supply was only enough to achieve about 80% of the maximum yield [53]. In fact, this reduction of crop yield has been influenced by many environmental factors. Among these factors, salinity is one of the major causes for the yield reduction [54, 55]. A similar result was found in these study locations where 92 percent of the cropping area is affected by the salinity problem. This remarkable salinity intrusion into the cropping areas has tremendously reduced the crop production across the coastal belt in Bangladesh (Table 9) which might have led to the shortage of food availability in Bangladesh.

Salinity has been convenient for shrimp cultivation across the coastal belt, but it has accelerated negative effects on the diversity of fresh water fish. Some of the inland fresh water species have become extinct due to the connectivity with saline water [56]. The rest of the fish species are only living in the fresh water ecosystem that are also likely to be extinct forever (Tables 10 and 11). Moreover, this salinity problem includes large-scale degradation of mangroves, alteration of wetlands, land subsidence, salinization of groundwater and surface water, pollution of agricultural lands and coastal waters by pond effluents and sludge, introduction of exotic species or pathogens into the coastal environment, loss of wild larvae, and subsequent loss of goods and services generated by natural common property resources [57]. However, coastal areas are naturally vulnerable and survival strategies are very limited for people in these communities, so they prefer shrimp cultivation which is responsible for further increasing salinity (Sarwar, 2009). This saline water intrudes in the inland riverine areas which contributes to the reduction of fresh water bodies. This result is creating even more negative effects on the diversity of fish in the inland riverine areas across the coastal belt in Bangladesh (Tables 10 and 11).

An extreme scarcity of salinity free water was recorded in the coastal belt of Bangladesh because of natural disasters such as sea levels rising, cyclones, floods, and land erosion which brought saline water from the sea that mixed with surface and groundwater [58]. Water sources such as rivers, ponds, and tube wells are becoming unable to provide sustainable fresh water for people in the coastal community. Many key determinants of human health, such as food availability, fresh water availability, physical safety, and the microbiological environment, are strongly influenced by salinity [59]. As saline water mixes with inland water it becomes unsustainable for consumption by livestock and fish. People have started suffering from various kinds of health problem such as high blood pressure, diarrhea, and cholera [60]. Not only through water but also through consumption of food raised in these highly saline areas, people are getting more saline than they require for optimum health [61]. The most vulnerable groups are the pregnant women and the children. Higher rates of hypertension affecting pregnant women in the southwestern coast of Bangladesh, compared with noncoastal pregnant women, were hypothesized to be caused by salinity contamination [24]. Higher salinity from food grains also might have caused a higher rate of birth defects which is of great concern to the future of Bangladesh. Cholera sometimes spreads as an epidemic after a disaster such as flood or cyclone. Lack of drinking water and overconsumption of saline water influence malnutrition, undernutrition, water borne diseases, and food borne diseases and even lead to starvation among coastal people [62].

Not only crops and fish have been negatively affected due to the high salt in the coastal belt of Bangladesh (Tables 8, 9, 10, and 11). Saline water also has a detrimental effect on livestock production [63]. Survival of livestock is dependent on the field grass, water, and dairy feed. These types of natural resources are connected to saline water. Due to the shortage of fodder crops, livestock has been affected in this coastal region of Bangladesh (Table 8). Tolerance of the saline water varies between livestock species. Pregnant, lactating, and younger classes of livestock are less tolerant than mature dry stock. For optimum production in these classes of livestock, water supplies should not exceed the optimum salinity levels in the food for livestock [64]. Livestock grazing green feed can better tolerate salinity levels at the upper limit of each category compared with those grazing dry feed or salt bush or on a high salt diet since the high water content of green feed will dilute the salinity levels of the water supply [65]. Salinity affected livestock may be able to transmit various diseases into human bodies. For this reason, salinity levels should be controlled in the coastal region for the production of livestock also.

3.6. Mitigation Techniques

3.6.1. Construction of Embankment across the Bank of Sea

Array of sea is connected with the inland riverine body. It should have been isolated through an embankment between the bank of the river and the sea. This land could be protected from inundation of saline water through the establishment of an embankment of suitable size. The recommended size should be 5–10 meters higher than the high tide level. Brammer [66] suggested that the Coastal Embankment Project is a requirement for protection from saline water crossing into the inland areas. He also recommended that it should have more consistent maintenance than in the past [66].

3.6.2. Provision of Sluice Gate on the Embankment

The sluice gate is a connection between inland and salt water bodies in the coastal region of Bangladesh. This sluice gate which is placed in the embankment systems is responsible for the control of excess water. This makes it possible to prevent intrusion of saline water during high tide in the coastal belt. This sluice gate across the embankment can remove excess saline water during high tide [2].

3.6.3. Leveling of Land

Slight variations in the land lead to salt accumulation in the crop fields. Land should be properly leveled to prevent accumulation of water in the low-lying patches with shallow groundwater tables and to facilitate a uniform drainage system for removing excess water. It will also help to apply irrigation water uniformly in the field during Rabi season (January–March), which will facilitate uniform germination of seeds and better growth of crops. Haque [2] recommends that the leveling of soil also supplies nutrients uniformly in the salinity affected crop fields.

3.6.4. Harvesting of Rain Water for Irrigation

Tidal water is generally salty. This water is not useful for the production of crops in the coastal belt. During the rainy season excess rain water should be stored in ponds and canals. Later, this harvested rain water will be valuable for crop irrigation during the dry season. Climate change has caused rising sea levels along the coastal belt. This in turn has contributed to the rise in salinity intrusion in the region. One result of this is a severe scarcity of potable water at the south western coastal area of Bangladesh. This rainwater harvesting system is proposed solution to provide fresh water for crop cultivation and domestic uses during the rainy season across the coastal belt in Bangladesh [67].

3.6.5. Salinity Tolerant Cultivars

Even though the coastal area is relatively flat, there exist some altitude differences in areas where depths of standing water can reach 10–100 cm. Varieties of cultivars should be selected on the basis of tolerance to standing water and the extent of salinity in the field to maximize productivity of the available land. Utilizing salt-tolerant crops is one of the most important strategies to solve the problem of salinity. Qualitative and quantitative protein synthesis in plants have been altered under these saline conditions. When a plant is subjected to abiotic stress, a number of genes are turned on, resulting in increased levels of several metabolites and proteins, some of which may be responsible for conferring a certain degree of protection from the salinity stress [68].

3.6.6. Introduction of Crop in Rabi (Winter) Season

Cropping intensity should be modified in slightly saline areas by adopting proper soil and water management practices with the introduction of salt-tolerant crop varieties. During this dry season, salt-tolerant minor cereal crops such as lentil, mung bean, and pea and different vegetables might be cultivated through the proper management of drainage systems [19].

3.6.7. Use of Fallowing Lands

Groundwater is saline and present at a shallow depth (about 1.0 meter). Keeping lands fallow leads to high salinity in soil due to the evaporation of excessive soil moisture. Therefore, it is recommended to avoid fallowing of lands during Rabi season (winter season). Salt-tolerant crops should be chosen and grown. This can be done by reintroduction of deep rooted perennial plants that continue to grow and use water during the seasons that do not support annual crop plants. This may restore the balance between rainfall and water use, thus preventing rising water tables and the movement of salt to the soil surface [69]. This will be helpful for maintaining of soil salinity profile.

3.6.8. Application of Potash Fertilizer

Since soils in general are poor in fertility with low organic matter content, it is necessary to apply appropriate fertilizers to increase crop production. Potash fertilizer has an added advantage in saline soil. It lowers Na uptake by plants and increases K uptake. Thus K fertilization protects crops from harmful effects of Na. This crop nutrient management is one of the best options to increase the plant productivity in saline soils. For this, an application of potassium sulfate (K₂SO₄) can improve the plant productivity and nutrient uptake for food crops in a saline environment. It was observed that the uptake and accumulation of nutrients like calcium, magnesium, potassium, and phosphorus increase in plants subjected to K fertilizer application under saline environments [70].

3.6.9. Reducing of Groundwater Level

In many parts of the coastal region, salinity is highly visible. To grow crops successfully in those areas, it is necessary to bring down the salinity by leeching the salts. It is also necessary to decrease the water table level and maintain it below the critical depth to prevent the salt from having an effect on crops. To achieve this objective, a proper subsurface drainage has to be installed to keep the groundwater at least 1.5 meters below the soil surface. Salinity is managed by a combination of vegetation and engineering strategies—designed to create the reduction of water in these areas. The planting of vegetation with high water usage can be utilized to reduce groundwater recharge and to intercept water as it moves through the soil [71].

3.7. Possible Adaptation Strategies and Practices

Strengthening adaptation capacity requires blending individual skills and household capacity with external institutional supports for technological acceptance. The dynamic geomorphological nature in coastal areas along with spontaneous natural disasters often exceeds the knowledge of the local people and use of available resources to reduce the problems in the long run. Adaptation practice is mostly dependent upon institutional response for promotional activities and to managing observed risks in Bangladesh and less focusing on integrating other social constructions at the community level. Making long-term decisions for coastal adaptation depends on climate change and complexities and levels of stakeholder support [72].

Coastal adaptation can be reached through adjustment of ecological, social, or economic systems to actual or expected climatic impacts. Social, ecological, and institutional capacities are significantly important to the coastal communities to adapt themselves in an adverse situation. These communities of people need to adapt with the changing environmental conditions caused by salinity. They have been following traditional cropping patterns for crop cultivation across the coastal saline environment [73]. They have continued to adapt during the period of rapid change since the 1950s when the first major flood embankments were constructed and, later, with the spread of dry-season irrigation and the introduction of high-yielding crop varieties. In this situation, it is highly recommended to change the traditional cropping patterns as per the guidelines of Agriculture Extension Department in Bangladesh to ones that will provide more protection from salinity intrusion across this costal belt.

Introducing fast growing and improved varieties fish across the costal belt might be a way of supplying fresh water fish. Though coastal areas are dominated by groups of fishermen, with the changing environment and extreme events, most of the people are experiencing a decrease in the seasonal fish catch from the sea and rivers in the region. The channel system can secure additional or alternative sources of income through fish cultivation in two seasons of the year. By excavating a single ditch, a family can produce an estimated 200 kg of fish annually which secures their household protein and additional income after consumption. Harvesting of rain water in these ditches also supports regular water supply to plantations on the channel and increases fresh water security as it doubles as a reservoir.

The plantation of the correct varieties of vegetables can provide an immediate opportunity for household consumption in these communities. Different hanging vegetables including country bean, cucumber, bottle, bitter, and sweet gourds (cucurbitaceous vegetables) and other creeper vegetables may be cultivated widely across the coastal belt. This cultivation system will be helpful for supplying needed nutrients during adverse conditions of salinity intrusion across the coastal environment.

Agricultural practice is increasingly constrained with a high level of salinity ingress and frequent and severe impacts of natural disasters in coastal areas. Given the impacts of seasonal water logging and salinity on land and lack of irrigation in dry seasons, alternative cropping practices through use of climate resilient rice varieties have been a vital need for agricultural production in the area. The salt-tolerant rice variety (BR 47) has already been introduced in four coastal districts. Considering lower land productivity, this rice variety has been considered a potential crop in this coastal area. This BR 47 rice variety might be introduced due to its high yield in extreme saline conditions in this coastal region.

3.8. Policy Implications and Gaps in These Salinity Affected Areas

3.8.1. Fragile Water Governance Systems at Local Level

Weak water governance systems at the local level are another cause of the salinity increase. Salinity intrusion not only is a natural phenomenon but also is caused by human activities. Numerous human activities—such as untimely water use, unplanned shrimp culture, insufficient or poorly maintained infrastructure, and inadequate management systems—can contribute to salinity intrusion.

3.8.2. Cross Boundary River Policy

A total of 57 major rivers are located in the country of Bangladesh, of which 54 rivers enter from India and 3 rivers from Myanmar [74]. But among the 54 rivers, twenty-five rivers face one or more upstream diversions primarily in the dry months. For this reason, water scarcity during nonmonsoon months causes the salinity to increase in the soil and water of the coastal belt of Bangladesh.

3.8.3. Lack of Capacity of Local Government

Local government reforms in Bangladesh have evolved very distinctly according to the needs of the ruling elites [75]. With the change of government, the policy of local government has also kept changing. As a consequence, Local Government Institute (LGI) has not had any opportunity to act with any effective tiers of government because mandates and limited funds prevent them from being able to carry out their roles and responsibilities. Independent reviews stated that Bangladesh has not been successful in establishing a decentralized system of governance and accountability. A World Bank review of the decentralization process in 19 countries ranks Bangladesh lowest in the decentralization scale [76]. Due to the lack of capacity of LGIs, they cannot take the initiative to protect coastal polders, embankments, roads, and other kinds of infrastructure as well as the unplanned shrimp culture. As a result, salinity has continued to increase across the costal belt in Bangladesh.

3.8.4. Weak Structure and Poor Maintenance

Bangladesh has a 5,017 km embankment protecting the polders in coastal areas of the Bay of Bengal. The primary goal of launching polderization in Bangladesh was to protect the coastal inhabitants from regular natural disasters and to boost the agricultural production [77]. Bangladesh Water Development Board (BWDB) formerly known as Water and Power Development Authority (WAPDA) is in charge of maintaining and conducting the rehabilitation project of the polders [78]. But due to the poor maintenance, coastal polders in many places have not been protected from salinity intrusion into the agricultural fields. The BWDB has categorized 51 polders as “most vulnerable” and another 55 polders as “medium vulnerable.” To cope with vulnerability, it is necessary to rehabilitate the damaged infrastructure of the polders. Most of the sluice gates have been damaged which enables the saline water to continuously flow inland. In addition, shrimp farmers cut the embankment to get saline water into their shrimp fields which also makes the embankment weak. This weak embankment is easily damaged due to tidal pressure, particularly during full moon, and the saline water can then enter the polders.

3.8.5. Lack of Coordination among Different Organization

Local government has connected with the federal government. Government personnel in the departments of extension, disasters, fisheries, livestock, engineering, and water development boards might have a lack of coordination to be able to implement any of the government policies together. On the contrary, researchers, nongovernment officers (NGOs), and international and national groups have been working without coordination with the national government. Due to the lack of integration between the organizations, proposed activities for the reduction of salinity across the coastal belt have not been substantially implemented throughout the country.

4. Conclusion

The coastal belt is at an extreme risk due to high soil and water salinity. This salinization in water and soil is the major natural hazard hampering crop and livestock production. This is also producing a negative impact on the diversity of fish across this costal belt. This coastal area in Bangladesh constitutes 20% of the country of which about 53% is affected by different degrees of salinity. In fact, declining land, fish, and livestock productivity with a shift toward negative nutrient balance is among the main concerns for food security problems in the country. Several cations and anions in water and soil such as conductivity, F⁻, Cl⁻, , Na⁺, and K⁺ were found at higher than recommended values for a sustainable environment across the Kalapara coastal belt of Bangladesh. About 200 ha fodder crop areas are affected each year due to salinity. Among 36 cropping patterns, 92 percent of these were identified as salinity affected areas. Out of 857 ha water bodies, 2-3% are occupied by shrimp culture which has contributed to the salinity of inland and fresh water bodies across the coastal belt. Twenty-five percent of shrimp species were recorded in the extinct category. Due to the weak policy implementation, this salinity problem is increasing which has enhanced the negative impacts on food security. It is significantly important to explore the possibilities for increasing agricultural production for the growing population throughout the world as well as the coastal region of Bangladesh. Thus, combating this land salinization problem is a vital issue for food security in the country through adoption of long-term land management strategies.

Disclosure

This research is a national issue for Bangladesh. The authors are all working in the Government Institute of Bangladesh. Their job is to conduct research and teaching on the national issues in Bangladesh. For this reason, they do not need to receive approval for sample collection from any authority of Bangladesh. Sampling areas are not indicated as protected or endangered species areas in Bangladesh.

Conflicts of Interest

The authors declare that no conflicts of interest exist regarding the publication of this paper.

Acknowledgments

The authors would like to acknowledge the Laboratory of Environmental Science at Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU) and Biological Research Division at Soil and Environment Section of Bangladesh Council of Scientific and Industrial Research (BCSIR). The authors are also thankful to the Department of Agricultural Extension (DAE), Department of Fisheries (DOF), and Department of Livestock Services (DLS) at Kalapara Upazila for their support to collect data on salinity issues across the coastal belt of Bangladesh. Finally, they are especially thankful to the Ministry of Science and Technology, Bangladesh, for their valuable funding.

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