metadata: authors: 0: author: Blankespoor,Brian
1: author: Dasgupta,Susmita
2: author: Huq,Mainul
3: author: Khan,Zahirul Huque
4: author: Mustafa,Md Golam
5: author: Wheeler,David J.
count: Bangladesh,World
docna: 0: docna: Fishing and Climate Change in Coastal
            Bangladesh : The Economic and Health Impacts of Increasing Salinity
docty: Policy Research Working Paper
theme: Renewable Natural Resources Asset Management,Mitigation,Data Development and Capacity Building,Environment and Natural Resource Management,Public Sector Management,Biodiversity,Oceans,Climate change,Adaptation,Data production, accessibility and use
abstracts: cdata!: The composition of flora and fauna in
            low-lying coastal regions worldwide is being altered by
            sea-level rise in a changing climate, favoring
            saline-tolerant species. These shifts are projected to have
            significant implications for nature-based livelihoods,
            resource availability, market prices, and the food and
            nutrition security of coastal populations, particularly
            those with limited choices and affordability. The
            vulnerabilities arising from these changes underscore the
            critical need for adaptation planning to build resilience.
            In the southwest coastal region of Bangladesh, rising sea
            levels and upstream changes in freshwater flux are
            intensifying riverine salinity, with annual flux dynamics
            driving substantial salinity changes and providing insights
            into future trends as high-salinity water encroaches further
            inland. In this study, river salinity monitor data were
            combined with fish sales records from nearby wholesale
            markets to evaluate the magnitude, spatial distribution, and
            fishing impact of salinity changes throughout 2023.
            Significant impacts on fish quantities were observed, and
            analysis of associated child health data revealed that
            salinity-related health challenges persist despite steady
            poverty reduction. Econometric analysis of fish catch
            records demonstrated that salinity changes differentially
            affect the availability of fish species with varying
            salinity tolerances, reflecting the interplay of
            species-specific salinity aversion and fishers&#x2019;
            adaptive strategies to optimize profitable catches. These
            findings highlight the importance of complementing technical
            assessments of species-specific salinity tolerances with
            empirical salinity and catch data to improve projections of
            salinity impacts on fish consumption in affected regions.
            The results provide actionable insights into the dynamic
            interactions between environmental change, ecological
            responses, and human adaptation in coastal settings.
display_title: Fishing and Climate Change in
            Coastal Bangladesh : The Economic and Health Impacts of
            Increasing Salinity
listing_relative_url: /research/2025/01/34450063/fishing-climate-change-coastal-bangladesh-economic-health-impacts-increasing-salinity
topicv3: Integrated Coastal Zone Management
            m1325969 1958,Climate Change m1326829 567,Capture Fisheries m1327379 1985,Coastal and Marine Ecosystems m1327594 596
publishtoextweb_dt: 2025-01-27T00:00:00Z
dois: 10.1596/1813-9450-11048
origu: Off of Sr VP Dev Econ/Chief Econ (DECVP)
no_of_pages: 24
author_keys: 0: author_key: 957135
1: author_key: 95558
2: author_key: 95595
3: author_key: NA
4: author_key: 2424381
5: author_key: 1048754
model_extractions: Policy Research Working Paper 11048

# Fishing and Climate Change in Coastal Bangladesh The Economic and Health Impacts of Increasing Salinity

_Brian Blankespoor Susmita Dasgupta Mainul Huq Zahirul Huque Khan Md. Golam Mustafa David Wheeler_ Development Research Group Development Data Group & Environment Global Department January 2025 A verified reproducibility package for this paper is available at http://reproducibility.worldbank.org, click **here** for direct access.
Policy Research Working Paper 11048

# **Abstract**

The composition of flora and fauna in low-lying coastal regions worldwide is being altered by sea-level rise in a changing climate, favoring saline-tolerant species. These shifts are projected to have significant implications for nature-based livelihoods, resource availability, market prices, and the food and nutrition security of coastal populations, particularly those with limited choices and affordability. The vulnerabilities arising from these changes underscore the critical need for adaptation planning to build resilience. In the southwest coastal region of Bangladesh, rising sea levels and upstream changes in freshwater flux are intensifying riverine salinity, with annual flux dynamics driving substantial salinity changes and providing insights into future trends as high-salinity water encroaches further inland. In this study, river salinity monitor data were combined with fish sales records from nearby wholesale markets to evaluate the magnitude, spatial distribution, and fishing impact of salinity changes throughout 2023. Significant impacts on fish quantities were observed, and analysis of associated child health data revealed that salinity-related health challenges persist despite steady poverty reduction. Econometric analysis of fish catch records demonstrated that salinity changes differentially affect the availability of fish species with varying salinity tolerances, reflecting the interplay of species-specific salinity aversion and fishers’ adaptive strategies to optimize profitable catches. These findings highlight the importance of complementing technical assessments of species-specific salinity tolerances with empirical salinity and catch data to improve projections of salinity impacts on fish consumption in affected regions. The results provide actionable insights into the dynamic interactions between environmental change, ecological responses, and human adaptation in coastal settings.

This paper is a product of the Development Research Group and the Development Data Group, Development Economics and the Environment Global Department. It is part of a larger effort by the World Bank to provide open access to its research and make a contribution to development policy discussions around the world. Policy Research Working Papers are also posted on the Web at http://www.worldbank.org/prwp. The authors may be contacted at sdasgupta@worldbank. org. A verified reproducibility package for this paper is available at http://reproducibility.worldbank.org, click **here** for direct access.

<!-- Start of picture text --> TRANSPARENT<br>ANALYSIS<br>G<br>R E<br>N<br>S<br>I P<br>Y E<br>K A<br>C A<br>R P<br>LI R<br>O E<br>O C<br>W R<br>H<br>S<br>P<br><!-- End of picture text --> _The Policy Research Working Paper Series disseminates the findings of work in progress to encourage the exchange of ideas about development issues. An objective of the series is to get the findings out quickly, even if the presentations are less than fully polished. The papers carry the names of the authors and should be cited accordingly. The findings, interpretations, and conclusions expressed in this paper are entirely those of the authors. They do not necessarily represent the views of the International Bank for Reconstruction and Development/World Bank and its affiliated organizations, or those of the Executive Directors of the World Bank or the governments they represent._ Produced by the Research Support Team
# **Fishing and Climate Change in Coastal Bangladesh: The Economic and Health Impacts of Increasing Salinity**

Brian Blankespoor Senior Geographer, World Bank Susmita Dasgupta Lead Environmental Economist Mainul Huq Consultant, World Bank Zahirul Huque Khan Advisor, Coastal Zone and River Management, Institute of Water Modeling, Bangladesh Md. Golam Mustafa World Fish, Bangladesh David Wheeler Consultant, World Bank _Corresponding author:_ Susmita Dasgupta, Lead Environmental Economist, Development Economics Research Group, The World Bank, 1818 H Street, Washington, DC 20008, USA. Tel: 1-202-473-2679. Email: <u>sdasgupta@worldbank.org</u> _Funding_ : This research was funded by a grant from the Global Environment Facility to a World Bank program managed by Nagaraja Harshadeep Rao, Susmita Dasgupta and Brian Blankespoor.

_Acknowledgments:_ We extend our gratitude to Ms. Ajanta Dey, Mr. Mohammed Nesaruddin, and Mr. Pritthijit (Raja) Kundu for providing the photos. Special thanks to Dr. Md. Istiak Sobhan for his assistance with logistics and to Mr. Pritthijit (Raja) Kundu for his contributions to the graphics.

The findings, interpretations, and conclusions expressed in this paper are entirely those of the authors. They do not necessarily represent the views of the International Bank for Reconstruction and Development/World Bank and its affiliated organizations, or those of the Executive Directors of the World Bank or the governments they represent.

_Keywords_ : Climate change; River salinity; Fishing; Child health; Bangladesh _JEL Code:_ Q21; Q22; Q25; Q54; I14
# **1. Introduction**

Climate change is impacting every region on Earth at an unprecedented scale, with overwhelming scientific evidence documenting its accelerating effects (IPCC, 2023). A key consequence of climate change is the rising sea level, which has increased substantially since 1900. NASA reports that the current rise in global sea levels surpasses historical rates over at least the past 3,000 years. In the past century alone, sea level rose by approximately 0.15 to 0.25 meters (6–10 inches), with nearly half of this increase occurring since 1993. The pace of this rise has also quickened: from 2006 to 2018, the rate reached 3.7 mm per year, compared to 1.9 mm per year between 1971 and 2006, and 1.3 mm per year from 1901 to 1971.<sup>1</sup> Even with stabilized greenhouse gas emissions, it is virtually certain that sea levels will continue to rise beyond 2100. Conservative projections suggest that sea levels could rise by 1 meter by the end of the century. Recent data on deglaciation rates in Greenland and Antarctica, coupled with uncertainties around the dynamics of outlet glaciers, indicate that rapid breakups of the Greenland and West Antarctic ice sheets could result in an even more dramatic rise, potentially reaching 3 to 5 meters.

Sea-level rise exerts multifaceted impacts on coastal regions, including permanent inundation, cycloneinduced flooding, accelerated erosion, wetland loss, and the salinization of soil and water resources. While extensive research has highlighted land loss due to permanent flooding as a key risk (for example, see Blankespoor, Dasgupta and Laplante 2014; Dasgupta et al. 2009), salinization remains an underexplored yet critical consequence of rising seas. Regions such as the Nile Delta, Mekong Delta, and GangesBrahmaputra Delta are already experiencing significant salinity intrusion. For instance, in the Arab Republic of Egypt, 30%–40% of soils in the Nile Delta are adversely affected by salt, while seawater intrusion in the Mekong Delta poses serious threats to agriculture. The rising salinity is driving shifts in the composition of flora and fauna, favoring saline-tolerant species in low-lying coastal areas worldwide. These ecological changes have far-reaching implications for resource availability, market prices, and the food and nutrition security of coastal populations, particularly for those with limited resources and adaptive capacity. Addressing these vulnerabilities necessitates proactive adaptation planning to foster resilience in these increasingly fragile ecosystems. This paper examines a critical aspect of this poverty-environment nexus by analyzing the impact of increased salinity on fishing in coastal waters, with a focus on the southwest coastal region of Bangladesh.

The southwest coastal region of Bangladesh was selected as the study area as this area is among the poorest regions in the country and faces compounding challenges from climate change, including increased flooding, storm surges, and rising salinity (Dasgupta et al., 2021a,b; 2018; 2017; 2016a,b; 2015a,b; 2014; Steele et al. 2017). Poor households in this region are particularly vulnerable due to their reliance on fragile local ecosystems for livelihoods and the constraints imposed by poverty on their mobility.

Extensive research has documented that coastal fisheries play a vital role in sustaining the livelihoods and nutritional needs of the region’s poor households (World Bank, 2000; Alam and Thomson, 2001; Thilsted, 2010; Fernandes et al., 2015). However, these fisheries are increasingly threatened by climate-induced salinity changes resulting from sea-level rise and altered riverine flows (Dasgupta et al., 2016a; Gain, Uddin, and Sana, 2008). Local fish species, which vary in salinity tolerance, are adapting their ranges in response to shifting salinity patterns (Dasgupta et al., 2017). Such changes in the spatial and temporal

> 1 <u>htps://sealevel.nasa.gov/understanding-sea-level/by-the-numbers/</u>

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# **2. Data**

# **2.1 River Salinity**

Our salinity data are drawn from river monitoring stations spread across the southwest coastal region in five areas (Figure 2a): Khulna (Rupsha River), Mongla (Passur), Sarankhola (Boleshor), Amtali (Paira) and Galachipa (Ramnabad). Figure 3 displays monthly mean salinity readings for [2020 – 2022], which display the same peak salinity in the spring. However, Figure 3 and the table in Figure 2b also show that typical annual readings vary greatly from west to east because varying flux conditions create different mixing ratios for fresh and salt water. Each location has minimum salinity below 0.25 ppt, but maximum salinity varies from 0.23 ppt (Amtali) to 12.75 ppt (Mongla).

**Figure 2:  River monitoring stations**

**(2a) Station locations                                                  (2b) Salinity readings**

|<br>Station<br>|Salinity (ppt)<br>Min Max|
|---|---|
|Khulna|0.13<br>8.89|
|Mongla|0.21<br>12.75|
|Sarankhola|0.13<br>1.18|
|Amtali|0.06<br>0.23|
|Galachipa|0.07<br>0.58|

Source: The Institute of Water Modeling, Bangladesh

## **Figure 3:  Monthly salinity readings**

**(3a) Khulna [Min 0.13; Max 8.89]                   (3c) Sarankhola [Min 0.13; Max 1.18]                   (3d) Amtali [Min 0.06; Max 0.23]**

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#

|**Species**|**Common Name**|**Mean**<br>**Wholesale**<br>**Price**<br>**(taka/kg)**|**Total**<br>**Catch**<br>**Quantity**<br>**(kg)**|**Maximum**<br>**Salinity**<br>**(ppt)**|
|---|---|---|---|---|
|_Coilia dussumieri_|Goldspotted anchovy|102|1844|20|
|_Thunnus obesus_|Bigeye tuna|122|549|30|
|_Johnius coitor_|Coitor croaker|139|551|30|
|_Ilisha elongata_|Herring|155|1936|20|
|_Escualosa thoracata_|White sardine|170|4183|30|
|_Setipinna phasa_|Gangetic hairfin anchovy|181|2087|20|
|_Setipinna taty_|Scaly hairfin anchovy|205|369|20|
|_Euthynnus affinis_|Kawakawa|215|1047|30|
|_Labeo bata_|Bata labeo|233|245|20|
|_Sillaginopsis panijus_|Flathead silago|279|2608|20|
|_Pseudapocryptes elongatus_|Pointed-tail goby|299|2470|10|
|_Platycephalus indicus_|Bartail flathead|318|171|30|
|_Scomberomorus guttatus_|King mackerel|323|1509|30|
|_Pomadasys maculatus_|Blotched grunter|325|310|30|
|_Mystus gulio_|Gulio catfish|341|3146|20|
|_Stigmatogobius sadanundio_|Knight goby|351|665|10|
|_Otolithoides pama_|Pama croaker|393|9917|30|
|_Scomberomorus commerson_|Spanish mackerel|397|1176|30|
|_Lobotes surinamensis_|Tripletail|398|1016|20|
|_Rastrelliger kanagurta_|Indian mackerel|426|841|30|
|_Parastromateus niger_|Black pomfret|457|723|30|
|_Otolithes ruber_|Tigertooth croaker|481|906|30|
|_Plotosus canius_|Eeltail catfish|576|577|20|
|_Polynemus paradiseus_|Paradise threadfin|583|5845|20|
|_Pangasius pangasius_|Fatty catfish|727|3817|20|
|_Pampus argenteus_|Silver pomfret|747|3946|30|
|_Lates calcarifer_|Lates perch|769|5594|30|
|_Tenualosa ilisha_|Hilsa shad|812|41826|30|
|_Arius arius_|Catfish|891|105|20|

6
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# **3.3 Econometric Measurement of Catch Quantity Response**

We use econometric estimation to generate species-level measures of salinity response elasticity: the percent change in catch quantity associated with a 1 percent change in riverine salinity. Our econometric model captures interactions between local riverine salinity and species identity. We estimate the model in logarithm form because the estimated salinity parameters can be interpreted as elasticity measures. (1) 0+ + 0 ii ii ii UUii jj jj FFjj ii jj jj FFjj ii ii ln (QQ ) = ββ ∑ββ DD ∑γγ DD + εε ln(SS ) + ∑εε DD ln(SS ) + εε where Qi = Catch quantity at market location (upazila) i DUi = Dummy variable for upazila i (1 if upazila i; 0 otherwise) DFj = Dummy variable for fish species j (1 if fish species j; 0 otherwise) Si = River salinity near upazila i In model (1), the log of a catch quantity recorded at the market in upazila i is a function of upazila-specific factors ( ), the species caught ( ), the log of riverine salinity near the market ) , and the interaction of salinity with species factors ( ) ). For each species (j), the salinity response elasticity ii UUii jj FFjj ii ββ DD γγ DD (SS is given by: FFjj ii DD ln(SS (2) 0 FFjj jj εε = εε + εε We have estimated the model with 832 observations; full results are presented in Appendix Table A1. The model fit is robust, with an adjusted R<sup>2</sup> of 0.55 and high significance for many parameter estimates. The results have been combined with equation (2) to produce the species salinity response elasticities in Table 2. These vary from -.49 for _Labeo bata_ (0.49% _decline_ in catch size for each 1% increase in salinity) to 0.20 for _Platycephalus indicus_ (0.20% _increase_ in catch size for each 1% increase in salinity). For our two illustrative examples, Table 2 shows that _Scomberomorus guttatus_ (King mackerel) has an overall saline _Scomberomorus commerson_ response elasticity of -.08. For (Spanish mackerel), the elasticity is +0.07.

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**Table 2:  Species salinity response elasticities**

|Species|Common Name|ε0|εj|εFj|
|---|---|---|---|---|
|_Labeo bata_|Bata labeo|-0.26|-0.22|-0.49|
|_Arius arius_|Catfish|-0.26|-0.14|-0.40|
|_Sillaginopsis panijus_|Flathead silago|-0.26|-0.09|-0.35|
|_Otolithoides pama_|Pama croaker|-0.26|-0.08|-0.35|
|_Euthynnus affinis_|Kawakawa|-0.26|-0.05|-0.31|
|_Tenualosa ilisha_|Hilsa shad|-0.26|0.00|-0.26|
|_Setipinna phasa_|Gangetic hairfin anchovy|-0.26|0.05|-0.21|
|_Pangasius pangasius_|Fatty catfish|-0.26|0.06|-0.20|
|_Pampus argenteus_|Silver pomfret|-0.26|0.13|-0.14|
|_Johnius coitor_|Coitor croaker|-0.26|0.13|-0.13|
|_Pomadasys maculatus_|Blotched grunter|-0.26|0.14|-0.12|
|_Polynemus paradiseus_|Paradise threadfin|-0.26|0.15|-0.11|
|_Coilia dussumieri_|Golds potted anchovy|-0.26|0.15|-0.11|
|_Scomberomorus guttatus_|King mackerel|-0.26|0.18|-0.08|
|_Pseudapocryptes elongatus_|Pointed-tail goby|-0.26|0.19|-0.07|
|_Escualosa thoracata_|White sardine|-0.26|0.20|-0.06|
|_Rastrelliger kanagurta_|Indian mackerel|-0.26|0.22|-0.05|
|_Ilisha elongata_|Herring|-0.26|0.23|-0.04|
|_Thunnus obesus_|Bigeye tuna|-0.26|0.23|-0.03|
|_Lobotes surinamensis_|Tripletail|-0.26|0.23|-0.03|
|_Plotosus canius_|Eeltail catfish|-0.26|0.24|-0.02|
|_Setipinna taty_|Scaly hairfin anchovy|-0.26|0.25|-0.01|
|_Stigmatogobius sadanundio_|Knight goby|-0.26|0.28|0.01|
|_Mystus gulio_|Gulio catfish|-0.26|0.29|0.03|
|_Otolithes ruber_|Tigertooth croaker|-0.26|0.31|0.05|
|_Parastromateus niger_|Black pomfret|-0.26|0.33|0.06|
|_Scomberomorus commerson_|Spanish mackerel|-0.26|0.33|0.07|
|_Lates calcarifer_|Lates perches|-0.26|0.33|0.07|
|_Platycephalus indicus_|Bartail flathead|-0.26|0.46|0.20|

12
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# **5 Potential Health Impacts**

The results in Section 3 show a large decline in the food-fish catch as riverine salinity moves from its minimum to maximum level during the year. A decline of this magnitude has potentially serious health implications for the region, since ample previous research has documented the role of fish protein intake in promoting mother/child health in Bangladesh (Rifata et al. 2023; Andrews et al. 2022; Dasgupta et al. 2021; Dasgupta and Wheeler 2019; Ferdous et al. 2015; Bogard et al. 2015). As Figure 3 and our econometric results show, the decline of food fish supplies is concentrated during the period of rapid riverine salinity increase in the spring. The magnitude of the associated health impacts depends upon whether mothers have the resources to compensate for declining fish supplies by increasing consumption of other protein sources. In this context, Bangladesh’s recent progress in reducing poverty is notable. According to the World Bank’s World Development Indicators, the country’s multidimensional poverty headcount ratio was 31.3% in 2010, 20.5% in 2016 and 6.6% in 2022. While the southwest coastal area remains relatively poor when compared with other regions, it has undoubtedly benefited from this trend.

Under current conditions, are the resources of poor households adequate to compensate for the sharp salinity-induced swings in riverine fish supplies in the southwest coastal region? To address this question, we have extracted the relevant individual and household data from the two most recent Bangladesh Demographic and Health Surveys (DHS): 2022 and 2018. We have limited our sample to household clusters in the six southwest coastal districts that are most strongly impacted by salinity-driven fluctuation in fish supplies. The two most recent DHS surveys do not include survey information for the peak salinity months, so we cannot draw direct inferences from the data. However, they do include information about the birth months of surveyed children. This permits investigation of differences in child morbidity and mortality measures for children born during the three peak salinity months (March, April, May) when food fish stocks are sharply lower.

Table 3 reports our results for DHS sampling clusters in southwest coastal Bangladesh during the survey years 2018 and 2022. Sample sizes for the two years are 1,271 and 1,344 individuals. The table reports means and percent differences for probabilities of mortality, diarrhea and stunting for children born in peak salinity months and off-peak months.<sup>2</sup>

**Table 3:  Southwest coastal Bangladesh – peak salinity at birth and child morbidity/mortality**<sup>**3**</sup>

|||Peak<br>Salinity<br>|||||||
|---|---|---|---|---|---|---|---|---|
|N|Year|Birth<br>Month|Prob.<br>Death|%<br>Difference|Prob.<br>Diarrhea|%<br>Difference|Prob.<br>Stunted|%<br>Difference|
|1,271|2018|0|0.039||0.037||0.258||
||2018|1|0.048|25.187|0.062|69.896|0.280|8.787|
|1,344|2022|0|0.025||0.048||0.100||
||2022|1|0.028|13.333|0.040|-16.478|0.127|26.543|

> 2 We use the conventional definition of moderate to severe stunting, which corresponds to a height-for-age z-score below -2.0.

> 3 The probability of death in Table 3 is the incidence of children reported dead for whom birth months are provided.

15
These results provide evidence that, despite recent poverty reduction in Bangladesh, children born in the southwest coastal region during peak salinity months have suffered from higher morbidity and mortality rates. For children born in peak salinity months, death probabilities in the 2018 and 2022 surveys are 25.2% and 13.3% higher, respectively. The evidence for diarrhea is mixed, with a probability 69.9% higher in 2018 but 16.5% lower in 2022. For stunting, children born in the peak salinity months have probabilities 8.8% higher in 2018 and 26.5% higher in 2022.

# **6 Summary and Conclusions**

the southwest coastal region of Bangladesh. At the same time, annual flux dynamics propel salinity changes so large that they can provide insights into future changes as high-salinity water moves steadily inland. This paper combines measures from river salinity monitors with fish sales records from neighboring wholesale markets to assess the magnitude, spatial distribution and fishing impact of salinity changes over the annual cycle in 2023. In traditional analyses, measured changes in river salinity are combined with species-level saline tolerance parameters to project changes in the spatial distribution of fish stocks. In this analysis, we incorporate two additional factors: differential responses to salinity change by fish species with similar survival limits for salinity exposure; and fishers’ search for more profitable fishing grounds as the fish respond to changing salinity. Together, these two factors determine fluctuations in fish catches as salinity changes.

Our econometric analysis shows that the complex interplay of species-specific relocation behavior and fishers’ search can generate very different catch patterns for fish that have similar or identical salinity tolerance ranges. For some species increasing salinity induces a sharp decline in the catch, while for others the interplay of relocation and fishers’ profit-motivated search can induce an increase in the catch. The strength of our results suggests that technically determined saline tolerance parameters have limited utility as predictors of the magnitude and spatial distribution of fish catch quantities as salinity changes. Since fish catch records of the type we have surveyed are commonly available, we believe that future analyses could profit from the evidence they provide.

To assess the implications for households at different income levels, we have performed separate econometric analysis for low-, medium, and high-price fish. We find great responsiveness to salinity change in all groups, but the response of the fish catch to salinity change is greatest in the high-price group. In a parallel exercise, we have performed an econometric analysis of the fish price response as varying salinity changes the typical catch size. We find a statistically significant but relatively modest price response for high-price fish, perhaps reflecting a greater quantity response for luxury commodities. However, for low- and medium-price fish we find no significant price response to salinity change. This somewhat surprising result may warrant further research, since it suggests that fish sellers in southwest coastal Bangladesh choose to keep prices relatively stable for fish that are marketed to households of more modest means. By implication, reduced stocks in high-salinity periods are rationed by non-price methods.

protein consumption in low-income households, with associated impacts on maternal/child nutrition and health. The magnitude of the impact will depend on whether poor consumers’ resources enable them to substitute other protein sources. Poverty has fallen significantly in Bangladesh during the past two decades, although the southwest coastal region has remained relatively poor by national standards. To test whether recent income growth has increased household resilience in this context, we analyze over 16
2,500 case records from DHS survey clusters for the southwest coastal region in 2018 and 2022. Our analysis asks whether three standard measures of child health – mortality, diarrhea incidence and stunting – are worse for children born during the annual peak salinity months. We find substantially higher mortality and stunting rates for children born during those months, while the results for diarrhea are mixed.

In summary, our research suggests two basic conclusions about salinity responses in southwest coastal Bangladesh. First, the results show that salinity change in riverine Bangladesh has very large consequences for fish protein availability, and the available evidence suggests that this remains a significant child health problem despite the continuing fall in the national poverty rate. The second conclusion relates to methodology. Traditionally, projections of salinity impacts on the size and spatial distribution of fish stocks have relied on technically determined salinity tolerance parameters. However, the results of our econometric analysis suggest that these parameters have limited utility for projecting the impact of salinity changes on actual fish catches. Future projection exercises might well benefit from using more empirical evidence on the timing and magnitude of fish catches as salinity changes.

With the near certainty that sea-level rise will persist beyond 2100, even with immediate stabilization of greenhouse gas emissions, coastal regions like Bangladesh are at the forefront of climate change impacts. Our research highlights how coastal communities adapt to increasing river water salinization by modifying their behaviors. These adaptive strategies provide valuable insights into the potential responses of millions of households worldwide who will confront similar challenges by the end of the century.

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