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