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The shrimp industry in Bangladesh is an important economic sector with growing demand, export potential, and employment opportunities. However, the industry is threatened by external and local production and market risks. Risk management strategies can be implemented through farming systems modification developing of different types of shrimp and prawn-based systems, although the adaptive capacity and economic and socio-ecological impacts are unclear. This study evaluated risks, adaptation strategies, profitability, and socio-ecological dynamics in two shrimp-based (shrimp/shrimp/shrimp and wet season (WS) rice/shrimp/shrimp) and two prawn-based (prawn/dry season (DS) rice/prawn and prawn/DS rice/prawn/dike crops) farming systems. Data was collected using focus group discussions (n = 45), household case studies (n = 18), household surveys (n = 120), and key informant interviews (n = 20). Major risks identified included disease outbreaks, lack of tidal water, salinisation, heat extremes, irregular and reduced rainfall, and price fluctuations. Agronomic management (modifying production systems, adjusting farming operations, input applications, dike cropping) was the dominant adaptation strategy in addition to financial mechanisms (market update, selling live stocks and inputs credits), gher management (water management, excavation, dike management) and water management. Adverse socio-ecological impacts of shrimp farming included salinisation, biodiversity loss, soil and water contamination, and reduced crop and livestock production. In contrast, positive impacts of prawn farming included crop diversification and livestock production and decreased salinisation, soil degradation, and biodiversity loss. Despite higher production costs, prawn-based systems generated net income nearly three times higher (USD 3410 to 4470) as compared to shrimp-based systems (USD 1570 to 1790) because dike crops added about 25% extra income. A critical insight of the research is that the prawn-based systems (prawn/DS rice/prawn/dike crop and prawn/DS rice/prawn) were economically more viable (profitable and less risky) than the shrimp-based system. However, neither the shrimp nor prawn system is feasible in all locations. Improved and semi-intensive shrimp farming in high salinity areas with available tidal water and an integrated prawn-based farming system in low to moderate salinity areas can be a viable agricultural land use planning in southwest coastal Bangladesh. This research can contribute to sustainable land use planning for brackish water shrimp and fresh water prawns, and planning to increase the profitability, risk resilience and competitiveness of the shrimp- and prawn-based farming systems with less socioecological impacts.

The potential existence of threshold yield loss in dry season rice growing systems under coastal saline environment remains unexplored, a scenario that could have policy relevance in government planning of rice intensification in the coastal areas of Bangladesh. This study applied the adaptation tipping points (ATPs) approach to investigate threshold yield loss from multiple perspectives of farmers affected by salinity. Data were generated from 280 randomly-selected farmers (rice farmers, n = 109; shrimp farmers, n = 107; salt farmers, n = 64) from two coastal sub-districts using a semi-structured survey. Key informant interviews and focus group discussions were conducted to complement the survey results. Our study revealed that despite government actions to promote dry season rice cultivation, farmers have been growing less rice in this season, with salinity-affected yield loss being the prime reason. Most of the rice farmers have considered that they would discontinue rice cultivation in this season due to yield loss, while shrimp and salt farmers have already reduced rice cultivation for the same reason and shifted to shrimp and salt farming as they perceived these enterprises as highly profitable and require less labour than rice farming. Rice farmers would tolerate a greater rice yield loss (23%) under saline conditions compared with the shrimp (16%) and salt farmers (14%). The yield loss thresholds indicate the need for government actions to support and encourage integrated land management for rice, shrimp and salt farming, rather than research and extension efforts for dry season rice expansion alone. These actions could strengthen sustainable livelihood options to ensure food security, and contribute to the achievement of sustainable development goals, for instance no poverty (SDG-1), zero hunger (SDG-2), and good health and well-being (SDG-3).