Agricultural systems are increasingly considered complex adaptive systems. They are dependent on the integrated nature of biophysical and social subsystems , continuously adapt to changing conditions and often display non-linear responses to various drivers of change at multiple scales. This research applied the lens of complex adaptive systems theory to analyze current and historical drivers of change and adaptation pathways of agricultural systems to increased salinity intrusion in coastal areas of the Red River and Mekong deltas in Vietnam since 1975. The analysis is based on 27 in-depth interviews with officials of local and national authorities as well as 198 semi-structured interviews and 11 focus group discussions conducted with farmers along three salinity transects in both deltas in 2015-2016. The results show that a dynamic interplay and feedback of various drivers of change such as policy intervention, farmers' desire for profit maximization, changing salinity conditions, and technological development at different levels of the deltaic social-ecological system have shaped the changes and adaptations in agricultural systems over the last decades. In response to increased salinity intrusion, as exemplified by the historic salinity levels recorded in the Mekong Delta in 2015-2016, various adaptation options have been considered. These include adaptations that would lock-in agricultural production in particular agricultural systems or constrain changes in others, potentially problematic in light of the high uncertainty related to future changes. The study recognizes the need to apply both incremental and transformative changes and select adaptation pathways which allow for continuous change or that are reversible in order to avoid lock-ins and address future challenges. Additionally, attention should be drawn to interactions and feedbacks in future changes within and across adaptation pathways in order to prevent further increases in salinity intrusion and lock-in effects in agricultural systems within the deltas.

Vietnam is exposed to different types of floods that cause severe economic losses, damage to infrastructure, and loss of life. Reliable information on the drivers, patterns and dynamics of flood risk is crucial for the identification, prioritization and planning of risk reduction and adaptation measures. Here, we present a systematic review of existing flood risk assessments in Vietnam. We evaluate the current status, persisting gaps, and challenges regarding the understanding and assessment of flood risk in the country. The literature review revealed that: (i) 65 % of the reviewed papers did not provide a clear definition of flood risk, (ii) assessments had a tendency to prioritize physical and environmental drivers of risk over social, economic or governance‐related drivers, (iii) future‐oriented assessments tended to focus on hazard and exposure trends, while vulnerability scenarios were often lacking, (iv) large and middle‐sized cities were assessed more frequently than others, (v) only few studies engaged with relevant local stakeholders for the assessment of risk and the development of potential solutions, and (vi) ecosystem‐based adaptation and flood risk insurance solutions were rarely considered. Based on these findings, we point out several directions for future research on flood risk in Vietnam.

The resilience concept has provided a new insight and approach to the conventional perspective of agricultural management by emphasizing the need to maintain a diversity of future options to adapt to inevitable and often unpredictable changes. The concept has been taken up by various academic disciplines and development sectors, yet ways to define and operationalize resilience as a measurable concept are still being developed. We contributed to this ongoing effort by implementing a subjective resilience assessment method based on farmers' perceptions of three resilience components: (1) the sensitivity of their agricultural systems to increased salinity intrusion, (2) the capacity to recover from salinity damage, and (3) the capacity to change to other systems if salinity increases in the future. We conducted 27 in-depth interviews with local and national authorities, 11 focus group discussions, and 118 semistructured and 219 structured interviews with farmers in case study villages located along salinity transects in the Mekong Delta and at different distances to sea dikes in the Red River Delta in Vietnam in 2015-2016. Results from the subjective resilience assessment reveal that none of the agricultural systems studied systematically scored higher than the other systems on all three resilience components, implying that an increase in one resilience component by switching agricultural systems would negatively affect others. Agricultural responses to this salinity problem will influence current and long-term adaptability of the systems to future changes in salinity intrusion and other social-ecological developments in the deltas. Improving resilience components, e.g., through policies and interventions, resource allocation, and farming system changes, to sustain agricultural production or facilitate transformation to alternative systems when necessary is critically important for agricultural systems facing stress. Complementing subjective resilience assessments with qualitative data is thus crucial for understanding the drivers of resilience to improve components of resilience for agricultural systems in the respective deltas.