Factors influencing farming households’ climate change adaptation strategies in Central Vietnam

PLOS One | https://doi.org/10.1371/journal.pone.0328058 July 10, 2025 4 / 22 RQ2. How do behavioral attributes—such as risk perception, farming experience, and intra-household dynamics— interact with structural constraints to influence the selection of specific adaptation strategies to saltwater intrusion and drought? RQ3. Based on empirical evidence from multivariate modeling, what context-specific and scalable policy recommenda- tions can be formulated to enhance the adaptive capacity of smallholder farmers facing climate-induced risks in Viet- nam’s coastal regions? This study makes some novelties and contributions to the literature on climate change adaptation, particularly within the context of transitional economies in Southeast Asia. First, it provides one of the few empirical investigations into household-level adaptation strategies in coastal and salinity-prone regions of Vietnam—an area highly vulnerable to climate- induced hazards yet underrepresented in current academic discourse. Second, the study advances methodologi- cal rigor by employing a Multinomial Logit (MNL) model to capture the differentiated nature of adaptation decisions across multiple strategies, moving beyond aggregate or binary analyses commonly used in prior research. Third, it integrates a multidimensional framework that simultaneously considers socio-economic, demographic, institutional, and environmen- tal determinants, offering a more holistic understanding of adaptation behavior. Fourth, the study addresses the often-

overlooked behavioral and psychological aspects of adaptation, including gender dynamics, experience, and perception of risk, which are critical in shaping real-world decision-making under uncertainty. Fifth, by disaggregating adaptation responses to specific stressors such as saltwater intrusion and drought, the research provides context-sensitive insights that can inform localized adaptation planning. Finally, the study contributes practical value by generating evidence-based policy recommendations tailored to different household profiles, thereby supporting the development of inclusive and scal- able adaptation strategies aligned with national climate resilience goals. 2. Materials and methods 2.1 Study site This study was conducted in Quang Binh province in the Central region of Vietnam, specifically in Tuyen Hoa district (17.7882° N, 106.2051° E) in the upper reaches of the Gianh River, which has been severely affected by drought and saltwater intrusion over the past 10 years. Gianh River is originated from the 2,017 m high Co Pi mountainside area in the Truong Son range, flowing through the districts of Minh Hoa, Tuyen Hoa, Bo Trach, Quang Trach, and Ba Don commune, then going to the East Sea at Cua Gianh. The Gianh River upstream is located in the northwest of Tuyen Hoa district, from the mountains on the Lao Bao peninsula. Mountainous terrain and steep hills, with small streams, waterfalls, and lakes, characterize this area. In the Tuyen Hoa district, the Gianh River upstream flows through the production areas of three

communes Chau Hoa, Phong Hoa, and Duc Hoa [46,47] Tuyen Hoa is always affected by northern air masses in winter (Southeast wind) and hot, dry West winds in summer (Laos wind). The average annual temperature ranges from 24°C - 25°C, the average annual rainfall is about 2,100– 2,300 mm and is divided into two distinct seasons: the rainy season and the low-rainy season. The rainy season is from September to March of the following year, the average temperature is from 22°C - 23°C, the lowest temperature is in January (about 10°C – 14°C) [48]. Rainfall is concentrated in September, October and November, accounting for 70% − 80% of the total annual rainfall reaching 2,000–2,300 mm, due to the influence of the northeast monsoon combined with disturbances that cause heavy rain such as storms and high pressure. Tropical lows, tropical convergence zones, leading to flooding in the delta. The rainy season is from April to August, the average temperature is about 26°C −27°C. The hot- test month can reach 39°C (June, July and August), the average rainfall only accounts for 20% − 30% of the total annual rainfall [35,47]. The economy of Tuyen Hoa district and the three above communes is mainly based on agriculture. In particular, water from the river has played an essential role in developing agriculture and enriching the locality. This is also where