Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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Do field-level practices of Cambodian farmers prompt a pesticide lock-in?
Flor, Rica Joy ; Maat, Harro ; Hadi, Buyung Asmara Ratna ; Kumar, Virender ; Castilla, Nancy - \ 2019
Field Crops Research 235 (2019). - ISSN 0378-4290 - p. 68 - 78.
Agronomic practices - Integrated Pest Management - Mekong Delta - Pesticide lock-in - Sustainability

Agronomic practices such as fertilizer application or seed rates have been known to affect rice pests and damage, but the evidence is often blurred in studies on pest management decisions and invisible in studies on pesticide lock-in. Combined agronomic practices and pesticide use may create technological lock-in, occurring when the combination has accumulated advantages over time which encourages its continued use, even if better options are available. We present results from a survey among farmers (N = 400) from five provinces in Cambodia. We asked about field-level, agronomic practices and applied a regression analysis to determine whether these practices affect pesticide application. Farmers from the selected provinces produce rice intensively, particularly those in provinces in the Mekong Delta where a percentage of farmers would aim for three crops per year. Cambodian farmers in the five sampled provinces rely on pesticides for pest control with an average of 2–5 applications each for herbicide and insecticide, and 1–6 applications of fungicide per season. Farmers from the Mekong Delta, particularly Prey Veng Province, made more pesticide applications. Interestingly, of nine agronomic practices tested, six were found to significantly correlate with no applications as in organic management recommendations, as well as misuse of pesticides. Varied combinations of agronomic practices including seed rate, crop establishment method, seed treatment, cultivating larger landholdings, irrigation through gravity irrigation system, and number of fertilizer applications predicted herbicide, insecticide and fungicide application. Interactions varied across wet and dry season. Pesticide use makes sense to farmers given a specific combination of agronomic practices. Therefore we argue that field-level agronomic practices contribute to pesticide lock-in as much as wider innovation system conditions such as trade and regulation of pesticides. These findings imply that addressing the pesticide lock-in to facilitate a shift to more sustainable practices, such as Integrated Pest Management, should not only aim at broader innovation systems or industry level changes. There are adjustments and fine-tuning of agronomic practices that also need to be made to wean farmers from pesticide reliance.

Do strategic delta plans get implemented? The case of the Mekong Delta Plan
Seijger, Chris ; Hoang, Vo Thi Minh ; Halsema, Gerardo van; Douven, Wim ; Wyatt, Andrew - \ 2019
Regional Environmental Change 19 (2019)4. - ISSN 1436-3798 - p. 1131 - 1145.
Governance - Mekong Delta - Social learning - Soft implementation - Strategic planning - Transitions

A strategic delta plan can alter the course of delta management. Implementation of such a plan essentially involves a change of minds about delta management priorities and strategies for sustainable livelihoods. Such a change of minds, or “soft implementation”, must come before material, or “hard”, implementation can take off. To explore the influence of strategic delta plans in bringing about a change of minds among the actors involved, we examined four features of soft implementation: prospects for change, new mental models, consent and decision-making. We then applied these features to analyse implementation of the Mekong Delta Plan (MDP). The MDP envisions agro-industrialisation in the Mekong Delta, with dynamic land use, high-value commodities and enhanced interprovincial collaboration. We found that 3 years after its completion, the MDP has indeed been influential in introducing new ways of thinking about both delta problems and transformative strategies for agribusiness development. Minds have changed at all levels of the planning system, though change at the local level remains most limited. Implementation is fragile, however, as a small though influential group actively promotes and subscribes to the MDP’s precepts. The plan has influenced national policies, provincial project proposals and donor loans. We found the four features to provide a valuable entry point for assessing the influence and effectiveness of the strategic delta plan. They might prove useful to planners, investors and researchers too in designing and evaluating strategic planning processes for more sustainable land and water resources management.

Integrating farmers’ adaptive knowledge into flood management and adaptation policies in the Vietnamese Mekong Delta : A social learning perspective
Tran, Thong Anh ; Rodela, Romina - \ 2019
Global environmental change : human and policy dimensions 55 (2019). - ISSN 0959-3780 - p. 84 - 96.
Adaptation - Flood management - Knowledge brokers - Mekong Delta - Shadow systems - Social learning - Vietnamese

Flood management and adaptation are important elements in sustaining farming production in the Vietnamese Mekong Delta (VMD). While over the past decades hydraulic development introduced by the central government has substantially benefited the rural economy, it has simultaneously caused multiple barriers to rural adaptation. We investigate the relational practices (i.e., learning interactions) taking place within and across the flood management and adaptation boundaries from the perspective of social learning. We explore whether and how adaptive knowledge (i.e., experimental and experiential knowledge) derived from farmers’ everyday adaptation practices contributes to local flood management and adaptation policies in the selected areas. We collected data through nine focus groups with farmers and thirty-three interviews with government officials, environmental scientists, and farmers. Qualitative analysis suggests that such processes are largely shaped by the institutional context where the boundary is embedded. This study found that while the highly bureaucratic operation of flood management creates constraints for feedback, the more informal arrangements set in place at the local level provide flexible platforms conducive to open communication, collaborative learning, and exchange of knowledge among the different actors. This study highlights the pivotal role of shadow systems that provide space for establishing and maintaining informal interactions and relationships between social actors (e.g., interactions between farmers and extension officials) in stimulating and influencing, from the bottom-up, the emergence of adaptive knowledge about flood management and adaptation in a local context.

Modelling seasonal flows alteration in the Vietnamese Mekong Delta under upstream discharge changes, rainfall changes and sea level rise
Anh, Duong Tran ; Hoang, Long Phi ; Bui, Minh Duc ; Rutschmann, Peter - \ 2019
International Journal of River Basin Management 17 (2019)4. - ISSN 1571-5124 - p. 435 - 449.
climate change - Mekong Delta - MIKE 11 modelling - River flow regime

The Vietnamese Mekong Delta (VMD) is one of the world’s most vulnerable deltas to climate change and sea level rise. Adequate understandings of future hydrological changes are crucial for effective water management and risk-proofing, however, this knowledge body is currently very limited. This study quantifies the responses of the VMD’s river flow regime to multiple stimuli, namely future upstream inflow variation, local climate change, and sea level rise. The one-dimensional hydrodynamic model MIKE 11 was used to simulate discharges and water levels across the delta. We developed four scenarios to represent changes in the upstream discharges, precipitation changes and sea level rise, covering the 2036–2065 period. We downscaled climate data and applied three bias-correction methods for five General Circulation Models (GCM), and two Representative Concentration Pathways (RCPs). The climate change projections show similar trends of increasing wet season precipitation and decreasing dry season precipitation. However, cross-scenario variations are sometimes large, depending on the individual GCMs, the RCPs and specific locations. The hydraulic simulation results indicate that, under discharge changes between −20% and +10%, combined with in-delta precipitation variations during the dry season, river discharges at the four representative stations could reduce substantially from −2.5% to −100.2%. During the wet season, the calculated river discharges show increase between 7.3% and 46.7% under four considered scenarios. Substantial changes in the VMD’s river flow regime could have potentially serious implications for water management, especially saltwater intrusion, and therefore calling for timely adaptation measures.

Simulating future flows and salinity intrusion using combined one- and two-dimensional hydrodynamic modelling-the case of Hau River, Vietnamese Mekong Delta
Duong, T.A. ; Phi, Long H. ; Bui, Minh D. ; Rutschmann, Peter - \ 2018
Water 10 (2018)7. - ISSN 2073-4441
Climate change - Mekong Delta - MIKE modelling - Salinity intrusion - Sea level rise

Salinity intrusion in the Vietnamese Mekong Delta (VMD) has been exacerbated significantly in recent years by the changing upstream inflows, sea level rise resulting from climate change, and socioeconomic development activities. Despite significant damage to agricultural production and freshwater supplies, quantitative assessments of future flows and salinization remain limited due to lack of observation data and modelling tools to represent a highly complex hydraulic network. In this study, we combine 1D-MIKE 11 and 2D-MIKE 21 hydrodynamic models to simulate future flows, water level and salinity intrusion in the Hau River-one main river branch in the Mekong Delta. Future hydrological changes are simulated under multiple scenarios of upstream inflow changes, climate change and sea level rise for the 2036-2065 period. We first use the 1D-MIKE 11 to simulate the flow regime throughout the whole VMD using upstream discharges, outlet water levels and rainfall data as boundary conditions. Output from this step is then used to force the 2D-MIKE 21 model to estimate flow velocity, water level and salinity concentration in the Hau River, focusing on the salinization-prone section between Can Tho, Dinh An, and Tran De estuaries. Simulation results show that salinization will increase substantially, characterized by (1) higher salinity intrusion length under spring tide from 6.78% to 7.97%, and 8.62% to 10.89% under neap tide; and (2) progression of the salinity isohalines towards the upper Mekong Delta, from 3.29 km to 3.92 km for 1 practical salinity unit (PSU) under spring tide, and 4.36 km to 4.65 km for 1 PSU concentration under neap tide. Additionally, we found that salinity intrusion will make it more difficult to re-establish the freshwater condition in the estuary in the future. In particular, the flushing time required to replace saltwater with freshwater at the estuaries tends to increase to between 7.27 h for maximum discharge of 4500 m3/s and 58.95 h for discharge of 400 m3/s under the most extreme scenario. Increasing salinization along the Hau River will have important consequences for crop production, freshwater supplies and freshwater ecosystems, therefore requiring timely adaptation responses.

Stakeholders’ assessment of dike-protected and flood-based alternatives from a sustainable livelihood perspective in An Giang Province, Mekong Delta, Vietnam
Tran, Dung Duc ; Halsema, Gerardo van; Hellegers, Petra J.G.J. ; Ludwig, Fulco ; Seijger, Chris - \ 2018
Agricultural Water Management 206 (2018). - ISSN 0378-3774 - p. 187 - 199.
Dike - Flood-based farming systems - Livelihoods - Mekong Delta - Multi-criteria analysis

Construction of extensive high dike compartments has spurred land use intensification on the upper floodplains of the Vietnamese Mekong Delta. Increasingly intense rice-based farming within these compartments has changed the water dynamics of the delta, making it impossible to exploit the erstwhile benefits of floodwaters. Progressive contraction of the natural floodplains has led to reduced deposition of fertile sediments and environmental degradation, endangering the sustainability of farmers’ livelihoods. The Mekong Delta Plan recommends discontinuance of high dike construction in the upper delta and restoration of the floodplains. However, this requires a radical shift in the agricultural economy, halting intensification of rice-based farming systems and developing alternative farming systems that can flourish on restored floodplains using “living with floods” livelihood strategies. This paper explores stakeholders’ perceptions and appreciation of these contrasting farming and livelihood systems for the upper delta. It also examines the extent that alternatives to flood-based agricultural systems are viewed as feasible and attractive. We applied multi-criteria analysis (MCA) with analytic hierarchy process (AHP) to explore the views of double and triple rice farmers and experts on alternatives based on a set of economic, water management and environmental aspects. MCA results indicate a clear preference among both farmers and experts for flood-based farming systems with low dikes. Floodwater retention capacity, infrastructure for flood protection, environmental sustainability, and market stability were ranked as the most important factors contributing to livelihood sustainability on the delta.

Managing flood risks in the Mekong Delta : How to address emerging challenges under climate change and socioeconomic developments
Hoang, Long Phi ; Biesbroek, Robbert ; Tri, Van Pham Dang ; Kummu, Matti ; Vliet, Michelle T.H. van; Leemans, Rik ; Kabat, Pavel ; Ludwig, Fulco - \ 2018
Ambio 47 (2018)6. - ISSN 0044-7447 - p. 635 - 649.
Challenges - Climate change - Flood-risk management - Mekong Delta - Socioeconomic developments - Solutions
Climate change and accelerating socioeconomic developments increasingly challenge flood-risk management in the Vietnamese Mekong River Delta—a typical large, economically dynamic and highly vulnerable delta. This study identifies and addresses the emerging challenges for flood-risk management. Furthermore, we identify and analyse response solutions, focusing on meaningful configurations of the individual solutions and how they can be tailored to specific challenges using expert surveys, content analysis techniques and statistical inferences. Our findings show that the challenges for flood-risk management are diverse, but critical challenges predominantly arise from the current governance and institutional settings. The top-three challenges include weak collaboration, conflicting management objectives and low responsiveness to new issues. We identified 114 reported solutions and developed six flood management strategies that are tailored to specific challenges. We conclude that the current technology-centric flood management approach is insufficient given the rapid socioecological changes. This approach therefore should be adapted towards a more balanced management configuration where technical and infrastructural measures are combined with institutional and governance resolutions. Insights from this study contribute to the emerging repertoire of contemporary flood management solutions, especially through their configurations and tailoring to specific challenges.
Barriers to Implementing Irrigation and Drainage Policies in An Giang Province, Mekong Delta, Vietnam
Tran, D.D. ; Weger, J. - \ 2018
Irrigation and Drainage 67 (2018)51. - ISSN 1531-0353 - p. 81 - 95.
Delta du Mékong - Dike protection - Floodplain - Irrigation and drainage - Irrigation et drainage - Livelihoods - Mekong Delta - Moyens de subsistance - Plaine d'inondation - Protection des digues
Water management in delta floodplains worldwide faces many challenges due to the changing climate and increasing human intervention in the hydrological regimes of rivers. Irrigation and drainage systems are necessary components of a water management strategy that aims to support human habitation and agricultural production, but which need effective coordination in order to adapt to exogenous impacts. However, management of such systems often fails for a variety of reasons. In the floodplain of the Vietnamese Mekong Delta, irrigation and drainage systems under dike protection confront ineffective implementation of water management policy, posing a challenge for adaptation to exogenous impacts on the hydrological regime. Over the past two decades, farmers have increasingly cultivated annual triple-rice crops in high-dike compartments, ignoring government regulations that call for flood retention. This study analyses interviews with farmers to identify their motivation for not implementing the triennial cropping off-season advised by the local government (3-3-2 cycle). Our findings show that farmers have avoided implementing the 3-3-2 cycle because of various disadvantages that the system presents for them. Local officials, in turn, have accepted farmers' disregard of the rule. Lessons learnt from this study are considered to explore measures to effectively adapt to future hydrological changes.
Mapping land-use dynamic in the Vietnamese mekong delta
Le, Thuy Ngan ; Bregt, Arnold K. - \ 2017
In: SGEM2017 Conference Proceedings SGEM (International Multidisciplinary Scientific GeoConference & EXPO SGEM 23) - ISBN 9786197408034 - p. 589 - 594.
GIS - Land-use - Mekong Delta - Time-series map - Vietnam

Policies supporting rice cultivation and investments in water infrastructures facilitated intensification and diversification of land-use in the Vietnamese Mekong Delta. Although the major changes are acknowledged in the literature, few studies have examined the dynamism of land-use across the delta. Overlaying land-use maps, we identified land-use dynamic by the number of changes observed during the 11-year study period. Land-use was found to be highly variable, changing by 14.94% annually between 2001 and 2012. Rice cropping underwent the greatest change, evolving from single cropping of traditional varieties towards double and triple cropping of highyielding varieties. A clear trend was observable in the upper delta, where large expanses of triple rice cropping, especially within the dyke systems. Changes in land-use were also observed in the central delta and coastal zone, but here the pattern was more fragmented. Meanwhile, aquaculture remained stable after rapid expansion in the early 2000s.

A Decision Tree Analysis to Support Potential Climate Change Adaptations of Striped Catfish (Pangasianodon hypophthalmus Sauvage) Farming in the Mekong Delta, Vietnam
Nguyen, L.A. ; Verreth, J.A.J. ; Leemans, H.B.J. ; Bosma, R.H. ; Silva, S. De - \ 2016
Tropicultura 34 (2016)Special. - ISSN 0771-3312 - p. 105 - 115.
Mekong Delta - Striped cathfish culture - Climate change - Adaption - Vietnam
This study uses the decision tree framework to analyse possible climate change impact adaptation options for pangasius (Pangasianodon hypopthalmus Sauvage) farming in the Mekong Delta. Here we present the risks for impacts and the farmers' autonomous and planned public adaptation by using primary and secondary data. The latter studies showed that a proportion of the pangasius farms located in the coastal provinces will be affected by salinity intrusion in the dry season. Options to adapt to this are: modify pangasius farming practice, stock other species or stock saline-tolerant pangasius. With research and extension support, farmers can further improve their already adapted practice to deal with salinity or use water recirculation systems for prolonged nursery rearing. A breeding program for saline­ tolerant striped catfish requires a medium-to long­ term investment (0.4 % of the production cost) from government and/ or private company. Pangasius farms in up- and mid-stream regions and in coastal areas, which are not located within upgraded government dyke-protected areas, will be affected by flooding at the end of each rainy season. This implies an increased cost for dykes to about 0.34% and 0.25% of the total variable costs for one harvest per ha in the up- and mid-stream regions, and in the downstream region, respectively.
An evaluation of fish health-management practices and occupational health hazards associated with Pangasius catfish (Pangasianodon hypophthalmus) aquaculture in the Mekong Delta, Vietnam
Phu, Tran Minh ; Phuong, Nguyen Thanh ; Dung, Tu Thanh ; Hai, Dao Minh ; Son, Vo Nam ; Rico Artero, Andreu ; Clausen, Jesper Hedegaard ; Madsen, Henry ; Murray, Francis ; Dalsgaard, Anders - \ 2016
Aquaculture Research 47 (2016)9. - ISSN 1355-557X - p. 2778 - 2794.
Pangasianodon hypophthalmus - Antimicrobials - Catfish - Fish disease - Mekong Delta - Occupational health

This study aimed to evaluate the current status on the use of probiotics, disinfectants and antimicrobials in hatcheries, nurseries and grow-out farms producing Pangasius catfish (Pangasianodon hypophthalmus) in the Mekong Delta, Vietnam. Semi-structured interviews were conducted with 83 aquaculture enterprises (15 hatcheries, 32 nurseries and 36 grow-out farms). Farmers reported use of a total of 24 different antimicrobials, e.g. for treatment of bacillary necrosis and motile aeromonad septicaemia, and a variety of disinfectants, probiotics and nutritional supplements. In contrast to small-scale farmers, all large-scale grow-out farmers studied were certified and therefore had higher levels of formal education and specialized aquaculture training to diagnose and treat diseases. All farmers prepared their own medicated feed with a high risk of treatment failure, negative environmental impact from released antimicrobials and resistance development. Small-scale farmers were at particular occupational health risks when handling antimicrobials and other chemicals, e.g. mixing medicated feed with bare hands. There is an urgent need to improve knowledge and use innovative approaches, e.g. private-public partnerships, to assure a prudent use of chemicals, to improve capacity and access to disease diagnosis, particularly for small-scale grow-out farmers and nurseries. Efforts to control use of antimicrobials in aquaculture should be coordinated with the livestock and human health sectors taking an One-Health approach.

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