Does Adaptation to Saltwater Intrusion Improve the Livelihoods of Farmers? Evidence for the Central Coastal Region of Vietnam
Abstract
:1. Introduction
2. Literature Review
2.1. Economic Indicators
2.2. Social Indicators
3. Material and Methods
3.1. Study Area
3.2. Data Collection
3.3. Overview of SWI Adaptation Methods in the Study Area
- Switching to new salt-tolerant varieties of rice: Farmers continue to produce rice but switch to new varieties that are more salt-tolerant. The local cooperatives sell new rice varieties to farmers at a price below that of the market as a result of government subsidies. The main disadvantage of this method is that the yield is about 25% lower than that of traditional rice.
- Moving to planting papyrus: This method implies that farmers convert their paddy plots into papyrus fields. This crop is neither labor, nor capital, nor time-intensive. The main limitation of this adaptation method is that the consumption market tends to be unstable: papyrus is the main input of the mat industry, which faces a narrowing demand as consumer preferences change.
- Moving to shrimp cultivation: Farmers convert their land to build ponds for shrimp cultivation. In the process, the land is sometimes combined with that of the farmer’s neighbors. This adaptation method requires high initial investments and technical support from the staff of the agricultural extension office. Shrimp production can bring about higher profits but farmers face many risks ranging from diseases to fluctuating selling prices.
- Moving to vegetable cultivation: Farmers convert their paddy plots into vegetable fields. Farmers can produce three seasons per year while the type of vegetables depends on the season. For example, spring onion, cabbage, and peas will be cultivated from March until May; cucumber, okra, and courgettes will be cultivated from June to September; and sweet potatoes, pumpkins, and potatoes from July to February. However, in our study, we do not distinguish between different types of vegetables being produced. Revenues for farmers typically increase, yet profits may not as this method is labor-intensive (planting, caring, and harvesting). Moreover, cultivating vegetables requires substantial amounts of irrigation and farmers may face water shortages in the dry season.
- Moving to lotus-fish cultivation: Farmers convert their paddy fields into fish ponds in which lotus plants are grown and fish are kept at the same time. Farmers get revenues from both fish and lotus products. This method requires lower initial investments than shrimp cultivation, and also the risks involved are lower.
3.4. Conceptual Framework and Econometric Approach
4. Results
4.1. Farm Households’ Characteristics
4.2. Outcome Variables
- Saline-land productivity is calculated as the total output produced on salted land per one hectare of the salted land. The total output is expressed in monetary terms based on market prices in the study period.
- Net farm income is calculated as the total net income from on-farm agricultural activities per one hectare of farm size. The total income is expressed in monetary terms based on the market price in the study period.
- Food security is evaluated by the number of affirmative responses to the six questions in the short form of the Household Food Security Scale (see also Appendix C):
Food security situation | Number of affirmative responses |
1 = Food secure | 0 |
2 = Food secure—at risk | 1 |
3 = Food insecure without hunger | 2–4 |
4 = Food insecure with moderate hunger | 5–6 |
- The rate of children attending school is calculated as the ratio of school-aged children in the household that go to school to the total number of children in the household in that age range (<18 years).
- Life satisfaction is evaluated using 5 statements taken from the Satisfaction With Life Scale (SWLS) (see also Appendix D).
4.3. Probit Models
4.4. Estimated Effects of Adaptation Methods
5. Discussion
6. Conclusions
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
Appendix A
No | Current Status of Rice Production | Impact of SWI |
---|---|---|
1 | Rice plays an important role | Rice production output decline |
2 | The rice planted area has been fluctuating by the conversion of agricultural land into industrial or urban land and by farmers moving away from rice production to other crops or even to aquaculture | Rice production surface decline |
3 | Rice quantities have slightly decreased | Fresh water was inadequate for irrigation |
4 | Changes in the sowing date for winter-spring rice | |
5 | Changes in crops that are being cultivated—e.g., Moving to drought-tolerant crops | |
6 | Rice-fish rotation systems |
Appendix B
No | Social Indicators | Economic Indicators |
---|---|---|
1 | Food security | Land productivity |
2 | Housing facilities | Profitability |
3 | Social equity in income and welfare distribution | Yield per hectare (crop productivity) |
4 | Farmers knowledge | Net farm income |
5 | Awareness of resource conservation | Benefit and cost ratio |
6 | Education level of household members. | |
7 | Calories supply, micronutrient supply | |
8 | Child nutritional status | |
9 | Number of migrated household member |
Appendix C
- In the last 12 months, did you or any other adults in your household ever have to cut the size of your meals or skip meals entirely because there wasn’t enough money for food?
- □
- Yes
- □
- No
- □
- Don’t know
- □
- Refused
- How often did this happen?
- □
- Almost every month
- □
- Sometimes, but not every month
- □
- Only one or two months
- □
- Don’t know
- □
- Refused
- In the last 12 months, did you ever eat less than you felt you should because there wasn’t enough money to buy food?
- □
- Yes
- □
- No
- □
- Don’t know
- □
- Refused
- In the last 12 months, were you ever hungry but didn’t eat because you could not afford enough food?
- □
- Yes
- □
- No
- □
- Don’t know
- □
- Refused
- The food that I/we bought just didn’t last, and I/we didn’t have money to get more. Was this often, sometimes, or never true for you or the other members of your household in the last 12 months?
- □
- Often
- □
- Sometimes
- □
- Never true
- □
- Don’t know
- □
- Refused
- I/we couldn’t afford to eat balanced meals. Was this often, sometimes, or never true for you or the other members of your household in the last 12 months?
- □
- Often
- □
- Sometimes
- □
- Never true
- □
- Don’t know
- □
- Refused
Appendix D. Questions in the Satisfaction With Life Scale (SWLS)
- Strongly disagree.
- Disagree.
- Slightly agree.
- Neither agree nor disagree.
- Slightly agree.
- Agree.
- Strongly agree.
Appendix E
Method | Frequency | Description |
---|---|---|
Non-adaptation | 229 | Farmers do not apply any adaptation methods and keep producing traditional rice varieties. |
NR | 89 | Farmers continue to produce rice but switch to new varieties that are more salt-tolerant. The local cooperatives sell new rice varieties to farmers at a price below that of the market (Agricultural materials are subsidized by the local governments). The main disadvantage of this method is that the yield is about 25% lower than that of traditional rice (Estimates from key informant interviews). |
PP | 29 | Farmers convert their paddy plots into papyrus fields. This crop is neither labor, nor capital, nor time-intensive. The main limitation of this adaptation method is that the consumption market tends to be unstable: papyrus is the main input of the mat industry, which faces a narrowing demand as consumer preferences change. |
SR | 46 | Farmers convert their land to build ponds for shrimp cultivation. In the process, the land is sometimes combined with that of the farmer’s neighbors. This adaptation method requires high initial investments and technical support from the local agricultural extension office. Shrimp production can bring about higher profits but farmers face many risks ranging from diseases to fluctuating selling prices. |
VG | 10 | Farmers convert their paddy plots into vegetable fields. Income from vegetable production of farmers typically increase, yet profits may not as this method is labor-intensive (planting, caring, and harvesting). Moreover, cultivating vegetables requires substantial amounts of irrigation and farmers may face water shortages in the dry season. |
LF | 11 | Farmers convert their paddy fields into fish ponds in which lotus plants are grown and fish are kept at the same time. Farmers get revenues from both fish and lotus products. This method requires lower initial investments than shrimp cultivation, and also the risks involved are lower. |
Total | 414 |
Appendix F
Variables (Unit) | Total Sample | Non-Adapter | Adapters | ||||
---|---|---|---|---|---|---|---|
NR | PP | VG | SR | LF | |||
Household characteristics | |||||||
Family size (No.) | 6.27 (0.06) | 6.33 (0.89) | 5.80 *** (0.16) | 6.13 (0.26) | 6.0 (0.43) | 7.08 *** (0.20) | 5.81 (0.41) |
Dependents in the household (%) | 41.33 (1.32) | 42.86 (1.93) | 40.07 (3.52) | 37.72 (5.69) | 28.3 (9.3) | 44.97 (4.52) | 25.54 ** (8.9) |
Family labor (no.) | 4.54 (0.05) | 4.56 (0.76) | 4.25 ** (0.14) | 4.51 (0.22) | 4.7 (0.36) | 4.95 ** (0.17) | 4.63 (0.35) |
Age of household head (years) | 50.73 (0.28) | 50.27 (0.39) | 51.69 (0.76) | 52.82 ** (1.17) | 50.6 (1.93) | 50 (0.91) | 50 (1.82) |
Education level of household head (1 = secondary or above, 0 otherwise) | 0.4 | 0.4 | 0.29 ** | 0.79 *** | 0.6 | 0.21 ** | 0.3 |
Farm characteristics | |||||||
Proportion of salted land (%) | 78.03 (0.82) | 78.42 (0.98) | 67.52 (1.96) | 80.98 (2.96) | 82.89 (4.82) | 90.18 * (2.34) | 92.2 *** (0.14) |
Land certificate (1 = long-term owner, 0 otherwise) | 0.57 | 0.62 | 0.67 | 0.79 * | 0.6 | 0.72 ** | 0.27 ** |
SWI situation (1 = Mild 2 = Moderate 3 = High) | 2.01 (0.04) | 2.05 (0.5) | 1.87 * (0.10) | 2.51 ** (0.15) | 1.5 ** (0.25) | 1.86 (0.12) | 2.09 (0.24) |
Social capital | |||||||
Member of Vietnamese Women’s Union (1 = member, 0 otherwise) | 0.88 | 0.87 | 0.91 | 0.75 | 0.9 | 0.93 | 1 |
Member of Farmer’s Union (1 = member, 0 otherwise) | 0.89 | 0.89 | 0.87 | 0.86 | 0.9 | 0.93 | 0.91 |
N° of Observations | 414 | 229 | 89 | 29 | 10 | 46 | 11 |
Appendix G. Covariate Balance Summaries with and without Matching for the Different Models of Individual Adaptation Methods
Variable | Standardized Difference | Variance Ratio | ||
---|---|---|---|---|
Raw | Matched | Raw | Matched | |
Family labor (no.) | −0.054 | 0.031 | 1.028 | 1.010 |
Dependents in the household (%) | −0.098 | −0.072 | 0.878 | 0.966 |
Age of HH head | −0.076 | −0.018 | 1.202 | 1.112 |
SWI situation | 0.084 | −0.069 | 1.186 | 1.106 |
Proportion of salted land | 0.180 | −0.032 | 1.412 | 1.160 |
Land certificate | −0.287 | −0.029 | 1.046 | 1.008 |
Variable | Standardized Difference | Variance Ratio | ||
---|---|---|---|---|
Raw | Matched | Raw | Matched | |
Family labor (no.) | 0.313 | 0.002 | 1.119 | 1.014 |
Dependents in the household (%) | −0.322 | −0.148 | 0.776 | 0.951 |
Age of HH head | −0.283 | −0.088 | 0.756 | 0.989 |
SWI situation | −0.358 | 0.025 | 0.859 | 0.904 |
Proportion of salted land | 0.246 | −0.002 | 0.666 | 0.684 |
Land certificate | −0.245 | −0.043 | 1.045 | 1.024 |
Variable | Standardized Difference | Variance Ratio | ||
---|---|---|---|---|
Raw | Matched | Raw | Matched | |
Family labor (no.) | −0.179 | −0.004 | 1.163 | 1.120 |
Dependents in the household (%) | 0.081 | −0.051 | 0.772 | 0.951 |
Age of HH head | −0.153 | 0.023 | 1.206 | 1.121 |
SWI situation | −0.139 | −0.012 | 1.134 | 1.124 |
Proportion of salted land | −0.087 | 0.031 | 1.058 | 0.992 |
Land certificate | −0.116 | 0.033 | 1.074 | 0.952 |
Variable | Standardized Difference | Variance Ratio | ||
---|---|---|---|---|
Raw | Matched | Raw | Matched | |
Family labor (no.) | 0.055 | 0.311 | 1.305 | 1.223 |
Dependents in the household (%) | 0.066 | −0.077 | 1.468 | 1.279 |
Age of HH head | −0.196 | −0.068 | 1.207 | 0.957 |
SWI situation | 0.119 | 0.049 | 1.087 | 1.049 |
Proportion of salted land | 0.141 | −0.069 | 0.604 | 0.654 |
Land certificate | 0.193 | −0.044 | 0.949 | 1.008 |
Variable | Standardized Difference | Variance Ratio | ||
---|---|---|---|---|
Raw | Matched | Raw | Matched | |
Family labor (no.) | 0.060 | 0.051 | 1.292 | 1.176 |
Dependents in the household (%) | 0.082 | −0.059 | 1.418 | 1.261 |
Age of HH head | −0.184 | −0.057 | 1.264 | 0.881 |
SWI situation | 0.044 | −0.018 | 1.158 | 1.114 |
Proportion of salted land | 0.078 | −0.058 | 0.611 | 0.768 |
Land certificate | 0.265 | −0.039 | 0.933 | 1.012 |
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Variables (Unit) | Total Sample | Non-Adapter | Adapter | ||||
---|---|---|---|---|---|---|---|
NR | PP | VG | SR | LF | |||
Saline-land productivity (USD/ha) | 7187.14 (1473.68) | 1829.52 (24.27) | 1764.28 (162.23) | 2348.57 (25.48) | 7126.19 (356.3) | 47,236.19 (535.56) | 7910.95 (652.2) |
Net farm income (USD/ha) | 2710.32 (326.05) | 1633.87 (94.12) | 1491.58 (181.44) | 2010.88 (26.83) | 2266.19 (455.25) | 10,665.71 (552.68) | 3951.55 (434.26) |
Rate of children attending school (%) | 54.58 (1.84) | 48.01 (2.43) | 47.95 (4.49) | 53.44 (7.29) | 53.3 (11.92) | 90.21 (5.64) | 100 (11.14) |
Food secure (1 = Food secure to 4 = Food insecure with moderate hunger) | 2.74 (0.05) | 2.95 (0.06) | 3.04 (0.11) | 2.68 (0.19) | 2.6 (0.32) | 1.45 (0.15) | 1.72 (0.31) |
Life satisfaction (1 = Totally dissatisfied to 5 = totally satisfied) | 2.75 (0.03) | 2.67 (0.43) | 2.71 (0.76) | 2.48 (0.12) | 2.8 (0.21) | 3.2 (0.1) | 3.45 (0.2) |
N° of observations | 414 | 229 | 89 | 29 | 10 | 46 | 11 |
Model 1 | Model 2 | |||||
---|---|---|---|---|---|---|
Variables | Adapter | NR | PP | VG | SR | LF |
Family labor (no.) | −0.14 (0.11) | −0.31 *** (0.08) | 0.01 (0.14) | −0.11 * (0.18) | 0.63 *** (0.17) | 0.19 (0.20) |
Dependents in the household (%) | −0.008 ** (0.004) | −0.008 *** (0.003) | −0.005 (0.004) | −0.01 (0.007) | 0.01 ** (0.006) | −0.008 (0.008) |
Age of HH head | 0.08 *** (0.02) | 0.01 (0.01) | 0.03 (0.02) | 0.01 (0.03) | 0.07 ** (0.02) | 0.06 * (0.03) |
SWI situation | −0.12 ** (0.03) | −0.12 (0.09) | 0.41 ** (0.15) | −0.46 ** (0.22) | −0.13 (0.16) | 0.09 (0.23) |
Proportion of salted land | −0.006 (0.006) | −0.02 *** (0.005) | 0.02 *** (0.007) | 0.007 (0.01) | 0.04 *** (0.009) | 0.06 *** (0.02) |
Land certificate | −1.05 *** (0.25) | 0.09 (0.21) | 0.19 (0.30) | 0.03 (0.4) | −2.54 *** (0.38) | −1.17 *** (0.43) |
Number of observations | 414 | 318 | 258 | 239 | 275 | 240 |
Wald Chi 2 | 27.37 *** | 47.63 *** | 16.47 *** | 8.88 * | 119.64 *** | 24.35 *** |
Pseudo R2 | 0.14 | 0.12 | 0.09 | 0.10 | 0.48 | 0.27 |
Log Likelihood | −270.12 | −164.68 | −82.45 | −37.08 | −64.35 | −32.47 |
Saline-Land Productivity (USD/ha) | Net Farm Income (USD/ha) | Rate of Children Attending School (%) | Food Security (1–4) | Life Satisfaction (1–5) | |
---|---|---|---|---|---|
Number of treated (Adapters) | 185 | 185 | 185 | 185 | 185 |
Number of control (Non-Adapters) | 229 | 229 | 229 | 229 | 229 |
ATT | 11428.57 *** (303.76) | 2238.09 *** (480.01) | 16.20 | −0.49 *** | 0.18 ** |
Wilcoxon signed rank (WSR) p-value | 0.00 | 0.00 | 0.41 | 0.06 | 0.01 |
Variable | Standardized Difference | Variance Ratio | ||
---|---|---|---|---|
Raw | Matched | Raw | Matched | |
Family labor (no.) | −0.057 | −0.039 | 0.719 | 0.789 |
Dependents in the household (%) | −0.126 | 0.011 | 0.656 | 0.674 |
Age of HH head | 0.179 | 0.020 | 0.762 | 0.908 |
SWI situation | −0.106 | 0.009 | 0.923 | 0.932 |
Proportion of salted land | −0.122 | 0.071 | 1.677 | 1.578 |
Land certificate | −0.250 | 0.019 | 1.172 | 0.995 |
Outcome Variables | NR | PP | VG | SR | LF | |
---|---|---|---|---|---|---|
Number of treated (Adapters) | 89 | 29 | 10 | 46 | 11 | |
Number of control (Non-Adapters) | 229 | 229 | 229 | 229 | 229 | |
Economic indicator | Saline-land productivity | −19.36 ** (14.81) | 549.67 ** (62.97) | 5253.8 *** (962.71) | 44848.09 *** (6993.49) | 4601.9 *** (846.91) |
Net farm income | −244.12 * (180.20) | −11.26 (322.24) | 947.66 * (1542.97) | 11783.8 *** (1297.16) | 1735.87 * (763.17) | |
Social indicator | Rate of children attending school | 3.40 (5.57) | 21.77 ** (7.38) | 3.92 (11.18) | 11.54 * (9.54) | 10.54 * (0.04) |
Food security | −0.006 (0.12) | −0.36 ** (0.21) | −0.39 ** (0.27) | −1.34 ** (0.29) | −0.94 *** (0.43) | |
Life satisfaction | 0.14 (0.08) | −0.13 (0.11) | 0.15 * (0.14) | 0.61 ** (0.19) | 0.98 *** (0.24) |
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Nguyen, T.D.L.; Defloor, B.; Speelman, S.; Bleys, B. Does Adaptation to Saltwater Intrusion Improve the Livelihoods of Farmers? Evidence for the Central Coastal Region of Vietnam. Sustainability 2024, 16, 6216. https://doi.org/10.3390/su16146216
Nguyen TDL, Defloor B, Speelman S, Bleys B. Does Adaptation to Saltwater Intrusion Improve the Livelihoods of Farmers? Evidence for the Central Coastal Region of Vietnam. Sustainability. 2024; 16(14):6216. https://doi.org/10.3390/su16146216
Chicago/Turabian StyleNguyen, Thi Dieu Linh, Bart Defloor, Stijn Speelman, and Brent Bleys. 2024. "Does Adaptation to Saltwater Intrusion Improve the Livelihoods of Farmers? Evidence for the Central Coastal Region of Vietnam" Sustainability 16, no. 14: 6216. https://doi.org/10.3390/su16146216
APA StyleNguyen, T. D. L., Defloor, B., Speelman, S., & Bleys, B. (2024). Does Adaptation to Saltwater Intrusion Improve the Livelihoods of Farmers? Evidence for the Central Coastal Region of Vietnam. Sustainability, 16(14), 6216. https://doi.org/10.3390/su16146216