Research Article

Cash for carbon: A randomized trial of payments for ecosystem services to reduce deforestation

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Science  21 Jul 2017:
Vol. 357, Issue 6348, pp. 267-273
DOI: 10.1126/science.aan0568
  • Table 1 Summary statistics for treatment and control groups.

    Observations for treatment and control: PFOs, 564 and 535; villages, 60 and 61. Subsample means with standard deviations in brackets. The last column reports the regression-adjusted difference in means between the treatment and control subsample divided by the pooled standard deviation. None of the differences has a P < 0.10. The standardized difference and P values are based on a regression with subcounty fixed effects and clustering at the village level. IHS denotes inverse hyperbolic sine. Tree cover in village, percentage of village with tree cover, and percentage change in vegetation in village are at the village level. The data source for variables with Tree cover in the variable name is the baseline QuickBird satellite image. The source for percentage change in vegetation is 1990 and 2010 Landsat satellite images. The source for all other variables is the baseline survey.

    TreatmentControlND
    Household head’s age 47.499 [13.605]47.589 [14.659]0.003
    Household head’s years of education 7.715 [4.003]7.931 [4.187]–0.056
    IHS of self-reported land area (ha) 4.062 [1.021]4.004 [0.968]0.053
    Self-reported forest area (ha) 1.727 [3.318]2.068 [12.413]–0.042
    Cut any trees in the last 3 years 0.845 [0.362]0.858 [0.350]–0.031
    Cut trees to clear land for cultivation 0.236 [0.425]0.241 [0.428]–0.016
    Cut trees for timber products 0.704 [0.457]0.721 [0.449]–0.037
    Cut trees for emergency/lumpy expenses 0.25 [0.433]0.292 [0.455]–0.088
    IHS of total revenue from cut trees 1.238 [2.118]1.397 [2.248]–0.085
    Rented any part of land 0.163 [0.370]0.198 [0.399]–0.091
    Dispute with neighbor about land 0.218 [0.413]0.206 [0.405]0.035
    Involved in any environmental program 0.100 [0.301]0.111 [0.315]–0.035
    Agree: Deforestation affects the community 0.539 [0.499]0.548 [0.498]–0.014
    Agree: Need to damage environ. to improve life 0.064 [0.245]0.043 [0.204]0.089
    Tree cover in village (ha) 134.515 [108.800]159.18 [178.011]–0.169
    Percentage of village with tree cover 0.247 [0.122]0.263 [0.132]–0.122
    Percentage change in vegetation in village, 1990–2010 0.036 [0.041]0.041 [0.033]–0.128
    Tree cover in PFO land circle (ha) 4.355 [12.466]3.845 [9.178]0.050
    Percentage of PFO land circle with tree cover 0.199 [0.161]0.209 [0.157]–0.044
    Percentage change in vegetation in PFO land circle, 1990–2010 0.035 [0.066]0.037 [0.058]–0.016
  • Table 2 Program enrollment, compliance, and payments.

    All columns include subcounty fixed effects and the four village-level baseline variables used to balance the randomization: number of PFOs in baseline sample, average weekly earnings per capita, distance to the nearest main road, and average size of the reported land nearest the dwelling. Amount paid is in units of 10,000 UGX. Calculated values are means; standard errors are clustered by village. Asterisks denote significance: ***P < 0.01. Outcome data are from CSWCT administrative data.

    EnrolledEnrolled and deemed to
    have conserved forest
    Amount paidProportion of eligible
    amount paid
    Treatment group0.320***0.282***9.023***0.238***
    [0.030][0.028][1.872][0.024]
    Control group 0.0090.0090.4170.007
    Observations1099109510951095
  • Table 3 Effect of the PES program on tree cover.

    All regressions and means are weighted by the proportion of available tree-classification data for the observation. All columns include subcounty fixed effects and the four village-level baseline variables used to balance the randomization. Columns 2, 3, 5, and 6 also control for dummy variables for the date of the baseline satellite image, and columns 2 and 3 control for 1990 and 2010 area covered by photosynthetic vegetation within the village polygon and in aggregate in PFO land circles for the village; columns 5 and 6 control for 1990 and 2010 area covered by photosynthetic vegetation within the village polygon and in the PFO’s land circle. Standard errors are heteroskedasticity-robust in columns 1 to 3 and clustered by village in columns 4 to 6. Significance: *P < 0.10, **P < 0.05, ***P < 0.01.

    Village boundariesPFO-level land circles
    ΔTree
    cover (ha)
    ΔTree
    cover (ha)
    ΔLog of
    tree cover
    ΔTree
    cover (ha)
    ΔTree
    cover (ha)
    ΔIHS of
    tree cover
    (1)(2)(3)(4)(5)(6)
    Treatment group5.549*5.478**0.0521**0.245**0.267**0.0447*
    [2.888][2.652][0.021][0.110][0.106][0.023]
    Control group –13.371–13.371–0.095–0.349–0.349–0.073
    Control variablesNoYesYesNoYesYes
    Observations121121121995995995
  • Table 4 Effects of the PES program on secondary outcomes.

    All columns include subcounty fixed effects and the four village-level baseline variables used to balance the randomization. Columns 1, 4, 5, and 6 control for the baseline value of the outcome. Baseline data on the outcomes in columns 2 and 3 were not collected. IHS denotes inverse hyperbolic sine. For observations where the baseline outcome is missing, the value is imputed as the sample mean, and the regression includes an indicator variable for whether the baseline value is imputed. Standard errors are clustered by village. Significance: *P < 0.10, **P < 0.05, ***P < 0.01.

    Cut any trees in
    the past year
    Allow others
    to gather firewood
    from own forest
    Increased patrolling
    of the forest in
    last 2 years
    Has any fence around
    land with
    natural forest
    IHS of food
    expend. in past
    30 days
    IHS of nonfood
    expend. in past
    30 days
    (1)(2)(3)(4)(5)(6)
    Treatment group–0.140***–0.170***0.109***0.0360.0650.156**
    [0.034][0.033][0.039][0.033][0.074][0.066]
    Lee bound (lower)–0.161***–0.185***0.094**0.007–0.0290.053
    [0.034][0.033][0.039][0.033][0.070][0.064]
    Lee bound (upper)–0.104***–0.148***0.132***0.0550.144*0.215***
    [0.033][0.032][0.039][0.034][0.075][0.064]
    Control group mean0.4530.4270.3780.6672.5244.363
    Control group SD[0.498][0.495][0.485][0.472][1.177][1.354]
    Observations10189767984102010201020
    Observations (Lee bounds)994957965998998998
  • Table 5 Cost-benefit analysis.

    The costs of the PES program compared with the social benefit of delayed CO2, both measured per MT of averted CO2. The base case assumes (i) an average 3-year delay in deforestation (treatment effects undone over 4 years), (ii) no further treatment effects during the 0.5 years between endline QuickBird data collection and program end, (iii) average time from tree-cutting to CO2 emissions of 10 years, and (iv) a monitoring rate of 2 spot checks per monitor per day. Row 2 modifies (i) to assume a 1-year delay in deforestation (treatment effects undone immediately when the program ends). Row 3 modifies (i) to assume the averted deforestation and all subsequent deforestation are delayed by the 2-year duration of the program. Row 4 maintains the base case assumptions but uses the treatment effect estimated using PFO land circles instead of village boundaries. Row 5 modifies (ii) to assume the treatment effects accumulate at the same rate in the final months as we observe in the period before endline data collection. Rows 6 and 7 modify (iii) to shorten and lengthen the gap between tree-cutting and emissions. Row 8 modifies (iv) to assume one spot check per monitor per day. See SM section 4 for further details.

    ScenarioBenefit per MT
    of CO2 ($)
    Cost per MT
    of CO2 ($)
    Benefit-cost ratio
    1. Base case: Program effects undone over 4 years1.110.462.4
    2. Program effects undone immediately0.370.460.8
    3. Deforestation resumes at normal rate (permanent delay)0.740.0514.8
    4. Base case except using effect size from PFO-level analysis1.110.631.8
    5. Program effects accumulate for final 6 months1.110.343.2
    6. Average time until emissions is halved to 5 years1.170.462.6
    7. Average time until emissions doubled to 20 years1.000.462.2
    8. Monitoring rate of 1 spot check per day per staff person1.110.532.1

Supplementary Materials

  • Cash for carbon: A randomized trial of payments for ecosystem services to reduce deforestation

    Seema Jayachandran, Joost de Laat, Eric F. Lambin, Charlotte Y. Stanton, Robin Audy, Nancy E. Thomas

    Materials/Methods, Supplementary Text, Tables, Figures, and/or References

    Download Supplement
    • Materials and Methods
    • Figs. S1 to S5
    • Tables S1 to S10
    • References

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