[論文レビュー] When Does Agroforestry Income Reduce Deforestation? Evidence from a Natural Experiment in Madagascar

Camille DeSisto, Ranaivo Rasolofoson+2 more|arXiv (Cornell University)|Mar 14, 2026

Conservation, Biodiversity, and Resource Management被引用数 0

ひとこと要約

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ABSTRACT

Tropical deforestation and rural poverty are deeply intertwined, yet isolating the causal effect of income on forest loss remains challenging. We use the 2015 global vanilla price boom, triggered by food-industry shifts toward natural flavoring, as an exogenous income shock affecting Madagascar's primary vanilla-producing region. Using a matching-augmented synthetic control design, we estimate that income gains reduced annual deforestation by 1.7 percentage points in 2017, equivalent to approximately 701 hectares of avoided forest loss. Under a monotonicity assumption linking the price boom to farmers' income, the sign of this reduced-form effect is informative about the causal direction of income on deforestation. However, effects were strongly heterogeneous: higher incomes reduced deforestation in drier, more accessible municipalities but increased clearing in wetter, low-elevation areas with high agricultural potential. These divergent patterns suggest that income simultaneously relaxes subsistence pressures driving forest dependence and raises the opportunity cost of conservation where agricultural returns are high. Our findings indicate that commodity-based agroforestry can align poverty alleviation with forest conservation under conditions of low agricultural opportunity cost. Still, policies must anticipate contexts where rising incomes amplify deforestation in agriculturally suitable land. The strategic targeting of livelihood interventions based on local agricultural potential may help reconcile development and conservation objectives in tropical forest frontiers.

研究の動機と目的

• Motivate the study by linking tropical deforestation with rural poverty and the challenge of identifying causal income effects on forest loss.
• Exploit an exogenous income shock from the 2015 vanilla price boom in Madagascar's vanilla-producing region.
• Estimate the causal impact of income changes on annual deforestation using a matching-augmented synthetic control design.
• Assess heterogeneity in effects across municipalities with different climate, accessibility, elevation, and agricultural potential to illuminate contextual channels.

提案手法

• Use a natural-experiment approach leveraging the 2015 vanilla price surge as an exogenous income shock.
• Apply a matching-augmented synthetic control design to estimate counterfactual deforestation trajectories.
• Impose a monotonicity assumption linking the price boom to farmers’ income to interpret the sign of the reduced-form effect as causal direction.
• Quantify the reduced-form effect as annual deforestation change (percentage points) and translate to area (hectares) avoided.
• Interpret results in light of subsistence pressures, opportunity costs of conservation, and agricultural potential across municipalities.

実験結果

リサーチクエスチョン

• RQ1 Does an income increase from the vanilla price boom reduce deforestation in Madagascar?
• RQ2 How does the income-deforestation effect vary across environmental and agricultural context (dry vs. wet areas, elevation, accessibility, agricultural potential)?
• RQ3 Under what conditions do commodity-based agroforestry interventions align poverty alleviation with forest conservation?

主な発見

• Income gains reduced annual deforestation by 1.7 percentage points in 2017, corresponding to about 701 hectares of avoided forest loss.
• Effects were highly heterogeneous across municipalities.
• Higher incomes reduced deforestation in drier, more accessible municipalities, but increased clearing in wetter, low-elevation areas with high agricultural potential.
• The divergent patterns suggest income relaxes subsistence forest dependence and raises conservation opportunity costs where agricultural returns are high.
• Commodity-based agroforestry can align poverty alleviation with forest conservation when agricultural opportunity costs are low, but may amplify deforestation where land is highly agriculturally suitable.