New estimates of the impacts of germplasm improvement in the major staple crops between 1965 and 2004 on global land-cover change are presented, based on simulations carried out using a global economic model (Global Trade Analysis Project Agro-Ecological Zone), a multicommodity, multiregional computable general equilibrium model linked to a global spatially explicit database on land use. We estimate the impact of removing the gains in cereal productivity attributed to the widespread adoption of improved varieties in developing countries. Here, several different effects—higher yields, lower prices, higher land rents, and trade effects—have been incorporated in a single model of the impact of Green Revolution research (and subsequent advances in yields from crop germplasm improvement) on land-cover change. Our results generally support the Borlaug hypothesis that increases in cereal yields as a result of widespread adoption of improved crop germplasm have saved natural ecosystems from being converted to agriculture. However, this relationship is complex, and the net effect is of a much smaller magnitude than Borlaug proposed. We estimate that the total crop area in 2004 would have been between 17.9 and 26.7 million hectares larger in a world that had not benefited from crop germplasm improvement since 1965. Of these hectares, 12.0–17.7 million would have been in developing countries, displacing pastures and resulting in an estimated 2 million hectares of additional deforestation. However, the negative impacts of higher food prices on poverty and hunger under this scenario would likely have dwarfed the welfare effects of agricultural expansion.

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Increasing agricultural yields seem an obvious way to satisfy increasing demands for food and fuel while minimizing expansion of agriculture into forest areas; however, an influential literature worries that promoting agricultural innovation could enhance agriculture's profitability thereby encouraging deforestation. Clarifying the effects of agricultural technological progress on deforestation is therefore crucial for designing effective policy responses to the challenges faced by global agriculture. In this article we review the empirical evidence on these effects and synthesize estimates of future global cropland expansion. Our main insights are that: (i) the empirical evidence on a positive link between regional technological progress and deforestation is much weaker than what seems generally accepted; (ii) at a global level, most analysts expect broad based technological progress to be land saving; however, composition effects are important as low‐yield, land‐abundant regions are likely to experience further land expansion. Toward the future, empirical work understanding how localized technological progress in agriculture transmits through international trade and commodity markets will help to bridge the gap between the findings of local, econometric, studies on the one hand and global, model based, studies on the other.

SUMMARYAccurate crop varietal identification is the backbone of any high-quality assessment of outcomes and impacts. Sweetpotato (Ipomoea batatas) varieties have important nutritional differences, and there is a strong interest to identify nutritionally superior varieties for dissemination. In agricultural household surveys, such information is often collected based on the farmer's self-report. In this article, we present the results of a data capture experiment on sweet potato varietal identification in southern Ethiopia. Three householdbased methods of identifying varietal adoption are tested against the benchmark of DNA fingerprinting: (A) Elicitation from farmers with basic questions for the most widely planted variety; (B) Farmer elicitation on five sweet potato phenotypic attributes by showing a visual-aid protocol; and (C) Enumerator recording observations on five sweet potato phenotypic attributes using a visual-aid protocol and visiting the field. In total, 20% of farmers identified a variety as improved when in fact it was local and 19% identified a variety as local when it was in fact improved. The variety names given by farmers delivered inconsistent and inaccurate varietal identities. Visual-aid protocols employed in methods B and C were better than those in method A, but greatly underestimated the adoption estimates given by the DNA fingerprinting method. Our results suggest that estimating the adoption of improved varieties with methods based on farmer self-reports is questionable and point towards a wider use of DNA fingerprinting in adoption and impact assessments.

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Recent literature is sceptical about the ability of aquaculture development to enhance equity and reduce poverty. This article investigates the issue empirically by surveying 148 households randomly selected in five coastal communities of the Philippines. There is overwhelming evidence that aquaculture benefits the poor in important ways and that it is perceived very positively by poor and non‐poor alike. In particular, the poor derive a relatively larger share of their income from it than the rich, and a lowering of the poverty line only reinforces this result. A Gini decomposition exercise also shows unambiguously that aquaculture represents an inequality‐reducing source of income, providing employment to a large number of unskilled workers in communities characterised by large labour surpluses.