Hertel Thomas W, Ramankutty Navin, Baldos Uris Lantz C
Department of Agricultural Economics, Purdue University, West Lafayette, IN 47907; and
Department of Geography, McGill University, Montreal, QC, Canada H3A 0B9.
Proc Natl Acad Sci U S A. 2014 Sep 23;111(38):13799-804. doi: 10.1073/pnas.1403543111. Epub 2014 Sep 8.
There has been a resurgence of interest in the impacts of agricultural productivity on land use and the environment. At the center of this debate is the assertion that agricultural innovation is land sparing. However, numerous case studies and global empirical studies have found little evidence of higher yields being accompanied by reduced area. We find that these studies overlook two crucial factors: estimation of a true counterfactual scenario and a tendency to adopt a regional, rather than a global, perspective. This paper introduces a general framework for analyzing the impacts of regional and global innovation on long run crop output, prices, land rents, land use, and associated CO2 emissions. In so doing, it facilitates a reconciliation of the apparently conflicting views of the impacts of agricultural productivity growth on global land use and environmental quality. Our historical analysis demonstrates that the Green Revolution in Asia, Latin America, and the Middle East was unambiguously land and emissions sparing, compared with a counterfactual world without these innovations. In contrast, we find that the environmental impacts of a prospective African Green Revolution are potentially ambiguous. We trace these divergent outcomes to relative differences between the innovating region and the rest of the world in yields, emissions efficiencies, cropland supply response, and intensification potential. Globalization of agriculture raises the potential for adverse environmental consequences. However, if sustained for several decades, an African Green Revolution will eventually become land sparing.
农业生产力对土地利用和环境的影响再度引发了人们的关注。这场辩论的核心观点是，农业创新能够节约土地。然而，众多案例研究和全球实证研究几乎没有发现产量提高伴随着耕地面积减少的证据。我们发现，这些研究忽略了两个关键因素：对真实反事实情景的估计以及采用区域而非全球视角的倾向。本文介绍了一个通用框架，用于分析区域和全球创新对长期作物产量、价格、土地租金、土地利用及相关二氧化碳排放的影响。这样做有助于调和关于农业生产力增长对全球土地利用和环境质量影响的明显相互冲突的观点。我们的历史分析表明，与没有这些创新的反事实世界相比，亚洲、拉丁美洲和中东的绿色革命无疑是节约土地和减少排放的。相比之下，我们发现未来非洲绿色革命对环境的影响可能并不明确。我们将这些不同的结果归因于创新地区与世界其他地区在产量、排放效率、农田供应反应和集约化潜力方面的相对差异。农业全球化增加了产生不利环境后果的可能性。然而，如果持续几十年，非洲绿色革命最终将实现土地节约。
