Crop intensification, land use, and on-farm energy-use efficiency during the worldwide spread of the green revolution
Crop intensification, land use, and on-farm energy-use efficiency during the worldwide spread of the green revolution
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DOI：
10.1073/pnas.1717072115
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发表时间：
2018-02
期刊：
影响因子：
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通讯作者：
Pedro Pellegrini;R. Fernández
中科院分区：
文献类型：
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作者：
Pedro Pellegrini;R. Fernández
意义 在过去 50 年中，全球农作物产量增加了两倍，主要是由于单产（产量/面积）的增加。我们的研究表明，全球范围内主要石油投入品（机械、燃料和化肥）中蕴藏的能源增长速度最初比农作物生产的增长速度要快，但在过去几十年里却变慢了，导致最近能源使用效率（EUE）总体提高。这是由于氮肥工业、灌溉和其他技术的进步以及可能的一些环境变化造成的。我们的结果符合“杰文斯悖论”：EUE 和土地（产量）的效率提升并没有带来资源节约。正如增加产量并不能保证减轻饥饿一样，技术使节约土地（和生物多样性）成为可能，但实现这些目标取决于大胆的政治决策。我们分析了国家层面的农作物生产、实物投入和土地利用，以评估从 1961 年到 2014 年全球农作物产量增长三倍背后的技术变革。我们将机械、燃料和化肥转化为嵌入式能源单位，这些能源单位经过总结，为占全球产量 95% 的 58 个国家的农作物提供了农业集约化程度（每公顷人类补贴）。在全球范围内，每公顷投入物使用量增加了 137%，达到 13 EJ，即世界一次能源供应的 2.6%，而土地使用量仅增加了 10%。亚洲和拉丁美洲的集约化程度明显，其投入使用水平达到了该时期早期北美和欧洲的水平；无论在哪个大陆，对于主要依靠灌溉生产的 12 个国家来说，增长更为显着。半数国家（28/58）（主要是发达国家）的平均补贴>5吉焦/公顷/年（1961年化肥占27%，2014年占45%），其中大多数国家（23/28）使用的面积与1961年大致相同或更少（净土地节约量为31兆公顷）。其余大多数国家（24/30，投入<5 GJ/ha/y），主要是发展中国家，增加了作物面积（土地净扩张为 135 Mha）。总体而言，能源利用效率（作物产出/投入）遵循 U 形轨迹，从大约 3 开始，结束于接近 4。讨论了更可持续的集约化的前景，并强调了通过集约化农业保护荒野的土地节约模型预期的不足。
Significance Global crop production tripled during the last 50 years, mainly by an increase in yield (production/area). We show that the energy embedded in the main oil-based inputs (machinery, fuel, and fertilizers) increased worldwide at a rate at first larger, but in the last decades slower, than crop production, resulting in a recent overall improved energy-use efficiency (EUE). This was explained by advances in the nitrogen fertilizer industry, irrigation, and other technologies and perhaps some environmental changes. Our results fit the “Jevons paradox”: Efficiency gains, both for EUE and land (yield), did not lead to resource savings. Just as increasing production does not guarantee alleviating hunger, technologies make land (and biodiversity) savings possible, but realizing them depends on bold political decisions. We analyzed crop production, physical inputs, and land use at the country level to assess technological changes behind the threefold increase in global crop production from 1961 to 2014. We translated machinery, fuel, and fertilizer to embedded energy units that, when summed up, provided a measure of agricultural intensification (human subsidy per hectare) for crops in the 58 countries responsible for 95% of global production. Worldwide, there was a 137% increase in input use per hectare, reaching 13 EJ, or 2.6% of the world’s primary energy supply, versus only a 10% increase in land use. Intensification was marked in Asia and Latin America, where input-use levels reached those that North America and Europe had in the earlier years of the period; the increase was more accentuated, irrespective of continent, for the 12 countries with mostly irrigated production. Half of the countries (28/58), mainly developed ones, had an average subsidy >5 GJ/ha/y (with fertilizers accounting for 27% in 1961 and 45% in 2014), with most of them (23/28) using about the same area or less than in 1961 (net land sparing of 31 Mha). Most of the remaining countries (24/30 with inputs <5 GJ/ha/y), mainly developing ones, increased their cropped area (net land extensification of 135 Mha). Overall, energy-use efficiency (crop output/inputs) followed a U-shaped trajectory starting at about 3 and finishing close to 4. The prospects of a more sustainable intensification are discussed, and the inadequacy of the land-sparing model expectation of protecting wilderness via intensified agriculture is highlighted.