Linkages among climate change, crop yields and Mexico-US cross-border migration
Linkages among climate change, crop yields and Mexico-US cross-border migration
复制标题
气候变化、农作物产量和墨西哥-美国跨境移民之间的联系
DOI：
10.1073/pnas.1002632107
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发表时间：
2010-08-10
影响因子：
11.1
通讯作者：
Oppenheimer, Michael
中科院分区：
文献类型：
--
作者：
Feng, Shuaizhang;Krueger, Alan B.;Oppenheimer, Michael
气候变化预计将导致大规模的人口迁移，包括跨越国际边界的移民。本研究采用工具变量方法，定量研究了气候变化、农业产量和人口迁移反应之间的联系。我们的方法使我们能够确定作物产量和迁移之间的关系，而无需明确控制所有其他混杂因素。利用墨西哥州一级的数据，我们发现气候驱动的作物产量变化对移民美国的速度有显著影响。移民相对于农作物产量的估计半弹性约为-0.2，即，农作物减产10%将导致另外2%的人口移民。然后，我们使用估计的半弹性，以探讨未来移民的潜在规模。根据所使用的变暖情景和假设的适应水平，在其他因素保持不变的情况下，估计到2080年左右，气候变化将导致140万至670万墨西哥成年人（占目前15至65岁人口的2%至10%）因农业生产力下降而移民。虽然这些结果不能机械地外推到其他地区和时间段，但从全球角度来看，我们的研究结果具有重要意义，因为许多地区，特别是发展中国家，预计将因预测的变暖而出现农业产量大幅下降。
Climate change is expected to cause mass human migration, including immigration across international borders. This study quantitatively examines the linkages among variations in climate, agricultural yields, and people's migration responses by using an instrumental variables approach. Our method allows us to identify the relationship between crop yields and migration without explicitly controlling for all other confounding factors. Using state-level data from Mexico, we find a significant effect of climate-driven changes in crop yields on the rate of emigration to the United States. The estimated semielasticity of emigration with respect to crop yields is approximately -0.2, i.e., a 10% reduction in crop yields would lead an additional 2% of the population to emigrate. We then use the estimated semielasticity to explore the potential magnitude of future emigration. Depending on the warming scenarios used and adaptation levels assumed, with other factors held constant, by approximately the year 2080, climate change is estimated to induce 1.4 to 6.7 million adult Mexicans (or 2% to 10% of the current population aged 15-65 y) to emigrate as a result of declines in agricultural productivity alone. Although the results cannot be mechanically extrapolated to other areas and time periods, our findings are significant from a global perspective given that many regions, especially developing countries, are expected to experience significant declines in agricultural yields as a result of projected warming.