一份報告說，到2080年,，氣候變化造成的農(nóng)業(yè)生產(chǎn)力喪失可能導致有100萬到700萬成年墨西哥人移民到美國。Michael Oppenheimer及其同事使用1995年到2005年的墨西哥移民,、作物產(chǎn)量和氣候數(shù)據(jù)估計了作物產(chǎn)量對墨西哥人移民美國的影響,。這組科學家的方法把氣候引起的移民從同樣可能影響移民決定的其他經(jīng)濟和政策因素中分離了出來。
這組作者報告說,，根據(jù)農(nóng)業(yè)進步是否會幫助農(nóng)民適應更炎熱干燥的氣候,，至多10%的墨西哥成年人（即大約670萬人）可能在未來70年里僅僅因為農(nóng)業(yè)生產(chǎn)力的衰退而移民美國。這組作者指出,，盡管這一分析取決于被研究的時期內(nèi)墨西哥特有的因素,，諸如墨西哥和美國之間的相對經(jīng)濟穩(wěn)定性，研究結(jié)果提示,，大批人——特別是在發(fā)展中國家——可能由于氣候變化引起的農(nóng)業(yè)壓力而移民到其他國家,。(生物谷Bioon.com)
生物谷推薦原文出處：
PNAS doi:10.1073/pnas.1002632107
Linkages among climate change, crop yields and Mexico–US cross-border migration
Shuaizhang Fenga,b, Alan B. Kruegera,c,d, and Michael Oppenheimera,e,1
a Woodrow Wilson School of Public and International Affairs, Princeton University, Princeton, NJ 08544;
b School of Economics, Shanghai University of Finance and Economics, Shanghai 200433, China;
Departments of c Economics and
eGeosciences, Princeton University, Princeton, NJ 08544; and
dUS Department of Treasury, Washington, DC 20220
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.
