Looking ahead: economic and climate change factors will combine to increase migratory pressures
Income differentials between rich and poor countries, disparities in educational levels and demography combine to determine migratory pressures (according to U.N. data and projections, the share of population in high-income—by and large OECD countries—has fallen from 32.2 percent to 17.9 percent since World War II while the African population is projected to double to 2 billion by 2040, though converging to a 2 percent per annum growth by the end of the century). Suppose then that recent migratory flows and trends in productivity growth follow those of the past two decades with Africa failing to converge towards the U.S. productivity levels while the EU converges, then the share of highly qualified emigrants in the African population would increase from 16 percent in 2000 to 20 percent by 2025, and 23 percent by 2050, while the African population continues to grow (a similar trend is projected for low-qualified persons). And because the EU15 is projected to catch up with the U.S., migratory pressure would be felt most strongly in Europe (see here).
Further migratory pressures related this time to climate change and attendant increases in conflicts can also be expected. Drawing on gridded data, satellite measurements, and longer time spans, the new climate-economy literature is producing increasingly convergent evidence from studies focusing on changes in weather realizations within a country or spatial area. Extreme temperature and precipitation are influencing economic agricultural output, labor productivity outcomes with persistent effects, especially in low-income countries. Though contested by participants in the recent fifth assessment report of the IPCC which concludes that scientific research on climate and conflict has produced mixed and inconclusive results, a recent analysis of 60 studies in a common framework finds strong causal evidence linking climatic events to human conflict across a range of spatial and temporal scales and across all major regions of the world (see here and here).
As a final exploratory exercise, consider the potential effects of the recent IPPCC projections of a 4 degree Celsius rise in temperature expected by the end of the 21st century in the absence of aggressive mitigation. Then agricultural lands would be displaced by 1,000 km from the equator and sea level would rise another 70 centimeters by the end of the century, or about 3.5 times the rise in sea level over the past 150 years. This would put in jeopardy the 44 percent of world population currently living within 150 km from the coastline. Abstracting from other likely disastrous side effects (acidification of oceans, loss of biodiversity, possibility of life collapse), can we adapt to such changes? Since 72 percent of the population and 90 percent of world GDP is located on 10 percent of the Earth’s land, there is ample room for people to move if they are allowed to. Simulations from a two-sector spatial growth model combined with a standard model of climate change where production causes carbon emissions and global emissions show that the welfare effects of climate change would be small as production would relocate to newly productive lands. But suppose that a border were to be imposed at the 45th parallel north making migration between South and North impossible. Then while overall welfare change would still be small, distributive effects would be large as the North would gain twice, from higher productivity and from no reduction in wages as southerners would be excluded. With no migration allowed, polar regions would become twice as well off as equatorial regions in present value terms.