Nonlinear permanent migration response to climatic variations but minimal response to disasters

Pratikshya Bohra-Mishra; Michael Oppenheimer; Solomon M. Hsiang

doi:10.1073/pnas.1317166111

New Research In

Edited by B. L. Turner, Arizona State University, Tempe, AZ, and approved May 27, 2014 (received for review September 12, 2013)

Significance

In the context of global climate change and increasing impact of some types of natural disasters, there has been significant interest in investigating the influence of climatic factors on human migration. We explore a more comprehensive set of climatic factors than used in most previous work to predict the effects of sudden natural disasters and climatic variations on migration. By following province-to-province movement of more than 7,000 households in Indonesia over a decade and a half, this study reveals that an increase in temperature (e.g., due to natural variations or global warming) and, to a lesser extent, variations in rainfall are likely to have a greater effect on permanent outmigration of households than natural disasters.

Abstract

We present a microlevel study to simultaneously investigate the effects of variations in temperature and precipitation along with sudden natural disasters to infer their relative influence on migration that is likely permanent. The study is made possible by the availability of household panel data from Indonesia with an exceptional tracking rate combined with frequent occurrence of natural disasters and significant climatic variations, thus providing a quasi-experiment to examine the influence of environment on migration. Using data on 7,185 households followed over 15 y, we analyze whole-household, province-to-province migration, which allows us to understand the effects of environmental factors on permanent moves that may differ from temporary migration. The results suggest that permanent migration is influenced by climatic variations, whereas episodic disasters tend to have much smaller or no impact on such migration. In particular, temperature has a nonlinear effect on migration such that above 25 °C, a rise in temperature is related to an increase in outmigration, potentially through its impact on economic conditions. We use these results to estimate the impact of projected temperature increases on future permanent migration. Though precipitation also has a similar nonlinear effect on migration, the effect is smaller than that of temperature, underscoring the importance of using an expanded set of climatic factors as predictors of migration. These findings on the minimal influence of natural disasters and precipitation on permanent moves supplement previous findings on the significant role of these variables in promoting temporary migration.

Footnotes

↵¹To whom correspondence should be addressed. E-mail: pbohra{at}princeton.edu.

Author contributions: P.B.-M. designed research; P.B.-M., M.O., and S.M.H. performed research; P.B.-M. and M.O. analyzed data; and P.B.-M., M.O., and S.M.H. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
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