The heat is on for migration

Climate-related heat stress, not high rainfall, flooding or moisture, has increased long-term human migration in rural Pakistan over the past 20 years. This finding, published in Nature Climate Change, provides the first quantitative evidence of how long-term migration decisions in Pakistan are affected by weather extremes.

Pakistan is known to be vulnerable to climate change and subsequently, involuntary displacement within its population is common. Efforts have been made to try to counteract this, but the country’s social protection strategies and international relief efforts have been most responsive to flood victims.

Valerie Mueller and colleagues examine the long-term migration of 4,428 individuals from 583 households in rural Pakistan between 1991 and 2012 and find that individuals consistently move out of villages in response to extreme temperatures (usually from November to April), but very little movement is observed in response to excessive rainfall. They suggest that people’s decision to move may be influenced by a fall in income during times of extreme heat. Indeed, the team calculate that agricultural income suffers greatly when temperatures are extremely high, wiping out over a third of farming income. Non-farm income also experiences losses from heat stress, but to a lesser extent (16%). They note, however, that high rainfall increases all sources of income substantially.

Based on these findings, the authors propose that relief efforts should be shifted to help improve individuals’ ability to adapt and prepare for extreme temperature conditions. They also suggest that continuing work that expands knowledge of what motivates migration is important for designing appropriate policies that respond to natural disasters, migration and displacement.

doi: 10.1038/nclimate2103

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