Over the past three decades, China has seen a significant migration of its population from rural areas to cities. During the same time period, poor air quality and other environmental problems in urban China have gained increased attention. Now, a University of Missouri researcher has found a strong correlation between the influx of labor migrants from rural to urban areas and negative environmental effects on those destination cities.

Hua Qin, an assistant professor of rural sociology and sustainable development at MU, says this study could apply to other developing countries and could help shape public policy regarding population movement and distribution.

"Many developing countries around the world are experiencing rural-to-urban migration patterns similar to those in China," Qin said. "It stands to reason that this negative environmental impact could be associated with these migration flows in other countries as well."

For this study, Qin and his coauthor Tim Liao from the University of Illinois studied environmental and census data gathered in 2004 from major cities across China, and then compared that information with data collected again in 2010.

They also adjusted the analysis to take into account other variables that may influence the urban environment, including population density, economic development level, and industrial structure. While these factors did play important roles in affecting the environmental change of Chinese urban areas, their results suggested that the overall impact of rural-to-urban migration on urban air quality in China was still negative.

Despite the negative implication of such migration patterns for urban air conditions, Qin says policymakers should not discourage labor out-migration in rural areas, but rather encourage a more strategic population redistribution.

"Even though negative environmental effects can occur due to rural-to-urban migration, there also are plenty of positive societal impacts caused by this migration, including improved economies and an overall higher standard of living," Qin said.

"While it would be anti-human rights to prevent people from relocating to where they wish to be, it would be prudent for policymakers in China and other countries experiencing similar phenomena to guide rural migrants toward less population-dense urban areas, perhaps through population policy reform, economic support or other incentives."

For example, Qin says that the Chinese government has already been encouraging population migration away from the mega-cities on the east coast of China, such as Shanghai and Beijing, and into urban areas in the middle-western portions of the country. He says cities in these areas have less population density, yet like other higher density urban areas, they still offer similar benefits of improved infrastructure and job opportunities.

"While these major Chinese cities saw a sharp increase in population influx during the study period, the levels of urban air pollution declined significantly due to the more developed economy, increased technological efficiency, and better environmental regulations," Qin said.

"Nevertheless, China's urbanization process could be transitioned to a more sustainable track with more balanced regional development patterns and less population concentration in large metropolitan areas."

This study was published in Regional Environmental Change.