A consistent feature of the last few decades has been the growth of cities, with people around the world flocking to ever expanding urban conurbations to live and work.  New research from Texas A&M shows that as cities grew in population, they tended to sprawl outwards, thus becoming less dense.

This trend was especially prominent in small-and medium-sized cities in Europe, North America, China and India.  They highlight how around 60% of this urban expansion has occurred in areas that were formerly agricultural land.

“If urban population densities had remained unchanged since 1970, more than 48,000 square miles (roughly the size of North Carolina) would have been saved from conversion to urban and instead could have remained in cultivation or as natural vegetation,” the researchers say.

This reduction in population density comes with a number of problems, with the loss of fertile land especially challenging in the likes of India and Nigeria.  These countries, along with China, are expected to account for over 1/3 of the global increase in the urban population by 2050.  They have millions of small farmers working the land on the outskirts of cities, so their livelihoods would be greatly affected by any urban expansion.

This is a particular problem in India, which suffers both from poor quality land and a steep decline in urban land-use efficiency.  At the moment, the country also has the largest rural population in the world.

“Our findings suggest that decreasing urban population densities in India and Nigeria since 1970 caused 85 percent and 30 percent more land, respectively, to be converted to urban,” the researchers say.

Low density

This decrease in population density as cities sprawl outwards puts considerable pressure on both local and regional governments to provide appropriate infrastructure, including in areas such as transportation, housing and water.  These challenges were especially pronounced in smaller cities of fewer than 2 million people.

“Furthermore, small-medium cities in India, China, Southeast Asia, Africa and Europe are following in the footsteps of the United States in declines in urban population densities,” the researchers explain. “These findings are important because, globally, it is these small-medium sized cities with limited institutional and financial capacity that are growing the fastest.”

The United States has tended to lead the way in terms of low urban population density over the last four decades, which the researchers believe inspired many other countries to follow suit.  They believe this has been a hugely negative trend, with the inefficient use of resources resulting from it.

“It is important for urban areas to attain densities that would both improve living conditions in urban landscapes and promote efficient use of resources including land,” they conclude.