The biggest city in Xinjiang has expanded its footprint more than four times in less than three decades, mainly because of a rapidly rising population, according to a new study.

The population of Urumqi has increased more than a third over the last 10 years. This has led to an unprecedented expansion of urban areas that have severely stretched land and water resources in the regional capital and pushed it to the brink of ecological disaster, scientists warn.

All things considered, “population size has the biggest impact”, said the team led by Shi Tiange of the Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, in Urumqi in a paper published last week in the journal Arid Land Geography.

Urumqi is a 2,000-year-old city on the ancient Silk Road. Today it plays an important role in the Belt and Road Initiative, an ambitious programme launched by the Chinese government to link Asian, European and African countries via infrastructure construction, trade and investment.

A major transport hub and business centre on China’s western frontier, Urumqi contributes a quarter of the GDP of Xinjiang, the largest region in China with an area three times the size of France.

Shi’s team used government statistics and satellite data, including Google Earth images, to track the evolution of Urumqi’s urban area from 1990 to 2018.

Most cities in China were expanding in area at a pace outstripping population growth. Their main driving force came from commercial activities or aggressive local government urbanisation policies.

But in Urumqi, the population grew from less than 1.5 million in 1990 to over 3.5 million in 2018, with nearly half the increase occurring within the past decade. The population boom drove the city’s urban footprint to expand 4.26 times in the same period to more than 360 square kilometres (139 square miles).

“Population agglomeration has led to an increase in the demand for construction of homes, public service facilities and park green spaces,” Shi said in the paper.

Xinjiang has the fastest population growth in China and youngest demographic structure because of its large proportion of people from ethnic minorities, who were among the groups exempted from the one-child policy.

The rapid population growth fuelled the expansion of Urumqi as more young people moved into the city for job opportunities and a higher living standard, the paper said.

But such rapid expansion is not sustainable. In recent years, the local government had to fill valleys to make room for urban development projects as the supply of flat land ran out, especially to the south of Urumqi, according to Shi. The city expansion also threatened protected zones of natural habitat and meltwater resources at the foot of the Tianshan mountains, a water tower for central Asia.

“There is not enough water for more people,” an ecologist with Xinjiang Normal University in Urumqi said.

“Our water per capita is only one-eighth compared to the national average. We have been overpumping groundwater for the increasing population. This will lead to a collapse of the ecological system,” said the researcher who asked not to be named.

Urumqi has run into a dilemma, according to some local scientists. The city is under pressure to achieve rapid economic growth to support the belt and road programme while protecting and improving the environment.

To attempt to solve the problem, the city government has recently introduced a regulation to cap the local population at four million residents, according to another researcher.

“I don’t think it will work as the population keeps growing,” he said.