This is the first in a series of stories exploring the importance of the Mekong River in China.

Along the waterfront of the small town of Simaogang, in southwestern China’s Yunnan province, the rusted bolts and gears of an aging crane scream in protest as load after load of wet sand from the Mekong River is dumped into the holds of the dredging barges. From atop a concrete wall high above the thrum, the company’s owner watches his fleet begin another day.

Sand that covers the bottom of the Mekong — which is known as the Lancang River in China — is the area’s major commercial resource. And around Chinese New Year is when Shen, who commands several barges on this stretch of the Mekong and only gave his last name, makes the best profits.

“The busiest time of year is around the lunar new year, which people believe is an auspicious time for construction,” Shen said. “They either start new projects or finish the ones they have already started because it’s considered a lucky time of year.”

With his four boats and about a dozen crew members, Shen can dredge up to 850 cubic meters of sand from the riverbed per day. Larger dredges, meanwhile, can mine as much as 5,000 cubic meters of sand per day. In 2014, a cubic meter of sand sold for 90 yuan — meaning a single large dredge can excavate 450,000 yuan worth of sand in one day.

Most people pay little attention to sand. It’s one of the planet’s most unglamorous resources, and it is unremarkable to look at, though seemingly everywhere, and in great quantities. But Shen and other sand miners have not overlooked its importance: Without sand, there can be no cement, and without cement, there can be no concrete — the main building material for new roads, houses, and skyscrapers to accommodate the world’s increasingly urbanized population. Even the ancient Egyptians knew how to make what is today the world’s most widely used building material.

Two hundred tons of sand are needed for an average-sized house; 30,000 for a kilometer of highway. Unfortunately, sand is a finite resource, contrary to how it may seem from the perspective of a beachgoer on vacation.

Little data on the usage of sand is available, but the United Nations Environment Programme (UNEP) has put the world’s consumption of sand and gravel at more than 40 billion tons a year — twice as great as the amount of sediment transported annually by all the world’s rivers. After water, sand and gravel are the most used raw materials on earth, and because it takes thousands of years for sand to form, the current usage rate far outpaces the replenishing rate.

In China, demand for sand is greater than anywhere else in the world. China’s economic growth, which has already slowed down to around 7 percent, is increasingly reliant on the country’s housing boom. And although the stock of unsold property has skyrocketed in recent years, it hasn’t prevented new construction from breaking ground, according to research from Fathom Consulting, a global financial consulting firm.

Between 2000 and 2010, the Economist Intelligence Unit found, China built as much new housing as all of Japan had at the time, and this unchecked construction has had a tremendous impact on natural resources like sand. “At current rates of construction,” the report reads, “China can build a city the size of Rome in only two weeks. This means China is underpinning demand in global markets for many key commodities.”

According to the U.N., China’s demand for cement increased by more than 400 percent from 1994 to 2012, with the preferred ingredient being river sand, as desert sand is too round to bind well, and the salinity of marine sand makes it susceptible to erosion.

“Sometimes the river moves very fast, and it is harder to collect sand,” said Shen, adding that his team always manages to find a way to get at the precious resource. While watching his ships perform the monotonous job of bringing the Mekong’s sand to the surface, Shen explained how he first saw the chance to turn the natural resource into quick cash.

The 53-year-old worked in a wire factory in Kunming, Yunnan’s capital, for most of his life before starting in the dredging business several years ago, seeing an opportunity to supply the booming construction industry with sought-after building materials.

As the two larger of Shen’s four dredges loosed their mooring lines and reversed slowly into deeper water, the two smaller boats stayed close to shore, their cranes swinging in and out of the water with practiced speed.

While some of this sand is needed for local construction purposes, most of it will be transported to Jinghong — a stone’s throw from the borders shared with Laos and Myanmar — to support the area’s ambitious housing and infrastructure projects.

The process is relatively simple: Dredges suck the sand from the river bottom through snaking lengths of piping, or scoop it up with a mechanized chain of metal buckets. The methods employed by the dozens of boats along the shore seem little more than an industrial manifestation of a playing child’s imagination. For the ecosystem, however, the impact of this enterprise can be devastating.

“Sand dredging changes the structure and appearance of the riverway,” Huang Daoming, deputy chief engineer at the Institute of Hydroecology at the Chinese Academy of Sciences in Wuhan, told Sixth Tone. Depleting the riverbed of sand not only leads to the erosion of riverbanks, but also threatens fish populations.

The thousands of fish species found in the Mekong have adapted to the river’s unique habitat, which needs to remain stable to ensure the long-term survival of the species. Even small changes can be so disruptive that they could cause an entire species to go extinct.

Structured riverbeds also offer a refuge from the current and serve as protection from predators. Even if fish species survive physical alterations to their habitat, dredging kills their eggs, which are commonly deposited in the sediment. “So [dredging] will affect the fish resources in a negative way,” Huang said. Indeed, Researchers have already shown that sand dredging decreases overall fish populations and reduces the diversity of aquatic life.

But despite the impact dredging has on riparian ecosystems, the issue has been ignored by policymakers across the globe and remains largely unknown by the general public, wrote Pascal Peduzzi, one of the world’s few experts on sand mining, in an article for UNEP.

Fueled by international demand, mainly from countries like Singapore, vast sand dredging operations in some Southeast Asian countries have severely depleted local resources. In Indonesia, for example, several islands disappeared before a ban on sand exports was imposed, and yet the practice still continues today.

Vietnam, one of the countries along the Mekong, and Malaysia have also banned the export of sand, citing environmental concerns. In Cambodia, where $750 million worth of sand has been exported to Singapore over the past eight years, environmental groups are pushing for a ban.

But although operations often affect several countries, especially if they are located in international waters or on transnational rivers like the Mekong, which runs through China, Myanmar, Laos, Thailand, Cambodia and Vietnam, there are no international regulations when it comes to mining river sand.

In China, sand dredging is generally allowed with permission from county or provincial authorities. Shen, who set up his business right next to a government office, is properly licensed — though permits to dredge in the area can be purchased online for around 300,000 yuan. On the Yunnan stretch of the Mekong, the provincial government has banned sand dredging in certain places, usually in ecological hotspots with high biodiversity. In fact, dredging is banned up- and downstream of Simaogang, but not around the town itself.

There hasn’t yet been a clear assessment of how exactly sand dredging operations in Yunnan have affected the biodiversity and fish populations of the Mekong. The overall loss of sediment, however, has demonstrably affected the natural landscape in countries like Vietnam, where the Mekong forms a delta so rich in nutrients that it produces the vast majority of the country’s staple foods, including rice.

On the Lower Mekong, between Laos and Vietnam, about 50 million tons of sand — more sediment than the river produces in one year — were extracted in 2011, according to a World Wildlife Fund estimate. This huge loss of sand has caused water levels on main channels to drop by more than a meter from 1998 to 2008, allowing salty seawater to flood rice paddies and ruin crops.

But none of that concerns Shen and his fleet of barges in Simaogang. For him, sand dredging simply offers a better way of life, even if he has to work from 8 a.m. until 7 p.m., pausing only at midday for noodles, tea, and cigarettes.

This story was published in collaboration with A River’s Tail, a yearlong exploration of the Mekong from the river’s delta in Vietnam to its source in the Tibetan Plateau. For more stories from the Mekong, visit www.ariverstail.com.

With contributions from Wang Yiwei.

(Header image: A man shovels sand onto a conveyor belt, which moves it from the dredge to the shore for drying, Simaogang, Yunnan province, Jan. 30, 2016. Luc Forsyth for Sixth Tone)