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How much is the world’s most productive river worth? This is how experts estimate the value of nature


The Mekong in Southeast Asia is perhaps the most important river in the world. Known as the ‘mother of the waters’, it is home to the world’s largest inland fishery, and the vast amounts of sediment it transports nourish some of the most fertile farmland in the world. Tens of millions of people depend on it for their livelihoods.

But how valuable is it in monetary terms? Is it possible to put a dollar value on the multitude of ecosystem services it provides, to keep those services healthy in the future?

That’s my research colleagues and me try to find out, to focus on two countries holding on the most productive areas of the river for fisheries and agriculture: Cambodia and Vietnam.

Understanding the value of a river is essential for good management and decision-making, such as where to develop infrastructure and where to protect nature. This is special where from the Mekongwhich one has come under enormous pressure due to overfishing, dam building and climate change, and where decisions on development projects often fail to take environmental costs into account.

The Mekong River meanders through six countries, covering 2,700 miles (about 4,350 kilometers) from the mountains to the sea.
Leisa Tyler/LightRocket via Getty Images

“Rivers like the Mekong function as life support systems for entire regions,” said Rafael Schmitt, chief scientist with the Natural Capital Project at Stanford University, who has studied the Mekong system for years. “Understanding their values, in monetary terms, can be critical to fairly assessing the impact infrastructure development will have on these functions.”

However, calculating that value is not easy. Most of the natural benefits that a river brings are naturally submerged and thus hidden from direct observation. Ecosystem services can be difficult to track because rivers often flow over long distances and sometimes across national borders.

Enter natural capital accounting

The theory of natural capital suggests that ecosystem services provided by nature – such as water filtration, flood control and resources – have economic value which must be taken into account when making decisions that affect these systems.

Some people claim it is morally wrong to put a financial price on nature, and that this undermines people’s intrinsic motivation to value and protect nature. Critics say ratings often not captured the whole value of a natural service.

Proponents argue that natural capital accounting highlights the value of natural systems when weighed against commercial pressures. They say it gives visibility to natural benefits that are otherwise hiddenin language that policymakers can better understand and use.

Two people in a motorboat sail through a part of the lake with trees and small islands of vegetation.
More than a million people live on or around Tonlé Sap Lake, the world’s largest inland fishery. Climate change and dams can affect water levels and fish stocks.
Tang Chhin Sothy/AFP via Getty Images

Several countries have introduced natural capital accounting during the past yearsincluded Costa Rica, Canada and Botswana. Often it has led to better protection of natural resources, such as mangrove forests that protect fragile coastlines. The US government too announced a strategy in 2023 to begin developing metrics to take into account the value of underlying natural resources, such as critical minerals, forests and rivers.

However, natural capital studies have largely focused on terrestrial ecosystems, where the interplay between human interventions and conservation is easier to see.

When valuing rivers, the challenges go much deeper. “When you cut down a forest, the impact is immediately visible,” Schmitt explains. “A river may look pristine, but its functioning can be dramatically altered by a distant dam.”

Consider hydropower

Hydropower is an example of the challenges of making decisions about a river without understanding its full value. That is often much easier calculate the value of a hydropower dam than the value of the river’s fish, or sediment that eventually becomes fertile farmland.

The rivers of the Mekong basin have been extensively exploited for energy production in recent decades, with a proliferation of dams in China, Laos and elsewhere. The Mekong Dam monitorrun by the non-profit organization Smith centermonitors dams and their environmental impacts in the Mekong basin in near real-time.

Map showing the river through Vietnam and Cambodia
The Lower Mekong River.

While hydropower is clearly an economic advantage – power homes and businesses, and contribute to a country’s GDP – also dams river flows change and block both fish migration and sediment release.

Drought in the Mekong in recent years, linked to El Nino and exacerbated by climate change, were exacerbated by dam managers holding back water. As a result, water levels fell to historically low levels, with devastating consequences for fisheries. Tonlé Sap Lake, the largest lake in Southeast Asia and the heart of the Mekong fishery, was home to thousands of fishermen forced to give up their professionand many commercial fishing had to close.

Hydropower dams like the one in the photos above in Cambodia can disrupt a river’s natural resources. The Sesan River (Tonlé San) and the Srepok River are tributaries of the Mekong. Move the slider to see how the dam changed the water flow. NASA Earth Observatory

A project now under investigation in the Mekong basin is a small dam being built in the Sekong River, a tributary, in Laos, near the Cambodian border. Although the dam is expected to generate a very small amount of electricity, show preliminary studies it will have a dramatic negative effect on many migratory fish populations in the Sekong, which remains the last major free-flowing tributary in the Mekong basin.

Appreciation for the ‘lifeline of the region’

The Mekong River rises in the Tibetan highlands and runs for 2,700 miles (about 4,350 kilometers) through six countries before emptying into the South China Sea.

Are ecological and biological resources are clearly significant. The river system is home to over 1,000 species of fish, and the annual catch of fish in the Lower Basin alone, below China, is estimated to be more than 2 million tons.

“The river has been the lifeblood of the region for centuries,” said Zeb Hogan, a biologist at the University of Nevada, Reno, who led the USAID-funded Wonders of the Mekong research project I am working on. “It’s the ultimate renewable resource — if it’s allowed to function properly.”

However, determining the financial value of fish is more complicated than it seems. Many people in the Mekong region are livelihood fishermen for whom fish have little or no market value, but are crucial to their survival.

Two women row a small boat through a narrow canal in the Mekong Delta.  Another boat passes them.
The Mekong Delta in Vietnam is essential for transportation, food and culture.
Sergi Reboredo/VW PICS/Universal Images Group via Getty Images

The river is also home to some of the largest freshwater fish in the world, such as giant stingray and catfish and critically endangered species. “How do you value the right to exist of a species?” asks Hogan.

Sediment, which fertilizes floodplains and builds up the Mekong Delta, is relatively easy to quantify, says Schmitt, the Stanford scientist. According to his analysis, the Mekong performs in its natural state 160 million tons of sediment per year.

However, checkers only let through about 50 million tons, while sand mining in Cambodia and Vietnam raises 90 million, meaning more sediment is blocked or removed from the river than is delivered to its natural destination. As a result, the Mekong Delta, which would naturally absorb much of the sediment, has suffered massive river erosionthousands of homes were swept away.

A potential ‘World Heritage Site’ designation

A river’s natural services may also include cultural and social benefits that can be difficult to place monetary values ​​on.

a new proposal aims to designate a bio-rich stretch of the Mekong River in northern Cambodia as a UNESCO World Heritage Site. If successful, such a designation may carry a degree of prestige that is difficult to quantify.

The complexity of the Mekong River makes our project a challenging undertaking. At the same time, it is the rich diversity of natural benefits offered by the Mekong that makes this work important so that future decisions can be made based on real costs.

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