Thu, Feb 13, 2020 - Page 9 News List

Action needed now to prevent the death of the world’s rivers

By Brahma Chellaney

From the Tigris to the Indus and the Yangtze to the Nile, rivers were essential to the emergence of human civilization. Millennia later, hundreds of millions of people still depend on rivers to quench their thirst, grow food and make a living.

Yet we are rapidly destroying the planet’s river systems, with serious implications for our economies, societies and even our survival.

China is a case in point. Its dam-building frenzy and over-exploitation of rivers is wreaking environmental havoc on Asia, destroying forests, depleting biodiversity and straining water resources.

China’s first water census, released in 2013, showed that the number of rivers — not including small streams — had plummeted by more than half over the previous six decades, with more than 27,000 rivers lost.

The situation has only deteriorated since then. The Mekong River is running at a historically low level, owing largely to a series of Chinese-built mega-dams near the border of the Tibetan Plateau, just before the river crosses into Southeast Asia.

The Tibetan Plateau is the starting point of most of Asia’s major rivers, and China has taken advantage of that, not least to gain leverage over downstream countries.

China might be the world’s largest dam builder, but it is not alone; other countries, from Asia to Latin America, have also been tapping long rivers for electricity generation.

The diversion of water for irrigation is also a major source of strain on rivers. Crop and livestock production absorbs almost three-quarters of the world’s freshwater resources, while creating runoff that, together with industrial waste and sewage discharge, pollutes those very resources.

In total, almost two-thirds of the world’s long rivers have been modified, and some of the world’s longest — including the Nile and the Rio Grande — now qualify as endangered.

Of the 21 rivers longer than 1,000km that still flow freely from their mountain sources to the sea, most are in remote regions of the Arctic, and in the Amazon and Congo basins, where hydropower development is not yet economically viable.

These trends strain water resources, destroy ecosystems and threaten human health.

For example, heavy upstream diversions have turned the deltas of the Colorado River and the Indus River into saline marshes.

Moreover, lower river-water levels impede the annual flooding cycle, which in tropical regions helps to r-fertilize farmland naturally with nutrient-rich sediment.

In periods of below-average rainfall, a number of rivers increasingly run dry before reaching the ocean, and even when they do make it, they are depositing less of the nutrients and minerals that are vital to marine life.

Globally, aquatic ecosystems have lost half of their biodiversity since the mid-1970s, and about half of all wetlands have been destroyed over the past century.

A recent UN study said that up to 1 million animal and plant species are threatened with extinction, many within decades.

Humans are hardly exempt from the health consequences of river destruction.

In Central Asia, the Aral Sea has all but dried up in less than 40 years, owing to the Soviet Union’s introduction of cotton cultivation, for which water was siphoned from the sea’s principal sources, the Amu Darya and Syr Darya rivers.

Today, particles blown from its exposed seabed — thick with salts and agricultural chemical residue — not only kill crops; they are sickening local people with everything from kidney disease to cancer.

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