Adventures in the Anthropocene. Gaia Vince

the potential to quickly and cheaply reverse the warming effect of a doubled carbon dioxide concentration. And, since we already know what happens when a volcano erupts, it is arguably one of the safest methods – safer than the impacts of global warming, for example. The technique could be used continually to avoid catastrophic climate change, or in times of severe drought or heatwaves, hopefully under the auspices of an internationally agreed treaty. And, carefully deployed, such techniques could potentially maintain or bring back glaciers over entire mountain ranges. But, while the world ponders the feasibility, ethics and wisdom of global-scale cooling, Norphel and other architects of the mountains are devising practical and effective local solutions to a warming planet.

3

       RIVERS

       Water that falls from the sky, leaks from a lake, rises from a spring or melts out of a glacier will make its way from land to ocean in a river. These freshwater conduits are life-giving. They irrigate forests and meadows, create wetlands and deltas, transport nutrients and sediments, and nurture entire ecosystems – self-contained watery worlds of animals, plants and microorganisms.

       And yet, rivers owe their very existence to life forms. For billions of years, terrestrial fresh water flowed to the oceans in vastly broad, shallow sheets – like floods – across the planet’s hard barren surface. It took the arrival on land of root-based plants, around 420 million years ago, for rivers to evolve. Plant roots weakened the surface of rocks, making them crumble, producing mud that eroded channels through which water then coursed. The plants’ strong root systems then further channelled the water, strengthening the muddy banks and creating a deeper, meandering path that we would recognise as a river. As these proto-rivers flooded and receded, sediments were periodically dumped, creating deeper, richer soils where huge woody plants took root. Forests diversified and enhanced the channels, helping produce the vital network of wetlands that exists today.

       The world’s rivers drain nearly 75% of Earth’s land surface, from the icy polar regions to the steamy tropics. Although they hold only about 0.0001% of the world’s water (and less than one-third of all fresh water), rivers are a key part of the global hydrological cycle, describing the geography of accessible fresh water for plants and animals. Hundreds of thousands of species have evolved to rely for all or part of their lifecycles on freshwater bodies, from the trickling source of a mountain stream, the torrential violence of waterfalls and rapids, the calm deep waters that flow between riparian forests, to the wide-open, sediment-flooded wetlands and deltas.

       The rejuvenating flow of Earth’s powerful arteries appears timeless. Dinosaurs lived and died on riverbanks that exist today. They fed on fish, some of which – such as sturgeon and gars, and the arowana and arapaima of the Amazon – still swim the rivers. These ancient creatures are joined by a vast array of newer fish, reptiles, mammals, birds and insects that contribute to making freshwater ecosystems some of the world’s most diverse.

       Humans have also been a part of this ecosystem, relying almost exclusively on rivers and lakes for drinking, bathing, food, waste disposal and transport. Fresh water is so essential to humans that you can map society by it. River deltas have proved fertile culturally as well as agriculturally – the great religions have rivers as gods, such as the Ganges, or as important parts of their narrative, such as Moses’ journey on the Nile, or Jesus’ baptism in the Jordan. Historically, cities were built in fertile river valleys and at river mouths. Agricultural run-off of sediment, water and nutrients created rich coastal deltas that could support greater food production. This and the good maritime and river connections for trade and transport made deltas ideal places to live. Human civilisation was born on a riverbank. The Tigris, Euphrates, Indus and Nile spawned humankind’s first great experiments in urban living, shifting our species firmly on to the trajectory we have followed ever since.

       In the Anthropocene, humanity is draining the world’s rivers and other sources of fresh water. Climate change has altered the global water cycle from Holocene norms, intensifying evaporation and precipitation. There is now greater flooding, worsening droughts and a general loss of predictability that makes planning more difficult for people trying to adapt. Greater water extractions by humans for agriculture, industry and energy mean that many rivers have dried up, while others are now too polluted to use.

       Of all the ways we’ve engineered Earth in the Anthropocene, little rivals our audacious planetary-wide replumbing of the world’s waterways. We have straightened and diverted them, buried them, dammed them and drained them for irrigation, filled or emptied them of fish, dug their beds for construction materials, used their flows to drive turbines for hydropower, and even created our own canals to bridge cities and divide continents. Humans now control more than two-thirds of the world’s fresh water. We’ve captured so much water that we’ve redistributed its weight around the world and the globe now spins a fraction slower.

      In the past century, we have drained half of the world’s wetlands, built 48,000 large dams and diverted most of the world’s large rivers – only 12% still run freely now from source to sea.1 Major rivers, such as Mexico’s Rio Grande, China’s Yellow River and Australia’s Murray River, frequently no longer reach the sea. Inland seas, such as the Aral or Lake Chad, have dried up with the use for agriculture of their feeder rivers. Dams, diversions and extractions are preventing river sediments from flowing downstream to maintain deltas against erosion. That, combined with groundwater extraction in coastal cities, is causing two-thirds of major deltas to sink.2 Around a quarter of people rely on groundwater that is being extracted faster than it is being replenished, more than 800 million have no safe drinking water at all, while four in five of us live in a place where the water supply is at risk.3 It’s not just humans that get thirsty, all species need water, and ecosystems around the world are suffering from a decline in supply – 30% of freshwater species are now endangered, the highest proportion of any ecosystem.⁴

       And our demands on the planet’s rivers are growing ever greater. Despite all the ways we’ve cosseted ourselves in the Anthropocene against the hazards and unpredictability of the natural world, we remain desperately dependent on rivers for drinking, for agriculture, for fisheries and, increasingly, for our energy.

       In many ways, the Anthropocene will be shaped by how we manage our rivers – it’s already proving emotive and political territory in different parts of the world.

      The southernmost habitable region of our planet is an untamed wilderness of glaciers and mountain peaks, subantarctic forest and scrub desert, volcanoes and turquoise lakes. Home to condors, puma and blue whales, Patagonia is the tail end of the Americas, one of the last accessible nowhere lands on Earth and the jumping-off point for Antarctica. It contains the Southern Ice Field, the world’s most important reserve of fresh water after Antarctica and Greenland. Forests of Antarctic beech bear testimony to a time when these lands were part of the warm Gondwana supercontinent, while frequent earthquakes and fiery volcanoes are evidence of continuing geological movement.

      This extraordinary landscape is the focus of a bitter international battle over plans to build a cluster of hydroelectric dams on three of Chile’s mightiest rivers. It is an issue so divisive, it is tearing apart some of the country’s biggest corporations and risks unseating the president. I went there in the hope of learning whether in the Anthropocene, people will choose the promise of cheap electricity and associated economic development, or the preservation of a natural wilderness that few will ever visit.

      Deep in the heart of Patagonia, I find the churning glacial blue of Chile’s most voluminous river, the Baker. The river cuts fast and furious through the mountains here, a tumultuous pulse that roars in defiance of any checks or dams. It is wild, wet and loud. Rainbows flash in the spray and the rocky banks glisten in the wash. I fancy I hear bird call drowned out in the background, but I cannot be sure. Beyond the surging river, all is still and silent. Two large hydroelectric dams are planned for the Baker – a cacophony of concrete, steel and asphalt to tap the river’s immense natural power for city-dwelling