But, just as was learned in Kruger, damming benefits come at a price.Īs the number and size of dams being built across the world exploded in the 20 th century, and into the 21 st, the ecological, social and economic costs rippled far beyond local dam sites, having regional and global ramifications. Over the centuries, dams - and massive, well-funded, government-supported dam-building initiatives - have been used to manage floods and provide water for drinking, crop irrigation, industry and power generation.
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This turnaround in policy is in line with increasing global criticism of one of humankind’s oldest tools for securing water supplies. Today, “Restoring river connectivity is a critical focus,” says Eddie Riddell, the park’s aquatic biodiversity manager. Over the past two decades, people and nature worked to undo the damming 42 dams inside Kruger were breached and demolished mechanically or by floods. Those that prefer drier areas, away from water where there are fewer predators, less competition and trampling - animals like sable and roan antelope - floundered. Species that prefer habitat close to water, such as zebra and wildebeest, flourished.
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Lessons on how to balance their benefits against the environmental harm they do are already available to us: removing some existing dams, for example, and not building others.Ĭatchment basins and stagnant waters behind dams silted up and accumulated hippo dung, nurturing cyanobacteria and poisoning the animals that drank the water. But dams are needed for energy, agriculture and drinking water, and are an inevitable part of our future.Dams also impact Earth’s climate in complex ways via modification of the carbon cycle. More than a quarter of Earth’s land-to-ocean sediment flux is trapped behind dams. Dams have contributed to an 84% average decline in freshwater wildlife population sizes since 1970. This global fragmentation of rivers has led to severe impacts.Natural flows will be altered for 93% of river volume worldwide by 2030, if all planned and ongoing hydropower construction goes ahead. Only 37% of rivers longer than 1,000 km (620 mi) remain free-flowing, and just 23% flow uninterrupted to the sea. The flows of most major waterways have been impacted by dams globally.The practice reached a peak internationally in the 1960s and ’70s, but in recent years dam construction has faced increasing global criticism as the hefty environmental price paid for their benefits piles up. Dam construction is one of the oldest, most preferred tools to manage freshwater for various uses.