Original title: Mapping the world’s free-flowing rivers
A free-flowing riverA river whose flow and connections along its course remain largely uninterrupted. is one whose water and connected river system are not broken up by barriers or changes in flow. The researchers assessed connectivityHow well a river remains connected along its length, including its flow and the movement of water through the river system. across 12 million kilometres of rivers worldwide. Only 37 per cent of rivers longer than 1,000 kilometres remain free-flowing for their full length, and 23 per cent reach the ocean without interruption. Dams and reservoirs are the leading causes of lost connectivity. The maps can help guide efforts to protect or restore rivers.
Imagine carrying a bucket of water along a path to a friend’s house. A wall or a change in the path can stop the water from reaching its destination. In this paper, the path is a river, and dams and reservoirs are the barriers that interrupt its flow; the maps show which rivers still run freely along their length or to the ocean.
Rivers support ecosystems, biodiversity, and services people rely on. The map shows where dams and reservoirs interrupt river connections, giving countries a basis for deciding where to protect or restore them.
The abstract reports a global assessment and identifies dams and reservoirs as the leading contributors to lost connectivity. It does not describe the method in detail, assess the condition of each river’s ecosystems, or show whether using the maps leads to successful protection or restoration.
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Mapping the world’s free-flowing rivers — Günther Grill, Bernhard Lehner, Michele L. Thieme et al. — Nature — doi:10.1038/s41586-019-1111-9
Abstract licence: CC BY
Explanation generated by Synthesis from the abstract — it is not the original paper.