Mapping the world’s free-flowing rivers
Günther Grill, Bernhard Lehner, Michele Thieme, Bart Geenen, David Tickner, Francesca Antonelli, Suresh Babu, Pasquale Borrelli, Linyin Cheng, H. Crochetiere, Heloisa Ehalt Macedo, Raquel Filgueiras, Marc Goichot, Jonathan Higgins, Zeb Hogan, B. Lip, Michael E. McClain, Jing Meng, Mark Mulligan, Christer Nilsson, Julian D. Olden, Jeffrey J. Opperman, Paulo Petry, Catherine Reidy Liermann, Leonardo Sáenz, Sergio A. Salinas‐Rodríguez, P. Schelle, Rafael Schmitt, James Snider, Florence Tan, Klement Tockner, Paula Hanna Valdujo, Arnout van Soesbergen, Christiane Zarfl
Abstract
Free-flowing rivers (FFRs) support diverse, complex and dynamic ecosystems globally, providing important societal and economic services. Infrastructure development threatens the ecosystem processes, biodiversity and services that these rivers support. Here we assess the connectivity status of 12 million kilometres of rivers globally and identify those that remain free-flowing in their entire length. Only 37 per cent of rivers longer than 1,000 kilometres remain free-flowing over their entire length and 23 per cent flow uninterrupted to the ocean. Very long FFRs are largely restricted to remote regions of the Arctic and of the Amazon and Congo basins. In densely populated areas only few very long rivers remain free-flowing, such as the Irrawaddy and Salween. Dams and reservoirs and their up- and downstream propagation of fragmentation and flow regulation are the leading contributors to the loss of river connectivity. By applying a new method to quantify riverine connectivity and map FFRs, we provide a foundation for concerted global and national strategies to maintain or restore them.