Anthropogenic noise pollution is an emerging stressor for aquatic animals, especially whales, dolphins, and porpoises, which rely heavily on sound production, transmission, and reception (1, 2). Yet ocean soundscapes have aroused great concern (3), whereas little attention has been paid to anthropogenic noise pollution in riverine habitats.

Unlike the marine environment, riverine ecosystems are constricted to areas that often face inevitable competition with humans. All cetaceans that live in rivers, including five dolphin species and a porpoise, have declined substantially both in range and numbers, especially in Asia (4). The Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis), the sole freshwater porpoise in the world, which is only found in two Chinese lakes and some parts of the Yangtze River, is listed as Critically Endangered by the International Union for Conservation of Nature (5).

Noise pollution affects freshwater cetaceans across regions. The Yangtze has been the world’s busiest inland river in terms of shipping since 2005 (6), and its daily average vessel flow and annual cargo movement have increased over the past decade (7). Noise levels at approximately 88% of the river’s porpoise distribution area are sufficient to disrupt the behavior of the finless porpoise, and 40% of the river has noise levels high enough to cause reduction in the porpoise’s hearing sensitivity (8, 9). Underwater noise exposure from vessels in the Ganges River in India elevated metabolic stress in Ganges river dolphins (Platanista gangetica gangetica) (10). Busy vessel traffic in the Indus River in Northern Pakistan threatens the Indus River dolphin (P. g. minor) (11). Compared with coastal Irrawaddy dolphins (Orcaella brevirostris), freshwater Irrawaddy dolphins in Indonesia’s Mahakam River showed a hypersensitivity to intensive boat traffic (12).

 

Addressing noise pollution will require improvements to shipping lanes, ports, and ships. Shipping lanes should be regulated to protect channel resources. Optimal navigation speeds and restrictions of ship speeds in ecologically important areas would help mitigate noise pollution in cetacean habitats. The government should identify and eliminate illegal ports, especially those that have been built along the Yangtze in China. Ships that are docked should be required to use power from land rather than continuing to run their engines. The construction and renovation of environmentally friendly and economical ships should be developed and put to use. Subsidies should be provided to companies using outdated vessels to help them replace the ships with newer, quieter technology, such as more efficient propellers. Finally, governments should require all river traffic to meet operation and management standards that reduce noise pollution.

References and Notes

1. S. L. King, V. M. Janik, Proc. Natl. Acad. Sci. U.S.A. 110, 13216 (2013). 

2. S. D. Simpson et al., Nat. Commun. 7, 10544 (2016).