There are an estimated 33 million boats, including more than 90,000 ships, among the world’s commercial fleets, and most are powered by engines, propellers or other machinery that makes noise. A study published in the journal Sciencefound that the increase in shipping has contributed to an increase in low-frequency sound pollution that can negatively affect fish, invertebrates, marine mammals and birds by impacting foraging, mating and resting. 

The sequestration of additional greenhouse gases in the oceans has changed their sound-absorbing capabilities, making them potentially noisier. Other climate changes, such as warmer surface temperatures, changes in salinity due to melting polar ice and more frequent and violent storms, may also contribute to the problem. Additional research is needed to help policymakers implement appropriate countermeasures.