Although ships are the most energy-efficient method to move a given mass of cargo a given distance, the sheer size of the industry means that it has a significant effect on the environment.[4] The annual increasing amount of shipping overwhelms gains in efficiency, such as from slow-steaming. The growth in tonne-kilometers of sea shipment has averaged 4 percent yearly since the 1990s,[5] and it has grown by a factor of 5 since the 1970s.[citation needed]
The fact that shipping enjoys substantial tax privileges has contributed to the growing emissions.[6][7][8]
^Walker TR, Adebambo O, Del Aguila Feijoo MC, Elhaimer E, Hossain T, Edwards SJ, Morrison CE, Romo J, Sharma N, Taylor S, Zomorodi S (2019). "Environmental Effects of Marine Transportation". World Seas: An Environmental Evaluation. pp. 505–530. doi:10.1016/B978-0-12-805052-1.00030-9. ISBN978-0-12-805052-1. S2CID135422637.
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