Do cargo ships pollute the earth?

Yes. Anything that is in the ocean unnaturally has an effect and 'pollutes' the earth. Some effects on the maritime population include accidental chemical or waste spills, trash dumping, and destroying algae or other plants (or animals) that live on the surface of the ocean. Also, they run off either steam or diesel. The use of steam effects the hydrologic cycle and the diesel pollutes the atmosphere.