Doing things in the ocean that have economic value generally results in some modification of the natural environment. When we develop or manage marine resources, either within the ocean itself or on the ocean bottom, but especially along the coastal margins, then we are influencing the physical and biological state of the ocean in some manner that will have not only certain shortrange effects, but also good or bad long-range effects. As we look to the future, we can see that our scale of development of marine resources is going to increase tremendously and so, therefore, must our concern with the resulting modifications. The exploitation of offshore oil and offshore sulphur has increased by leaps and bounds; thanks to modern techniques of electronic location and catching, fishing activities are now able to wipe out a complete fishery in a short time unless controlled. The blue whale has essentially disappeared; although we are not aware yet of any ecological consequences following from this disappearance, we can observe the population dynamics and the substitution of fisheries when we overfish, for example, the California sardine or the Atlantic menhaden. The construction of shipping canals has led to biological and ecological modification, e.g., the invasion of the Great Lakes by the lamprey or the invasion of the Mediterranean through the Suez Canal by species from the Red Sea. Pollution of the marine environment, again in the coastal zone, has been increasing at a rapid rate through continuous discharge as well as through accidents.