What does the speaker emphasize as the reason for maintaining sea resources?

During the 19th century, it was common to hear people in Europe and America say that the resources of the sea were unlimited. Today, there is evidence that the resources of the sea are as seriously endangered as those of the land and air, and that the endangered species now include Herring and Carp as well as the African Elephant, Indian Tiger, and the American Eagle. Further, the threats to fish are more alarming in some ways that the threats to animals and birds. This is because fish are much needed food resource and people throughout the world depend on fish as an important part of their diet, and the decline in the fish supply could have extensive effects on hunger and population. Fishermen in the North Atlantic alone annually harvest 20 billion pounds of fish to satisfy food demands, but it is important to recognize that these practices can not continue without depleting fish reserves within the next few years. Sea resources are rapidly declining in many parts of the world, and the problem cannot be ignored. We can predict that food supplies in the sea can not last forever.