Henry George pointed out:
Here is a difference between the animal and the man. Both the jay-hawk and the man eat chickens, but the more jay-hawks the fewer chickens, while the more men the more chickens. Both the seal and the man eat salmon, but when a seal takes a salmon there is a salmon the less, and were seals to increase past a certain point salmon must diminish; while by placing the spawn of the salmon under favorable conditions man can so increase the number of salmon as more than to make up for all he may take, and thus, no matter how much men may increase, their increase need never outrun the supply of salmon. [Progress and Poverty, Book II, Chapter 3, by Henry George, par. II.III.5.]
