Read the following passage and answer the item that follows. Your answer to this item should be based on the passage only.

Phosphorus is not manufactured. It is mined, from a small number of deposits, and once it has washed off a field it is effectively gone. Of the phosphate applied to cropland worldwide, only a modest fraction is taken up by the crop in the season it is applied; much of the rest is bound in the soil or carried into water, where it feeds the algal blooms that strip the oxygen from lakes and estuaries. So the same tonne of a finite mineral is at once a shortage the world will feel within a few generations and a pollutant it is dealing with now.

Which one of the following statements best reflects the most logical, rational and crucial message implied by the passage?