Human population growth is clearly outstripping the possibilities of increasing the supply of food and other prerequisites for satisfactory existence. Already, with around four thousand million people on Earth, the race appears to have been lost by agriculture. The prospect of doubling this population by shortly after the turn of the century is bleak indeed. It is the belief of many, however, that zero population growth will be reached earlier by a catastrophic increase in the number of deaths—most probably from starvation. This also bodes ill for conservation; for as people get more and more hungry, their behaviour towards wildlife and what remains of the natural environment is going to become more and more reckless. The destruction of both wildlife and its habitat may be expected to extend to quite devastating proportions, which will require understanding action in both over- and under-developed countries to counter with any degree of success.
Man is inexorably changing the face of the Earth and weather patterns in directions which could have all manner of widespread ill-effects, and already have had some catastrophic local ones. Yet more and more of the world's productive lands are being paved with concrete, and the productivity of even wider areas is being permanently lost through erosion and laterization following the clearing of forests and other binding vegetation. Simultaneously, many strains of crop plants are being lost which are essential to humanity because they enable plant breeders to develop new agricultural varieties to help keep abreast of changes in pests and weather, and to raise production levels.