(i) Food: The first and most important need of the humans (or any living organism) is food. But with the production of food rising by arithmetic progression and population growing by geometric progression i.e. the number at each step is being multiplied. At the same time growing population is increasing the use of more and more agricultural land to build houses. Thus it is evident that food would be running short for the unchecked rising population.
(ii) Water: Availability of clean and germ-free water for drinking purposes would be more and more scarce with increase in population; the reason would be mainly, the pollution of rivers, ponds, lakes etc.
(iii) Land: Man is bringing more and more land under cultivation and also using up land for building more residential colonies, factories and industries. Usable land would thus become less and less available.
