It's no doubt that the prophecy made by Malthus is of great warn that the world would soon be inhabitable due to
1) Scarce food 2) Pollution that arises from overpopulation - during his time the Industrial Revolution had just began to take speed and Malthus does stand very correct. In "Essay on the Principle of Population", he made two 'postulata' : First, That food is necessary to the existence of man. Secondly, That the passion between the sexes is necessary and will remain nearly in it present state.

He therefore implies that everyone needs food but people will continue reproducing - at current pace - due to their sex drive. He suggests that while the global food output would grow with arithmetical progression - say in arbitrary unit 10,20,30,40... - the population would proliferate with a geometrical progression - beginning with 2,4,8,16,32,64...-. It's easy to see that according to this reasoning, population would soon outpace food supply in the world, and famine and starvation would set in. IINM, Malthus also mentioned that, war, albeit its harmful ramification, is necessary to reduce the world population to its balance state. However absurd the last statement sounds, the Club of Rome actually commissioned a study on consequences unchecked growth to the world and published its work "The Limits of Growth" in 1972, echoing Malthus' concern and provided a pessimistic outlook of the future, mar by pollution and high living cost.

However, while poor Malthus did take into account the drawback of potential growth of the world population, he certainly overlook technological advances that would gain enormous pace after his work. (In fact, during his time, England's population was booming but never reach a geometrical progression and the food output was always enough to sustain the nation's need. We might say that his assumption was utterly wrong, because people actually plan to lower the number of kids they have regarding their financial options ( Not just their sexual desire) , as we can see family size grows smaller towards the end of industrialization. 200 years later, China even has policy that only allows 1 children in each urban family !) Lastly, technological advances in agricultural field also ensure that food output could keep up with the population boom. Despite an exponential growth in population, the danger of a food crisis eventually was ousted by country finding ways to plant food more efficiently and scientifically according to climate and suitability. Can you believe that Saudi Arabia used to import water from the sea to aid the country's water irrigation ?

All the above are addressed in Tim Harford's "The Logic Of Life" and "New Ideas from the Dead Economists"