In Malthus, "An essay on the principle of population", he states that due to the disproportional increase of the human population, this pathway will lead to high poverty, low wages for labor, and competition. He also stated due to the linear growth of the food production the gap between food and population will lead to the decline of society.
In my perspective, his assumptions are pretty close and accurate to certain situations third world countries are experiencing today. However, Shah critiques his arguments because he neglects certain aspects the prove some his arguments incorrect. In "Ecology and the Crisis of Overpopulation: Future Prospects for Global Sustainability, Shah suggest land availability and technical processes have contributed to the increase of food population Malthus refused to believe. He does agree in the idea that population growth will contribute to poverty and low wages. He refers to the rich as a fenced land in a mesa, where the poor started surrounding the fences until their increase in population starts pushing them off the mesa. This also contributes to the idea Shah has that Malthus had about when more there is more "room and resources" in the land, the families will have more children. This is not true, due to in the decline in society when Western Europe wealthy. The education contributes to the decline of population, and you can see it today in modern society. The rich and educated families are more likely to have less children, than those who are poor. Also, the developing technology played an important role in food production will led to the increase of it and more availability of it to the people.