Final answer:
Thomas Malthus theorized that unchecked population growth would eventually exceed the carrying capacity due to slower food production, leading to a 'Malthusian catastrophe' of famine, war, and disease. His ideas highlight positive checks that reduce overpopulation and preventive checks that aim to control population growth proactively.
Step-by-step explanation:
Thomas Malthus was an English economist and demographer who is best known for his predictions regarding population growth and its impact on resources, specifically food supply. In his seminal work, 'An Essay on the Principle of Population', Malthus posited that while population tends to increase in a geometric progression, food production can only increase in an arithmetic progression. As a result, he theorized that if left unchecked, population growth would eventually outpace food production, leading to a situation where the carrying capacity of the environment is exceeded. This would result in positive checks, such as famine, war, and disease, which would effectively reduce the population to sustainable levels.
Malthus identified these positive checks as essential to controlling the human population when it exceeds the earth's carrying capacity, which is the maximum population size that the environment can sustain indefinitely given the food, habitat, and other necessities available in the environment. His theory suggested that without these checks, populations would face catastrophic consequences or a 'Malthusian catastrophe'. Alternately, 'preventive checks' such as birth control and celibacy could help to control population growth proactively.
Although Malthus's predictions have been criticized and his theories not fully realized due to improvements in technology and agricultural productivity, his ideas continue to influence discussions on overpopulation and environmental sustainability to this day.