The belief that population growth tends to outstrip expansion of food production, leading to natural curbs on the population such as famine and war, is called:

The belief that population growth tends to outstrip expansion of food production, leading to natural curbs on the population such as famine and war, is called: malthusianism.
The term malthusianism stands for the idea that population tends to increase faster, at a geometrical ratio, than the means of 
subsistence, which increases at an arithmetical ratio. 
This results in an inadequate supply of the goods.