The action that will likely decrease a population's size is decreasing the food supply available to the population.
The population size or density refers to the average population per unit area; especially, the average number of organisms who live on each square kilometer of land.
The size of a population can be affected by several factors including both biotic and abiotic factors.
However, decreasing the food supply available to a population will ultimately decrease the population size of the organisms.
Learn more about population size at: https://brainly.com/question/1581160
#SPJ2