Population viability refers to the ability of a species to survive and reproduce over time in a given environment. It is often assessed using models that predict the likelihood of a population persisting for a certain number of years, taking into account factors like birth rates, death rates, and environmental conditions. Conservationists use population viability analysis to identify species at risk of extinction, such as tigers or sea turtles. By understanding the factors that affect a population's health, strategies can be developed to enhance their chances of survival, ensuring biodiversity and ecosystem stability.