well, i think it is due to the killing on them.
A natural cause of decline in a population could be disease outbreak or an epidemic. Diseases can spread rapidly through a population, resulting in a significant decrease in the number of individuals. This decline in population can occur in both plants and animal species.
Hij
disease.
disease.
What will cause a decline in the human population is loss of fish, dirty water, a whole in the ozone layer. These are just three causes that could decrease mankind.
The direct cause of the formation of the Bracero Program was decline of the rural population. The southwest saw the biggest drop in this population.
The introduction of diesease by contact with Europeans
Emigration.
If something is removed or damaged, that part of their life is removed. Damage to water, food, or shelter sources, cause an animal to go without, which can cause death or a population decline.
A natural disaster is considered a density-independent limiting factor because its impact on a population does not depend on the population's size or density. Events such as hurricanes, earthquakes, and wildfires can affect large areas and populations regardless of how many individuals are present. This means that even in low-density populations, a natural disaster can cause significant mortality and disruption, leading to a decline in population numbers without being influenced by the population's density.
The epidemic disease was the cause of population decline of the American natives due to their lack of immunity to the new diseases brought from Europe.
Loss of habitat to human intervention seems to always be the #1 cause of the decline of animal species.