How does population growth affect biodiversity?

Every ecosystem has a particular capacity to hold the number of species of a population. This capacity is termed as the carrying capacity of a population. If the population growth is more than the carrying capacity, then resources such as food, shelter, water etc will become limited. The organisms will fight for the scarce resources that are present. As a result, many species will die due to lack of resources. Others might tend to migrate to better places. Hence, the ecosystem would become unstable.