What is meant by population growth?

Population growth refers specifically to the increase in the number of individuals within a defined area over a certain period. This can occur through various factors, including higher birth rates, lower mortality rates, and migration into an area. Understanding population growth is crucial for analyzing how societies develop, how resources are managed, and how urban planning is conducted. By recognizing that population growth indicates a rise in population size, one can better assess the implications for infrastructure, environment, and social services within that region.

The other options diverge from this definition; for example, a decrease in population density relates to the distribution of individuals rather than their overall number. Local biodiversity pertains to the variety of species in an ecosystem, which is distinct from human population figures. An increase in territory size relates to area expansion rather than population counts. Thus, option D accurately encapsulates the meaning of population growth.