What does the population growth rate explain?

The population growth rate specifically measures how fast a given population grows over a certain period of time. It typically expresses the change in the number of individuals in a population, often as a percentage of the population size per year. This rate incorporates factors such as birth rates, death rates, and migration patterns.

Understanding the population growth rate helps in various fields such as urban planning, resource management, and environmental studies, as it indicates trends in population dynamics. For example, a high growth rate may signal the need for more housing, schools, and healthcare facilities, while a low or negative growth rate may have different implications for resource allocation and economic planning.

The other options, while they relate to aspects of population dynamics, do not directly define the concept of growth rate itself. For instance, sustainability and resource availability are influenced by growth rates but are not what the growth rate describes. Similarly, immigration impacts the growth rate, but it is just one of several factors that contribute to it.