Population Density: Population density refers to the number of individuals inhabiting a specific area, such as people per square mile. It is closely related to the carrying capacity concept since it helps determine how densely populated an area can be without exceeding its sustainable limits.
Ecological Footprint: The ecological footprint is a measure of human impact on the environment, including resource consumption and waste production. It helps assess whether the demand for resources by a population exceeds the Earth's carrying capacity.
Malthusian Theory: The Malthusian theory, proposed by economist Thomas Malthus, suggests that population growth will eventually outpace available resources, leading to social and environmental problems. This theory ties into discussions about carrying capacity in human geography.