The resources to be considered when evaluating whether an ecological niche is overpopulated include clean water, clean air, food, shelter, warmth, and other resources necessary to sustain life. If the quality of human life is addressed, there may be additional resources considered, such as medical care, education, proper sewage treatment and waste disposal. Overpopulation places competitive stress on the basic life sustaining resources, leading to a diminished quality of life.
If resources required to sustain the organism are being consumed by the organism faster than the resource can be renewed, then the organism is overpopulated. For example, humans are destroying topsoil and consuming fossil fuels much faster than the planet can renew them and those resources are currently required to produce and distribute the necessary quantity of food to feed the population, and therefore humans are overpopulated on Earth.