Paul Ehrlich, Bing Professor of Population Studies in the department of Biological Sciences at Stanford University, along with his wife Anne, point out in The Population Explosion (1990: 37–40), that the “key to understanding overpopulation is not population density but the numbers of people in an area relative to its resources and the capacity of the environment to sustain human activities”. An area can be densely populated by people, but it might not be overpopulated if resources are used in such a way as to allow for the indefinite continuation of the high density of people living there.

Using the above definition of overpopulation, the Ehrlichs state unambiguously that “the entire planet and virtually every nation is already vastly overpopulated” – note that the statement was made in 1990, when the human population was at 5,278 billion1, versus 7.244 billion in mid 20142. They draw attention to issues that have already been detailed at this blog – for example, the deforestation that is occurring globally, widespread fresh water scarcity, loss of topsoil, the destruction of biodiversity, and the release of carbon dioxide into the atmosphere.

The impact of the 7 billion people and their over-use of resources on the ecology of the planet is addressed in the Living Planet Report Summary of 20123; it states that, in 2008, humanity’s “Ecological Footprint exceeded the Earth’s biocapacity by more than 50 per cent in 2008”. This means, quite simply, that the amount of resources used by human beings in 2008, and the impact (e.g. release of carbon dioxide) that this use of resources had on the ecology of the planet, took 1.5 years for the planet to regenerate and absorb. The full Living Planet Report of 20124 (page 40) draws attention to the obvious question, how can this be possible when there is only one Earth? The report offers the following explanation:

“Just as it is possible to withdraw money from a bank account faster than to wait for the interest this money generates, renewable resources can be harvested faster than they can be re-grown. But just like overdrawing from a bank account, eventually the resource will be depleted. At present, people are often able to shift their sourcing when this happens; however at current consumption rates, these sources will eventually run out of resources too – and some ecosystems will collapse even before the resource is completely gone.”

Clearly, the above concise information regarding overpopulation and resource over-use constitute yet another aspect of the ecological crisis – not only are human beings threatened by their own actions, but so is the environment (fauna and flora) from which resources are extracted; again, this issue of the impact on the ecology of the planet has been addressed collectively by previous sub-sections.