Peak Oil, which some of argued was reached in 2006, is the point at which we have used up about half of the world’s oil supplies and after which oil is increasingly difficult and costly to access.
From Wikipedia:
“M. King Hubbert created and first used the models behind peak oil in 1956 to accurately predict that United States oil production would peak between 1965 and 1970.[1] His logistic model, now called Hubbert peak theory, and its variants have described with reasonable accuracy the peak and decline of production from oil wells, fields, regions, and countries[2] . . .”
The concern is that post-peak production decline and therefore decrease in availability of oil together within predicted increasing demand for oil worldwide will have catastrophic consequences for the world economy and for our industrial way of life.
Some solutions are being proposed. For example, Transition Initiatives call for communities to generate their own “energy descent plans” and Lester Brown’s “Plan B” involves switching to renewable forms of energy, like wind, geothermal, solar, microhydro.