To deal with peak oil and gas production as well as dangerous levels of greenhouse gas emissions, Earth will need to
move faster into a post-fossil fuel age. During this period a much larger human population will need much larger
renewable energy supplies, which could require vast tracts of land or sea. If, on the other hand, population is allowed
to decrease steadily while new forms of sustainable energy are developed, land will be released from urbanisation, the
number of consumers would fall, and energy targets should become easier to achieve.