An Independent Online [1]article [1] quotes a Professor Chris Rapley, the director of the British Antarctic Survey, who says that the rise in human population may be a more pressing issue even than climate change. Rapley estimated that the earth can sustain around 2-3 billion people at a good standard of living over the long term -- a pessimistic view when you consider that the current population is 6.5 billion and that it is expected to rise to 8 billion by mid-century.

Those are daunting numbers, but should be taken, primarily, as a stark reminder of how urgent it is to reduce humankind's environmental footprint -- and especially our per capita use of fossil fuels.