Depleted
As natural sources of fuel deplete there is, not unnaturally, a concern to introduce more efficiency, to conserve our resources. The idea is that by producing more efficient cars, heating systems or whatever we’ll decrease fuel use and buy ourselves more time to do whatever it is we need to do: melt the polar icecaps, most likely.
Unfortunately, this is exactly wrong. If we make more efficient use of fuel we will use it faster and probably do more damage than if we stagger along in our current fashion. This is the Jevons’ paradox, a mode of market failure that should make grown environmentalists weep, if they weren’t too busy saving the few remaining penguins by smothering them in oil retardant chemicals.