Well, according to mother_of_another's argument, something will be invented (http://prometheusfusionperfection.com), or something we already have (solar) improved enough, before the resources we currently use for energy production will be depleted. (if we continue in this manner without new/better technology, these natural resources will be used up at some point, according to ender's argument)

Now just because in the past it has been the case that we always shifted our technology in time, this doesn't, in my mind, allow us to stand by and just assume this will be the case in the future.

If we fail this and humans are extinct, the question of wether or not we left a "better" planet, is not one we can answer, because life after us might have a wholly different set of values and judge that diffently. But that's not the point.

I'm not really sure any more about my original point, but I'm still of the opinion that we as western citizens should reduce exploiting both nature and other people in order to protect our outrageous wealth and become even more obese and unhappy.

I have a feeling (for wholly unscientific reasons), that bitcoin might play a role in this process.