5. What about oil, natural gas and coal reserves?

Fossil fuels were formed hundreds of millions of years ago by nature from marine or terrestrial biomass. Unfortunately, they are in finite supply and will one day be virtually exhausted. This may be rapid if we consume them abundantly, or slower if we are thrifty, but in any case, they will one day become scarce. As our civilization relies heavily on these fuels for energy, we will gradually have to do without them and replace them with other resources. Will we make this transition before they are completely exhausted (in the economic sense of the term), or will we go on until they are completely depleted? For the moment, we don't have enough information to answer this question, which depends on factors other than science and technology.

• We are undoubtedly very close to having exhausted half of the proven reserves of so-called conventional...