Between 2005 and 2050 the gross world product is expected to grow by 6.3 times, from 67 trillion dollar in 2005 to 420 trillion dollars in 2050. In the assumption that the population grow slow down to achieve 8 billions -instead of the forecast of 9.2 billions- the world gross product will rise to 365 trillion dollars. If 67 gross world product is already unsustainable, can you imagine what would happen with a five times growth figure?