While the possible depletion of energy sources has been emphasized in most literatures, this book aims to show that the increase of entropy in the biosphere, resulting since the dawn of industrial era, is a cause for urgent concern. As the entropy release puts a limit on sustainable growth, and the CO¿ atmospheric content is a reliable indicator of global entropy release that threatens the biospheric balance, a change of paradigm is necessary with the need to switch from an economy of exploitation to an economy of entropy.