The most important factor in all environment threats is overpopulation. This can be quantified: 70 %, if the individual consumption stays high, and still 40 %, if this consumption is halved. Remedies are tackling specific environmental problems (deforestation, desertification, etc.) on one hand, and controlling migration and birth rates on the other. Implementation will have to meet moral, ethical, legal, ...standards. This book aims to show the way.