Humanity is overshooting the limits of what is biologically sustainable on the planet Earth. This overshoot will result in the collapse of the environment's ability to support much of the biosphere. We must act rapidly and effectively to reverse this calamity and reduce our ecological footprint. The past thirty years have been largely wasted since the consequences of our failing to act were detected and detailed. This book gives a picture of the upcoming dark 30 to 100 years and attempts to shed some light to guide the reader in seeing what the alternatives are. Unlike other books in this field, it explores and sets a target to be achieved in order to avert disaster. This target is based on the function and relationship of life to the sun and the Earth.