Dr. William E. Rees is the scientific pioneer of the quantification of "overshoot", through his notion of our Ecological Footprint, the best global indicator of the way and the degree the human enterprise exceeds the ecological capacities of our ecosystem. His extensive research and writings on the subject, over several decades, along with his public lectures and the translation of his books into several languages, make him arguably one of the most consequential figures for anyone wanting to know the common factor behind the metacrisis, aka the "meta" factor of the word.