Life on Earth is hard to spot

International audienceThe triumph of the Gaia hypothesis was to spot the extraordinary influence of Life on the Earth. 'Life' is the clade including all extant living beings, as distinct from 'life' the class of properties common to all living beings. 'Gaia' is Life plus its effects on habitability. Life's influence on the Earth was hard to spot for several reasons: biologists missed it because they focused on life not Life; climatologists missed it because Life is hard to see in the Earth's energy balance; Earth system scientists opted instead for abiotic or human-centred approaches to the Earth system; Scientists in general were repelled by teleological arguments that Life acts to maintain habitable conditions. Instead, we reason from organisms' metabolisms outwards, showing how Life's coupling to its environment has led to profound effects on Earth's habitability. Recognising Life's impact on Earth and learning from it could be critical to understanding and successfully navigating the Anthropocene