For tens of thousands of years, indigenous cultures around the world have recognized cycles and systems in the environment, and that humans are an integral part of these. However, it was only in the early 20th century that contemporary systems thinking was applied to the Earth, initiating the emergence of Earth System Science (ESS). Building on the recognition that life exerts a strong influence on the Earth's chemical and physical environment, ESS originated in a Cold War context with the rise of environmental and complex system sciences 1-3. The ESS framework has since become a powerful tool for understanding how Earth operates as a single, complex, adaptive system, driven by the diverse interactions between energy, matter and organisms. In particular, it connects traditional disciplines-which typically examine components in isolation-to build a unified understanding of the Earth. With human activities increasingly destabilizing the system over the last two centuries, this perspective is necessary for studying global changes and their planetary-level impacts and risks, including phenomena science in the 1980s, global expansion in the 1990s and present-day ESS. A timeline of key events, publications and organizations that characterize the evolution of ESS is shown in Fig. 1. Beginnings (pre-1970s). Past conceptualizations of the Earth formed important precursors to the contemporary understanding of the Earth System. Examples include J. Hutton's 1788 'theory of the Earth' , Humboldtian science in the 19th century and V. Vernadsky's 1926 'The Biosphere' 7. Understanding the historical roots of ESS, however, requires a focus on the second half of the 20th century when, in a Cold War context, important shifts occurred in the Earth and environmental sciences 8. Thanks to military patronage taking precedence over traditional sources of funding for Earth sciences, geophysics experienced unprecedented growth 9. Moreover, surveying and monitoring the global environment became a strategic imperative, providing information that would later be useful for contemporary ESS 10,11. In the middle of the 20th century, international science started to develop, epitomized by the International Geophysical Year (IGY) 1957-1958 (reF. 12). This unprecedented research campaign coordinated the efforts of 67 countries to obtain a more integrated understanding of the geosphere, particularly glaciology, oceanography and meteorology. One of the key impacts of the IGY was a lasting transformation in the practices used to understand how the Earth works. The interpretative and qualitative geological and climatological research based on field observations-as classically studied by geographers-was replaced by field instrumentation, continuous and quantitative monitoring of multiple variables and numerical models 13. This transformation led to the two contemporary paradigms that structure the Earth sciences: modern climatology and plate tectonics 14,15. Ecology and environmental sciences also developed rapidly 16. Ecosystem ecology emerged with th...

The 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.

Nous préférons parler de "champ" plutôt que de théorie, d'hypothèse ou de disciplines dans la mesure où ce terme rend mieux compte à la fois de l'hétérogénéité des explanandumque cet article contribue à souligner -et de la diversité des contenus publiés sous l'un ou l'autre des labels -modèles de genres différents, exemples empiriques, arguments verbaux, discussions théoriques, etc. 2