Summary
Highlights
The course begins by introducing the Anthropocene, the current geological epoch where human activities profoundly impact Earth. Visual examples such as deforestation, city sprawl, extraction sites, and large-scale artificial land creation (like Flevoland) illustrate how humanity has become a geological force, transforming the planet on various scales.
The concept of the 'Great Acceleration' is presented, highlighting the exponential increase in socio-economic trends (population, GDP, investments, resource consumption) since the Industrial Revolution, particularly from 1950 onwards. This acceleration has led to improved quality of life, education, and health for a growing population, but also to a significant increase in environmental impacts, pushing the Earth system into a 'danger zone'.
The course reviews the laws of matter and energy conservation ('nothing is lost, nothing is created, everything is transformed') and the second law of thermodynamics (entropy, or the tendency of energy to degrade). It explains how living organisms, as open systems, counteract entropy by continuously taking energy and matter from their environment to maintain their form and reproduce, a process called metabolism.
Living beings form complex trophic networks where they consume each other, illustrating the flow of energy. Photosynthesis is identified as the primary access point for solar energy into most ecosystems, though chemosynthesis in deep-sea hydrothermal vents demonstrates alternative energy sources for life. The crucial point is the availability of metabolizable energy to sustain ecosystems.
The concept of the biosphere, defined as the region of Earth's crust where life transforms cosmic rays into active energy, is introduced. It highlights how life interacts with air, land, and water within a thin layer around the planet. The biosphere provides essential support, supply, control, and cultural functions. The immense diversity of life, with millions of species, mostly undescribed, is emphasized, along with the biomass distribution where plants dominate, and humans constitute a tiny fraction compared to livestock.
The deep interdependence within the biosphere is explored through complex trophic networks and collaborative relationships, such as the 'wood wide web' mediated by fungi. This leads to the concept of biogeochemical cycles, where essential elements like carbon, nitrogen, phosphorus, and oxygen circulate between living organisms and environmental reservoirs (atmosphere, lithosphere, hydrosphere) over various timescales. The 'breathing' of Earth through annual carbon absorption is presented as an illustration.
The concept of 'ecological engineer species' is introduced, exemplified by beavers, mangroves, corals, earthworms, and termites, which significantly transform their environment. Cyanobacteria are highlighted as ancient ecological engineers whose oxygen production drastically reshaped Earth's atmosphere and life. The summary concludes by positioning homo sapiens as a powerful ecological engineer, whose economic activities move vast amounts of matter, profoundly altering the environment and producing non-metabolizable waste, leading to pollution. The next session will explore how human activities transform the biosphere's metabolism.