Aside from its inner core, planet Earth is made up of 3 outer layers. First, a solid outer part, the lithosphere, which is made up of the Earth's crust. Second, a surface which is made up of liquid water (hydrosphere) and solid water (cryosphere). And third, a layer of gas (the atmosphere) which separates it from space. Living organisms have made their homes here, thus creating the biosphere which encompasses all ecosystems.

Catalysed by these living organisms, all of these components interact, infl uence each other and generate environments with extremely complex relationships, including chemical transformations and material and energy fl ows. These interactions have very slowly evolved to their current dynamic equilibrium, and have gone through various natural cycles (such as carbon, nitrogen and phosphorous). The Earth system has remained relatively stable for the last 11,000 years, from the start of the Holocene epoch ending today at the start of the Anthropocene (this concept is further explored in Topic 2).

The example of soil, detailed in the documentary by Lydia and Claude Bourguignon, as well as by Olivier de Schutter, illustrates the complexity of interdependence in these terrestrial habitats. But above all, this example demonstrates the vulnerability of the Earth system and the anthropisation of Nature (further explored in Topic 4). Since the beginning of the Anthropocene, under the cumulative eff ect of their chemical, physical and biological interactions, humans have aff ected all variables of the Earth system. The system thus fi nds itself in an unstable position and is looking for a new equilibrium by integrating the new “anthropic force” and its impacts. But there are two key factors when it comes to a balanced system. First of all, this balance is dependent on the fact that humans have managed to stabilise this “anthropic force”, thereby containing their interactions to a certain degree. Secondly, the destructive nature of change will depend on the intensity of this force, in other words, how far humans will go before stabilising it.

Mathieu Ricard talks about planetary boundaries. The concept of planetary boundaries is an easy-to-use, comprehensive tool. It allows us to gauge the Earth system's limits, what it can withstand before changing, and to assess the maximum thresholds which would cause destabilisation if exceeded. The scientifi c community has identifi ed 10 of the main interdependent processes which regulate our Earth system and fully infl uence the presence of life as we know it today, for example, the presence of hominids on its surface. Vandava Shiva refers to the loss of biodiversity, one of the 10 planetary boundaries, and talks about tipping points. As it stands, out of our 10 planetary boundaries, six thresholds have already been crossed. These thresholds include:

1. Loss of biodiversity (our system can handle a maximum of 10 species extinctions /year/ million species, but, unfortunately, we have currently already reached 100 species extinctions/year/million ten times more than the allowed limit);

2. Biogeochemical phosphorus cycle disruption (which has close ties to intensive farming, as previously mentioned by one of the speakers. Every year, we’re releasing over twice as much of the maximum allowable threshold per year);

3. Biogeochemical nitrogen cycle disruption (which has close ties to intensive farming, the burning of fossil fuels and industrial activity. Every year, we’re emitting over double the maximum allowable annual threshold);

4. Climate change (our current system can handle a CO2 concentration of no more than 350ppm in the atmosphere; in 2020, we were at 412 ppm, an all-time record in the last 3 million years);

5. The anthropisation of soil (our system can handle a change in the use of these soils as long as at least 75% of forestland is conserved. As it stands, we only have 62%).

6. The presence of new, unquantifi ed entities in the biosphere, have just been declared as off -limits (among them, micro-plastics, nanoparticles and, especially, persistent organic pollutants (POPs), which are synthetic chemical substances resulting predominantly from industrial farming, and which pose a major risk worldwide because they're “persistent, bioaccumulative, toxic and, above all, they can travel very long ranges”). The 4 remaining ones are:

7. Ocean acidifi cation (due to increasing CO2 levels in the atmosphere, acidifi cation impacts exoskeleton growth for marine species and jeopardises food chains);

8. The anthropic use of water;

9. Stratospheric ozone;

10. Atmospheric aerosol loading: poses a serious health risk for humans, and aerosols also play a part in climate disruption).

​

So, shall we change or disappear?

​

Ilya Prigogine's work has really contributed to our understanding of these complex systems and their irreversible nature. Since then, discoveries have continued to be made, and the more we learn, the more we're realising how unpredictable certain mechanisms are. By crossing a threshold, we're irreparably drawing closer to breaking point. Even if some tipping points have been identified by the scientific community, the complexity of the Earth system makes the knock-on effects unpredictable. Using methane (CH4) as an example can help us understand these phenomena which are amplifying each other and creating a kind of domino effect. Methane is a powerful greenhouse gas. Its presence contributes to global warming. Since temperatures are rising, this causes part of the permafrost to thaw, a ground which has a temperature that remains below 0°C throughout the year. This thawing means that previously-frozen organic matter (leaves, branches...) will be exposed. This matter will then deteriorate and release methane. This means that the concentration of methane in the atmosphere is rising and exacerbating the global warming phenomenon which, in turn, causes the permafrost to thaw... However, it also exacerbates melting polar ice which, in turn, disrupts ocean currents that regulate the habitability of our planet... This runaway system is discussed in the documentary by Sofi a Stril-Rever, as well as in the sequence of a collapsing tower, or even through the butterfly effect metaphor.

Nowadays, as Vandana Shiva reveals, the Western world is still not seeing the impact of these changes, whereas other humans living in less prosperous parts of the globe are often already having to deal with them. The solutions within our reach are both varied and complex, but they all have one thing in common: they require a deep and immediate shift in our mindset and culture. Matthieu Ricard poses a difficult dilemma: what will come first: change or disappearance... or something else?