Article and infographic inspired by the book: Planetary Boundaries [Boutaud & Gondran, 2020]
The question of planetary boundaries appeared in the debates in the19th century with the first Malthusian concerns (noting a shift in evolution between demography and resource productivity) quickly swept away by a Cornucopian reaction excluding the nature of the economic equation since the progress of science "are as infinite and, at least, as rapid as those of the [Engels, 1844] population". The notion of natural capital secretly symbolizes this relegation of nature to a sub-category of capital.
Now with undeniable multi-source anthropogenic pressures and multi-effects, the question of planetary boundaries also extends to the processes of regulation of the Earth system. It is precisely the object of this book that plunges us into the main variables that determine the biophysical balances of the planet, from the beginnings of the Holocene to their disruptions of the Anthropocene, with an outstanding question: to what limits will the Earth system be able to absorb anthropogenic pressures without compromising the living conditions of the human species?
To begin with, let's talk about borders rather than boundaries:
Defining planetary boundaries arouses a real scientific craze. It is true that the task is urgent and could help to define an inescapable repository of decision-making, but this is so difficult scientifically and technically (extreme complexity, loops of positive and negative feedbacks difficult to model) awakening some skepticism and criticism in the scientific community. It is true that the science of the Earth system is a young and complex science. But in any case, the challenges of the21st century invite us to learn more about the ecosystem functioning of our "Earth [Boulding,1966] spaceship".
The Stockholm Resilience Centre team is working on this notion of planetary boundaries by modeling the 9 main processes of regulation of the Holocene that have allowed an extreme diversification of the Living and the prosperity of the human species. For each of these processes, they select one or more control variables as the majority explanatory factor (e.g. C02 for climate change) and observe responses following the evolution of this control variable.
It is clear from the reading that it seems more sensible and prudent to define planetary boundaries (i.e. the low value of uncertainty, which equates to an increased risk of disruption to the regulatory process) than limits (tipping point or tipping point) because breakpoints are [Zimmer, 2009] unpredictable, or virtually non-existent in most cases (CNRS, 2020) but also because regulatory processes interact and the disruption of one affects the regulation and/or resilience of others (see infographic below).
Let us review all these regulatory processes, their current state vis-à-vis the planetary borders defined by the Stockholm Resilience Centre and their systemic relationships.
3 global processes affected, conducive to international mobilization: ozone erosion, climate change and ocean acidification
- ozone erosion: an "easy" entry into international cooperation
The first global symptom of anthropogenic impact, chlorinated molecules (including CFCs)were singled out as the majority responsible for the "hole in the ozone layer" and banned as a result of the Montreal Protocol (1987). The boundary measuring the overall average thickness of the ozone layer had been almost reached (due to the catalytic reaction of chlorine destroying ozone molecules), resulting in an increase in UVB reaching the ground whose increased exposure is harmful to biodiversity (photosynthesis, plant growth, animals).
Since this protocol, CFCs have been replaced by HCFCs and then HFCs, re-increased stratospheric ozone thickness. This is a success, but it has been facilitated by the combination of two factors: the number of sectors and companies involved with an existing and satisfactory alternative technology. Factors missing for the next border.
- climate change, a symptom of the huge carbon transfer and a symbol of international failures
The human species has made a huge transfer of carbon from the lithosphere to the atmosphere for the development of thermo-industrial society. Atmospheric gas concentrations speak for themselves: since 1850, we have seen an increase of 280 to 415 ppm for CO2 (up 48%), from 800 ppb to 1800 ppb for methane (up 125%). All this leads to a gigantic greenhouse effect by radiative forcing, and thus, a very rapid climate change of anthropogenic origin.
Two control variables have been selected to define the boundary of climate change: the CO2 concentration with a border at 350 ppm and the radiative forcing (in W/m2) which seems more robust since it takes into account all greenhouse gases (GHGs) but its measurement involves a fairly strong uncertainty. Whatever the control variable, the boundary of climate change has been largely transgressed, will continue to be so (particularly with the threat of permafrost) and impacts other processes, especially those related to biodiversity (which must adapt very quickly) and the oceans.
The Kyoto Protocol (1997) and the countless MOPs have failed to reverse this trend. These repeated failures in international cooperation can be explained in part by the lack of satisfactory alternative technology to fossil fuels; The magnitude of the changes to be made in all companies and sectors; uneven effects of climate change and non-binding targets set on a state variable (temperature) and not control.
- ocean acidification, a negative feedback that runs out
The oceans are the first carbon sink: the more atmosphericCO2 there is, the more CO2 is dissolved in the oceans. However, this carbon sequestration leads to acidification of marine water (up 30% since 1990). This negative feedback (since it mitigates climate change), so tested, decreases the photosynthesis of phytoplankton, threatens coral reefs and thus the entire fish biodiversity by trophic effects.
The control variable is the level of saturation in aragonite (1 of the 2 calcium carbonates produced per marine organism for calcification) and the boundary is set at 80% of the pre-industrial era. The value is now 84%, close to the border.
Biogeochemical cycles far too disrupted: between nitrogen leakage, phosphorus waste and anthropogenic water cycle
- Azote (N) and Phosphorus (P), symbols of the unsusability of our agricultural production
Nitrogen plays a central role in biomass production. At the beginning of the20th century, chemical processes (notably the Haber-Bosch process) provided humans with a considerable artificial supply of reactive nitrogen via nitrogen fertilizers, boosting global agricultural productivity.Artificial intakes of reactive nitrogen are now up to five times higher than natural inputs resulting in a definite imbalance in the nitrogen cycle. This excess nitrogen is only partially absorbed by plants (60%), reflects in the food chain resulting in nitrate pollution of soils and waters multiplying the risks of eutrophiation of rivers and oceans (proliferation of algae and risk of asphyxiation of aquatic fauna and flora).
Denitrifying bacteria limit this problem of nitrogen leakage (negative feedback) but their capacity is limited and their overactivity generates a release of nitrogen oxide, which is a powerful greenhouse gas, thus accentuating climate change (reverse of the coin).
Phosphorus is also essential in our agricultural production as it is the first nutrient of photosynthesis and therefore acts as a limiting factor. Its natural origin (rock alteration) was supplemented by a surplus from the extraction of phosphate rocks that are then found in our chemical fertilizers. The two major problems are the phenomenon of scarcity (depletion of reserves estimated between 50 and 100 years) and a big loss in this anthropogenic cycle: only 1/5 of the mined phosphate is found in our diet. The rest disperses into ecosystems and becomes harmful in aquatic environments with eutrophiizations that become widespread resulting in dead zones (e.g. Dead Sea), called Oceanic Anoxic Environment (EAO).
For these two elements, the values of control variables (nitrogen and anthropogenic phosphorus injected into nature) are more than twice as high as defined planetary boundaries (which in addition do not take into account the risk of scarcity and adverse effects on other regulatory processes).
- The freshwater cycle entered the Anthropocene
Humanity has become the main source of river flow change, as evidenced by the Aral Sea or the fertile river in Iran: 25% of watersheds are drained before reaching the ocean, leading to conflicts around the resource and a very damaging loss of biodiversity (wetlands).
Humanity is also the first agent for altering evaporation flows (mainly due to climate change and deforestation). It is also time to correct all the patterns of the water cycle and add the anthropogenic impact since it can – among other things – modify the water retention of soils and the regional climate by upsetting the rainfall regime of a geographical area.
The volume of fresh water collected from surface and groundwater (the control variable) has not reached the global border, but numerous regional overruns and uneven resource distribution suggest complementing the global border with a watershed-wide border.
Biodiversity and soils, a sign of biosphere resilience, in agony
We think metaphorically of the biosphere as a patchwork composed of three types of biodiversity: fibers (gene diversity), wires (species diversity) and pieces of tissue (ecosystem diversity).
The more important these 3 biodiversitys are, the more flexible (adaptable) and solid (resilient) the living web. The integrity of the biosphere (of which we are a part) is therefore intimately linked to its biodiversity: "a mesh unravels and it is all the garment that [Barbault, 2006] tears".
As we all know, the observation is clear: whatever the chosen ethic (environmental ethics with strong preservation or utilitarian ethics with weak preservation), defined planetary boundaries (species erosion or functional diversity) are largely transgressed creating the sixth great [Elizabeth Kolbert, 2014] extinction. This extinction rate, 100 to 1000 times higher than the natural rate, risk of worsening since abundance indicators (e.g. vertebrates – 60% since 1970, [WWF, 2018] -80% for mammals [IPBES, 2019] , – 75% for insects in 30 years in [Hallmann, 2017] Europe) portend imminent extinctions and biodiversity is threatened by other border crossings (see infographic of planetary borders) including land use change.
Urbanization and deforestation destroy, pollute or fragment biodiversity habitats. Forest cover is in sharp decline with a rather striking figure: – 1000 hectares per hour on average since 1990 [WWF, 2016] . Half of this deforestation is attributable to commercial agriculture (extensive farming, forage plants, agrofuels, coffee, palm oil, etc.). has different effects depending on biomes, climate, species, age of trees or forestry management, but the effects are much more negative for tropical and boreal forests (the most massively deforested areas). Clearly, in addition to deforesting too much, we deforest in the wrong places.
Erosion of forest cover (variable control) is well above the defined boundary and does not take into account the qualitative gap in ecosystem services between a destroyed natural forest and its replacement by single-species forestry.
This change in land use affects four other processes: biodiversity, climate change and ocean acidification through the release of C02 and finally the water cycle by altering soil infiltration capabilities, evapotranspiration and even local climate.
And to season: a stock of potentially harmful substances at unknown borders and a stock of non-renewable resources close to exhaustion
- Atmospheric load in aerosols, a health issue
Air pollution, especially fine particles mainly from combustion, is a concern because it remains suspended, aggregates other pollutants and enters the airways. This pollution sometimes reaches extreme levels with the famous episodes of airpocalypse in China.
This atmospheric load in aerosols measured by the optical thickness of suspended aerosols has no determined planetary limit. It is difficult to estimate the climate impact since, depending on the particles, the effect may be cooling (suffers) or warming (soot).
- A cocktail of artificial features incorporated into the cycles of life
Artificial entities include chemicals (solvents, biocides, CFCs.), materials created or modified (GMOs, nanoparticles, plastics) or natural elements concentrated by human activities (heavy metals). 500 million tonnes of chemicals are produced each year and released in all life cycles, along our production and consumption chain. 500 times the volume of 1930! The dose does not necessarily make the poison [Cicolella,2013] , other factors such as the duration of exposure or the effects of cocktails between substances affect the harmful and make the definition of a border too complex. What is certain are the potential cascading effects as illustrated by POPs (bioaccumulators, bio amplifiers, mobiles) or insecticides affecting the entire food chain.
- Risks of shortages in many sectors
Fossil energy, minerals, rare earths, phosphorus or sand… our thermo-industrial society will sooner or later face the inevitable depletion of non-renewable resources with a risk of serial shortages that discoveries or technological advances will struggle to fill.
In any case, before talking about scarcity, natural resources have a decreasing yield (the rate of energy return) which therefore requires more energy for extraction and affects the cost of production. This interdependence between minerals and energy accelerates the scarcity of resources: the scientist Heinberg deduces that peak oil would have chain consequences, leading to a peak everything [Heinberg, 2010] .
This overview of planetary boundaries, although demoralizing and imperfect by our partial knowledge of the Earth system, provides us with a global view of our impacts (and their interactions) on the regulatory processes that underseed the conditions for our expansion.
It allows us to reflect on the same pattern all the disturbances associated with these famous negative externalities of human activity that inevitably reverberate in the biosphere (central factor of planetary balances). The study of borders allows us to point to two sectors at the heart of these global border crossings: the fossil fuel sector and the food production sector, which are difficult to blame for (because we owe our demographic expansion and our comfort of life to them) but which need to be profoundly changed.
Some suggest that these negative externalities and outdated planetary boundaries find their primary causality in our population growth, others (as with ExNaturae) in the logic specific to capitalism, deeming the term Capitalocene [Malm, 2017] more appropriate to describe our brief geological episode.
Like theoverview effect,the question of planetary limits is an invitation to modesty, to an introspective pause, to reconnection to the Living, to "the acceptance that we are not all-powerful […] in a world that will become more and more constrained, no matter [Vincent Mignerot, 2020] what.
This is not a Manichean issue of technophiles versus technophobes, Malthusians versus cornucopians. It is much more complex than that with uncertainty that should not defy us of our common responsibility or legitimize inaction. And as the infographic of planetary frontiers and their interactionsillustrates, it is illusory to believe in simple solutions or desperate "dressing solutions". The problem will only be pushed back to another location (or create others).
The answers must be systemic. And at the height of the stakes raised by planetary boundaries.