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France and the nine planetary boundaries
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Part 1

Boundaries: historical perspective and general framework



This first part presents the origin and general framework of the concept of planetary boundaries, proposed in 2009 by an international team of researchers at the Stockholm Resilience Resilience Centre. Planetary boundaries are in line with the Meadows report « Limits to Growth », published in 1972 and considered as one of the first major texts warning of the destructive consequences for the planet of unlimited economic growth in a world of finite resources. The planetary boundaries framework aims to define a "safe operating space for humanity", based on the evolution of nine complex and interconnected phenomena. The contours of this evolving framework are defined and presented in its 2015 version. The possibilities of adapting this framework on a smaller scale are questioned.

The limits to growth

The concept of planetary boundaries (Rockström et al., 2009) is not the first attempt to shed light on the impact of human activities on the environment and human well-being. Several decades earlier, in 1972, at the request of the Club of Rome, a group of scientists from the Massachusetts Institute of Technology (MIT) in the USA, led by Professor Dennis Meadows, published the famous report The limits to Growth, also known as the Meadows Report or the Club of Rome Report. A landmark initiative, the report left its mark on the environmental movement (Vieille Blanchard, 2011) and sparked numerous debates that shed some light on the position adopted in drawing up the planetary boundaries.

Published fifty years ago, the limits to Growth was one of the first reports to warn of the destructive consequences for the planet of unlimited growth in a world of finite resources. This report aims to explain that exceeding the physical boundaries of the Earth system will have a major influence on global development over the next hundred years.

Using computer models unheard of at the time (early computers), Dennis Meadows and his team represented the Earth system based on a few variables describing world population, industrial growth, food production, consumption of natural resources and pollution (see glossary).

Several dozen relationships link the evolution of these variables together. Known as "feedback loops", these are chains of cause-and-effect relationships that can lead to change or have a stabilizing effect. A "positive feedback loop" occurs when a chain of reactions amplifies a phenomenon, and a "negative feedback loop" when it tends to regulate a phenomenon or return it to a stable state.

The Meadows model identifies pollution growth as having a negative impact on life expectancy, and therefore on population size, which in turn leads to less pollution; growth in industrial product per capita contributes to growth in industrial capital, which in turn leads to an increase in agricultural production, but also in pollution, and so on. Each loop corresponds to a causal relationship that may be linear (i.e., the effect is proportional to the cause) or non-linear, i.e., immediate or delayed, positive or negative, and subject or not to threshold effects.

Based on these models, the scientists identified twelve possible scenarios for the 21st century and drew the following main conclusions:

  • If current growth trends continue, the planet's physical boundaries will be reached within the next hundred years. This could lead to a sudden, uncontrolled decline in human systems and well-being.
  • It is still possible to modify these growth trends and establish conditions of ecological and economic stability that are sustainable over the long term.
  • The sooner the world's populations mobilize to achieve this ecological and economic stability, the greater their chances of success.

Diagram 1 illustrates Scenario 1 as a starting point and point of comparison. This scenario describes the "probable general behavior of the system". The left half of the graph shows the evolution of the curves up to 2000: world population and industrial production increase, then their growth is halted by increasingly inaccessible non-renewable resources. At the turn of the 21st century, pollution is on the rise, and industrial production is declining due to a lack of resources. The rising cost of non-renewable resources then had repercussions on all economic sectors, particularly agricultural production.

Diagram 1: Scenario 1, a benchmark - State of the world

Source: Dennis L. Meadows et al, 1972. The limits to Growth. New-York: Universe Books

When updated in 1992 and again in 2004, the report drew the same conclusions as in 1972, confirming the destructive impact of human activities on natural resources and general pollution of the planet. Subsequent studies have shown strong similarities between the first scenario established in 1972 and the evolution of the "real world" (Turner, 2008).

The limits to growth have thus enabled us to move from an environmental discourse focused on local pollution to one encompassing all environmental issues on a planetary scale.

Ecological footprint

In 1996, Mathis Wackernagel and William Rees5 developed a new indicator called the "ecological footprint" (see glossary) to measure the pressure exerted on natural resources by human activities, more specifically by a population's consumption of goods and services: food, transport, housing and services. The ecological footprint estimates the biologically productive surfaces required to regenerate the natural resources used, and assimilate the waste generated (typically, to absorb greenhouse gas emissions). These surfaces are measured in global hectares (gha). Since 2003, the ecological footprint has been calculated by the Global Footprint Network (GFN).

This footprint can then be compared with the productive area actually available (see glossary). When the global footprint exceeds the planet's biocapacity, this means that to satisfy the consumption of all human being, the total natural resources produced by the Earth in one year are not sufficient, and it is necessary to draw on "natural capital". This is known as "ecological overshoot" or "ecological deficit". - which ties in with the notion of planetary boundaries.

The "day of overshoot" set by the GFN corresponds to the date from which humanity has consumed all the resources that the planet is capable of regenerating in one year. While the Ecological Footprint has been the subject of various methodological criticisms6, this highly communicative indicator has the advantage of highlighting the role of consumption patterns in the depletion of the planet's resources, and of being able to be broken down by country. In 1999, for example, the global exceedance day was calculated as September 29, whereas in 2022 it occurred on July 28, two months earlier. In France, the day of exceedance was May 5 in 2022.

5 Mathis Wackernagel and William Rees, 1999. Our ecological footprint. Éditions Écosociété.
6 Global Footprint Network, 2020. Ecological Footprint Accounting: Limitations and Criticism.

Planetary boundaries

Following on from the work undertaken by Dennis Meadows and his team, and in order to raise awareness of the risks of abrupt global environmental change, a new approach was introduced in 2009: the concept of planetary boundaries (Rockström et al.). This concept defines a "safe operating space for humanity" based on monitoring the evolution of nine complex, interconnected phenomena: climate change, biodiversity loss, biogeochemical cycles of nitrogen and phosphorus, land-system change, freshwater use, ocean acidification, stratospheric ozone depletion, atmospheric aerosol loading, introduction of novel entities into the biosphere. This concept focuses on describing and observing the Earth system, not the socio-economic factors behind its evolution. Exceeding the boundaries of "safe operation" for each of these phenomena can provoke potentially irreversible chain transformations, destabilizing the planetary equilibrium and rendering the planet uninhabitable for mankind.

By focusing on the planet's physical, climatic, biogeochemical and ecological processes (carbon, nitrogen, phosphorus, biodiversity, water, soil), the framework of planetary boundaries aims to:

  • get away from the debate on the boundaries to growth, which is rooted in two visions: the "pessimistic view of resource constraints", and the "optimistic view of technological progress", leading to only two possible models of action for the future: limiting the exploitation of resources, or promoting technological innovation;
  • The aim is "to create a safe space for human development" . A multiplicity of paths is then possible in this space of life preserved for humanity, in which economic growth can also find its place;
  • "define more precisely the threshold values associated with each natural process" .

The planetary boundaries framework represents a strategic shift from the boundaries to growth framework, insofar as the critical thresholds taken into account "exist independently of human preferences, values or trade-offs based on political and socio-economic feasibility, such as expectations related to technological disruptions and fluctuations in economic growth" (Folke, 2019).

Some definitions specific to the planetary boundaries framework

To study the evolution of the nine biophysical processes that make it possible to estimate the contours of a living space preserved for mankind, the planetary boundaries framework uses various notions that need to be defined to better understand the issues at stake: control variable, threshold, boundary, limit.

A "control variable" is an indicator defined on a global scale to measure the evolution of each of the nine processes. Some processes can be represented by two control variables, to provide a more detailed understanding of the biophysical or territorial issues that characterize them. For example, the "Global water use" process is represented, on a global scale, by freshwater withdrawals; on a local scale, by water withdrawals in watersheds and according to seasonal hydrological regime.

For each of the control variables, the researchers set a critical "threshold" (tipping point) that must not be exceeded to guarantee the stability of the Earth system as we know it today. Given the complexity of the exercise, they defined an uncertainty zone consisting of two values : a low value ("boundary") and a high value ("limit"). The boundary represents the danger zone that precedes the limit beyond which ecosystems could tip over into an unknown state that is probably unfavorable to mankind.

For example, for the "climate change" process, the control variable is "CO2 concentration in the atmosphere", for which a zone of uncertainty has been defined between 350 ppm (boundary) and 450 ppm (limit).

Depending on the evolution of the control variable, the biophysical process is likely to be modified and to have repercussions on the functioning of the earth system. Some processes may have direct effects on a planetary scale, while others have mainly local impacts but may become global at a later stage.

An evolving conceptual framework

The revision of the planetary boundaries framework (Steffen et al., 2015) leads to the conclusion that four planetary boundaries have been crossed (climate change, land-system change, biodiversity loss, disruption of nitrogen and phosphorus biogeochemical cycles).

According to the two founding studies of the planetary boundaries framework (Rockström et al. 2009, Steffen et al. 2015), human activities bear a major responsibility for the overstepping of boundaries. It illustrates the transition from the Holocene to the Anthropocene, a new geological era in which humans have become the main driving force behind the changes affecting the planet's natural balances on an unprecedented scale.

Since 2015, researchers have been trying to define how to characterize or specify certain boundaries. In 2021, a new study (Personn et al.) found that a fifth boundary had been exceeded: the introduction of novel entities into the biosphere, in particular synthetic chemicals.

In 2022, another scientific study (Wang-Erlandsson et al.) announced the crossing of a sixth boundary: water resources, and more specifically, "green water", a new variable taken into account for the first time in the approach to planetary boundaries (Figure 1).

In September 2023, a new publication from the Stockholm Resilience Centre presents a revised version of the nine planetary boundaries framework (Richardson et al.). New variables are defined for certain boundaries (functional biodiversity, blue water, aerosols in the atmosphere, new entities) and values are updated. For the first time, all nine planetary boundaries are quantified, with six of the nine considered exceeded. As this update took place after this publication was finalized, it could not be taken into account here. However, a quick comparison between the variables and values used in this document (those known at the beginning of 2023) and those in the Stockholm Resilience Centre's September publication is provided in the appendix.

Separate but interacting planetary boundaries

When designing the planetary boundaries framework, scientists chose to treat the various issues separately, in silo, while emphasizing the many interactions that exist between them. In this way, planetary boundaries form a complex system that needs to be approached in a global, cross-disciplinary manner. This means linking issues together, to better study, in one system, the causes of a problem, and the consequences it may have on another system. The example of CO2 is particularly significant. It is an indicator of climate change, but its increase in the atmosphere has a strong impact on ocean acidification or biodiversity erosion, for example.

A global approach first and foremost

The planetary boundaries framework focuses on the Earth system and considers the planet as a whole, based on nine biophysical processes that maintain it in a state of equilibrium. This framework nevertheless includes attempts at territorialization to take account of local issues and be closer to reality. When the model was revised in 2015, the authors supplemented the analysis grid with specific geographical variables for each territory. In the case of the "land-system change" limit, for example, they distinguished the situation of temperate forests from that of tropical or boreal forests.

The authors also point out that the framework of planetary boundaries is not designed to be declined to smaller levels, such as countries or local communities (Steffen et al., 2015). However, they recognize that it is at the local scale that political action most often occurs. They agree on the value of an integrated approach that combines the definition of boundaries at regional and global levels with development objectives, to enable the application of "planetary boundaries thinking" at the local level.

Figure 1: The nine planetary boundaries of the 2015 framework, updated to 2022

Sources: Steffen et al., 2015; Personn et al., 2021; Wang-Erlandsson et al., 2022

The framework for analyzing planetary boundaries thus constitutes a new frame of reference for governments, a methodological tool for structuring environmental governance. It offers a global vision of a complex system with interacting processes at different scales. It's an evolving conceptual framework, which researchers are constantly adjusting and defining in line with the data they collect.

Applying planetary boundaries to a sub-planetary scale and allocation principles

Several countries7 have applied the planetary boundaries framework to a sub-planetary scale. Given the economic, social and ecological disparities between countries, the work involved defining national shares to determine the safe operating space within countries. Planetary boundaries are then interpreted as global budgets allocated each year to countries on the basis of allocation principles.

Six allocation modes are possible, based on six principles: equality, needs, right to development, sovereignty, capacity, responsibility. The principles of "equality ", "needs " and "right to development" generally refer to individuals, while "sovereignty", "capacity" and "responsibility" are discussed at country level.

7 Sweden (Eriksson L., 2022), Switzerland (Dao et al., 2015, 2018), European Union (Hoff et al., 2014).

These allocation methods can be combined with a production or consumption approach to pressures. In the case of consumption, we speak of a "footprint" approach (Table 1). The footprint aims to account for the environmental pressures induced in a third country to satisfy the country's final demand for goods and services, via imports.

For example, like other footprints (carbon, water, forest, etc.), the "materials footprint" can be used to describe all the raw materials mobilized to satisfy a country's final consumption. The results more accurately reflect the real impact of resource use, both those extracted domestically and those mobilized abroad to produce and transport imported products.

Table 1: territorial approach versus "footprint" (or consumption)

* Environmental pressures linked to production, use and landfill.
Source : Hy Dao et al., 2018. National environmental boundaries and footprints based on the Planetary Boundaries framework: The case of Switzerland, Global Environmental Change, volume 52, pp. 49-57

Several publications analyze the impact of one allocation method versus another on the thresholds to be set at country level (Lucas et al., 2020). In part 2 of this publication, where a territorial approach at French level is possible, the French contribution is analyzed in relation to the planetary boundary allocated on an egalitarian basis (with reasoning by number of inhabitants) or on a sovereign basis (in proportion to our territory).

Numerous publications also propose "Absolute Environmental Sustainability Assessment" (AESA) methods, which aim to assess the sustainability of a given activity (service, product, company) or territory, based in particular on the use of the planetary boundaries framework. Depending on the EASA approach chosen, this requires the selection of sharing principles to distribute global environmental impacts between different human activities. This approach is detailed in Part 3 of this publication.

Safe and just Earth system boundaries

In June 2023, a multidisciplinary team of researchers working for the Earth Commission published a new study: "Safe and just Earth system boundaries" (ESB ) (Rockström et al., 2023).

Considering that the stability of the Earth system and human well-being are inseparable, the researchers propose a new model based on the definition of safety and justice thresholds, on a global and regional scale, for the following areas: climate, natural ecosystems, the functional integrity of the biosphere, surface water, groundwater, nitrogen, phosphorus and aerosols. These thresholds aim to preserve the Earth system's equilibrium by avoiding the crossing of tipping points, and to limit the exposure of populations to significant damage, while respecting justice between species, between generations, and, within the same generation, between countries, communities and individuals. This new analysis builds in part on previous work, notably in relation to the Planetary Boundaries ( PB) framework, taking up the notion of "safe" biophysical boundaries (Rockström et al., 2009).

In the analysis for 2023, the authors decide to abandon certain boundaries that are too difficult to quantify (ocean acidification, stratospheric ozone and novel entities). Conversely, they have expanded the "freshwater" boundary to include groundwater. The boundary on land-system change is not included as such, but its issues are reintegrated into the limit relating to the functional integrity of the biosphere. All in all, the eight boundaries selected by the researchers make it easier to set global and local targets to ensure that safe and fair habitability conditions are respected.

Further information