Planetary Boundaries and the Donut Economy - SUM: Sustainability Management Wiki

Authors: David Koch, Florian Pfeiffer, Yannick Borchers, Timon Bloemen, Amelie Harms
Last updated: December 21, 2022

1 Introduction

Climate change and sustainable behavior are two important topics in the 21st century and will continue to influence the thoughts and actions of people, companies, and politicians in the future. Hardly any resource in the world is infinite, which is why a conscious approach to the world and its resources is essential. In 2009, about 30 scientists published the article “A safe operating space for humanity”, in which nine planetary boundaries are described, which make it clear that some changes in the ecosystem of the earth are interrelated and can be accompanied by risky interactions and environmental changes due to climate change. ¹

Five out of nine planetary boundaries have already been crossed, which once again makes it clear that action and rethinking in society and politics is necessary in order not to be faced with major problems in the future. ²

*Figure 1: Planetary boundary and their current estimated status (own illustration, based on ³).*

What exactly planetary boundaries are, what problems they cause, and how to stop them, is explained in more detail in the following text.

2 Background

Humanity can no longer rule out the possibility that firmly anchored thresholds will be exceeded at a planetary level. This is suggested by findings on global environmental change. ⁴

Human civilizations and societies over the past 10,000 years developed within a favorable Holocene state of the Earth. However, crossing thresholds could threaten the planet’s self-regulating capacity and thus jeopardize its favorable Holocene state. Richardson et al. (2011) emphasize that the Holocene state was very stable, especially from an ecological perspective. This state formed the foundation for full-fledged humans over the last 200,000 years. Only in this way were conditions for human development given from the emergence of agriculture to today’s modern industrial societies. ⁵

The sustainable development agenda changes fundamentally when findings from resilience research are combined with evidence regarding anthropogenic pressures at the planetary level. As a result, the focus is now on human development within the safe operating space of a desirable range of stability for our planet. ⁶

To be able to ensure a safe habitat in the long term, the concept of Planetary Boundaries was published by Rockström et al. in 2009. Rockström’s concept was one of the first attempts to make an integrated assessment of all major environmental threats to the sustainability of humanity and the Earth’s ecosystems. Nine processes and systems that should lead to Earth system stability and resilience are identified by the concept. ⁷

The nine planetary boundaries include:

Climate Change
Biodiversity loss and species extinction
Stratospheric Ozone Depletion
Ocean Acidification
The Phosphorus and Nitrogen Cycle (Biogeochemical flows)
Land-system change (e.g. deforestation)
Freshwater use
Atmospheric Aerosol Loading
Chemical Pollution (e.g. organic pollutants, radioactive materials, and plastics). ⁸

The scientific understanding that the Earth is a single complex, integrated system, with boundaries functioning as an interdependent system, provides the frame of reference for planetary boundaries. The fact that processes and interactions on Earth can create stabilizing and destabilizing backlashes has profound implications for global sustainability. It reinforces Rockstrom’s concept, which addresses multiple interacting environmental processes simultaneously. ⁹

The nine planetary boundaries provide a framework for addressing the complexity of the Earth and the interconnectedness of Earth systems understandably and comprehensively. Crucially, the concept keeps each of the systems and processes within fixed, measurable boundaries (upper limits), thus minimizing irreversible and potentially catastrophic changes to the Earth system. ¹⁰

The risk of human activities placing the Earth’s system in an unstable state increases dramatically when boundaries are crossed. Human activities have currently transgressed four of the nine planetary boundaries. Of these four boundaries, biodiversity loss and climate change are considered core boundaries. Boundary crossings of a core boundary result in the Earth system being placed into a new state. A new state includes, for example, ecosystems changing radically, affecting ocean acidification, ambient temperatures, and eutrophication. ¹¹

Richardson et al. (2011) express that planetary boundaries define the planetary playing field for humanity. ¹²

3 The Planetary Boundaries

3.1 Ocean acidification

Definition

The planetary boundary of ocean acidification is understood to be the lowering of the pH of the oceans. Due to the global increase in CO₂ emissions, this is absorbed by the oceans from the atmosphere and appears in the water as carbonic acid. In this process, more than 25% of the annual CO₂ emission is absorbed by the waters. The more CO₂ enters the oceans, the more the pH of the water drops. The more this value falls, the more acidic the water is. After the onset of globalization and especially industrialization, the oceans acidified by almost 30%. This is not only the highest value in two million years but also the fastest increase in 26,000 years. ¹³

The PH value indicates whether a liquid is acidic or basic. If the value is above 7, the liquid is acidic, if it is below 7, it is basic and if it takes a value of exactly 7, the liquid is PH neutral. In comparison, the PH value of the oceans before industrialization was 8.2, currently, the value is 8.1, which corresponds to an increase in emissions in the water of 26%. The regions at the north and south poles are particularly affected, as cold water can absorb more CO2 than warm water. How much acid is produced also depends on water pressure, movement, chemical composition, and the amount of photosynthesis in the oceans. ¹⁴

Why this boundary?

This has a strong impact on the living organisms of the ocean. For many aquatic organisms, especially those with calcium skeletons, or calcareous shells, this is a major problem. Their shells consist largely of carbonate ions, which occur much less in acidic water. They get difficulties building their shells and bodies, which strongly threatens the existence of affected species. Similarly, living organisms possess an endogenous balance of acids and bases. If this balance is upset, the body consumes significantly more energy at this point, which is no longer available elsewhere, for example for growth or other important processes in the body. This is particularly dangerous for shellfish, as their skeletons can even dissolve in acidic water, which is life-threatening. ¹⁵

This also applies to the particularly important species of plant plankton. They can convert the CO₂ that enters the water into oxygen through exposure to sunlight. They thus play an important role in supplying the ocean with oxygen and contribute to the survival of other living organisms. It is also an important source of food for the much larger animal plankton. If the CO₂ content in the water increases to such an extent that the plant plankton dies out, this will lay the foundation for an even greater increase in carbonic acid in the water, as this can no longer be broken down by the plankton and the earth’s atmosphere will absorb even greater amounts of CO₂. Likewise, existing food chains fall away, change, or force organisms to change, which threatens further species in their existence. ¹⁶

Coral reefs, which not only represent an important habitat but also offer protection to many weaker species, are also changing. Across borders, the progressive lowering of PH levels has a strong impact on marine biodiversity. Only a small number of fish and plant species will benefit from the more acidic environment. ¹⁷

The acidification of the oceans also plays a major role in the advancement of climate change. To counteract this, CO2 emissions must be reduced. According to scientists of the Helmholtz Climate Initiative, 10% of the affected emissions cannot be saved. However, it is possible to compensate for these emissions, for example through improved filter technologies, or the reforestation of forests and the creation of moors and grass meadows.

Current status

Now, the planetary limit for ocean acidification has not been exceeded. The global aragonite saturation in surface water was determined as the unit of measurement here. The defined limit is 2.75 units. Currently, the value is around 3 units and still in the green zone. In the future, it is assumed, that the pH value could drop by an additional 0.3 to 0.4 by the year 2100. This would correspond to acidification of 100 to 150%. ¹⁸

3.2 Freshwater consumption

Definition

Another planetary boundary describes the load limit of freshwater consumption. The availability of freshwater resources determines the survival of plants, animals, and humans.

Freshwater is divided into “blue” and “green” water. The “blue” water describes direct deposits, such as the water in lakes, rivers, groundwater stored in the soil, and freshwater frozen at the polar ice caps and in glaciers. The “green” water includes the freshwater reservoirs in plants, soil, and rain.

Why this boundary?

Especially the reservoirs of “green” water are becoming increasingly scarce. The defined planetary limit has already been exceeded in 2022. The Amazon plays an important role here. As the largest rainforest on earth, it stores a large amount of CO2. The ongoing deforestation of the rainforest is not only harming the creatures that live there, but also the global climate. If the Amazon is cut down to the point of complete destruction, the resulting savannah area will create a stronger greenhouse effect, since the CO2 stored in the soil and the plants will be released again. Ensuring an adequate supply of fresh water is thus also important for mitigating the advancing climate change.

Humans have a direct influence on this. The increasing building development, especially in cities, and the associated sealing of green areas, ensures that rainwater evaporates too quickly. This water cannot be stored and causes cities to heat up more in summer.

The “blue” water is currently still in a safe area. However, ecological changes are also being felt here, so that rivers and lakes are often overloaded with pollutants. The special protection of large water resources is additionally of great importance for the regulation of the climate. The evaporation of water lowers temperatures and influences the weather. ¹⁹

Current status

The planetary boundary has been defined so that there is enough “green” water to ensure soil moisture and absorb precipitation, and enough “blue” water to ensure the survival of the various ecosystems. If the freshwater reservoirs were to become dramatically scarce, this would also have serious consequences for human life. This would not only affect everyday life and important medical areas, but also the economy. Poor water quality and scarce resources have severe consequences on human health, and nutrition, and inhibit the production of both consumer goods and agricultural products. ²⁰

This can only be counteracted by special protection of forests and soils. In addition, people must be made aware of how to use water, a finite resource, more sparingly. For example, polluted water can be used several times, and when building residential areas or cities, care must be taken to create water reservoirs that regulate and slowly release it.

Likewise, a change in thinking must be brought about in the area of agriculture. This must act more sustainably and orient its cultivation according to the available water reserves. Additional savings are possible in the production of all consumer goods. One example is the fast-fashion industry, which can be counteracted by promoting second-hand platforms and thus shifting the focus from quantity to quality. ²¹

Freshwater consumption is measured in the global consumption of surface and groundwater. The planetary limit is 4,000 km3 per year. With a current consumption of 2,600 km3, reaching the defined limit in the near future is not likely and is therefore in the green zone. ²²

3.3 Biochemical flows

Definition

This scientific formulation describes the natural cycles of nitrogen and phosphorus. The problem is that the phosphorus cycle is still in balance, but the amount of nitrogen on earth is above the capacity limit. ²³

Why this boundary?

Nitrogen is essential on earth and is fundamentally important for, for example, the hereditary substance DNA, and plants also need nitrogen to grow. In larger quantities, however, nitrogen is dangerous for humans and is one of the greatest threats to the environment. Nitrogen released by humans, such as through wasteful consumption, agriculture, or combustion engines, pollutes lakes and rivers, alters soils, destroys biodiversity, harms health, and fuels climate change. ²⁴

Agriculture in particular (over 60% of nitrogen is produced there) exerts a considerable influence. Fertilizing with liquid manure and synthetic fertilizers releases nitrogen into the environment. As a result, plants cannot take up all the nitrogen. In particular, this problem with nitrogen is driven where many farm animals are kept in a confined space because too much manure is produced there as well, which cannot be further processed. Biogas plants are also a problem. Harmful fermentation residues are produced during the generation of electricity and heat.

To protect human health, a 1-hour limit of 200 µg/m3 has been set throughout Europe, which may not be exceeded 18 times per calendar year. The annual limit value is 40 µg/m3. For the protection of vegetation, an annual average limit value of 30 µg/m3 NO_x was set. ²⁵

Current status

Currently, excess nitrogen is causing immense harm to the environment in the form of nascent nitrous oxide, a nitrogen compound in the atmosphere that is not only harmful to the environment, but also to health. ²⁶

Biodiversity, many plants, the environment, and also the oceans suffer from excess nitrogen. Because agriculture is considered to be the main polluter, it is important to restructure and reorganize it. Politicians in particular must take action to ensure a stable income for farmers and to pass laws that regulate animal husbandry and the environmentally sound use of fertilizers. ²⁷

3.4 Atmospheric aerosol loading

Definition

Human-caused emissions of aerosols, small particles in the atmosphere, such as soot from burning, change the climate and have a negative impact on human health. ²⁸

Why this boundary?

The problem with aerosols is that they affect the Earth’s radiation balance. Depending on their properties and conditions, aerosols and particulates can absorb solar radiation, warming the air. In addition, aerosols directly affect the Earth’s water cycle. When water vapor is formed, cloud droplets can form around the aerosol particles, which have an immense influence on precipitation distribution and cloud properties, and thus directly affect the weather and climate. ²⁹

Mainly influence takes industry, traffic, agriculture or also the heating of dwellings. As already mentioned, combustion has the greatest influence on air pollution. As a result, urban areas are often affected, so there is smog, which means that especially many particles buzz through the air. ³⁰

The aerosol content in the air is measured with the measure “Aerosol Optical Thickness” (AOT), where the turbidity of the air is determined. The more turbid the air, the higher the aerosol load and therefore a high AOT value. ³¹

Current status

The exposure limit due to aerosols in the air is currently not fully quantified. However, it can be stated that regionally the air is highly polluted by aerosols. Therefore, it is even more important to reduce the harmful emissions of aerosols. ³²

3.5 Stratospheric ozone depletion

Definition

Another significant planetary boundary is stratospheric ozone depletion. This is because the ozone layer acts like a protective shield for the earth and should therefore not become too thin or be depleted too quickly without being able to renew itself. The ozone layer shields harmful ultraviolet rays from the sun, protecting all living organisms on Earth. Otherwise, ultraviolet radiation would damage the skin, the eyes, and the genetic information and have a significant impact on life on earth. ³³ For this reason, the planetary boundary of stratospheric ozone depletion is an important dimension to consider for ultraviolet radiation hazards.

Why this boundary?

Naturally, the ozone layer forms in the stratosphere through a reaction between oxygen and high-energy UV-C radiation. At the same time, the lower-energy UV-B radiation depletes ozone. In this way, the ozone layer remains in a natural balance and can serve as an efficient protective shield for the earth. ³⁴ This balance can be disturbed if additional human-emitted substances are released into the atmosphere and stratosphere. The compounds that enormously enhance ozone depletion are for example hydrochlorofluorocarbons (HCFCs), chlorofluorocarbons (CFC), hydrobromofluorocarbons (HBFCs), and halons. These compounds were commonly used in refrigerators, spray cans, or fire extinguishers in the mid-20th century and ended up in the environment in this way. They act as a catalyst for the depletion of the ozone layer, disturb the balance of the ozone layer, and cannot be depleted in the stratosphere itself. This destructive effect of some compounds became known to scientists in the 1970s and in the 1980s they discovered a huge hole in the ozone layer over Antarctica. As a result, politicians responded with an international agreement to protect the ozone layer. Among other things, it banned the use of hazardous substances such as CFCs or similar. The Montreal Protocol was agreed upon in 1987 and officially became effective in 1989. ³⁵

Current status

The planetary boundary for stratospheric ozone concentration is measured in Dobson units. This must be at least 275 DU for the thickness of the ozone layer to be within planetary boundaries. Since policies were established, the ozone layer has recovered and is largely within planetary boundaries. The current measured values are between 220 DU and 450 DU. The undercutting of the limit value of 275 DU is due to the periodically occurring ozone holes. ³⁶ In the process, however, the ozone layer continues to recover.

“The most recent Scientific Assessment of Ozone Depletion from WMO and the UN Environment Programme shows that the ozone layer in parts of the stratosphere has recovered at a rate of 1-3% per decade since 2000. At projected rates, Arctic and Northern Hemisphere mid-latitude ozone is expected to heal completely before the middle of the century (~2035) followed by the Southern Hemisphere mid-latitude around mid-century, and Antarctic region by 2060.” ³⁷

World Meteorological Organization

The example of the planetary boundary of stratospheric ozone depletion, therefore, shows well that human actions and political decisions can have an influence. Without the Montreal Protocol bans, ozone depletion might have continued at a rapid pace. But by the decided regulations of the protocol, the dangers of the fast depletion of the ozone layer could be avoided. This could also be a good model for other planetary boundaries that cannot currently be observed.

3.6 Climate change

Definition

Weather phenomena and environmental disasters such as heat waves, floods, or droughts make it clear that climate change is accelerating and global warming is becoming increasingly apparent. With every tenth of a degree Celsius rise in temperature, the risk of abrupt and irreversible changes in the Earth’s system increases. ³⁸ Along with the loss of biodiversity and the spread of novel entities, climate change is consequently one of the most important factors in the concept of planetary boundaries. ³⁹

In this context, climate change is defined as „[…] change of climate that is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and that is in addition to natural climate variability observed over comparable periods […]”. ⁴⁰

Why this boundary?

The direct and indirect impacts of climate change are manifold. According to Lewandowski, et al. (2018), they include the warming and acidification of the oceans, the melting of the Greenland and Arctic ice sheets, or the reduction of precipitation and increased drought, which increasingly affects agriculture. Furthermore, he refers to the negative impacts on human health due to the deterioration of air and water quality as well as increasingly frequent extreme and unpredictable weather events. ⁴¹

The impacts highlight the high importance of a planetary boundary for climate change. A boundary that takes into account the influences on important climate dynamic patterns, perturbations in regional climate systems, and other impacts. ⁴²

To be able to narrow down the planetary boundary climate change, a bipartite approach is followed. The first variable of the two-part approach is the global radiative forcing. Global radiative forcing measures the total anthropogenic emissions that affect the Earth’s energy balance. The variable is measured in watts per square meter (Wm-2). The second variable of the two-part approach is the atmospheric CO₂ concentration. The variable is measured in Parts Per Million (ppm). The need to measure the climate change boundary using a two-part approach is mainly due to the large amount of emissions – caused by humans – and the long residence time of the molecules in the atmosphere. ⁴³

Current status

According to Rockström, the defined limit for CO₂ in the atmosphere is 350 ppm with an uncertainty zone of 350 to 450 ppm. According to the current status, this limit is not met, as it has a concentration of 405 ppm. ⁴⁴ From year to year, the value increases by about 3 ppm. ⁴⁵

According to Rockström, the limit for global radiative forcing was set at +1.0 Wm-2 with an uncertainty zone of +1.1 to 1.5 Wm-2. This limit is also not currently being met, as the global radiative forcing has a value of 3.06 Wm-2. That means, according to the current status, both limits of the planetary boundary are already clearly exceeded. ⁴⁶

To return to a safe zone, or to be able to comply with the planetary boundaries, it is essential above all that the use of fossil fuels is significantly reduced or avoided altogether. This means that a net-zero reduction in carbon dioxide emissions can only be guaranteed if there is a shift in the future to other energy sources such as hydropower, wind power, geothermal energy, or photovoltaics. Wherever prevention of emissions is impossible, negative emissions must be removed from the atmosphere. A long-term safe operating space for human civilization results, provided that within planetary boundaries the goal is pursued to develop a carbon-neutral society as soon as possible. ⁴⁷

3.7 Land-system change

Definition

The planetary boundary Land System Change, as defined by the Stockholm Resilience Center, addresses the transformation of land carried out for human purposes. ⁴⁸^,⁴⁹ Even though the effects of transformation or land changes are originally local, in their totality they extend to the global scale. That is, this transformation has implications not only for itself but also for virtually all other planetary boundaries. Human activities that have quantitative, qualitative, functional as well as spatial dimensions are encompassed by the boundary. ⁵⁰

Why this boundary?

Until 2009, the conversion of forests and other ecosystems to agricultural land occurred at an average rate of 0.8% per year. It can be seen that non-compliance with the limit or further expansion of agricultural land on a global scale is bound to become a significant threat to biodiversity as well as undermine the regulatory capacities of the Earth system. ⁵¹

As an example, Rockström et al. (2009) refer to the Amazon. The conversion of rainforest to cropland or pasture systems there can reach a scale where future changes immediately lead to irreversible transformations. Food production may shift to marginal land with low yields and a high risk of degradation if more highly productive land is lost to degradation, biofuel production, or urbanization on a global scale. In such a scenario, even the smallest increase in additional food production leads to an exponential increase in cropland. ⁵²

Identifying a measurable indicator of land system change is particularly difficult at this planetary boundary. The continuous changes in land use are primarily responsible for this. Currently, the Global Forest Area is the preferred indicator for land use change. It was selected by the Stockholm Resilience Center in 2015, replacing the original choice of cropland. ⁵³ Cropland is defined as the proportion of the world’s land used for agriculture. Side effects occur as an increasing portion of ice-free land is used for food, feed, and energy crop production. As mentioned earlier, these side effects impact numerous other planetary boundaries, such as freshwater use the biogeochemical cycles, and the integrity of the biosphere. In the concept originally proposed by Rockström, the goal is to limit agricultural land to 15% of all ice-free land. At the time the concept was published in 2009, 12% of the land was already used for agriculture. ⁵⁴

Current status

Due to phenomena such as the evaporation effects in tropical rainforests or the influence on the back-radiation effect of boreal coniferous forests, the focus of the planetary boundary has been increasingly placed on the proportion of forest-covered land in recent years. Consequently, in its updated concept, the land system change boundary targets the proportion of existing land areas rather than solely the proportion of agricultural land. In this regard, the boundary has been set at 50% cover for temperate forests. In addition, a further limit specifies that the cover percentage for tropical and boreal forests is 85%. ⁵⁵. In addition to the two regional limits mentioned, it is also important not to neglect the global mean value of forest types. The limit of 75% of the pre-industrial global forest area was set for this purpose. ⁵⁶

According to the current status, the degree of coverage is about 62%. This means the planetary boundary Land-System Change is currently exceeded. ⁵⁷

3.8 Biodiversity

Definition

Another one of the three currently most severely strained planetary boundaries is biodiversity loss. To understand exactly what that means one first needs to understand what biodiversity is. Biodiversity is defined as the variety of life found in a place on Earth or broader the total variety of life on Earth and commonly measured with the count of species in said defined area. ⁵⁸ With that knowledge one is now able to conclude the definition of biodiversity loss, which is defined as a decrease in biodiversity within a species, an ecosystem, a given geographic area, or the Earth as a whole. ⁵⁹

Why this boundary?

As already clarified in the previous chapters the reasons for picking the specific boundaries are manifold, with the main goal of defining a safe operating space for humans. Species play different roles in ecosystems, meaning they influence ecosystems in many ways, like adaptability or resilience, so that the individual ecosystems are kept in balance. Without a variety of species, the ability the respond to change gets lowered or even lost completely, so ecosystem functionality and the accompanying prevention of ecosystems tipping into undesired states cannot be guaranteed. This all is important because of the interaction between the planetary boundaries, as functioning ecosystems are a prerequisite for defining the other planetary boundaries i.e., without functioning ecosystems the thresholds for climate change or ocean acidification would be lower. ⁶⁰

As with all the other planetary boundaries, there exists no single reason for how humans take influence. A few examples include industrial activity, land use, trophy hunting, or the introduction of invasive species through human error. ⁶¹ Even though all this, except hunting, doesn’t directly affect biodiversity, the results of these actions do. The biggest driver for biodiversity loss mfn]Rockström, J., Steffen, W., Noone, K., et al., Planetary Boundaries: Exploring the Safe Operating Space for Humanity. Ecology and Society 14(2), (2009).[/mfn]is land use and its effects such as loss of habitat. ⁶²

To summarize all the influences into a single key figure suitable for estimating a value of the planetary boundary “loss in biodiversity” scientists describe a two-component approach. That approach doesn’t perfectly what the boundary tries to reflect, but it currently is the only way for humans to estimate biodiversity loss. ⁶³

The first component would be “functional diversity”, which aims to capture the role of the biosphere in Earth-system functioning as well as capture the loss of biodiversity components. It is measured with the biodiversity intactness index (BII). ⁶⁴ The BII is an indicator that summarizes the change in ecological communities in response to human pressures. It estimates the original number and abundance of species that remain in any given area despite the pressure put on them by humans, in percent. ⁶⁵ The limit for the BII is estimated to be at around 90%, but with an error margin of 60%, which reflects the huge uncertainties given humanity’s limited knowledge of the BII–Earth-system functioning relationship. ⁶⁶

The second component is “genetic diversity”, which provides the long-term capacity of the biosphere to persist under and adapt to abrupt and gradual abiotic change. The only current way of measuring “genetic diversity” is by the extinction rate, which is defined by extinctions per million species-years (E/MSY). For genetic diversity the current limit is estimated to be 10 E/MSY, but with an aspirational goal of 1 E/MSY, which is the extinction rate of well-studied organisms over the past few million years. ⁶⁷

Current status

Currently, biodiversity loss is one of the most strained planetary boundaries. As of now, the extinction rate is estimated to be 100-1000 E/MSY. For the BII it is impossible to make profound assumptions because it has only been estimated for small-scale ecosystems that cannot be applied to planet Earth as a whole. ⁶⁸ In the 13 years since the first publication and estimation of the biodiversity loss, there hasn’t been any notable change, so one may speculate, that in the future it will continue at a similar rate. ⁶⁹

3.9 Novel entities

Definition

The last of the planetary boundaries is “chemical pollution” or broader “introduction of novel entities”. There are two reasons why it qualifies as a planetary boundary:

Firstly, there are impacts on human and/or ecosystem health, which ultimately limits adequate ecosystem functioning on a global level
Secondly, it has an impact on other planetary boundaries, i.e., pollution may reduce the abundance of species and therefore impacts the biodiversity boundary ⁷⁰

There exist three conditions that need to be met for a chemical to qualify as a pollutant that may be globally problematic:

It needs to be disruptive on a vital Earth-system process
It needs to be undiscovered until it’s problematic on a global scale
The effect it has isn’t easily reversible ⁷¹

Why this boundary?

Also, how these chemical pollutants find their way into the organism varies. One way is direct exposure to the pollutants. The other, lesser thought about, way bioaccumulation and biomagnification up food chains. ⁷² Bioaccumulation covers the intake of a chemical pollutant by all possible means, while biomagnification occurs when through predatory behavior up the food chain the chemical pollutants accumulate to such levels, that the concentration to be expected where equilibrium prevails between an organism and its environment is exceeded. ⁷³

The planetary boundary takes a variety of different pollutants, depending on the definition, even over 100,000, into account. ⁷⁴ The different pollutants include radioactive compounds, heavy metals, plastic polymers, nanomaterials, and a wide range of organic compounds of human origin. ⁷⁵ There are currently two approaches to identifying possible pollutants. The first focuses on persistent pollutants that distribute at a global scale, while the second one aims to detect unacceptable, long-term, and large-scale effects on living organisms through the pollutants. ⁷⁶ This in turn leads to the different proposed mechanisms of measuring these effects.

The first approach is measured by trying to quantify the effects of the pollutants on their own. This brings along the problem, that there are too many pollutants and the are effects too overlapping to precisely put a threshold on every pollutant. Only some pollutants could be clearly identified this way. Some examples include measuring the concentration of a certain pollutant in the eggshells of birds, that caused eggshell thinning and reproductive failure or observing higher concentrations of specific pollutants in top predators and humans. ⁷⁷

The second approach focuses more on quantifying the effects of the chemical pollutants instead of quantifying the pollutants themselves. Using that approach to set a planetary boundary one would need to include subtle effects that are visible on a global scale and affect the most delicate life stages in the most delicate creatures and/or people, that become visible i.e., in reduced or failed reproduction, neurobehavioral deficits, or compromised immune systems. ⁷⁸

Current status

Even though two approaches try to measure chemical pollution, there still does not exist a specific value that sets the planetary boundary. The process of setting an adequate value for the planetary boundary would ultimately necessitate the establishment of several sub-boundaries based on the impacts of numerous different chemicals as well as pinpointing particular effects on vulnerable organisms. ⁷⁹ The only thing that becomes clear in the process of setting the planetary boundary is, that the values emitted now by humanity are too high and already have a severe impact on ecosystems. ⁸⁰

In the future, more precautions and preventative measures can and need to be taken. Suggested measures include a focus on green chemistry, identifying synergies with risk-reducing interventions in other fields, learning from past errors, and investing in science to better understand and monitor crucial Earth-system processes. All this with the end goal to detect the harmful effects of chemical pollutants at the earliest possible time. ⁸¹

3.10 Hierarchy of boundaries

Now that all planetary boundaries have been discussed it becomes clear that some boundaries may have a larger influence on the Earth than others. To be exact there are two boundaries, climate change and loss of biodiversity, that impact the earth on a larger scale, than the other boundaries. That doesn’t mean that the other boundaries don’t affect human well-being but transgressing them ever so severely doesn’t lead to a new state of the Earth system. ⁸²

The climate change boundary is of higher importance as it directly impacts the climate system. The climate system is defined by the amount, distribution, and net balance of energy at the surface of the Earth, which is important as the total amount of energy sets the overall conditions for life. The circulation of the two big fluids, the ocean, and the atmosphere, is significantly influenced by the distribution of energy. The distribution of the biota, the structure and operation of ecosystems, and the management of biogeochemical processes are in return all strongly affected by the circulation. ⁸³

The loss of biodiversity interacts directly with the biosphere integrity of the Earth. Biosphere in this context spans the entirety of all terrestrial, freshwater, and marine ecosystems on Earth and its associated biota. These ecosystems and biota are essential for identifying how the Earth’s system is functioning and how it reacts to sudden and gradual changes. Terrestrial and marine ecosystems for example are resilient due to the biosphere’s diversity. Additionally, the biosphere affects the Earth system’s ability to maintain a certain condition even when these other planetary boundaries change. As a result, a loss in biodiversity most likely lowers the values for other boundaries. ⁸⁴

3.11 Interdependencies

There is undeniable scientific evidence that the Earth is a single, complex, interconnected system. As a result, the planetary boundaries function as an interdependent set. ⁸⁵

Shifts in one planetary boundary can therefore lower or rise the safe levels of another planetary boundary. ⁸⁶ This is best shown with an example.

The hydrological cycles as well as regional and global energy balances depend heavily on tropical forests. A sizeable portion of the water in the atmosphere is recycled by the vegetation in the Amazon basin. That recycling produces aerosol particles which in turn may create cloud droplets, which are the building blocks of clouds. ⁸⁷ The strength of the convective circulation and the likelihood that the clouds will generate rain are both influenced by changes in particle concentration. ⁸⁸ That knowledge concludes, that with less forest, aka a loss in biodiversity through i.e., deforestation, reduces the aerosol loading, which then could create a feedback loop as with less rain the vegetation in the Amazon could slowly die, aka a further loss in biodiversity. ⁸⁹

3.12 Criticism

The following is a critical reflection on planetary boundary setting.

According to experts, the greatest weakness of the planetary boundaries lies in unfulfilled scientific objectivity. Human survivability is defined as the success factor, whereas the habitability of a planet is not an objective measure. Instead, the focus is on a political decision, namely which risks and changes to the climate are acceptable and which must be avoided.

Likewise, the determination of the limit values and the defined ecological targets is incumbent on a very small group of scientists, so that arbitrariness and the inclusion of one’s own, personal interests cannot be avoided.

In addition, it can be noted that planetary boundaries are globally defined targets. This complicates the evaluation of the connection between set targets and possibly occurring effects. The evaluation would be easier if it were a matter of local correlations.
The attempt to set practical and political consequences of the planetary boundaries is considered to have failed. Regionally defined necessary actions to stay within the defined areas do not exist. Especially the worldwide heterogeneity not only in terms of natural, and ecological conditions but also the composition of the local population are strong influencing factors on the adaptability to environmental change.

Last, the system of planetary boundaries is based on reference values from the time of the Holocene. Since the change in ecological conditions is already very advanced, the reference values used are only marginally relevant. Instead, outdated policy processes and approaches need to be questioned and adapted to novel realities. Planetary boundaries are too static with respect to flexible and individual people. ⁹⁰

In summary, although the concept of planetary boundaries has some weaknesses and should be adjusted, if necessary, it is a suitable objective of what ecological conditions we want to protect and ensure.

4 Donut Economy

The planetary boundaries model by Rockstrom et al considers the ecological dimensions for long-term life on Earth. His model considers that infinite growth is not possible with limited resources on earth and that there are planetary boundaries that mean an end to this growth. However, the model neglects aspects of social justice. This non-consideration of human factors was criticized by economist Kate Raworth in an Oxfam report in 2012, which is why she expanded the planetary boundaries model to include humanity. These social foundations were inspired by the Social Development Goals of the United Nations. ⁹¹

According to Raworth, an ecological threshold of the respective planetary boundaries is not allowed to be exceeded. At the same time, a minimum of social and human standards must be guaranteed to ensure a dignified life for all people on earth. To represent this social dimension, Raworth uses the model of a donut. The donut is limited on the outside by the ecological dimension and on the inside by the social dimension. Between these two boundaries lies a donut-shaped area in which humanity can thrive in the long term. Only by respecting the two boundaries, Raworth says, would it be possible to ensure that human needs are met, and planetary boundaries are observed at the same time. Moreover, Raworth says that GDP growth is no longer the central goal of economies in the 21st century. This is because the endless pursuit of economic growth is not possible in the long term. Instead, the central goal of economies should be to operate within the donut to satisfy human and environmental needs equally. ⁹²

In the 2012 Oxfam paper, Raworth defines the social standards that should be met by economies in the donut model for humanity to thrive in the long term. These social standards and the corresponding percentages below the social thresholds are shown in the following.

For Raworth, the first social foundation is ensuring a society’s food supply. The indicator for this is the percentage of the population that is undernourished. In 2006-2008, this percentage was 13%. In this context, she argues that world hunger could be eradicated with only 1% of the current global food supply. Considering the food that is thrown away every day, a more efficient redistribution of food could solve this problem without threatening the planetary boundaries. ⁹³

Another social foundation is the daily income of the population of an economy. Raworth sets a limit of $1.25 per day. In 2005, 21% of humanity lived below this income threshold. This means existential threats to people when they can no longer adequately meet their vital needs due to a low income. Ending that income poverty would require just 0.2% of the global income. A redistribution of income or a fairer payment for the poorest population could therefore counteract this deplorable situation. ⁹⁴

In addition, Raworth lists water and sanitation as important social foundations. She states in the Oxfam Discussion paper that in 2008, 13% of the world’s population did not have access to an improved source of drinking water. Furthermore, in the same year, 39% of the world’s population did not have access to improved sanitation. Therefore, people are at existential risk from both water scarcity, contaminated drinking water, and poor hygienic sanitation. ⁹⁵

Raworth considers basic health care and access to essential medicines to be another social foundation. In 2004, 30% of the world’s population had no access to adequate medical care and medicines. According to her, this deficit must also be eliminated in the future so that humanity can live at a secure social level. ⁹⁶

Another central social foundation is education. According to Raworth, 10% of children were not sent to primary school in 2009. In the same year, 11% of people aged 15-24 were illiterate. Since education is the basis for welfare and social security, this is a central task of the population in the Donut Economy Model to achieve a social minimum. ⁹⁷

The next important social foundation mentioned in Raworth’s Oxfam discussion paper is the energy supply. In 2009, 19% of the world’s population had no access to electricity. Even 39% of the world’s population did not have access to clean and hygienic cooking facilities in the same year. This, too, must be remedied to achieve a minimum social standard for all people in the world, she said. To achieve this, global carbon emissions would only increase by 1%, according to Raworth. This is because industrialized nations and high-income countries consume above-average amounts of electricity. Specifically, she cites that wealthy nations, which together account for 16% of the world’s population, account for 57% of global electricity consumption. ⁹⁸

Moreover, gender equality is another important social foundation for Raworth in the Donut Economy model. The employment gap between men and women in paid work was 34% in 2009. Moreover, the representation gap in national parliaments was 77% in 2011. Thus, according to Raworth, it is particularly obvious that women are still extremely disadvantaged in large parts of the world and that there is still a long way to go before equality is achieved. ⁹⁹

According to Raworth, social justice is also an indicator of a satisfactory level of social foundation. As a benchmark, she cites the Gini coefficient, which measures the distribution of income in a country. Here she mentions that between 1995-2009, 33% of the world’s population lived on less than the median income in countries with a Gini coefficient exceeding 0.35. ¹⁰⁰

Last, Raworth lists three other categories that can serve as social foundations. However, according to the Oxfam discussion paper, there are no reference values that can represent the degree of fulfillment of the respective category. Specifically, these are the social foundation’s voice, jobs, and resilience. In the Voice foundation, indicators such as the political participation of the population or public freedom of expression can be used. In the Jobs category, this could be the labor force not employed in decent work, for example. In social foundation resilience, the proportion of the population confronted with various dimensions of poverty could be used as an indicator. ¹⁰¹

Achieving the global goal of living within the doughnut requires worldwide cooperation and the pursuit of a common goal. Individual interests of different countries should be subordinated to the common welfare of the world population, according to Raworth. Through a fairer distribution of income and wealth, it would be possible that the social foundations of all people in the world could be respected. At the same time, planetary boundaries could be considered. However, according to Raworth, this requires a change in thinking. It is doubtful whether GDP is sufficient as a measure of economic prosperity and whether economic growth should be the only goal of the world’s population. ¹⁰²

5 Conclusion

Overall, it can be stated that the planetary boundaries model includes the most important ecological dimensions that ensure long-term life on planet Earth. These dimensions are to be analyzed separately from each other since they address different problems of life on earth. Some dimensions exceed the load limit and dimensions that are still within an acceptable range. The dimension of climate change is above the limits because the CO2 concentration in the atmosphere is too high. Also, in the dimension of biogeochemical cycles, phosphorus, and nitrogen levels exceed the set planetary boundaries. In addition, the limit of land use is also exceeded, as too much forest land on earth is lost. In further development, the dimension of the biosphere is also above the limit, as the extinction rate of species is well above the planetary boundary. Other planetary boundaries, such as atmospheric aerosol loading or stratospheric ozone depletion, are at least temporarily or regionally above prescribed planetary boundaries. However, a positive trend can be observed here – for example in the thickness of the stratospheric ozone layer – as this is increasing again, and through human action and prohibitions, compliance with the planetary boundaries can be achieved. Only planetary boundaries for ocean acidification and freshwater consumption are met. Overall, it can be stated in this context that the planetary boundaries are only respected and observed for two out of nine boundaries. Humanity still faces great challenges to find ways to comply with the other planetary boundaries as well. Going further, the donut economy model also incorporates the social component. For a peaceful and sustainable coexistence not only the boundaries of the environment must be respected. But also, a minimum of social standards should apply to all people in the world. Here, too, humanity faces major challenges to ensure social justice and the basic needs of all people.

The Planetary Boundaries and Donut Economy model thus visualize the key ecological boundaries or minimum social standards to ensure that coexistence on Earth is sustainable and socially fair. In this way, framework conditions for political action and guidelines for human action can be derived.

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1 Introduction

2 Background

3 The Planetary Boundaries

3.1 Ocean acidification

3.2 Freshwater consumption

3.3 Biochemical flows

3.4 Atmospheric aerosol loading

3.5 Stratospheric ozone depletion

3.6 Climate change

3.7 Land-system change

3.8 Biodiversity

3.9 Novel entities

3.10 Hierarchy of boundaries

3.11 Interdependencies

3.12 Criticism

4 Donut Economy

5 Conclusion

References

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