How has the government exceeded its limits


Dr. Inge Paulini

The natural scientist Dr. Inge Paulini is President of the Federal Office for Radiation Protection (BfS). Inge Paulini has also been Secretary General of the WBGU (Scientific Advisory Board of the Federal Government on Global Change) since 2009. Inge Paulini initially carried out research in the field of nutritional science and toxicology. She then worked at the Federal Environment Agency on, among other things, the sustainable use of resources and sustainability strategies.

Dr. Benno Pilardeaux

Benno Pilardeaux is in charge of public relations at the WBGU. He has a PhD on Innovation and Development in Northern Pakistan. Among other things, he has accompanied the negotiations of the Desertification Convention (UNCCD), the World Food Summit, the World Settlement Conference Habitat II and the World Summit on Sustainable Development.

Dr. Carsten Loose

Carsten Loose is Deputy Secretary General of the WBGU and holds a doctorate in biology. Among other things, he accompanies the negotiations of the Biodiversity Convention (CBD) for the WBGU.

Dr. Astrid Schulz

Astrid Schulz is responsible for the topics of climate and energy in the WBGU office. She has a doctorate in physics and has researched and published in the field of climate and atmospheric physics. For the WBGU she has been following the negotiations of the UN Framework Convention on Climate Change and the IPCC for many years.

"Planetary Boundaries": A Framework for Global Sustainability Policy?

The concepts of the Planetary Boundaries and "Planetary Guardrails" are intended to make our earth safe and to navigate through the dangers and risks in the Anthropocene. But what are planetary limits and which have already been exceeded? How can strategies for a global sustainability policy look like, how can they be implemented internationally and become the benchmark for global environmental protection policy?

Will corals, sea urchins, sponges, snails, pipefish and other fish soon only be admired in museums? The causes of coral death include increased water temperatures due to global warming. (& copy dpa)

With Agenda 21, the outcome document of the United Nations Conference on Environment and Development (Earth Summit in Rio, UNCED), a catalog of development and environmental goals was agreed in 1992 that aimed to prepare the world for the challenges of the next century:

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Agenda 21 (1992)

Humanity is at a crucial point in its history. [...] An integration of environmental and development concerns and the increased focus on these will ... result in a meeting of basic needs, higher living standards for all, better protected and managed ecosystems and a more secure future with greater prosperity.

Source: Agenda 21, preamble, p. 1

Agenda 21 is the development and environmental action program for the 21st century that was adopted in Rio in 1992 and which at that time became a key program for international sustainability policy.

Creation of the concept of planetary guard rails or limits

In the spirit of this quote, the Earth Summit in Rio in 1992 also marked the birth of the German Advisory Council on Global Change (WBGU). Since 1995, the Advisory Board has dealt scientifically in numerous reports with the question of which conditions of the earth system and which environmental changes should be avoided in the sense of Agenda 21, while at the same time the greatest possible freedom is preserved.

As part of its scientific policy advice on global change, the WBGU describes planetary guard rails as "quantitatively definable damage limits, the exceeding of which would have intolerable consequences today or in the future, so that great benefits in other areas could not compensate for this damage" [1]. Within an area of ​​action limited by guard rails, there are many options for sustainable development paths and openness to social search processes. Beyond the guard rails, global change is becoming an intolerable risk for human civilization. Sustainable development paths can therefore only run within the area delimited by guard rails.

The complexity of the environmental system and the often fuzzy data situation mean that guard rails cannot be precisely defined. They are more to be understood as "border areas" with blurred edges [2]. The determination of such boundary areas can change over time, depending on the development of normative values ​​of a society and the existing knowledge about our environment.

An analogy to illustrate this: Guard rails behave like speed limits. A normative stipulation is made collectively that a maximum of 50 or 30 km per hour should be driven within localities. If you drive faster, the likelihood of accidents increases, but compliance with the speed limit cannot rule out accidents either. Accordingly, compliance with all guard rails is necessary for sustainable development, but in no way means that socio-economic grievances or ecological damage can be averted everywhere. One reason: global guard rails can by no means take into account all regional and sectoral effects of global change [3]. Guard rails are therefore not goals, values ​​or conditions to be striven for, but are minimum requirements that have to be met in terms of sustainable development.

In essence, it remains a social decision as to which interventions in the natural environment and the associated effects on the foundations of human life are no longer considered to be tolerable. Science makes proposals and societies must decide which guard rails are deemed necessary [4].

Using the example of climate change, the WBGU answered the question of which "tolerance windows" can be set for the permissible climate developments: "Ecological limits result from the maximum temperature and the temperature gradients to which the biosphere can still adapt. [5]" How a "dangerous man-made disturbance of the climate system" (Art. 2, Framework Convention on Climate Change (UNFCCC) 1992) [6]) can be prevented, the WBGU concluded:

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2 ° C - guard rail

A warming of more than 2 ° C (based on the pre-industrial value) or a warming rate of more than 0.2 ° C per decade therefore characterize climate changes that are in no case considered to be tolerable.

Source: WBGU, 1997: 15

This was followed by several reports in which the WBGU derived guard rails, most recently compiled in a policy paper on the Development Agenda 2030 [7]. These guard rails were supplemented by proposals for universal minimum standards for access to essential goods of general interest such as B. Water, Food and Modern Energy [8].

In 2014, the WBGU developed the neutrality concept for securing earth system services [9]: Development paths should be diverted in such a way that planetary guard rails are avoided. Drivers of accumulating regional or global environmental changes and irreversible use of necessary resources must be reduced to zero (zero targets). In order to stop e.g. climate change or the loss of biological diversity, it is necessary to bring the drivers to zero globally (e.g. CO2 emissions or the man-made extinction rate). This also requires that the drivers in each individual country be reduced to zero. If the drivers are not brought to zero globally, global environmental change will increase and the guard rail will be exceeded. This applies, for example, to the emissions of CO2 from fossil fuels, to the drivers of biodiversity loss (e.g. clearing of primeval forests) or to long-lived substances such as mercury or plastic.

Selection of the planetary guard rails and zero targets proposed by the WBGU



  1. Climate change: Limit warming of the climate system to 2 ° C. Stop global CO2 emissions from fossil sources by around 2070.

  2. Sea level rise: The absolute rise in sea level should not be more than 1 m permanently (even over many centuries), and the rate of rise should always remain below 5 cm per decade (WBGU, 2006).

  3. Ocean acidification: The pH value of the uppermost sea layer should not drop by more than 0.2 units compared to pre-industrial values. Stop global CO2 emissions from fossil sources by around 2070.

  4. Biodiversity and ecosystem services: Stop the loss of biodiversity and ecosystem services. To do this, bring direct anthropogenic drivers (e.g. conversion of natural ecosystems) to a standstill by 2050 at the latest.

  5. Land and soil degradation: Stop anthropogenic land and soil degradation. To do this, stop net land degradation worldwide and in all countries by 2030.

  6. Endangerment from long-lived anthropogenic pollutants: Stop the substitutable use of mercury and anthropogenic mercury emissions by 2050. Stop releasing plastic waste into the environment globally by 2050. Stop production of nuclear fuel for nuclear weapons and nuclear reactors by 2070.

  7. Loss of phosphorus: Phosphorus is an indispensable resource for agriculture and food security. Stop the release of non-recoverable phosphorus by 2050 so that recycling can be achieved worldwide.

    Sources for selection: WBGU, 2014, 2006

Planetary Boundaries: A safe space for mankind to act

The concept of the planetary boundaries, which is very similar to the planetary guard rails, was published in 2009 under the leadership of Johan Rockström, the director of the Stockholm Resilience Center and by 29 authors such as internationally renowned scientists, including WBGU chairman Hans Joachim Schellnhuber [10]. The starting point is not to leave the relatively stable conditions of the Holocene, in which human civilizations developed. The authors start from the concept of the Anthropocene, in which human activities became essential drivers of environmental change and could cause very harmful to catastrophic developments in large parts of the world [11].

Fig 1: Planetary limits ( Graphic for download) (& copy bpb)

With the help of this concept, a safe operating space is identified, which is defined by ten planetary boundaries (see table below). These planetary boundaries (see inner green area in Fig. 1 for the Planetarx Boundaries above) outline the dynamic biophysical "space" in which mankind has so far been able to develop and live well and successfully [12]. According to the authors, they also define the future "planetary playing field" of human society, which observes the "rules of the game" of the planet. Three of these limits (rate of biodiversity loss, climate change and human intervention in the nitrogen cycle) are considered to have already been exceeded (marked in red in the table and in the illustration of the planetary limits).

Table for the planetary limits:

Earth system processparameterPre-
hit limit
tiger status
trial value
Climate changei) Atmospheric CO2 concentration (ppmv)

ii) Change in radiative forcing (W per m2)



Loss of biodiversityExtinction rate (number of species per million species per year)10>1000,1-1
Nitrogen cycle (part of the boundary with the phosphorus cycle)Amount of nitrogen extracted from the atmosphere through anthropogenic use (million t per year)351210
Phosphorus cycle (part of the boundary with the nitrogen cycle)Amount of phosphorus entering the oceans (million tons per year)118,5-9,5-1
Stratospheric ozone depletionOzone column density (Dobson units)276283290
Ocean acidificationGlobally averaged aragonite saturation in surface water2,752,903,44
Global freshwater useHuman use of freshwater (km3 per year)4.0002.600415
Land use
Share of the global land area (in%) that has been converted into arable land1511,7low
Atmospheric aerosol pollutionTotal particle concentration in the atmosphere on a regional basisyet to be determined
Pollution from pollutantsFor example, the amounts emitted into the global environment or the concentrations of persistent organic pollutants, plastic, endocrine disruptors, heavy metals and nuclear waste, or their effects on ecosystems or the functioning of the earth systemyet to be determined

In contrast to Rockström et al. the WBGU does not define a “safe space for action” based on a geological past in which human civilization has not yet exercised any power to change the earth system. The WBGU sets the planetary guard rails with a view to preserving the foundations of life for human civilization. The question of whether a system state is tolerable or not is determined in the sense of a "moderate anthropocentric approach" [13] guardrail by guardrail based on the respective effects on people and society and is not based on a past earth system condition.

Despite these differences in detail, both concepts are very similar to each other. Both approaches point to the interdependencies between different guard rails as well as to the fact that the guard rails or boundaries offer good orientation, but that compliance with them does not guarantee absolute safety. What both approaches have in common is that they see the efforts required to adhere to the guard rails as a major and pressing challenge for global environmental policy. In a situation with large gaps in knowledge and a need for research about the dynamics of the earth system, guard rails make it easier to act under uncertainty.

The donut - linking planetary and socio-economic boundaries

A link between planetary and socio-economic boundaries was presented in a discussion paper for Oxfam in 2012 with the so-called donut [14] [15]. Oxfam is an international organization committed to fighting poverty with global information campaigns and local projects. The term donut refers to the shape of the concept presented and is derived from the shape of the sweet pastry of the same name. The starting point was the consideration that compliance with planetary boundaries alone is a necessary, but not sufficient, condition for sustainable development. At the same time, factors that are essential for the quality of people's living conditions, such as food, water, access to energy, health services, work, or opportunities to participate, should also be taken into account.

Fig 2: A safe and just space for mankind to act ( Graphic for download) License: cc by-nc-nd / 3.0 / de / (bpb)

Fig. 2 above shows this overall picture: in the outer ring are the Planetary Boundaries by Rockström et al. (here only nine, since nitrogen and phosphorus were combined to form a boundary), essentially the social basis that must be present to overcome extreme poverty and encompasses eleven dimensions. The green-colored space for action between the two border dimensions is not only safe in this logic, but also fair. This means that global resource use is organized in such a way that elementary needs for all people are ensured (food, drinking water, etc. - "safe"), and at the same time the disproportionate use of resources by the affluent part of humanity is reduced ("fair"). Within this space of action, inclusive and sustainable economic development is possible for everyone; in this respect, the approach combines the safeguarding of human rights with the preservation of the natural foundations of life.

Significance of planetary guard rails for global sustainability policy

Concepts like those of the planetary guard rails or the planetary boundaries help to describe the conditions of parts of the environmental or earth system and to deduce from them where measures have to be taken to avoid intolerable conditions.

Fig. 3: Relationship between guard rails, measures and future system development ( Graphic for download) (& copy bpb)

Figure 3 above shows possible states of a system with regard to its sustainability. The current state of a system relative to the guard rail can be in the green "sustainable" or in the red "unsustainable" area. If a system is in the unsustainable area, it must be steered into the sustainable area through suitable measures [16]. An example of this: Progressive soil degradation can be stopped and the vegetation cover can recover if suitable reforestation and protection measures are initiated in good time. With such measures, the water storage capacity of a region affected by water scarcity can also be improved at the same time. Overall, this will prevent the guard rail for land and soil degradation from being exceeded.

Achieving or guaranteeing a “safe and fair scope for action” [17] is a great challenge, because it requires a major transformation towards sustainability [18].For example, avoiding dangerous climate change requires a change in energy production and economic practices worldwide. Raworth (2012) makes it clear that improving the living conditions of the roughly 1 billion people living in extreme poverty does not conflict with maintaining planetary boundaries. Rather, it is the top 10% of the world's population who largely determine whether guard rails can be adhered to or not. The lifestyles of these most affluent population groups worldwide are responsible for the largest share of global greenhouse gas emissions and they use the majority of natural resources such as land and drinking water.

Planetary guard rails and boundaries as a compass for policymaking

The erosion of river banks and coastlines in Bangladesh due to rising sea levels are examples of creeping environmental changes. Many people lose their land and become homeless. (& copy picture-alliance,

In international climate policy, a temperature limit in the sense of a guard rail and the zero target to be derived from it - i.e. the insight that exceeding certain temperature limits can only be prevented if the CO2 emissions are brought to zero - have already been implemented.

The 2015 Paris Agreement aims to limit global temperature increases to 2 ° C and 1.5 ° C respectively and contains the goal of achieving a balance between the sources and sinks of anthropogenic greenhouse gases in the second half of this century, so that no further CO2 should then accumulate in the atmosphere. The concept of a “land degradation-neutral world”, for example, has established itself internationally as a guard rail for international soil protection and was included in the catalog of the 2030 Agenda in 2015. The demand for a “world without land degradation” (land-degradation neutral world) was agreed at the Rio + 20 conference [19]. There the goals were formulated to reverse the current trends of land degradation through quick action and to restore degraded land areas [20]. The political objectives for nature conservation worldwide (Aichi Targets) already agreed within the framework of the UN Biodiversity Convention are also in line with the WBGU's guard rail and the corresponding zero target of stopping the anthropogenic drivers of further loss of biological diversity:

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Aichi Biodiversity Targets

The Strategic Plan 2011-2020 for the preservation of biodiversity contains five strategic goals (A - E) (Strategic Goals), which are specified by 20 core goals (1 - 20) (Aichi Biodiversity Targets). The CBD contracting states are currently developing a system of indicators that will document the progress made towards achieving the goals.
  • Strategic goal A (core goals 1 - 4):
    Combating the causes of the decline in biodiversity by integrating it into all areas of government and society
  • Strategic goal B (core goals 5 - 10):
    Reduction of the direct pressures affecting biological diversity and promotion of sustainable use
  • Strategic goal C (core goals 11 - 13):
    Improving the status of biological diversity by safeguarding ecosystems and species as well as genetic diversity
  • Strategic goal D (core goals 14 - 16):
    Increasing the benefits for all resulting from biodiversity and ecosystem services
  • Strategic goal E (core goals 17-20):
    Improving implementation through participatory planning, knowledge management and capacity building
Source: Federal Agency for Nature Conservation (BfN)



In the area of ​​long-lived pollutants, further examples can be found in the Montreal Protocol (reduction of chlorofluorocarbons to protect the stratospheric ozone layer [21]), in the Stockholm Convention (prohibition of the most harmful persistent organic pollutants, especially pesticides) or the Minamata Convention (reduction toxic mercury emissions [22])

There is already work on how global guard rails can be translated for the local level [23]. The zero targets assigned to the guard rails can help with this implementation. If, for example, the emission stop for CO2 is to be complied with globally, it must also be complied with in all regions, countries, cities, industrial sectors and households. This automatically results in clear targets for all levels.

The outlined concepts offer answers to the question of how we can enable global development without endangering our natural foundations of life. They offer a kind of guide or compass on how society and politics can navigate the earth system through dangers and risks and at the same time guarantee good, humane development combined with the greatest possible social and economic freedom. The concept can be used as a starting point for civil society debates and thus support the processes for the overall societal design of sustainable development paths in the context of the Great Transformation.