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Planetary boundaries is a concept highlighting human-caused perturbations of Earth systems making them relevant in a way not accommodated by the environmental boundaries separating the three ages within the
Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togeth ...
epoch. Crossing a planetary boundary comes at the risk of abrupt environmental change. The framework is based on scientific evidence that human actions, especially those of industrialized societies since the
Industrial Revolution The Industrial Revolution was the transition to new manufacturing processes in Great Britain, continental Europe, and the United States, that occurred during the period from around 1760 to about 1820–1840. This transition included going f ...
, have become the main driver of global environmental change. According to the framework, "transgressing one or more planetary boundaries may be deleterious or even catastrophic due to the risk of crossing thresholds that will trigger non-linear, abrupt environmental change within continental-scale to planetary-scale systems." The
normative Normative generally means relating to an evaluative standard. Normativity is the phenomenon in human societies of designating some actions or outcomes as good, desirable, or permissible, and others as bad, undesirable, or impermissible. A norm in ...
component of the framework is that human societies have been able to thrive under the comparatively stable climatic and ecological conditions of the
Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togeth ...
. To the extent that these Earth system process boundaries have not been crossed, they mark the “safe zone” for human societies on the planet. The concept has since become influential in the international community (e.g.
United Nations Conference on Sustainable Development The United Nations Conference on Sustainable Development (UNCSD), also known as Rio 2012, Rio+20 (), or Earth Summit 2012 was the third international conference on sustainable development aimed at reconciling the economic and environmental goals ...
), including governments at all levels, international organizations, civil society and the scientific community. The framework consists of nine global change processes. In 2009, according to Rockström and others, two boundaries were already crossed, while others were in imminent danger of being crossed. In 2015, several of the scientists in the original group published an update, bringing in new co-authors and new model-based analysis. According to this update, four of the boundaries were crossed: climate change, loss of biosphere integrity, land-system change, altered biogeochemical cycles (phosphorus and nitrogen). The scientists also changed the name of the boundary "
Loss of biodiversity Biodiversity loss includes the worldwide extinction of different species, as well as the local reduction or loss of species in a certain habitat, resulting in a loss of biological diversity. The latter phenomenon can be temporary or permanent, de ...
" to "Change in biosphere integrity" to emphasize that not only the number of species but also the functioning of the biosphere as a whole is important for Earth system stability. Similarly, the "Chemical pollution" boundary was renamed to "Introduction of novel entities," widening the scope to consider different kinds of human-generated materials that disrupt Earth system processes. In 2022, based on available literature, the introduction of novel entities was concluded to be the 5th transgressed planetary boundary.


Framework overview and principles

The basic idea of the Planetary Boundaries framework is that maintaining the observed resilience of the Earth system in the
Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togeth ...
is a precondition for humanity’s pursuit of long-term social and economic development. The Planetary Boundaries framework contributes to an understanding of global sustainability because it brings a planetary scale and a long timeframe into focus. The framework described nine "planetary life support systems" essential for maintaining a “desired
Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togeth ...
state”, and attempted to quantify how far seven of these systems had been pushed already. Boundaries were defined to help define a "safe space for human development", which was an improvement on approaches aiming at minimizing human impacts on the planet. The framework is based on scientific evidence that human actions, especially those of industrialized societies since the
Industrial Revolution The Industrial Revolution was the transition to new manufacturing processes in Great Britain, continental Europe, and the United States, that occurred during the period from around 1760 to about 1820–1840. This transition included going f ...
, have become the main driver of global environmental change. According to the framework, "transgressing one or more planetary boundaries may be deleterious or even catastrophic due to the risk of crossing thresholds that will trigger non-linear, abrupt
environmental change Environmental change is a change or disturbance of the environment most often caused by human influences and natural ecological processes. Environmental changes include various factors, such as natural disasters, human interferences, or animal in ...
within continental-scale to planetary-scale systems." The framework consists of nine global change processes. In 2009, two boundaries were already crossed, while others were in imminent danger of being crossed. Later estimates indicated that three of these boundaries—
climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...
,
biodiversity Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') l ...
loss, and the biogeochemical flow boundary—appear to have been crossed. The scientists outlined how breaching the boundaries increases the threat of functional disruption, even collapse, in Earth’s biophysical systems in ways that could be catastrophic for human wellbeing. While they highlighted scientific uncertainty, they indicated that breaching boundaries could “trigger feedbacks that may result in crossing thresholds that drastically reduce the ability to return within safe levels”. The boundaries were "rough, first estimates only, surrounded by large uncertainties and knowledge gaps" which interact in complex ways that are not yet well understood. The planetary boundaries framework lays the groundwork for a shifting approach to governance and management, away from the essentially sectoral analyses of limits to growth aimed at minimizing negative
externalities In economics, an externality or external cost is an indirect cost or benefit to an uninvolved third party that arises as an effect of another party's (or parties') activity. Externalities can be considered as unpriced goods involved in either co ...
, toward the estimation of the safe space for human development. Planetary boundaries demarcate, as it were, the "planetary playing field" for humanity if major human-induced environmental change on a global scale is to be avoided.


Authors

The authors of this framework was a group of
Earth System Earth system science (ESS) is the application of systems science to the Earth. In particular, it considers interactions and 'feedbacks', through material and energy fluxes, between the Earth's sub-systems' cycles, processes and "spheres"— atmo ...
and
environmental scientists Environmental science is an interdisciplinary academic field that integrates physics, biology, and geography (including ecology, chemistry, plant science, zoology, mineralogy, oceanography, limnology, soil science, geology and physical geogra ...
in 2009 led by Johan Rockström from the Stockholm Resilience Centre and
Will Steffen Will Steffen (born 1947) is an American chemist. He was the executive director of the Australian National University (ANU) Climate Change Institute and a member of the Australian Climate Commission until its dissolution in September 2013. Fro ...
from the
Australian National University The Australian National University (ANU) is a public research university located in Canberra, the capital of Australia. Its main campus in Acton encompasses seven teaching and research colleges, in addition to several national academies an ...
. They collaborated with 26 leading academics, including Nobel laureate Paul Crutzen,
Goddard Institute for Space Studies The Goddard Institute for Space Studies (GISS) is a laboratory in the Earth Sciences Division of NASA's Goddard Space Flight Center affiliated with the Columbia University Earth Institute. The institute is located at Columbia University in N ...
climate scientist James Hansen, oceanographer Katherine Richardson, geographer
Diana Liverman Diana Liverman (born May 15, 1954, Accra, Ghana) is a retired Regents Professor of Geography and Development and past Director of the University of Arizona School of Geography, Development and Environment in the College of Social and Behavioral ...
and the
German Chancellor The chancellor of Germany, officially the federal chancellor of the Federal Republic of Germany,; often shortened to ''Bundeskanzler''/''Bundeskanzlerin'', / is the head of the federal government of Germany and the commander in chief of the Ge ...
's chief climate adviser
Hans Joachim Schellnhuber Hans Joachim "John" Schellnhuber (born 7 June 1950) is a German atmospheric physicist, climatologist and founding director of the Potsdam Institute for Climate Impact Research (PIK) and former chair of the German Advisory Council on Global ...
. Most of the contributing scientists were involved in strategy-setting for the
Earth System Science Partnership The Earth System Science Partnership (ESSP) was a partnership under the auspices of the International Council for Science (ICSU) for the integrated study of the Earth system, the ways that it is changing, and the implications for global and regional ...
, the precursor to the international global change research network
Future Earth Future Earth is an international research program which aims to build knowledge about the environmental and human aspects of Global change, and to find solutions for sustainable development. It aims to increase the impact of scientific research o ...
. The group wanted to define a "safe operating space for humanity" for the wider scientific community, as a precondition for sustainable development.


Nine boundaries


Thresholds and tipping points

The 2009 study identified nine planetary boundaries and, drawing on current scientific understanding, the researchers proposed quantifications for seven of them. These are: # climate change ( CO2 concentration in the atmosphere < 350 ppm and/or a maximum change of +1 W/m2 in
radiative forcing Radiative forcing (or climate forcing) is the change in energy flux in the atmosphere caused by natural or anthropogenic factors of climate change as measured by watts / metre2. It is a scientific concept used to quantify and compare the extern ...
); #
ocean acidification Ocean acidification is the reduction in the pH value of the Earth’s ocean. Between 1751 and 2021, the average pH value of the ocean surface has decreased from approximately 8.25 to 8.14. The root cause of ocean acidification is carbon dioxid ...
(mean surface seawater saturation state with respect to
aragonite Aragonite is a carbonate mineral, one of the three most common naturally occurring crystal forms of calcium carbonate, (the other forms being the minerals calcite and vaterite). It is formed by biological and physical processes, including pre ...
≥ 80% of pre-
industrial Industrial may refer to: Industry * Industrial archaeology, the study of the history of the industry * Industrial engineering, engineering dealing with the optimization of complex industrial processes or systems * Industrial city, a city dominate ...
levels); # stratospheric ozone depletion (less than 5% reduction in total atmospheric O3 from a pre-industrial level of 290
Dobson Unit The Dobson unit (DU) is a unit of measurement of the amount of a trace gas in a vertical column through the Earth's atmosphere. It originated, and continues to be primarily used in respect to, atmospheric ozone, whose total column amount, usually te ...
s); #
biogeochemical Biogeochemistry is the scientific discipline that involves the study of the chemical, physical, geological, and biological processes and reactions that govern the composition of the natural environment (including the biosphere, the cryosphere, th ...
flows in the nitrogen (N) cycle (limit industrial and agricultural fixation of N2 to 35 Tg N/yr) and phosphorus (P) cycle (annual P inflow to oceans not to exceed 10 times the natural background
weathering Weathering is the deterioration of rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little or no movement) ...
of P); # global freshwater use (< 4000 km3/yr of consumptive use of runoff resources); # land system change (< 15% of the ice-free land surface under cropland); # the erosion of biosphere integrity (an annual rate of loss of biological diversity of < 10 extinctions per million species). # chemical pollution (introduction of novel entities in the environment). For one process in the planetary boundaries framework, the scientists have not specified a global boundary quantification:
  1. atmospheric aerosol loading;
The quantification of individual planetary boundaries is based on the observed dynamics of the interacting Earth system processes included in the framework. The control variables were chosen because together they provide an effective way to track the human-caused shift away from Holocene conditions. For some of Earth’s dynamic processes, historic data display clear thresholds between comparatively stable conditions. For example, past ice-ages show that during peak glacial conditions, the atmospheric concentration of CO2 was ~180-200 ppm. In interglacial periods (including the Holocene), CO2 concentration has fluctuated around 280 ppm. To know what past climate conditions were like with an atmosphere with over 350 ppm CO2, scientists need to look back about 3 million years. The paleo record of climatic, ecological and biogeochemical changes shows that the Earth system has experienced tipping points, when a very small increment for a control variable (like CO2) triggers a larger, possibly catastrophic, change in the response variable (global warming) through feedbacks in the natural Earth System itself. For several of the processes in the planetary boundaries framework, it is difficult to locate individual points that mark the threshold shift away from Holocene-like conditions. This is because the Earth system is complex and the scientific evidence base is still partial and fragmented. Instead, the planetary boundaries framework identifies many Earth system thresholds at multiple scales that will be influenced by increases in the control variables. Examples include shifts in
monsoon A monsoon () is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with annual latitudinal osci ...
behavior linked to the aerosol loading and freshwater use planetary boundaries.


"Safe operating spaces"

The planetary boundaries framework proposes a range of values for its control variables. This range is supposed to span the threshold between a 'safe operating space' where Holocene-like dynamics can be maintained and a highly uncertain, poorly predictable world where Earth system changes likely increase risks to societies. The ''boundary'' is defined as the lower end of that range. If the boundaries are persistently crossed, the world goes further into a danger zone. It is difficult to restore a 'safe operating space' for humanity that is described by the planetary boundary concept. Even if past biophysical changes could be mitigated, the predominant paradigms of social and economic development appear largely indifferent to the looming possibilities of large scale environmental disasters triggered by human actions. Legal boundaries can help keep human activities in check, but are only as effective as the political will to make and enforce them.


Interaction among boundaries

Understanding the Earth system is fundamentally about understanding interactions among environmental change processes. The planetary boundaries are defined with reference to dynamic conditions of the Earth system, but scientific discussions about how different planetary boundaries relate to each other are often philosophically and analytically muddled. Clearer definitions of the basic concepts and terms might help give clarity. There are many many interactions among the processes in planetary boundaries the framework. While these interactions can create both stabilizing and destabilizing feedbacks in the Earth system, the authors suggested that a transgressed planetary boundary will reduce the safe operating space for other processes in the framework rather than expand it from the proposed boundary levels. They give the example that the
land use Land use involves the management and modification of natural environment or wilderness into built environment such as settlements and semi-natural habitats such as arable fields, pastures, and managed woods. Land use by humans has a long ...
boundary could “shift downward” if the freshwater boundary is breached, causing lands to become arid and unavailable for agriculture. At a regional level, water resources may decline in Asia if
deforestation Deforestation or forest clearance is the removal of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. The most concentrated ...
continues in the
Amazon Amazon most often refers to: * Amazons, a tribe of female warriors in Greek mythology * Amazon rainforest, a rainforest covering most of the Amazon basin * Amazon River, in South America * Amazon (company), an American multinational technolog ...
. That way of framing the interactions shifts from the framework’s biophysical definition of boundaries based on Holocene-like conditions to an anthropocentric definition (demand for agricultural land). Despite this conceptual slippage, considerations of known Earth system interactions across scales suggest the need for "extreme caution in approaching or transgressing any individual planetary boundaries." Another example has to do with
coral reef A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups. C ...
s and
marine ecosystem Marine ecosystems are the largest of Earth's aquatic ecosystems and exist in waters that have a high salt content. These systems contrast with freshwater ecosystems, which have a lower salt content. Marine waters cover more than 70% of the sur ...
s: In 2009, researchers showed that, since 1990, calcification in the reefs of the Great Barrier that they examined decreased at a rate unprecedented over the last 400 years (14% in less than 20 years). Their evidence suggests that the increasing temperature stress and the declining ocean saturation state of
aragonite Aragonite is a carbonate mineral, one of the three most common naturally occurring crystal forms of calcium carbonate, (the other forms being the minerals calcite and vaterite). It is formed by biological and physical processes, including pre ...
is making it difficult for reef corals to deposit calcium carbonate. Multiple stressors, such as increased nutrient loads and
fishing pressure Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing fish stock), resulting in t ...
, moves corals into less desirable ecosystem states. Ocean acidification will significantly change the distribution and abundance of a whole range of marine life, particularly species "that build skeletons, shells, and tests of biogenic calcium carbonate. Increasing temperatures, surface
UV radiation Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30  PHz) to 400 nm (750  THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...
levels and ocean acidity all stress marine biota, and the combination of these stresses may well cause perturbations in the abundance and diversity of marine biological systems that go well beyond the effects of a single stressor acting alone."


Proposed new or expanded boundaries since 2012

In 2012, Steven Running suggested a tenth boundary, the annual net global
primary production In ecology, primary production is the synthesis of organic compounds from atmospheric or aqueous carbon dioxide. It principally occurs through the process of photosynthesis, which uses light as its source of energy, but it also occurs through ...
of all
terrestrial plant A terrestrial plant is a plant that grows on, in, or from land. Other types of plants are aquatic (living in water), epiphytic (living on trees) and lithophytic (living in or on rocks). The distinction between aquatic and terrestrial plants i ...
s, as an easily determinable measure integrating many variables that will give "a clear signal about the health of ecosystems". In 2015, a second paper was published in ''
Science Science is a systematic endeavor that Scientific method, builds and organizes knowledge in the form of Testability, testable explanations and predictions about the universe. Science may be as old as the human species, and some of the earli ...
'' to update the Planetary Boundaries concept. The update concluded four boundaries had now been transgressed: climate, biodiversity, land use and biogeochemical cycles. The 2015 paper emphasized interactions of the nine boundaries and identified climate change and
loss of biodiversity Biodiversity loss includes the worldwide extinction of different species, as well as the local reduction or loss of species in a certain habitat, resulting in a loss of biological diversity. The latter phenomenon can be temporary or permanent, de ...
integrity as ‘core boundaries’ of central importance to the framework because the interactions of climate and the biosphere are what scientifically defines Earth system conditions. In 2017, some authors argued that marine systems are underrepresented in the framework. Their proposed remedy was to include the
seabed The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as 'seabeds'. The structure of the seabed of the global ocean is governed by plate tectonics. Most of ...
as a component of the earth surface change boundary. They also wrote that the framework should account for "changes in vertical mixing and ocean circulation patterns". Subsequent work on planetary boundaries begins to relate these thresholds at the regional scale.


Debate and further research per boundary


Climate change

A 2018 study calls into question the adequacy of efforts to limit warming to 2 degrees above pre-industrial temperatures, as set out in the Paris Agreement. The scientists raise the possibility that even if
greenhouse gas emissions Greenhouse gas emissions from human activities strengthen the greenhouse effect, contributing to climate change. Most is carbon dioxide from burning fossil fuels: coal, oil, and natural gas. The largest emitters include coal in China and ...
are substantially reduced to limit warming to 2 degrees, that might exceed the "threshold" at which self-reinforcing
climate feedbacks In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
add additional warming until the
climate system Earth's climate system is a complex system having five interacting components: the atmosphere (air), the hydrosphere (water), the cryosphere (ice and permafrost), the lithosphere (earth's upper rocky layer) and the biosphere (living things). '' ...
stabilizes in a hothouse climate state. This would make parts of the world uninhabitable for people, raise sea levels by up to 60 metres (200 ft), and raise temperatures by 4–5 °C (7.2–9.0 °F) to levels that are higher than any interglacial period in the past 1.2 million years.


Change in biosphere integrity

According to the biologist
Cristián Samper Cristián Samper (born September 25, 1965) is a Colombian-American tropical biologist specializing in conservation biology and environmental policy. He is the Managing Director and Leader of Nature Solutions at the Bezos Earth Fund. He served as ...
, a "boundary that expresses the probability of families of species disappearing over time would better reflect our potential impacts on the future of life on Earth." The biodiversity boundary has also been criticized for framing biodiversity solely in terms of the extinction rate. The global extinction rate has been highly variable over the Earth's history, and thus using it as the only biodiversity variable can be of limited usefulness.


Nitrogen and phosphorus

The biogeochemist
William Schlesinger William H. Schlesinger (born April 30, 1950) is a biogeochemist and the retired president of the Cary Institute of Ecosystem Studies, an independent not-for-profit environmental research organization in Millbrook, New York. He assumed that pos ...
thinks waiting until we near some suggested limit for nitrogen deposition and other pollutions will just permit us to continue to a point where it is too late. He says the boundary suggested for phosphorus is not sustainable, and would exhaust the known phosphorus reserves in less than 200 years. The ocean chemist Peter Brewer queries whether it is "truly useful to create a list of environmental limits without serious plans for how they may be achieved ... they may become just another stick to beat citizens with. Disruption of the global nitrogen cycle is one clear example: it is likely that a large fraction of people on Earth would not be alive today without the artificial production of fertilizer. How can such ethical and economic issues be matched with a simple call to set limits? ... food is not optional.".
Peak phosphorus Peak phosphorus is a concept to describe the point in time when humanity reaches the maximum global production rate of phosphorus as an industrial and commercial raw material. The term is used in an equivalent way to the better-known term peak o ...
is a concept to describe the point in time at which the maximum global
phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...
production rate is reached. Phosphorus is a scarce finite resource on earth and means of production other than mining are unavailable because of its non-gaseous environmental cycle. According to some researchers, Earth's phosphorus reserves are expected to be completely depleted in 50–100 years and peak phosphorus to be reached by approximately 2030.


Ocean acidification

Surface ocean acidity is clearly interconnected with the climate change boundaries, since the concentration of carbon dioxide in the atmosphere is also the underlying control variable for the ocean acidification boundary. The ocean chemist Peter Brewer thinks "ocean acidification has impacts other than simple changes in pH, and these may need boundaries too."


Land-system change

Across the planet, forests, wetlands and other vegetation types are being converted to agricultural and other
land use Land use involves the management and modification of natural environment or wilderness into built environment such as settlements and semi-natural habitats such as arable fields, pastures, and managed woods. Land use by humans has a long ...
s, impacting freshwater, carbon and other cycles, and reducing biodiversity. In the year 2015 the boundary was defined as 75% of
forest A forest is an area of land dominated by trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, and ecological function. The United Nations' ...
s rested intact, including 85% of
boreal forests Taiga (; rus, тайга́, p=tɐjˈɡa; relates to Mongolic and Turkic languages), generally referred to in North America as a boreal forest or snow forest, is a biome characterized by coniferous forests consisting mostly of pines, spruces, ...
, 50% of
temperate forest A temperate forest is a forest found between the tropical and boreal regions, located in the temperate zone. It is the second largest biome on our planet, covering 25% of the world's forest area, only behind the boreal forest, which covers abou ...
s and 85% of
tropical forest Tropical forests (a.k.a. jungle) are forested landscapes in tropical regions: ''i.e.'' land areas approximately bounded by the tropic of Cancer and Capricorn, but possibly affected by other factors such as prevailing winds. Some tropical fore ...
s. The boundary is crossed because only 62% of forests rested intact as of the year 2015. The boundary for land use has been criticized as follows: "The boundary of 15 per cent land-use change is, in practice, a premature policy guideline that dilutes the authors' overall scientific proposition. Instead, the authors might want to consider a limit on
soil degradation Soil retrogression and degradation are two regressive evolution processes associated with the loss of equilibrium of a stable soil. Retrogression is primarily due to soil erosion and corresponds to a phenomenon where succession reverts the land to ...
or soil loss. This would be a more valid and useful indicator of the state of terrestrial health."


Freshwater

The freshwater cycle is another boundary significantly affected by climate change. Overexploitation of freshwater occurs if a water resource is mined or extracted at a rate that exceeds the recharge rate.
Water pollution Water pollution (or aquatic pollution) is the contamination of water bodies, usually as a result of human activities, so that it negatively affects its uses. Water bodies include lakes, rivers, oceans, aquifers, reservoirs and groundwater. ...
and
saltwater intrusion Saltwater intrusion is the movement of saline water into freshwater aquifers, which can lead to groundwater quality degradation, including drinking water sources, and other consequences. Saltwater intrusion can naturally occur in coastal aquifers, ...
can also turn much of the world's underground water and lakes into finite resources with "
peak water Peak water is a concept that underlines the growing constraints on the availability, quality, and use of freshwater resources. Peak water was defined in a 2010 peer-reviewed article in the ''Proceedings of the National Academy of Sciences'' by ...
" usage debates similar to
oil An oil is any nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobic (does not mix with water) & lipophilic (mixes with other oils). Oils are usually flammable and surface active. Most oils are unsaturated ...
.. The hydrologist David Molden stated in 2009 that planetary boundaries are a welcome new approach in the "
limits to growth ''The Limits to Growth'' (''LTG'') is a 1972 report that discussed the possibility of exponential economic and population growth with finite supply of resources, studied by computer simulation. The study used the World3 computer model to simula ...
" debate but said "a global limit on water consumption is necessary, but the suggested planetary boundary of 4,000 cubic kilometres per year is too generous.".


= Green and blue water

= A study concludes that the 'Freshwater use' boundary should be renamed to the 'Freshwater change', composed of "green" and "blue" water components. 'Green water' refers to disturbances of terrestrial precipitation, evaporation and soil moisture.
Water scarcity Water scarcity (closely related to water stress or water crisis) is the lack of fresh water resources to meet the standard water demand. There are two types of water scarcity: physical or economic water scarcity. Physical water scarcity is whe ...
can have substantial effects in agriculture. When measuring and projecting water scarcity in
agriculture Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people t ...
for climate change scenarios, both "green water" and "blue water" are of relevance. In April 2022, scientists proposed and preliminarily evaluated 'green water' in the
water cycle The water cycle, also known as the hydrologic cycle or the hydrological cycle, is a biogeochemical cycle that describes the continuous movement of water on, above and below the surface of the Earth. The mass of water on Earth remains fairly cons ...
as a likely transgressed planetary boundary, as measured by root-zone soil moisture deviation from Holocene variability.


Ozone depletion

The stratospheric ozone layer protectively filters
ultraviolet radiation Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30  PHz) to 400 nm (750  THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...
(UV) from the
Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
, which would otherwise damage biological systems. The actions taken after the
Montreal Protocol The Montreal Protocol is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances that are responsible for ozone depletion. It was agreed on 16 September 1987, and entered into force o ...
appeared to be keeping the planet within a safe boundary. The Nobel laureate in chemistry,
Mario Molina Mario José Molina-Pasquel Henríquez (19 March 19437 October 2020), known as Mario Molina, was a Mexican chemist. He played a pivotal role in the discovery of the Antarctic ozone hole, and was a co-recipient of the 1995 Nobel Prize in Chemis ...
, says "five per cent is a reasonable limit for acceptable ozone depletion, but it doesn't represent a tipping point".


Atmospheric aerosols

Worldwide each year, aerosol particles result in about 800,000 premature deaths from
air pollution Air pollution is the contamination of air due to the presence of substances in the atmosphere that are harmful to the health of humans and other living beings, or cause damage to the climate or to materials. There are many different typ ...
. Aerosol loading is sufficiently important to be included among the planetary boundaries, but it is not yet clear whether an appropriate safe threshold measure can be identified.


Novel entities (chemical pollution)

Some chemicals, such as
persistent organic pollutants Persistent organic pollutants (POPs), sometimes known as "forever chemicals", are organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic processes. They are toxic chemicals that adversel ...
, heavy metals and radionuclides, have potentially irreversible
additive Additive may refer to: Mathematics * Additive function, a function in number theory * Additive map, a function that preserves the addition operation * Additive set-functionn see Sigma additivity * Additive category, a preadditive category with f ...
and synergic effects on biological organisms, reducing fertility and resulting in permanent
genetic damage In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, mitos ...
. Sublethal uptakes are drastically reducing marine bird and mammal populations. This boundary seems important, although it is hard to quantify. In 2019, it was suggested that novel entities could include genetically modified organisms, pesticides and even
artificial intelligence Artificial intelligence (AI) is intelligence—perceiving, synthesizing, and inferring information—demonstrated by machines, as opposed to intelligence displayed by animals and humans. Example tasks in which this is done include speech r ...
. A Bayesian emulator for persistent organic pollutants has been developed which can potentially be used to quantify the boundaries for chemical pollution. To date, critical exposure levels of polychlorinated biphenyls (PCBs) above which mass mortality events of marine mammals are likely to occur, have been proposed as a chemical pollution planetary boundary. There are at least 350,000 artificial chemicals in the world. They are coming from "
plastic Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adaptab ...
s, pesticides,
industrial chemicals The chemical industry comprises the companies that produce industrial chemicals. Central to the modern world economy, it converts raw materials (oil, natural gas, air, water, metals, and minerals) into more than 70,000 different products. The ...
, chemicals in consumer products, antibiotics and other pharmaceuticals". They have mostly "negative effects on planetary health". Their production increased 50 times since 1950 and expected to increase 3 times more by 2050. Plastic alone contain more than 10,000 chemicals and create large problems. The researchers are calling for limit on chemical production and shift to circular economy, meaning to products that can be reused and recycled. In January 2022 a group of scientists concluded that this planetary boundary is already exceeded, which puts in risk the stability of the Earth system. They integrated the literature information on how production and release of a number of novel entities, including plastics and hazardous chemicals, have rapidly increased in the last decades with significant impact on the planetary processes. In August 2022, scientists concluded that the (overall transgressed) boundary is a placeholder for multiple different boundaries for NEs that may emerge, reporting that PFAS pollution is one such new boundary. They show that levels of these so-called "
forever chemicals Per- and polyfluoroalkyl substances (PFASs) are synthetic Organofluorine chemistry, organofluorine chemical compounds that have multiple fluorine atoms attached to an alkyl chain. An early definition, from 2011, required that they contain at l ...
" in
rainwater Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water fo ...
are ubiquitously, and often greatly, above guideline safe levels worldwide. There are some moves to restrict and replace their use.


Related concepts


Planetary integrity

Planetary integrity, also called "earth’s life-support systems" or "ecological integrity", needs to be maintained for long-term sustainability. Text was copied from this source, which is available under
Creative Commons Attribution 4.0 International License
/ref> The notion of planetary integrity derives from its root term "ecological integrity", which was initially developed to describe the declining state of biodiversity on a sub-global scale. In this context, "integrity" is a way of thinking about
ecological health Ecological health is a term that has been used in relation to both human health and the condition of the environment. *In medicine, ecological health has been used to refer to multiple chemical sensitivity, which results from exposure to synthet ...
affected by human activities. The concept of planetary integrity is becoming popular at several levels of analysis. It is, for example, implied in the notion of planetary boundaries. An expert Panel on Ecological Integrity in 1998 has defined ecological integrity as follows: "An ecosystem has integrity when it is deemed characteristic for its natural region, including the composition and abundance of native species and biological communities, rates of change and supporting processes. In plain language, ecosystems have integrity when they have their native components (plants, animals and other organisms) and processes (such as growth and reproduction) intact.". There now seems to be general agreement that planetary integrity is being impacted in unprecedented ways, and that deliberate and thoroughgoing steering mechanisms, such as through the Sustainable Development Goals, are urgently needed. The signs of decaying planetary integrity are apparent from the negative
human impacts on the environment Human impact on the environment (or anthropogenic impact) refers to changes to biophysical environments and to ecosystems, biodiversity, and natural resources caused directly or indirectly by humans. Modifying the environment to fit the need ...
and predictions showing that we are fast approaching global tipping points.


The "Limits to Growth" (1972) and Gaia theory

The idea that there are limits to the burden placed upon our planet by human activities has been around for a long time. The Planetary Boundaries framework acknowledges the influence of the 1972 study, ''
The Limits to Growth ''The Limits to Growth'' (''LTG'') is a 1972 report that discussed the possibility of exponential economic and population growth with finite supply of resources, studied by computer simulation. The study used the World3 computer model to simula ...
'', that presented a model in which
exponential Exponential may refer to any of several mathematical topics related to exponentiation, including: *Exponential function, also: **Matrix exponential, the matrix analogue to the above *Exponential decay, decrease at a rate proportional to value *Expo ...
growth in
world population In demographics, the world population is the total number of humans currently living. It was estimated by the United Nations to have exceeded 8 billion in November 2022. It took over 200,000 years of human prehistory and history for th ...
, industrialization,
pollution Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the ...
, food production, and resources depletion outstrip the ability of technology to increase resources availability. Subsequently, the report was widely dismissed, particularly by economists and business people, and it has often been claimed that history has proved the projections to be incorrect. In 2008, Graham Turner from the
Commonwealth Scientific and Industrial Research Organisation The Commonwealth Scientific and Industrial Research Organisation (CSIRO) is an Australian Government agency responsible for scientific research. CSIRO works with leading organisations around the world. From its headquarters in Canberra, CSIRO ...
(CSIRO) published "A comparison of ''The Limits to Growth'' with thirty years of reality". ''The Limits to Growth'' has been widely discussed, both by critics of the modelling approach and its conclusions and by analysts who argue that the insight that societies do not live in an unlimited world and that historical data since the 1970s support the report’s findings. The ''Limits to Growth'' approach explores how the socio-technical dynamics of the world economy may limit humanity’s opportunities and introduce risks of collapse. In contrast, the Planetary Boundaries framework focuses on the biophysical dynamics of the Earth system. ''
Our Common Future __NOTOC__ ''Our Common Future'', also known as the Brundtland Report, was published on October 1987 by the United Nations through the Oxford University Press. This publication was in recognition of Gro Harlem Brundtland's, former Norwegian Prime M ...
'' was published in 1987 by United Nations'
World Commission on Environment and Development The Brundtland Commission, formerly the World Commission on Environment and Development, was a sub-organization of the United Nations (UN) that aimed to unite countries in pursuit of sustainable development. It was founded in 1983 when Javier Pé ...
. It tried to recapture the spirit of the Stockholm Conference. Its aim was to interlock the concepts of development and environment for future political discussions. It introduced the famous definition for sustainable development: Another key idea influencing the Planetary Boundaries framework is the Gaia theory or hypothesis. In the 1970s, James Lovelock and microbiologist
Lynn Margulis Lynn Margulis (born Lynn Petra Alexander; March 5, 1938 – November 22, 2011) was an American evolutionary biologist, and was the primary modern proponent for the significance of symbiosis in evolution. Historian Jan Sapp has said that "Lynn Ma ...
presented the idea that all
organisms In biology, an organism () is any life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy (biology), taxonomy into groups such as Multicellular o ...
and their
inorganic In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemist ...
surroundings on Earth are integrated into a single self-regulating system. The system has the ability to react to perturbations or deviations, much like a living organism adjusts its regulation mechanisms to accommodate environmental changes such as temperature (
homeostasis In biology, homeostasis (British also homoeostasis) (/hɒmɪə(ʊ)ˈsteɪsɪs/) is the state of steady internal, physical, and chemical conditions maintained by living systems. This is the condition of optimal functioning for the organism and ...
). Nevertheless, this capacity has limits. For instance, when a living organism is subjected to a temperature that is lower or higher than its living range, it can perish because its regulating mechanism cannot make the necessary adjustments. Similarly the Earth may not be able to react to large deviations in critical parameters. In Lovelock's book ''
The Revenge of Gaia ''The Revenge of Gaia: Why the Earth is Fighting Back – and How We Can Still Save Humanity'' (2006) is a book by James Lovelock. Some editions of the book have a different, less optimistic subtitle: ''Earth's Climate Crisis and the Fate of H ...
'', he suggests that the destruction of rainforests and biodiversity, compounded with global warming resulting from the increase of greenhouse gases made by humans, could shift feedbacks in the Earth system away from a self-regulating balance to a positive (intensifying) feedback loop.


Anthropocene

Scientists have affirmed that the planet has entered a new epoch, the Anthropocene. In the Anthropocene, humans have become the main agents of not only change to the Earth System but also the driver of Earth System ''rupture'', disruption of the Earth System's ability to be resilient and recover from that change, potentially ultimately threatening planetary habitability. The previous geological epoch, the
Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togeth ...
began about 10,000 years ago. It is the current interglacial period, and was a relatively stable environment of the Earth. There have been natural environmental fluctuations during the Holocene, but the key atmospheric and biogeochemical parameters have remained within relatively narrow bounds. This stability has allowed societies to thrive worldwide, developing agriculture, large-scale settlements and complex networks of trade. According to Rockström ''et al.'', we "have now become so dependent on those investments for our way of life, and how we have organized society, technologies, and economies around them, that we must take the range within which Earth System processes varied in the Holocene as a scientific reference point for a desirable planetary state." Various biophysical processes that are important in maintaining the Ecological resilience, resilience of the Earth system are also undergoing large and rapid change because of human actions. For example, since the advent of the Anthropocene, the rate at which species are going extinct has increased over 100 times, and humans are now the driving force altering global river flows as well as water vapor flows from the land surface. Continuing perturbation of Earth system processes by human activities raises the possibility that further pressure could be destabilizing, leading to non-linear, abrupt, large-scale or irreversible
environmental change Environmental change is a change or disturbance of the environment most often caused by human influences and natural ecological processes. Environmental changes include various factors, such as natural disasters, human interferences, or animal in ...
responses by the Earth system within continental- to planetary-scale systems.


Reception and debate about the overall framework

The 2009 report was presented to the General Assembly of the Club of Rome in Amsterdam. An edited summary of the report was published as the featured article in a special 2009 edition of ''Nature (journal), Nature'' alongside invited critical commentary from leading academics like Nobel laureate Mario J. Molina and biologist
Cristián Samper Cristián Samper (born September 25, 1965) is a Colombian-American tropical biologist specializing in conservation biology and environmental policy. He is the Managing Director and Leader of Nature Solutions at the Bezos Earth Fund. He served as ...
. Development studies scholars have been critical of aspects of the framework and constraints that its adoption could place on the Global South. Proposals to conserve a certain proportion of Earth's remaining forests can be seen as rewarding the countries such as those in Europe that have already economically benefitted from exhausting their forests and converting land for agriculture. In contrast, countries that have yet to industrialize are asked to make sacrifices for global environmental damage they may have had little role in creating. The biogeochemist
William Schlesinger William H. Schlesinger (born April 30, 1950) is a biogeochemist and the retired president of the Cary Institute of Ecosystem Studies, an independent not-for-profit environmental research organization in Millbrook, New York. He assumed that pos ...
queries whether thresholds are a good idea for pollutions at all. He thinks waiting until we near some suggested limit will just permit us to continue to a point where it is too late. "Management based on thresholds, although attractive in its simplicity, allows pernicious, slow and diffuse degradation to persist nearly indefinitely.".


Subsequent developments


The "safe and just space" doughnut


National environmental footprints

Several studies have assessed environmental footprints of nations based on planetary boundaries: for Sweden, Switzerland,Hy Dao, Pascal Peduzzi, Damien Friot
'' National environmental limits and footprints based on the Planetary Boundaries framework: The case of Switzerland''
, University of Geneva, Institute for Environmental Sciences, GRID-Geneva, EA - Shaping Environmental Action, 2018.
the Netherlands,Paul Lucas, Harry Wilting
''Towards a Safe Operating Space for the Netherlands: Using planetary boundaries to support national implementation of environment-related SDGs''
PBL Netherlands Environmental Assessment Agency 2018.
the European Union, India, many of Belt and Road Initiative countries as well as for the world’s most important economies. While the metrics and allocation approaches applied varied, there is a converging outcome that resource use of wealthier nations – if extrapolated to world population – is not compatible with planetary boundaries.


Boundaries related to agriculture and food consumption

Human activities related to agriculture and nutrition globally contribute to the transgression of four out of nine planetary boundaries. Surplus nutrient flows (N, P) into aquatic and terrestrial ecosystems are of highest importance, followed by excessive land-system change and biodiversity loss. Whereas in the case of biodiversity loss, P cycle and land-system change, the transgression is in the zone of uncertainty—indicating an increasing risk (yellow circle in the figure), the N boundary related to agriculture is more than 200% transgressed—indicating a high risk (red marked circle in the figure). Here, nutrition includes food processing and trade as well as food consumption (preparation of food in households and gastronomy). Consumption-related environmental impacts are not quantified at the global level for the planetary boundaries of freshwater use, atmospheric aerosol loading (
air pollution Air pollution is the contamination of air due to the presence of substances in the atmosphere that are harmful to the health of humans and other living beings, or cause damage to the climate or to materials. There are many different typ ...
) and stratospheric ozone depletion.


Individual and collective allowances

Broadly described proposed solution-approaches based on a general a framework of ecological limits include (transferable) personal carbon allowances and "legislated" national greenhouse gas emissions limits. Consumers would have freedom in their (informed) choice within (the collective) boundaries.


Usage at international policy level


United Nations

The United Nations secretary general Ban Ki-moon endorsed the concept of planetary boundaries on 16 March 2012, when he presented the key points of the report of his High Level Panel on Global Sustainability to an informal Plenary session, plenary of the UN General Assembly. Ban stated: "The Panel’s vision is to eradicate poverty and reduce inequality, to make growth inclusive and production and consumption more sustainable, while combating climate change and respecting a range of other planetary boundaries." The concept was incorporated into the so-called "zero draft" of the outcome of the
United Nations Conference on Sustainable Development The United Nations Conference on Sustainable Development (UNCSD), also known as Rio 2012, Rio+20 (), or Earth Summit 2012 was the third international conference on sustainable development aimed at reconciling the economic and environmental goals ...
to be convened in Rio de Janeiro 20–22 June 2012. However, the use of the concept was subsequently withdrawn from the text of the conference, "partly due to concerns from some poorer countries that its adoption could lead to the sidelining of poverty reduction and economic development. It is also, say observers, because the idea is simply too new to be officially adopted, and needed to be challenged, weathered and chewed over to test its robustness before standing a chance of being internationally accepted at UN negotiations." In 2011, at their second meeting, the High-level Panel on Global Sustainability of the United Nations had incorporated the concept of planetary boundaries into their framework, stating that their goal was: "To eradicate poverty and reduce inequality, make growth inclusive, and production and consumption more sustainable while combating climate change and respecting the range of other planetary boundaries." Elsewhere in their proceedings, panel members have expressed reservations about the political effectiveness of using the concept of "planetary boundaries": "Planetary boundaries are still an evolving concept that should be used with caution [...] The planetary boundaries question can be divisive as it can be perceived as a tool of the "North" to tell the "South" not to follow the resource intensive and environmentally destructive development pathway that rich countries took themselves... This language is unacceptable to most of the developing countries as they fear that an emphasis on boundaries would place unacceptable brakes on poor countries." However, the concept is routinely used in the proceedings of the United Nations, and in the ''UN Daily News''. For example, the UNEP Executive Director Achim Steiner states that the challenge of agriculture is to "feed a growing global population without pushing humanity's Ecological footprint, footprint beyond planetary boundaries." The United Nations Environment Programme (UNEP) Yearbook 2010 also repeated Rockström's message, conceptually linking it with ecosystem management and Sustainable Governance Indicators, environmental governance indicators. In their 2012 report entitled "Resilient People, Resilient Planet: A future worth choosing", The High-level Panel on Global Sustainability called for bold global efforts, "including launching a major global scientific initiative, to strengthen the interface between science and policy. We must define, through science, what scientists refer to as "planetary boundaries", "environmental thresholds" and "tipping points"."


European Commission

The planetary boundaries concept is also used in proceedings by the European Commission, and was referred to in the European Environment Agency synthesis report ''The European environment – state and outlook 2010''.


See also

* Ecological footprint * Global catastrophic risk * Global change * Holocene extinction * Human impact on the nitrogen cycle * Human impacts on the environment * Planetary health * Planetary management *Sustainability


References


Sources

* * * * * * * * * * * * * * * * * * * * * * * * See also: Peak water. * * * * * * * * * * * The web page inverts the book title. * * * * * * * * *


External links


Figures and data
for the updated Planetary Boundaries can be found at the Stockholm Resilience Centre website.
Planetary Boundaries: Specials
''Nature (journal), Nature,'' 24 September 2009.
Johan Rockstrom: Let the environment guide our development
TED (conference), TED video, July 2010
Transcript html
* {{Portal bar, Environment, Ecology, Earth sciences, Biology Earth sciences Global environmental issues Globalization Sustainability Criticism of capitalism