Planetary boundaries are a framework to describe limits to the impacts of human activities on theEarth system. Beyond these limits, the environment may not be able to continue to self-regulate. This would mean the Earth system would leave the period of stability of theHolocene, in which human society developed.[2][3][4]
These nine boundaries areclimate change,ocean acidification, stratospheric ozone depletion, biogeochemical flows in thenitrogen cycle, excess globalfreshwater use,land system change, the erosion of biosphere integrity, chemical pollution, andatmospheric aerosol loading.
The framework is based on scientific evidence that human actions, especially those of industrialized societies since theIndustrial Revolution, 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."[2]
Thenormative component of the framework is thathuman societies have been able to thrive under the comparatively stable climatic and ecological conditions of theHolocene. To the extent that these Earth system process boundaries have not been crossed, they mark the "safe zone" for human societies on the planet.[3] Proponents of the planetary boundary framework propose returning to this environmental and climatic system; as opposed to human science and technology deliberately creating a more beneficial climate. The concept doesn't address how humans have massively altered ecological conditions to better suit themselves. The climatic and ecological Holocene this framework considers as a "safe zone" doesn't involve massive industrial farming. So this framework begs a reassessment of how to feed modern populations.
The concept has since become influential in the international community (e.g.United Nations Conference on Sustainable Development), including governments at all levels, international organizations, civil society and the scientific community.[5] The framework consists of nine global change processes. In 2009, according toRockström and others, three boundaries were already crossed (biodiversity loss, climate change and nitrogen cycle), while others were in imminent danger of being crossed.[6]
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).[7] The scientists also changed the name of the boundary "Loss of biodiversity" 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 the available literature, the introduction of novel entities was concluded to be the 5th transgressed planetary boundary.[8] Freshwater change was concluded to be the 6th transgressed planetary boundary in 2023[9] before ocean acidification was documented to be the 7th crossed limit in 2025[1].
The basic idea of the Planetary Boundaries framework is that maintaining the observed resilience of the Earth system in theHolocene is a precondition for humanity's pursuit of long-term social and economic development.[10] The Planetary Boundaries framework contributes to an understanding of globalsustainability because it brings a planetary scale and a long timeframe into focus.[7]
The framework described nine "planetary life support systems" essential for maintaining a "desiredHolocene state", and attempted to quantify how far seven of these systems had been pushed already.[6] Boundaries were defined to help define a "safe space for human development", which was an improvement on approaches aiming at minimizinghuman impacts on the planet.[10]
The framework is based on scientific evidence that human actions, especially those of industrialized societies since theIndustrial Revolution, 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, abruptenvironmental change within continental-scale to planetary-scale systems."[10] The framework consists of nine global change processes. In 2009, two boundaries were already crossed, while others were in imminent danger of being crossed.[6] Later estimates indicated that three of these boundaries—climate change,biodiversity 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.[10]
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 negativeexternalities, toward the estimation of the safe space for human development.[11] Planetary boundaries demarcate, as it were, the "planetary playing field" for humanity if majorhuman-induced environmental change on a global scale is to be avoided.[7]
The authors of this framework was a group ofEarth System andenvironmental scientists in 2009 led byJohan Rockström from theStockholm Resilience Centre andWill Steffen from theAustralian National University. They collaborated with 26 leading academics, includingNobel laureatePaul Crutzen,Goddard Institute for Space Studies climate scientistJames Hansen, oceanographerKatherine Richardson, geographerDiana Liverman and theGerman Chancellor's chief climate adviserHans Joachim Schellnhuber.
Most of the contributing scientists were involved in strategy-setting for theEarth System Science Partnership, the precursor to the international global change research networkFuture Earth. The group wanted to define a "safe operating space for humanity" for the wider scientific community, as a precondition forsustainable development.
The 2009 study identified nine planetary boundaries with quantifications for seven of them, eight of them are now being quantified in 2025. These are :
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 clearthresholds between comparatively stable conditions. For example, pastice-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 whatpast climate conditions were like with an atmosphere with over 350 ppm CO2, scientists need to look back about 3 million years. Thepaleo record of climatic, ecological and biogeochemical changes shows that the Earth system has experiencedtipping points, when a very small increment for a control variable (like CO2) triggers a larger, possibly catastrophic, change in the response variable (global warming) throughfeedbacks 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.[6] Examples include shifts inmonsoon behavior linked to theaerosol loading andfreshwater use planetary boundaries.
| Earth-system process | Control variable[1][9] | Boundary value in 2025 | "Current" value
| Boundary now exceeded beyond the 2025 values? (based on "current" value) | Preindustrial Holocene base value |
|---|---|---|---|---|---|
| 1. Climate Change | Atmospheric carbon dioxide concentration (ppm by volume)[12] See also:Tipping point (climatology) | 350 ppm | 423 ppm | yes | 280 |
| Total anthropogenicradiative forcing at top-of-atmosphere (W/m2) since the start of the industrial revolution (~1750) | +1 Wm-2 | +2.97 Wm-2 | yes | 0 | |
| 2. Change in Biosphere Integrity[9] | Genetic diversity: Extinction rate measured as E/MSY (extinctions per million species-years) | <10 E/MSY but with an aspirational goal of ca. 1 E/MSY (assumed background rate of extinction loss) | >100 E/MSY | yes | 1 E/MSY |
| Functional diversity: energy available to ecosystems (NPP[a 1]) (% HANPP[a 2]) | HANPP (in billion tonnes of C year−1) <10% of preindustrial Holocene NPP, i.e., >90% remaining for supporting biosphere function | 30% HANPP | yes | 1.9% (2σ variability of preindustrial Holocene century-mean NPP) | |
| 3. Land System Change | Part of forests rested intact (percent)[7] | 75 % from all forests including 85 % fromBoreal forest andTropical forests, 50 % fromTemperate forests | Global: 59% | yes | 0 |
| 4.Freshwater Change | Blue water: human induced disturbance of blue water flow | Upper limit (95th percentile) of global land area with deviations greater than during preindustrial, Blue water: 12.9% | 22.6% | yes | 9.4% |
| Green water: human induced disturbance of water available to plants (% land area with deviations from preindustrial variability) | 12.4% | 22.0% | yes | 9.8% | |
| 5. Modification of Biogeochemical Flows | Phosphate global: P flow from freshwater systems into the ocean; regional: P flow from fertilizers to erodible soils (Tg of P year−1) | Global: 11 Tg of P year−1;regional: 6.2 Tg of P year−1 mined and applied to erodible (agricultural) soils. | Global: 4.4 Tg of P year−1; regional: 18.2 Tg of P year−1 | yes | 0 |
| Nitrogen global: industrial and intentional fixation of N (Tg of N year−1) | 62 Tg year−1 | 165 Tg year-1 | yes | 0 | |
| 6. Ocean Acidification | Global mean saturation state ofcalcium carbonate in surface seawater (omega units) | 2.86 | 2.84 | yes | 3.44 |
| 7.Increase in Atmospheric Aerosol Loading | Interhemispheric difference in AOD (Aerosol Optical Depth) | 0.1 (mean annual interhemispheric difference) | 0.063 | no | 0.03 |
| 8.Stratospheric Ozone Depletion | Stratospheric ozone concentration (Dobson units) | 277 | 285.7 | no | 290 |
| 9.Introduction of Novel Entities | Percentage of synthetic chemicals released to the environment without adequate safety testing | 0 | >0 (transgressed) | yes | 0 |
| |||||
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. Theboundary is defined as the lower end of that range. If the boundaries are persistently crossed, the world goes further into a danger zone.[6]
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.[10][13] Legal boundaries can help keep human activities in check, but are only as effective as the political will to make and enforce them.[14]
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 the planetary boundaries framework.[7][3] 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.[3] They give the example that theland use 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 ifdeforestation continues in theAmazon. 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."[3]
Another example has to do withcoral reefs andmarine ecosystems: In 2009, researchers showed that, since 1990, calcification in the reefs of theGreat Barrier that they examined decreased at a rate unprecedented over the last 400 years (14% in less than 20 years).[15] Their evidence suggests that the increasing temperature stress and the declining ocean saturation state ofaragonite is making it difficult for reef corals to deposit calcium carbonate. Multiple stressors, such as increased nutrient loads andfishing pressure, moves corals into less desirable ecosystem states.[16] 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, surfaceUV radiation levels and ocean acidity all stress marinebiota, 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."[17][18]
In 2012,Steven Running suggested a tenth boundary, the annual net globalprimary production of allterrestrial plants, as an easily determinable measure integrating many variables that will give "a clear signal about the health of ecosystems".[19][20][21]
In 2015, a second paper was published inScience to update the Planetary Boundaries concept.[7] 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 andloss of biodiversity 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.[22]
In 2017, some authors argued that marine systems are underrepresented in the framework. Their proposed remedy was to include theseabed as a component of the earth surface change boundary. They also wrote that the framework should account for "changes in vertical mixing andocean circulation patterns".[22]
Subsequent work on planetary boundaries begins to relate these thresholds at the regional scale.[23]
A 2018 study calls into question the adequacy of efforts to limit warming to 2 °C above pre-industrial temperatures, as set out in theParis Agreement.[23] The scientists raise the possibility that even ifgreenhouse gas emissions aresubstantially reduced to limit warming to 2 °C, that might exceed the "threshold" at which self-reinforcingclimate feedbacks add additional warming until theclimate system stabilizes in ahothouse climate state. This would make parts of the world uninhabitable for people, raise sea levels by up to 60 metres (200 feet), and raise temperatures by 4–5 °C (7.2–9.0 °F) to levels that are higher than anyinterglacial period in the past 1.2 million years.[24]
According to the biologistCristián Samper, 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."[25] 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.[22]
The biogeochemistWilliam Schlesinger 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.[26]
Theocean 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."[27]
Peak phosphorus is a concept to describe the point in time at which the maximum globalphosphorus 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.[28] 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.[29][30] However, recent evidence shows that if phosphorus applications to soil are matched to the agronomic optimum for crop yield, it would take >500 years to exhaust currently econimically viable phosphorus reserves.[31]
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.[32]
The ocean chemist Peter Brewer thinks "ocean acidification has impacts other than simple changes in pH, and these may need boundaries too."[27]
Across the planet, forests, wetlands and other vegetation types are being converted to agricultural and otherland uses, impacting freshwater, carbon and other cycles, and reducing biodiversity.[32] In the year 2015 the boundary was defined as 75% offorests rested intact, including 85% ofboreal forests, 50% oftemperate forests and 85% oftropical forests. The boundary is crossed because only 62% of forests rested intact as of the year 2015.[7]
The boundary for land use has been criticized as follows: "The boundary of 15 per centland-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 onsoil degradation or soil loss. This would be a more valid and useful indicator of the state of terrestrial health."[33]
Thefreshwater cycle is another boundary significantly affected by climate change.[32]Overexploitation of freshwater occurs if a water resource is mined or extracted at a rate that exceeds the recharge rate.Water pollution andsaltwater intrusion can also turn much of the world's underground water and lakes into finite resources with "peak water" usage debates similar tooil.[34][35]
The hydrologist David Molden stated in 2009 that planetary boundaries are a welcome new approach in the "limits to growth" 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."[36]
A study concludes that the 'Freshwater use' boundary should be renamed to the 'Freshwater change', composed of "green" and "blue" water components.[37] 'Green water' refers to disturbances of terrestrial precipitation, evaporation and soil moisture.[37]Water scarcity can have substantial effects in agriculture.[38][39] When measuring and projecting water scarcity inagriculturefor climate change scenarios, both "green water" and "blue water" are of relevance.[38][39]
In April 2022, scientists proposed and preliminarily evaluated 'green water' in thewater cycle as a likely transgressed planetary boundary, asmeasured by root-zone soil moisture deviation from Holocene variability.[37][40]
The stratosphericozone layer protectively filtersultraviolet radiation (UV) from theSun, which would otherwise damage biological systems. The actions taken after theMontreal Protocol appeared to be keeping the planet within a safe boundary.[32]
The Nobel laureate in chemistryMario Molina says "five per cent is a reasonable limit for acceptable ozone depletion, but it doesn't represent a tipping point".[41]
Worldwide each year,aerosol particles result in about 800,000 premature deaths fromair pollution.[42] 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.[32]
Some chemicals, such aspersistent organic pollutants,heavy metals andradionuclides, have potentially irreversibleadditive and synergic effects on biological organisms, reducing fertility and resulting in permanentgenetic damage. Sublethal uptakes are drastically reducing marine bird and mammal populations. This boundary seems important, although it is hard to quantify.[32][8][43] In 2019, it was suggested that novel entities could includegenetically modified organisms,pesticides and evenartificial intelligence.[5]
A Bayesian emulator for persistent organic pollutants has been developed which can potentially be used to quantify the boundaries for chemical pollution.[44] 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.[45]
There are at least 350,000 artificial chemicals in the world. They are coming from "plastics,pesticides,industrial chemicals, chemicals in consumer products,antibiotics and otherpharmaceuticals". They have mostly "negative effects onplanetary health". Their production increased 50 times since 1950 and is expected to increase 3 times more by 2050. Plastics alone contain more than 10,000 chemicals and create large problems. The researchers are calling for limit on chemical production and shift tocircular economy, meaning to products that can bereused andrecycled.[46]
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.[47] They integrated the literature information on how production and release of a number of novel entities, includingplastics andhazardous chemicals, have rapidly increased in the last decades with significant impact on the planetary processes.[8]
In August 2022, scientists concluded that the (overall transgressed) boundary is a placeholder for multiple different boundaries for NEs that may emerge, reporting thatPFAS pollution is one such new boundary. They show that levels of these so-called "forever chemicals" inrainwater are ubiquitously, and often greatly, above guideline safe levels worldwide.[48][49] There are some moves to restrict and replace their use.[48]
In 2024 a report byPlanet Tracker, dedicated to this planetary boundary stipulated thatThe Chemical Abstracts Service (CAS) registered more than 204,000,000 chemicals since the 19 century. From them, over 350,000 chemicals are allowed for production and use in North America and Europe and from those 350,000, most are untested and 14% are unknown because companies does not disclose their composition. Their negative impacts on health is more than a tenth of the global GDP and they can impact more than 1 planetary boundary:Chlorofluorocarbons, for example, can impact 3 at the same time.[50]
Planetary integrity is also calledearth's life-support systems orecological integrity.[51]: 140 Scholars have pointed out that planetary integrity "needs to be maintained for long-termsustainability".[51]: 140 The termintegrity refers toecological health in this context.[52] The concept of planetary integrity is interlinked within the concept of planetary boundaries.[53]
AnExpert Panel on Ecological Integrity in 1998 has definedecological integrity as follows: "Ecosystems have integrity when they have their native components (plants, animals and other organisms) and processes (such as growth and reproduction) intact."[54]
There are many negativehuman impacts on the environment that are causing a reduction in planetary integrity.[51]: 142 For example, the currentbiodiversity loss is threatening ecological integrity on a global scale.[51]: 140 TheSustainable Development Goals might be able to act as a steering mechanism to address the current loss of planetary integrity.[51]: 142
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, that presented a model in whichexponential growth inworld population,industrialization,pollution, food production, andresources depletion outstrip the ability of technology to increase resources availability.[55] Subsequently, the report was widely dismissed, particularly by economists and business people,[56] and it has often been claimed that history has proved the projections to be incorrect.[57] In 2008, Graham Turner from theCommonwealth Scientific and Industrial Research Organisation (CSIRO) published "A comparison ofThe Limits to Growth with thirty years of reality".[58]The Limits to Growth has been widely discussed, both by critics of the modelling approach and its conclusions[59][60] 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.[61][62] TheLimits 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.[7]
Our Common Future was published in 1987 by United Nations'World Commission on Environment and Development.[63] It tried to recapture the spirit of theStockholm Conference. Its aim was to interlock the concepts of development and environment for future political discussions. It introduced the famous definition forsustainable development: "Development that meets the needs of the present without compromising the ability of future generations to meet their own needs."[63]
Another key idea influencing the Planetary Boundaries framework is theGaia theory or hypothesis. In the 1970s,James Lovelock andmicrobiologistLynn Margulis presented the idea that allorganisms and theirinorganic surroundings on Earth are integrated into a single self-regulating system.[64] 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). 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.[7] In Lovelock's bookThe Revenge of Gaia, he suggests that the destruction of rainforests and biodiversity, compounded withglobal warming resulting from the increase ofgreenhouse gases made by humans, could shift feedbacks in the Earth system away from a self-regulating balance to a positive (intensifying) feedback loop.
From theStockholm MemorandumScience indicates that we are transgressing planetary boundaries that have kept civilization safe for the past 10,000 years. Evidence is growing that human pressures are starting to overwhelm the Earth's buffering capacity. Humans are now the most significant driver ofglobal change, propelling the planet into a new geological epoch, theAnthropocene. We can no longer exclude the possibility that our collective actions will trigger tipping points, risking abrupt and irreversible consequences for human communities and ecological systems.
Scientists have affirmed that the planet has entered a new epoch, theAnthropocene.[65] In the Anthropocene, humans have become the main agents of not only change to the Earth System[66] but also the driver of Earth Systemrupture,[67] disruption of the Earth System's ability to be resilient and recover from that change, potentially ultimately threateningplanetary habitability. The previous geological epoch, theHolocene began about 10,000 years ago. It is the currentinterglacial 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.[68] This stability has allowed societies to thrive worldwide, developing agriculture, large-scale settlements and complex networks of trade.[69]
According to Rockströmet 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."[10]
Variousbiophysical processes that are important in maintaining theresilience of the Earth system are also undergoing large and rapid change because of human actions.[70] For example, since the advent of the Anthropocene, the rate at which species are going extinct has increased over 100 times,[71] and humans are now the driving force altering global river flows[72] as well as water vapor flows from the land surface.[73] 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 irreversibleenvironmental change responses by the Earth system withincontinental- to planetary-scale systems.[7]
In summary, the planetary boundary concept is a very important one, and its proposal should now be followed by discussions of the connections between the various boundaries and of their association with other concepts such as the 'limits to growth'. Importantly, this novel concept highlights the risk of reaching thresholds or tipping points for non-linear or abrupt changes in Earth-system processes. As such, it can help society to reach the agreements required for dealing effectively with existing global environmental threats, such as climate change.
The 2009 report[3] was presented to the General Assembly of theClub of Rome in Amsterdam.[74] An edited summary of the report was published as the featured article in a special 2009 edition ofNature[2] alongside invited critical commentary from leading academics like Nobel laureateMario J. Molina and biologistCristián Samper.[41]
Development studies scholars have been critical of aspects of the framework and constraints that its adoption could place on theGlobal 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 benefited 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.[22]
The biogeochemistWilliam Schlesinger 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."[26]
In a global empirical study, researchers investigated how students of environmental and sustainability studies in 35 countries assessed the planetary boundaries. It was found that there are substantial global differences in the perception of planetary boundaries.[75]
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Several studies have assessed environmental footprints of nations based on planetary boundaries: for Portugal,[79] Sweden,[80] Switzerland,[81] the Netherlands,[82] the European Union,[83] India,[84][85] many of Belt and Road Initiative countries[86] as well as for the world's most important economies.[87][88] 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.
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) and stratospheric ozone depletion.[89]
Approaches based on a general framework of ecological limits include (transferable)personal carbon allowances and "legislated" national greenhouse gas emissions limits.[90] Consumers would have freedom in their (informed) choice within (the collective) boundaries.[91]
The United Nations secretary generalBan 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 informalplenary of the UN General Assembly.[92] 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."[93] The concept was incorporated into the so-called "zero draft" of the outcome of theUnited Nations Conference on Sustainable Development to be convened in Rio de Janeiro 20–22 June 2012.[94] 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."[95]
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."[96]
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."[97]
However, the concept is routinely used in the proceedings of the United Nations,[98] and in theUN Daily News. For example, theUnited Nations Environment Programme (UNEP) Executive DirectorAchim Steiner states that the challenge of agriculture is to "feed a growing global population without pushing humanity'sfootprint beyond planetary boundaries."[99] The UNEP Yearbook 2010 also repeated Rockström's message, conceptually linking it withecosystem management andenvironmental governance indicators.[100]
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"".[101]
The planetary boundaries concept is also used in proceedings by theEuropean Commission,[102][103] and was referred to in theEuropean Environment Agency synthesis reportThe European environment – state and outlook 2010.[104]
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