Planetary Boundaries

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= a specific point related to a global-scale environmental process beyond which humanity should not go; nine processes and systems regulate the stability and resilience of the earth system

URL = http://www.ecologyandsociety.org/vol14/iss2/art32 graphic


Definition

1. Scripps:

"The planetary boundaries concept, first published in 2009, identifies nine global priorities relating to human-induced changes to the environment. The science shows that these nine processes and systems regulate the stability and resilience of the earth system – the interactions of land, ocean, atmosphere and life that together provide conditions upon which our societies depend."


2. Rupert Medd:

"The SRC [Stockholm Resilience Centre] explain that the “planetary boundaries concept presents a set of nine planetary boundaries within which humanity can continue to develop and thrive for generations to come. The planetary boundaries approach is not intended as a replacement for ecosystem management approaches but a complement that takes Earth system considerations into consideration.”3 Unified, the boundaries form a synthesis of the intrinsic biophysical processes that regulate the stability of Earth. In turn, this acknowledges that Earth is a single complex and integrated system, functioning through interdependencies. Importantly, it is equally a measure of ecosystem health throughout these biophysical boundaries. Those that are now moving into the yellow are zones of “uncertainty,” whilst those already in the red have transgressed “safe operating spaces” where a stable planetary ecosystem can no longer be sustained. In January 2015, an update was published in Science revealing that an additional boundary had been breached ‒ Land-System Change, consequently leaving four out of nine borders crossed. So, Land-System Change (deforestation/agriculture/ damming); Biosphere Integrity (biodiversity losses and extinctions); and Biogeochemical Flows (industrial and agricultural processes/fertiliser usage) are all today at high-risk levels, and adding to the equally critical and accumulative effects of the Climate Change boundary. The latter is the top as it is connected to all other boundaries and operates at the level of the whole Earth system."

(https://www.alasdairlord.co.uk/downloads/first_chapter.pdf)


Typology

Nine planetary boundaries:

  1. Climate change
  2. Change in biosphere integrity (biodiversity loss and species extinction)
  3. Stratospheric ozone depletion
  4. Ocean acidification
  5. Biogeochemical flows (phosphorus and nitrogen cycles)
  6. Land-system change (for example deforestation)
  7. Freshwater use
  8. Atmospheric aerosol loading (microscopic particles in the atmosphere that affect climate and living organisms)
  9. Introduction of novel entities (e.g. organic pollutants, radioactive materials, nanomaterials, and micro-plastics)."

(https://scripps.ucsd.edu/news/earth-has-crossed-several-planetary-boundaries-thresholds-human-induced-environmental-changes)


Description

0. John Rockstrom

"Building on decades of advancements in Earth system science, the planetary boundary (PB) approach offers a framework for keeping world development within a safe operating space. PB analysis relies on the latest research to define tolerance levels of environmental processes that regulate the stability of the Earth system.

The framework emerges from three fundamental insights. First, the advent of the Anthropocene places humanity “in the planetary driver’s seat” for determining the future state of the Earth. Second, human activity has brought the Earth system—a complex, self-regulating biogeophysical system with mutual interactions among the cryosphere, atmosphere, hydrosphere, biosphere, and stratosphere—to tipping points, where both subsystems (e.g., the Greenland ice sheet) and the whole planet can shift states in irreversible and abrupt ways. Third, the Holocene, the interglacial epoch of the past 10,700 years, is the only known state of the planet that can support the world as we know it.


...


PB theory combines scientific knowledge of Earth-system functioning, an appreciation of the virtues of the Holocene, and an understanding of Earth’s capacity for resilience along with its potential tipping points. This perspective takes into account the existence of multiple stable states and focuses on how interactions and feedbacks can cross critical thresholds, inducing a shift in the state of the system itself.10 The PB approach asks two overarching questions: What are the processes and subsystems that keep Earth in a Holocene-like state, and what levels of human pressure on each of these could reach a threshold, thereby disrupting the continuity of the Earth system?

To implement this analytic program, “control variables” identify the state of each PB process/system. Needless to say, establishing the critical point at which a threshold is crossed poses a difficult challenge, given scientific uncertainty and the inherently complex interactions between boundaries. Consequently, each control variable is associated not with a sharp boundary, but with a scientifically determined zone of uncertainty. The PB is then placed at the lower end of this range, a procedure consistent with the precautionary principle. In this fashion, each PB signifies a level below which the probability of crossing a threshold is low. Above the boundary, we enter a danger zone characterized by increasing risk of crossing thresholds. Finally, if the high-risk zone at the upper end of the uncertainty range were to be reached, irreversible systemic change would be likely to take place.

The boundary levels delineate a safe operating space in which humanity can operate while preserving the continuity and resilience of the Earth system. Figure 3 displays the 2015 PB update: the green inner circle represents this safe operating space; the yellow zone, the zone of uncertainty with heightened danger of crossing thresholds; and the red areas, the zone of high risk of triggering severe dangerous imbalances." (https://greattransition.org/publication/bounding-the-planetary-future-why-we-need-a-great-transition?)


1. Will Steffen, Robert Constanza et al.:

"How do we begin to identify what aspects of our planet need boundaries and what those boundaries are? The concept of planetary boundaries, while building on earlier efforts, takes a rather different approach. It does not focus so directly on the human enterprise, as do most of these earlier approaches, but rather emphasizes the Earth as a complex system. Here we identify nine areas that are most in need of set planetary boundaries: climate change; biodiversity loss; excess nitrogen and phosphorus production, which pollutes our soils and waters; stratospheric ozone depletion; ocean acidification; global consumption of freshwater; change in land use for agriculture; air pollution; and chemical pollution.

What do we mean by “boundary”? This refers to a specific point related to a global-scale environmental process beyond which humanity should not go. The position of the boundary is a normative judgment, informed by science but largely based on human perceptions of risk. This doesn’t mean that any change in the Earth system is dangerous. Our planet can undergo abrupt changes naturally. An example is the sudden switch in North Atlantic ocean circulation when a critical level of freshwater input is reached. But these thresholds and abrupt changes are intrinsic features of the Earth system and cannot be eliminated or modified by human actions, such as the development of new technologies. We have to learn to live with thresholds and respect them. An abrupt change is a hardwired feature of the Earth system independent of human existence, while violation of a boundary is a subjective judgment by humanity about how close we wish to approach dangerous or potentially catastrophic thresholds in our own life-support system." (http://www.stwr.org/climate-change-environment/how-defining-planetary-boundaries-can-transform-our-approach-to-growth.html)

Source: "This article is based on the papers “A safe operating space for humanity,” published in Nature, and “Planetary boundaries: Exploring the safe operating space for humanity,” [1] published in Ecology and Society. See these papers for a complete description of the planetary boundaries."


2. From the Wikipedia:

"Planetary boundaries is the central concept in an Earth system framework proposed by a group of Earth system and environmental scientists led by Johan Rockström from the Stockholm Resilience Centre and Will Steffen from the Australian National University. In 2009, the group proposed a framework of “planetary boundaries” designed to define a “safe operating space for humanity” for the international community, including governments at all levels, international organizations, civil society, the scientific community and the private sector, as a precondition for sustainable development. This framework is based on scientific research that indicates that since the Industrial Revolution, human actions have gradually become the main driver of global environmental change. The scientists assert that once human activity has passed certain thresholds or tipping points, defined as “planetary boundaries”, there is a risk of “irreversible and abrupt environmental change”.[3] The scientists identified nine Earth system processes which have boundaries that, to the extent that they are not crossed, mark the safe zone for the planet. However, because of human activities some of these dangerous boundaries have already been crossed, while others are in imminent danger of being crossed.

Rockström and Steffen collaborated with 26 leading academics, including Nobel laureate Paul Crutzen, Goddard Institute for Space Studies climate scientist James Hansen and the German Chancellor's chief climate adviser Hans Joachim Schellnhuber. The group identified nine "planetary life support systems" essential for human survival, and attempted to quantify just how far seven of these systems have been pushed already. They then estimated how much further we can go before our own survival is threatened; beyond these boundaries there is a risk of "irreversible and abrupt environmental change" which could make Earth less habitable. Estimates indicate that three of these boundaries—climate change, biodiversity loss, and the biogeochemical flow boundary—appears to have been crossed. The boundaries are "rough, first estimates only, surrounded by large uncertainties and knowledge gaps" that interact in ways that are complex and not well understood. Boundaries can help identify where there is room and define a "safe space for human development", which is an improvement on approaches which aim at just minimizing human impacts on the planet.

The group published their full findings in a 2009 report[1] and presented it to the General Assembly of the Club of Rome in Amsterdam.[5] An edited summary of the report was subsequently published as the featured article in a special edition of Nature.[6] Nature also published critical commentary from leading academics they invited to comment on each of the seven planetary boundaries which had been quantified, including comments from Nobel laureate Mario J. Molina and biologist Cristián Samper." (https://en.wikipedia.org/wiki/Planetary_boundaries)


Examples

Climate change, biodiversity loss, and phosphorus and nitrogen production are just three areas in which boundaries can be determined and measured, and we will use these as examples.

Human-provoked climate change is no longer disputed. Scientists can measure climate change by studying the levels of CO2 in our atmosphere. Our proposed climate boundary is that human changes to atmospheric CO2 should not drive its concentration beyond 350 parts per million by volume, and that radiative forcing—the change in the energy balance at the Earth’s surface—should not exceed 1 watt per square meter above preindustrial levels. Transgressing these boundaries could lead to the melting of ice sheets, rising sea level, abrupt shifts in forest and agricultural land, and increasing intensity and frequency of extreme events like floods, wildfires, and heat waves.

A second example is biodiversity loss, which does occur naturally and would continue to some degree without human interference. However, the rate of animal extinction has skyrocketed in the postindustrial age. Compared with fossil records, today the rate of extinction per species is 100–1,000 times more than what could be considered natural. Human activities are to blame: urban and agricultural development, sprawl, increases in wildfires that destroy habitat, introduction of new species into environments, and the exploitation of land for human consumption—such as the destruction of the rainforests. We believe another 30 percent of wildlife will come under the threat of extinction this century if change is not made. The dangers of biodiversity loss go beyond nostalgia for certain animals: entire ecosystems rely on certain threatened species.

Setting a planetary boundary for biodiversity is difficult because there is so little known about the way in which species are interwoven and how they connect to the broader environment. However, we propose beginning by using the extinction rate as a flawed but acceptable indicator. Our suggested planetary boundary is that of ten times the background rate of extinction. More research may change this boundary.

In our third example, we propose that no more than 11 million tonnes of phosphorous should be allowed to flow into the ocean each year—which is ten times the natural background state. Excessive production of phosphorus, along with nitrogen, is a by-product of our agricultural system. Excessive phosphorous and nitrogen production pollutes waterways and coastal areas and adds harmful gases to the atmosphere. Current levels already exceed critical thresholds for many estuaries and freshwater sites, and so further research may reduce the current phosphorus and nitrogen boundaries.

We propose that a boundary be set for each of the nine areas and that it be respected globally, in order for humans to continue along a healthy, productive path for an indefinite amount of time. It is important to acknowledge that we don’t know precisely where the threshold might lie along the control variable (i.e., a variable—sometimes a human intervention—that can influence whether or not a threshold is crossed) or how much change in a slow process will undermine resilience at larger scales. Thus, we need to define a zone within which we are reasonably sure the threshold lies or beyond which we are reasonably sure that a significant degree of resilience will be lost.

Staying within the “planetary playing field” does not assure that humanity will thrive, or even survive, but straying outside the playing field will make it very difficult for humanity to thrive under any circumstances. Implementing the concept of planetary boundaries presents huge challenges for global governance and institutions."

(http://www.stwr.org/climate-change-environment/how-defining-planetary-boundaries-can-transform-our-approach-to-growth.html)


Status

1. Scripps media:

"Four of nine planetary boundaries have now been crossed as a result of human activity, says an international team of 18 researchers that includes Scripps Institution of Oceanography at UC San Diego Distinguished Climate and Atmospheric Scientist Veerabhadran Ramanathan.

The team reports in the Jan. 16 issue of the journal Science that in the planetary boundary categories of climate change, biosphere integrity, land-system change, and altered biogeochemical cycles, thresholds have been crossed that fundamentally change the functions of nature.

The scientists say that two of these, climate change and biosphere integrity, are “core boundaries.” Significantly altering either of these “core boundaries” would “drive the earth system into a new state.”

“This is one of the first attempts to undertake an integrated assessment of all the major environmental threats to sustainability of humanity and the ecosystem,” said Ramanathan. “The implications are sobering.”

Lead author Will Steffen from the Stockholm Resilience Centre at Stockholm University and the Australian National University, Canberra, said: “Transgressing a boundary increases the risk that human activities could inadvertently drive the earth system into a much less hospitable state, damaging efforts to reduce poverty and leading to a deterioration of human well-being in many parts of the world, including wealthy countries. In this new analysis, we have improved our quantification of where these risks lie.” (https://scripps.ucsd.edu/news/earth-has-crossed-several-planetary-boundaries-thresholds-human-induced-environmental-changes)


2. John Rocktrom:

  • PB Assessment and Advances

The first PB analysis was published in 2009 after a two-year research and consultation exchange among global change scientists.12 They focused on nine planetary boundary processes and systems for sustaining a Holocene-like state of the planet. Quantitative boundaries were proposed for seven of them, with three having relatively robust scientific support (climate change, stratospheric ozone depletion, and ocean acidification) and four carrying large uncertainties (land use change, freshwater use, rate of loss of biodiversity, and interference with nitrogen and phosphorous cycles). For the other two (aerosol loading and chemical pollution), limited information did not permit the determination of quantified boundaries. The analysis further suggested that humanity had transgressed three of the nine planetary boundaries: biodiversity loss, climate change, and nitrogen loading.

The initial effort met a major goal: to stimulate further research for refining criteria for safeguarding a stable Earth system. A wave of scientific discussion ensued, spurring engagement among researchers, civil society, policymakers, and the business community, and shaping the global change research agenda. More than five years on, more than thirty scientific articles have been published with “planetary boundaries” in the title, with the original paper garnering more than 1,000 citations.13 Encouraged by this response and mindful of advancements in Earth system science, a new round of PB research was conducted, with the update published in January 2015.14

In the latest findings, the original nine PBs remain germane. At the same time, the revised analysis includes several improvements. Chemical pollution has been renamed “introduction of novel entities” to include the release of radioactive materials and nanomaterials. The biodiversity boundary (referred to now as “biosphere integrity”) now has two dimensions: genetic diversity (as before) and functional diversity (using the “biosphere intactness index,” a measure of species abundance). The land use change boundary now considers minima for rainforests, temperate forests, and boreal forest cover, instead of the original proxy of maximum cropland. The nitrogen boundary has been extended to include human-induced reactive nitrogen from modern cultivation. The phosphorous boundary now has two definitions: one for oceans (the original boundary), the other for freshwater systems. Finally, the uncertainty range for the climate change boundary has been narrowed to 350 to 450 ppm CO2 (from 350 to 550 ppm CO2).15 The new analysis, furthermore, treats climate change and biosphere integrity as “core boundaries,” high-order manifestations of how breaching the other boundaries by can disrupt the Earth system.


  • Four Boundaries Transgressed

With these refined metrics, the analysis concludes that four out of nine boundaries have been transgressed (Figure 3). Two are in the high risk zone (biosphere integrity and interference with the nitrogen and phosphorous cycles), while the other two are in the danger zone (climate change and land use change)."

(https://greattransition.org/publication/bounding-the-planetary-future-why-we-need-a-great-transition?)


Policy

John Rockstrom's Two-Track Approach

John Rockstrom:

"The vision here posits a two-track approach. The fast track would operate within the current obsolete development paradigm through a series of global policy measures to nudge our dangerous trajectory away from the most immediate risks. This alone, however, will not suffice. The longer track of a Great Transition will entail a profound mind shift toward universal values that reconnect world development with a resilient Earth, recognize the right of all to development, and promote a shift from materialistic lifestyles to the pursuit of well-being and fulfillment.

Three critical transformations lie on the fast track pathway: decarbonizing the world economy by 2050 to 2070, feeding the world through sustainable agriculture by 2050, and improving resource-use efficiency and accelerating progress toward an economy of cyclic material flows. Increasing evidence indicates that these transformations are possible, even with current know-how and technologies. The world is already adopting a PB framework with regard to decarbonization with the recognition of a maximum planetary limit for warming of 2 ºC (3.6 ºF), although this is higher than the planetary boundary of 1.5 ºC (2.7 ºF).

The IPCC has determined that humanity must remain within a remaining global carbon budget of 1,000 Gt CO2 equivalents from 2011 in order to have a good chance of holding global warming under 2 ºC. Such a carbon budget gives us only twenty-five to thirty years more in the current fossil fuel-based world economy. Still, decarbonizing the world by the second half of this century is not only possible (through a wide strategy of energy efficiencies and applying multiple wedges of renewable energy options), but also compatible with economic development. Renewable sources like solar and wind are already competitive (without subsidies) in many economies, and they can and will generate new markets, innovations, and jobs.

Agricultural practices are implicated in almost all planetary boundaries, as agriculture is the largest single emitter of greenhouse gases, the largest single user of freshwater, a major trigger of biodiversity loss, and the main cause of nutrient loading and chemical use. A transformation to sustainable and resilient food systems that integrate water, land, and ecosystems in ways that guarantee the right of all to sufficient, safe, and nutritious food is both necessary and increasingly possible. Sustainable intensification—combining technologies, system improvements, and integrated land-water-nutrient management—can go a long way toward closing the yield gaps between current levels and those possible through ecological farming.

The “fast track” measures, aiming at bending the global curves of negative environmental change through immediate action, are essential but will not be enough. Recent analyses indicate that even a Great Transition in values and lifestyles, combined with resource efficiencies and technological improvements, will barely succeed in keeping world development within a safe operating space. This underscores the critical issue: how to promote wide adoption of universal values and stimulate a broad wave of civil mobilization in support of a new logic of development that pursues human prosperity within a stable planetary space. Such a movement would play a catalytic role in driving change in public awareness and societal institutions." (https://greattransition.org/publication/bounding-the-planetary-future-why-we-need-a-great-transition?)


Discussion

Critical Features of the Planetary Boundaries Concept

Will Steffen, Johan Rockström and Robert Costanza:

"Several features of the planetary boundaries conceptual framework are critical to understanding how the approach works.

First, planetary boundaries are explicitly designed for the global scale and are aimed at keeping the Earth within safe ranges that existed prior to the Industrial Revolution. Although some Earth-system processes, such as ocean acidification, are intrinsically global in scale, others become global only when they aggregate from much smaller scales.

In no way does this mean that local or regional environmental issues, which have largely been the focus of policy and management for decades, have become less important. Efforts to reduce pollution and limit and reverse ecosystem degradation at local and regional scales continue to be very important and in fact have become even more important because of their larger-scale implications. However, we must now also focus on the global scale explicitly—in addition to and not at the expense of the many environmental issues we still need to solve at smaller scales. A global solution to the sustainability challenge is thus a prerequisite for living sustainably at local and regional scales.

Second, there is much interaction among the planet’s features that lies at the heart of the planetary boundaries approach. This is not at all surprising given that the Earth behaves as a single, complex system at the global scale, but it does complicate the formulation and implementation of planetary boundaries. There are cascading impacts, in which transgressing one boundary can have implications for other boundaries. For example, converting the Amazon rainforest to a grassland or savanna could influence atmospheric circulation globally and ultimately affect water resources in East Asia through changes in rainfall.

Even small changes can have a synergistic effect when linked to other small changes. For example, conversion of forest to cropland, increased use of nitrogen and phosphorus fertilizers, and increased extraction of freshwater for irrigation could all act together to reduce biodiversity more than if each of these variables acted independently. Many changes feed back into each other. The processes involving ocean acidity and atmospheric CO2 concentration are an example of a reinforcing feedback loop. An increase in ocean acidity reduces the strength of the “biological pump” that removes carbon from the atmosphere, which in turn increases the atmospheric CO2 concentration, which increases the physical uptake of CO2 by the ocean, which further increases acidity, and so on.

Finally, the planetary boundaries approach doesn’t say anything explicit about resource use, affluence, or human population size. These are part of the trade-offs that allow humanity to continue to pursue increased well-being. The boundaries simply define the regions of global environment space that, if human activities push the Earth system into that space, would lead to unacceptably deleterious consequences for humanity as a whole.

Because the planetary boundaries approach says nothing about the distribution of affluence and technologies among the human population, a “fortress world,” in which there are huge differences in the distribution of wealth, and a much more egalitarian world, with more equitable socioeconomic systems, could equally well satisfy the boundary conditions. These two socioeconomic states, however, would deliver vastly different outcomes for human well-being. Thus, remaining within the planetary boundaries is a necessary—but not sufficient—condition for a bright future for humanity."

(http://www.stwr.org/climate-change-environment/how-defining-planetary-boundaries-can-transform-our-approach-to-growth.html)


History

Seth D. Baum and Itsuki C. Handoh:

"The PBs paradigm comes from the intellectual tradition of

  • Earth system science (Steffen et al., 2004). Likewise, PBs also follows in the tradition of research such as
  • limits to growth (Meadows et al., 1972),
  • ecological resilience theory (Holling, 1973),
  • ecological footprints (Wackernagel and Rees, 1996),
  • tolerable windows (Petschel-Held et al., 1999), and
  • Earth system tipping points (Lenton et al., 2008).


PBs emphasizes the importance of stable Holocene conditions to the success of human civilization, a theme developed by archeologists and others (Gupta, 2004, Richerson et al., 2001), as well as the related concept of the Anthropocene (Steffen et al., 2007). The PBs perspective highlights certain stressors that could tip the Earth system away from its stable Holocene state and into a new, dangerous state, with “unacceptable” consequences to humanity (Rockström et al., 2009a, 3). PBs also brings a holistic, systemic epistemology that is valuable for characterizing global environmental systems. A shortcoming of PBs is that it often says little about the impacts to humanity of crossing environmental boundaries."

(https://www.sciencedirect.com/science/article/abs/pii/S0921800914002262)


More Information

Bibliography

The original paper:


Latest full update of the framework:


Updated findings:

  • Persson, L. et al. 2022. Outside the safe operating space of the planetary boundary for novel entities. Environmental Science & Technology 56(3): 1510-1521. https://doi.org/10.1021/acs.est.1c04158
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