Planetary boundaries

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.

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.

[1]The basic idea of the Planetary Boundaries framework is that maintaining the observed resilience of the Earth system in the Holocene is a precondition for humanity's pursuit of long-term social and economic development.

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".

[9] 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, toward the estimation of the safe space for human development.

[7] The authors of this framework was a group of Earth System and environmental scientists in 2009 led by Johan Rockström from the Stockholm Resilience Centre and Will Steffen from the Australian National University.

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.

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.

[16] Their evidence suggests that the increasing temperature stress and the declining ocean saturation state of aragonite is making it difficult for reef corals to deposit calcium carbonate.

[17] 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.

"[18][19] In 2012, Steven Running suggested a tenth boundary, the annual net global primary production of all terrestrial plants, as an easily determinable measure integrating many variables that will give "a clear signal about the health of ecosystems".

[25] According to the biologist Cristián 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.

[38][additional citation(s) needed] The stratospheric ozone layer protectively filters ultraviolet radiation (UV) from the Sun, which would otherwise damage biological systems.

[43] 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.

[46] 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.

[55] In 2008, Graham Turner from the Commonwealth Scientific and Industrial Research Organisation (CSIRO) published "A comparison of The Limits to Growth with thirty years of reality".

[56] The Limits to Growth has been widely discussed, both by critics of the modelling approach and its conclusions[57][58] 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.

In the 1970s, James Lovelock and microbiologist Lynn Margulis presented the idea that all organisms and their inorganic surroundings on Earth are integrated into a single self-regulating system.

[62] 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).

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.

[67] 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.

[76] Several studies have assessed environmental footprints of nations based on planetary boundaries: for Portugal,[80] Sweden,[81] Switzerland,[82] the Netherlands,[83] the European Union,[84] India,[85][86] many of Belt and Road Initiative countries [87] as well as for the world's most important economies.

[88][89] 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.

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.

[93] 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.

[95] 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.

For example, the United Nations Environment Programme (UNEP) Executive Director Achim Steiner states that the challenge of agriculture is to "feed a growing global population without pushing humanity's footprint beyond planetary boundaries.