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Planetary Boundaries: Exploring the Safe Operating Space for Humanity

Johan Rockström, Stockholm Resilience Centre, Stockholm University; Stockholm Environment Institute
Will Steffen, Stockholm Resilience Centre, Stockholm University; Australian National University, Australia
Kevin Noone, Stockholm Resilience Centre, Stockholm University; Department of Applied Environmental Science, Stockholm University
Åsa Persson, Stockholm Resilience Centre, Stockholm University; Stockholm Environment Institute
F. Stuart III Chapin, Institute of Arctic Biology, University of Alaska Fairbanks
Eric Lambin, Department of Geography, University of Louvain
Timothy M Lenton, School of Environmental Sciences, University of East Anglia
Marten Scheffer, Aquatic Ecology and Water Quality Management Group, Wageningen University
Carl Folke, Stockholm Resilience Centre, Stockholm University; The Beijer Institute of Ecological Economics, Royal Swedish Academy of Sciences
Hans Joachim Schellnhuber, Potsdam Institute for Climate Impact Research; Environmental Change Institute and Tyndall Centre, Oxford University
Björn Nykvist, Stockholm Resilience Centre, Stockholm University; Stockholm Environment Institute
Cynthia A de Wit, Department of Applied Environmental Science, Stockholm University
Terry Hughes, ARC Centre of Excellence for Coral Reef Studies, James Cook University
Sander van der Leeuw, School of Human Evolution and Social Change, Arizona State University
Henning Rodhe, Department of Meteorology, Stockholm University
Sverker Sörlin, Stockholm Resilience Centre, Stockholm University; Division of History of Science and Technology, Royal Institute of Technology
Peter K Snyder, Department of Soil, Water, and Climate, University of Minnesota
Robert Costanza, Stockholm Resilience Centre, Stockholm University; Gund Institute for Ecological Economics, University of Vermont
Uno Svedin, Stockholm Resilience Centre, Stockholm University
Malin Falkenmark, Stockholm Resilience Centre, Stockholm University; Stockholm International Water Institute
Louise Karlberg, Stockholm Resilience Centre, Stockholm University; Stockholm Environment Institute
Robert W Corell, The H. John Heinz III Center for Science, Economics and the Environment
Victoria J Fabry, Department of Biological Sciences, California State University San Marcos
James Hansen, NASA Goddard Institute for Space Studies
Brian Walker, Stockholm Resilience Centre, Stockholm University; CSIRO Sustainable Ecosystems
Diana Liverman, Environmental Change Institute, School of Geography and the Environment; Institute of the Environment, University of Arizona
Katherine Richardson, Earth System Science Centre, University of Copenhagen
Paul Crutzen, Max Planck Institute for Chemistry
Jonathan Foley, Institute on the Environment, University of Minnesota

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Abstract

Anthropogenic pressures on the Earth System have reached a scale where abrupt global environmental change can no longer be excluded. We propose a new approach to global sustainability in which we define planetary boundaries within which we expect that humanity can operate safely. 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- to planetary-scale systems.

We have identified nine planetary boundaries and, drawing upon current scientific understanding, we propose quantifications for seven of them. These seven are climate change (CO2 concentration in the atmosphere <350 ppm and/or a maximum change of +1 W m-2 in radiative forcing); ocean acidification (mean surface seawater saturation state with respect to aragonite ≥ 80% of pre-industrial levels); stratospheric ozone (<5% reduction in O3 concentration from pre-industrial level of 290 Dobson Units); biogeochemical nitrogen (N) cycle (limit industrial and agricultural fixation of N2 to 35 Tg N yr-1) and phosphorus (P) cycle (annual P inflow to oceans not to exceed 10 times the natural background weathering of P); global freshwater use (<4000 km3 yr-1 of consumptive use of runoff resources); land system change (<15% of the ice-free land surface under cropland); and the rate at which biological diversity is lost (annual rate of <10 extinctions per million species). The two additional planetary boundaries for which we have not yet been able to determine a boundary level are chemical pollution and atmospheric aerosol loading.

We estimate that humanity has already transgressed three planetary boundaries: for climate change, rate of biodiversity loss, and changes to the global nitrogen cycle. Planetary boundaries are interdependent, because transgressing one may both shift the position of other boundaries or cause them to be transgressed. The social impacts of transgressing boundaries will be a function of the social–ecological resilience of the affected societies.

Our proposed boundaries are rough, first estimates only, surrounded by large uncertainties and knowledge gaps. Filling these gaps will require major advancements in Earth System and resilience science. The proposed concept of “planetary boundaries” lays the groundwork for shifting our 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. Planetary boundaries define, as it were, the boundaries of the “planetary playing field” for humanity if we want to be sure of avoiding major human-induced environmental change on a global scale.

Key words

atmospheric aerosol loading; biogeochemical nitrogen cycle; biological diversity; chemical pollution; climate change; Earth; global freshwater use; land system change; ocean acidification; phosphorus cycle; planetary boundaries; stratospheric ozone; sustainability
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Ecology and Society. ISSN: 1708-3087