Identifying and quantifying planetary boundaries that must not be transgressed could help prevent human activities from causing unacceptable environmental change, argue Johan Rockstrom and colleagues.

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A safe operating space for humanity

Plastics have outgrown most man-made materials and have long been under environmental scrutiny. However, robust global information, particularly about their end-of-life fate, is lacking. By identifying and synthesizing dispersed data on production, use, and end-of-life management of polymer resins, synthetic fibers, and additives, we present the first global analysis of all mass-produced plastics ever manufactured. We estimate that 8300 million metric tons (Mt) as of virgin plastics have been produced to date. As of 2015, approximately 6300 Mt of plastic waste had been generated, around 9% of which had been recycled, 12% was incinerated, and 79% was accumulated in landfills or the natural environment. If current production and waste management trends continue, roughly 12,000 Mt of plastic waste will be in landfills or in the natural environment by 2050.

Production, use, and fate of all plastics ever made

The planetary boundaries framework defines a safe operating space for humanity based on the intrinsic biophysical processes that regulate the stability of the Earth system. Here, we revise and update the planetary boundary framework, with a focus on the underpinning biophysical science, based on targeted input from expert research communities and on more general scientific advances over the past 5 years. Several of the boundaries now have a two-tier approach, reflecting the importance of cross-scale interactions and the regional-level heterogeneity of the processes that underpin the boundaries. Two core boundaries—climate change and biosphere integrity—have been identified, each of which has the potential on its own to drive the Earth system into a new state should they be substantially and persistently transgressed.

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Planetary boundaries: Guiding human development on a changing planet

Protecting the world’s freshwater resources requires diagnosing threats over a broad range of scales, from global to local. Here we present the first worldwide synthesis to jointly consider human and biodiversity perspectives on water security using a spatial framework that quantifies multiple stressors and accounts for downstream impacts. We find that nearly 80% of the world’s population is exposed to high levels of threat to water security. Massive investment in water technology enables rich nations to offset high stressor levels without remedying their underlying causes, whereas less wealthy nations remain vulnerable. A similar lack of precautionary investment jeopardizes biodiversity, with habitats associated with 65% of continental discharge classified as moderately to highly threatened. The cumulative threat framework offers a tool for prioritizing policy and management responses to this crisis, and underscores the necessity of limiting threats at their source instead of through costly remediation of symptoms in order to assure global water security for both humans and freshwater biodiversity.

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Global threats to human water security and river biodiversity

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.

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Planetary boundaries: Exploring the safe operating space for humanity

A soils history of Mesoamerica and the Caribbean Islands.

Introduction: The Big Picture

Contents: General editor's preface Introduction Commercialization without capitalism: processes of environmental change in South China, 1550-1850, Robert Marks Three thousand years of unsustainable growth: China's environment from archaic times to the present, Mark Elvin Of rats and men: a synoptic environmental history of the island Pacific, J. R. McNeill Coming to terms with nature: state and environment in maritime southeast Asia, Greg Bankoff Peripheral visions: Californian-Australian environmental contacts, c.1850s-1910, Ian Tyrrell Biotic change in 19th-century New Zealand, Alfred W. Crosby Population of the French overseas territories in the Pacific: past, present, and projected, J.-Louis Rallu Hydraulic society in California: an ecological interpretation, Donald Worster Humans and forests in pre-colonial southeast Asia, Anthony Reid Discrepancies between environmental attitude and behaviour: examples from Europe and China, Yi-Fu Tuan Toward an interactive theory of nature and culture: ecology, production, and cognition in the California fishing industry, Arthur E. McEvoy Putting a ceiling on sealing: conservation and co-operation in the international arena, 1909-1911, Kurk Dorsey A sacred mountain of gold: the creation of a mining resource frontier in Papua New Guinea, David Hyndman Ecology and the poor: a neglected dimension of Latin American history, Joan Martinez-Alier Patterns of landscape modification in relation to agricultural practice in Central Chile, Eduardo R. Fuentes and Ernst R. Hajek Resource use and environmental management in Japan, 1890-1990, A. Radha Krishnan and Malcolm Tull The forests of Tokugawa Japan: a catastrophe that was avoided, Conrad Totman Index.

John Robert McNeill

Papers

A soils history of Mesoamerica and the Caribbean Islands.

Introduction: The Big Picture

Environmental History in the Pacific World

Production, destruction, and connection, 1750–present: introduction

Environmental history in the Pacific world