Earth Has Crossed Several 'Planetary Boundaries,' Thresholds of Human-Induced Environmental Changes

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.”

The team will present its findings in seven seminars at the World Economic Forum in Davos Jan. 21-24.

“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.”

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.

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).

Managing these priorities at safe global levels will enable world development within a safe operating space on Earth, say the researchers. The new research builds on a large number of scientific publications critically assessing and improving planetary boundaries research since its original publication.  It confirms the original set of boundaries and provides updated analysis and quantification for several of them, including phosphorus and nitrogen cycles, land-system change, freshwater use, and biosphere integrity. Biosphere integrity relates to the scale and impact of humans on ecosystems.

As human activity pushes the earth system beyond planetary boundaries and into zones of increasing risk, marine ecosystems may change dramatically as a result of ocean acidification and eutrophication, or temperatures may rise so high as to pose significant threats to agricultural production, infrastructure, and human health. The paper reports that continuing degradation of biosphere integrity will likely further erode the provision of ecosystem services on which human societies depend.

“Past a certain threshold, curbing greenhouse gas emissions, biodiversity loss, or land-use change, for example, may not reverse or even slow the trends of earth system degradation, with potentially catastrophic consequences,” said Steffen.

“Planetary boundaries do not dictate how human societies should develop but they can aid decision-makers by defining a safe operating space for humanity,” says co-author Katherine Richardson from the Center for Macroecology, Evolution and Climate at the University of Copenhagen.

This week, co-author Johan Rockström, director of the Stockholm Resilience Centre, will present the new findings at the World Economic Forum.

“In the last four years we have worked closely with policymakers, industry and organisations like WWF to explore how the planetary boundaries approach can be used as a framework for sectors of societies to reduce risk while developing sustainably,” he said. “It is obvious that different societies over time have contributed very differently to the current state of the earth. The world has a tremendous opportunity this year to address global risks, and do it more equitably. In September, nations will agree to the UN’s Sustainable Development Goals. With the right ambition, this could create the conditions for long-term human prosperity within planetary boundaries.”

Eight of the nine planetary boundaries have been quantified. With climate change, for example, the team argues that carbon dioxide levels should not cross 350 parts per million (ppm) in the atmosphere, though it already has.

“This boundary is consistent with a stabilization of global temperatures at about 1.5 degrees Celsius above pre-industrial levels,” said Rockström.

Atmospheric concentrations of carbon dioxide are currently about 400 ppm and growing at about 3 ppm per year.

In December 2015, nations will meet in Paris to negotiate an international emissions agreement to attempt to stabilize temperatures at 2 degrees Celsius above pre-industrial levels.

“Our analysis suggests that, even if successful, reaching this target contains significant risks for societies everywhere. Two degrees must therefore be seen not only as a necessary but also a minimum global climate target,” said Rockström.    

The planetary boundaries research coincides with a second analysis, also led by Steffen, that charts “The Great Acceleration” in human activity since 1950. The paper, “The trajectory of the Anthropocene: the Great Acceleration,” focuses on a planetary “dashboard” of 24 social, economic and environmental indicators. The assessment concludes that the global economic system is the prime driver of change of key components of the earth system, supporting the need for a precautionary approach to transgressing planetary boundaries.

Other institutions contributing to the study include McGill University, Québec, Canada; Stellenbosch University, South Africa; University of Wisconsin, Madison, Wisc.; Wageningen University Alterra, Wageningen, The Netherlands; Stockholm University, Sweden; Beijer Institute of Ecological Economics, Stockholm, Sweden; Potsdam Institute of Climate Impact Research (PIK), Potsdam, Germany; University College, London, U.K.; Stockholm Environment Institute, Stockholm, Sweden; Council for Scientific and Industrial Research (CSIR), Stellenbosch, South Africa; Royal Institute of Technology (KTH), Stockholm, Sweden.

Planetary Boundaries

(Bold indicates a boundary has been transgressed)

Related Image Gallery: Planetary Boundaries