Four of nine planetary boundaries have now been crossed as a result of human activity, says an international team of 18 researchers in the journal Science (16 January). The four are: climate change, loss of biosphere integrity, land-system change, altered biogeochemical cycles (phosphorus and nitrogen). 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 their findings in seven seminars at the World Economic Forum in Davos (21-24 January).
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
- Climate change
- Change in biosphere integrity (biodiversity loss and species extinction)
- Stratospheric ozone depletion
- Ocean acidification
- Biogeochemical flows (phosphorus and nitrogen cycles)
- Land-system change (for example deforestation)
- Freshwater use
- Atmospheric aerosol loading (microscopic particles in the atmosphere that affect climate and living organisms)
- Introduction of novel entities (e.g. organic pollutants, radioactive materials, nanomaterials, and micro-plastics).
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 Professor 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, University of Copenhagen.
This week, co-author Professor 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.”
“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 the UN’s Sustainable Development Goals. With the right ambition, this could create the conditions for long-term human prosperity within planetary boundaries,” he said.
Eight of the nine planetary boundaries have been quantified (see table at end). With climate change, for example, the team argue that carbon dioxide levels should not cross 350 parts per million (ppm) in the atmosphere. “This boundary is consistent with a stabilisation of global temperatures at about 1.5 degrees Celsius above pre-industrial levels,” said Professor Rockström.
Atmospheric concentrations of carbon dioxide are currently about 399ppm (December 2014) and growing at about 3ppm per year. In December 2015, nations will meet in Paris to negotiate an international emissions agreement to attempt to stabilise 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 Professor Rockström.
The planetary boundaries research coincides with a second analysis, also led by Professor Will 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.
- The concept of planetary boundaries has been updated with new assessments and quantifications.
- Climate change and biosphere integrity identified as core planetary boundaries.
- Four boundaries are assessed to have been crossed, placing humanity in a danger zone: climate change, loss of biosphere integrity, land-system change, altered biogeochemical cycles (fertiliser use - phosphorus and nitrogen).
- Crossing boundaries raises the risks to current and future societies of destabilising the Earth System – the complex interactions of land, ocean, atmosphere, ice sheets, life and people.
- Internationally agreed upper climate limit of 2 degrees lies beyond the climate change boundary: which makes 2 degrees a risky target for humanity, and therefore an absolute minimum target for the global climate negotiations.
- Complementary research published simultaneously charts “The Great Acceleration” in human impact on the Earth System over the last 60 years.