Planetary boundaries crossed

THE concept of planetary boundaries, developed by a global community of scholars with the participation of the Potsdam Institute for Climate Impact Research (PIK) and 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 societies depend. In a recent issue of the journal Science, an international team of 18 researchers said that four boundaries—climate change, loss of biosphere integrity, land-system change and altered biogeochemical cycles—had now been crossed as a result of human activity. They said that climate change and biosphere integrity were “core boundaries” and significantly altering either would “drive the earth system into a new state”.

The new research confirmed the original set of boundaries and provided updated analysis and quantification for several of them. “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,” said Will Steffen, the lead author, of the Stockholm Resilience Centre. He is a professor at Stockholm University. Even some boundaries that have not yet been crossed at the planetary scale were found to exceed regional tolerance limits, such as freshwater use in the western U.S. and in parts of southern Europe, Asia and West Asia. “The challenges for society to stay within several planetary boundaries require balanced policies,” said co-author Dieter Gerten of the PIK. The boundaries are closely interlinked, and preventive measures relating to one of them can have negative repercussions on another one.

The CO level boundary (of 350 parts per million) is consistent with a stabilisation of global temperatures at about 1.5° C above pre-industrial levels. The current level is about 399 ppm (December 2014), growing by about 3 ppm a year. In December 2014 nations met in Paris to negotiate an international emissions agreement to attempt to stabilise temperatures at 2° C. “Our analysis suggests that, even if successful, reaching this target contains significant risks for societies everywhere,” said Johan Rockström, co-author from the Stockholm Resilience Centre. “Two degrees must therefore be seen not only as a necessary but also a minimum global climate target.”