First proposed by a group of Earth system and environmental scientists, planetary boundaries is an Earth system framework designed to define “safe operating space for humanity.” According to Wikipedia, this framework was designed for governments at all levels, international organizations, the scientific community, private sector and civil society, and is based on research that has shown that human activities have become the main driver of global environmental change since the Industrial Revolution. Once these planetary boundaries have been transgressed, there is a risk of “irreversible and abrupt environmental change” according to the authors of the original report.
In this milieu, a team of researchers has again come together in order to revise and update the planetary boundaries framework. In their recent report for Science magazine, the authors write that they have “focus[ed] on the underpinning biophysical science” based on conversations with expert research communities as well as scientific advances over the past 5 years in order to refine and elaborate on certain aspects of the original framework.
Originally, nine boundaries were proposed to form the planetary boundaries framework; however, the authors of the 2015 report write that, “There are many other ways that Earth System functioning could be described, including potentially valuable metrics for quantifying the human imprint on it.”
The updated boundaries include climate change, changes in biosphere integrity, stratospheric ozone depletion, ocean acidification, biogeochemical flows, land-system change, freshwater use, atmospheric aerosol loading and novel entities. Certain boundaries, such as novel entities and atmospheric aerosol loading, however, have not yet been quantified. Additionally, the authors of the new report introduced a two-tier approach for some boundaries, which reflects “the importance of cross-scale interactions and the regional-level heterogeneity of the processes that underpin the boundaries.”
The authors emphasize that two of the core boundaries — climate change and biosphere integrity — have the potential to “drive the Earth System into a new state should they be substantially and persistently transgressed.” These core boundaries, as well as the land-system change and the high level of phosphorus and nitrogen flowing into the oceans because of fertilizer use (components of the biochemical flows planetary boundary), have already exceeded “safe” levels.
As lead author Will Steffen, who holds appointments at the Australian National University and the Stockholm Resilience Center, told the Washington Post, “What the science has shown is that human activities — economic growth, technology, consumption–are destabilizing the global environment.”
Though there is no certainty that the world will end once these boundaries are transgressed, or even shortly thereafter, no one is sure what will happen as the Earth’s planetary conditions continue to change; though the authors do write that our planet “is likely to be much less hospitable to the development of human societies.” Indeed, as Steffen told Grist, “It’s clear the economic system is driving us towards an unsustainable future and people of my daughter’s generation will find it increasingly hard to survive.”
(Photo courtesy of Beth Scupham)