Human-driven activities caused 6 of Earth's nine planetary boundaries to exceed, finds study

Human activities are increasingly impacting the planet and, thereby, increasing the risk of triggering dramatic changes in overall Earth conditions, a study that updates the planetary boundary framework shows. The nine 'planetary boundaries' represent components of the global environment that regulate stability and livability of the planet for people, the researchers said.

The degree of breaching of the safe boundary levels is caused by human-driven activities impacting the components, they said. The planetary boundaries framework applies the newest scientific understanding of the functioning of the Earth system to identify a 'safe operating space' for humanity. It proposes limits for the extent to which human activities can be allowed to impact critical processes without risk of potentially triggering irreversible changes in the Earth conditions that support us.

The researchers noted that, for the first time, metrics for all boundaries are presented. Six of the boundaries are found to be transgressed, and transgression is increasing for all boundaries except the degradation of the Earth's ozone layer, they said.

A global focus on climate is not enough. Development of Earth system models that accurately reproduce interactions between boundaries, especially Climate and Biosphere Integrity, is an urgent priority, according to the researchers.

The study, published in the journal Science Advances, represents the third update of the framework carried out by 29 scientists from eight different countries.

The trend of increasing transgression of the boundaries is worrying, explained Katherine Richardson, professor at the University of Copenhagen in Denmark, and leader of the study.

"Crossing six boundaries in itself does not necessarily imply a disaster will ensue but it is a clear warning signal. We can regard it as we do our own blood pressure," Richardson said.

"A BP over 120/80 is not a guarantee of a heart attack but it increases the risk of one. Therefore, we try to bring it down. For our own—and our children's—sakes we need to reduce the pressure on these six planetary boundaries," the researcher added. An important conclusion of the study is that more focus is needed on interactions between the boundaries.

"Focus on human-caused climate change is not enough if we want to protect the Earth system from irreversible harm," said Johan Rockstrom, Director of the Potsdam Institute for Climate Impact Research (PIK), and original proposer of the framework in 2009.

"Next to climate change, integrity of the biosphere is the second pillar of stability of our planet. Our research shows that mitigating global warming and saving a functional biosphere for the future have to go hand in hand," said co-author Wolfgang Lucht, Head of PIK's department of Earth System Analysis.