‘Human activity weakened four planetary boundaries for survival’

The accelerated impact of human activity has started to destabilise our own planetary life support system, driving Earth into a new geological age, reveals a global study.

The team of 18 researchers found that of nine global-scale processes which underpin life on Earth, four have exceeded safe conditions – with two impacted so significantly as to pose serious risks to future human wellbeing.

Climate change, the loss of biosphere integrity, land-system change and altered biogeochemical cycles like phosphorus and nitrogen runoff have all passed beyond levels that put humanity in a “safe operating space”, they emphasised.

The findings, scheduled to be discussed next week at the World Economic Forum in Davos, Switzerland, showed that climate change and loss of biosphere integrity are core planetary boundaries which, once crossed, risk shifting the Earth to a new state.

According to professor Will Steffen from the Australian National University, “we have now entered a new geological epoch, named the Anthropocene, in which the global economic system is the primary driver of change on Earth”.

The research team compared 12 measures of human activity such as economic growth, population, energy use with 12 environmental factors such as biodiversity, and the carbon and nitrogen cycles.

They found they had all seen unprecedented growth in the latter half of the 20th Century.

“For climate change, the risk to humans begins increasing as carbon dioxide rises above 350 parts per million (ppm). We are now at nearly 400 ppm. We are coping so far but we are seeing extreme weather events become worse, loss of polar ice and other worrying impacts,” said professor Steffen.

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According to team member Steve Carpenter, director of the University of Wisconsin-Madison’s Centre for Limnology, “Phosphorus and nitrogen are widely used to fertilise crops and the rise of large-scale, industrial agriculture has led to an immense increase in the amount of the chemicals entering our ecosystems.”

It should be a wake-up call to policymakers that “we are running up to and beyond the biophysical boundaries that enable human civilisation as we know it to exist,” Carpenter said.

For the last 11,700 years until roughly 100 years ago, Earth had been in a “remarkably stable state”.

During this time, known as the Holocene epoch, “everything important to civilisation” has occurred.

But over the last century, some of the parameters that made the Holocene so hospitable have changed.

“We have become a planetary-scale force in a single lifetime,” professor Steffen concluded.

The papers appeared in the journal Science and new journal Anthropocene Review.

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