Six of the nine "planetary boundaries" that regulate the stability of our planet have been crossed, prompting scientists to warn that the Earth may now be "well outside of the safe operating space for humanity."
The planetary boundaries framework was introduced in 2009 to identify the so-called guardrails that govern the impact of our species on the planet.
Human activity within these boundaries can be tolerated by the Earth's systems. Activity that exceeds the guardrails could result in irreversible changes to the Earth's ability to support civilization.
Katherine Richardson, the lead scientist issuing the warning and a professor of biological oceanography at the University of Copenhagen's Globe Institute, told Newsweek: "We humans—just like all other living organisms—survive by using the Earth's resources but those resources are limited."
Richardson, who is also leader of the university's Sustainability Science Center, added: "We can think of the Earth's resources as the currency that supports us. The planetary boundaries framework is like a bank statement. It tells us how much of various components, or resources, of the Earth system we can allow ourselves to use without greatly increasing the risk that our activities will lead to dramatic and potentially irreversible changes in overall environmental conditions."
The nine planetary boundaries are:
- Climate change
- Biosphere integrity: the genetic and functional biodiversity of the planet
- Land system change
- Freshwater usage
- Biogeochemical flows: the natural cycles of nitrogen and phosphates, used in industrial fertilizers
- Novel entities: the percentage of synthetic chemicals released into the enviornment
- Stratospheric ozone depletion
- Atmospheric aerosol loading
- Ocean acidification
The planetary boundaries framework has to be updated regularly to reflect the latest research. In the latest update, published in the journal Science Advances on September 13, Richardson and fellow researchers concluded that six of the boundaries had already been crossed.
"Crossing six boundaries in itself does not necessarily imply a disaster will ensue, but it is a clear warning signal," Richardson said.
"We can regard it as we do our own blood pressure. 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 three boundaries that have not been crossed so far are ozone depletion, atmospheric aerosol loading and ocean acidification.
"The climate and biodiversity crises we experience today demonstrate that humanity's overall impacts on the planet are now so great that we must, for our societies to continue to flourish, manage our relationship with the planet as a whole," Richardson said.
Focusing on climate change alone is not enough. "Climate is not the only global process affected by human activities," she added.
The boundaries framework allows for a more holistic overview of humanity's impact and what we can do to tackle it.
Richardson said: "Hopefully, this new study will serve as a wake-up call for many and increase focus in the international community on the necessity of limiting our impacts on the planet, in order to preserve and protect the conditions that allow advanced human societies to flourish."
