Six of Nine Planetary Boundaries Have Now Been Exceeded, Study Says

A new study by an international team of 29 scientists from eight countries provides the third update to the planetary boundaries framework. The update shows how human activities are increasingly impacting our planet, thus augmenting the risk of triggering drastic changes in Earth’s overall conditions.

The nine planetary boundaries represent the limits within which humans can continue to thrive and develop.

“The planetary boundaries framework draws upon Earth system science,” the study said. “It identifies nine processes that are critical for maintaining the stability and resilience of Earth system as a whole. All are presently heavily perturbed by human activities. The framework aims to delineate and quantify levels of anthropogenic perturbation that, if respected, would allow Earth to remain in a ‘Holocene-like’ interglacial state. In such a state, global environmental functions and life-support systems remain similar to those experienced over the past ~10,000 years rather than changing into a state without analog in human history.”

The study found that two-thirds of the boundaries had already been breached, indicating the planet is entering dangerous, uncharted territory.

“This planetary boundaries framework update finds that six of the nine boundaries are transgressed, suggesting that Earth is now well outside of the safe operating space for humanity. Ocean acidification is close to being breached, while aerosol loading regionally exceeds the boundary. Stratospheric ozone levels have slightly recovered,” the study said.

Climate interacting with life on Earth has controlled our planet’s environmental conditions for more than three billion years, reported the University of Copenhagen. Human activities like altering water levels in soil and rivers, land-use changes, greenhouse gas emissions and the introduction of toxic chemicals into the environment have all had an influence on this delicate interplay.

“A world that develops within science defined boundaries is the only way to navigate our current situation with rising, potentially catastrophic risks, at the planetary scale. We already recognize this on climate, where the Paris agreement has adopted the climate planetary boundary of holding the 1.5°C limit. Similarly, the world has accepted the planetary boundary on biodiversity, when decided at the 2022 Montreal-Kunming COP15, to halt and reverse biodiversity loss on land and in the ocean,” said Johan Rockström, who is director of the Potsdam Institute for Climate Impact Research, as well as the original proposer, in 2009, of the planetary boundaries framework, the University of Copenhagen reported.

It is essential that interactions within Earth’s system are maintained and respected so that they do not deviate much from those that have been in control of planetary conditions for the past several millenia. Otherwise, drastic changes could cause a decrease in the ability of the planet to support modern human civilizations.

“Our study shows that humans are appropriating the equivalent of ~30 % of the energy that was available to support biodiversity before the Industrial Revolution,” said Katherine Richardson, leader of the study, a professor at Globe Institute and leader of University of Copenhagen’s Sustainability Science Center, as reported by University of Copenhagen. “Surely, the removal of so much of the energy that otherwise would have been available to nature must be a driver of biodiversity loss. Therefore, we propose the adoption of Human Appropriation of Net Primary Production (HANPP), i.e., biomass use, as one of two metrics when assessing human impacts on biodiversity.”

The nine planetary boundaries — climate change, stratospheric ozone depletion, atmospheric aerosol loading, ocean acidification, freshwater use, land system change, nitrogen and phosphorus cycles, chemical pollution and biodiversity loss — are environmental components that regulate the livability and stability of our planet for humans. Human activities have caused the breaching of safe levels that are affecting these components.

The planetary boundaries framework uses the most recent scientific knowledge of Earth’s system functioning to determine a “safe operating space” for humans and proposes limits to human activities’ impact on the planet’s essential processes.

In the study, measurements for all nine boundaries were presented. It was found that not only had six of them been transgressed, transgression was increasing for all of the boundaries except the degradation of Earth’s ozone layer.

“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. 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,” Richardson said, as University of Copenhagen reported.

The researchers concluded that there needs to be more focus on interactions between boundaries.

“The Planetary Boundaries science provides a ‘guide for action’ if we truly want to secure prosperity and equity for all on Earth, and this goes well beyond climate only, requiring novel Earth system modeling and analysis, and systematic efforts to protect, recover and rebuild planetary resilience,” Rockström said.

The study, “Earth beyond six of nine planetary boundaries,” was published in the journal Science Advances.

“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 Earth conditions that allow advanced human societies to flourish,” Richardson said.