According to a groundbreaking study, human actions and demands have eroded the Earth’s ability to cope, pushing it well past the boundaries of a ‘safe operating zone’ essential for the survival of most species, including humans.

Human activity and appetites have weakened Earth’s resilience, pushing it far beyond the “safe operating space” that keeps the world liveable for most species, including our own, a landmark study said Wednesday.

Six of nine planetary boundaries — climate change, deforestation, biodiversity loss, synthetic chemicals including plastics, freshwater depletion, and nitrogen use are already deep in the red zone, an international team of 29 scientists reported.

Two of the remaining three ocean acidification along with the concentration of particle pollution and dust in the atmosphere  are borderline, with only ozone depletion comfortably within safe bounds.

The planetary boundaries identify “the important processes that keep the Earth within the kind of the living conditions that prevailed over the last 10,000 years, the period when humanity and modern civilisation developed”, said lead author Katherine Richardson, a professor at the University of Copenhagen’s Globe Institute.

The study is the second major update of the concept, first unveiled in 2009 when only global warming, extinction rates, and nitrogen had transgressed their limits.

The study quantifies boundaries for all nine interlocking facets of the Earth system.

For biodiversity, for example, if the rate at which species disappear is less than 10 times the average extinction rate over the last 10 million years, that is deemed acceptable.

In reality, however, extinctions are occurring at least 100 times faster than this so-called background rate, and 10 times faster than the planetary boundary limit.

For climate change, that threshold is keyed to the concentration of atmospheric CO2, which remained very close to 280 parts per million (ppm) for at least 10,000 years prior to the industrial revolution.

That concentration is today 417 ppm, far above the safe boundary of 350 ppm.

Thousands upon thousands of chemical compounds created by humans from micro-plastics and pesticides to nuclear waste and drugs that have leached into the environment were quantified for the first time in the new research, and found to exceed safe limits.

Likewise for the depletion of “green” and “blue” water, freshwater coming from soil and plants on the one hand, and from rivers and lakes on the other.

An important finding of the new update is that different boundaries feed off and amplify each other.

The study examines in particular the interaction between increasing CO2 concentration and damage to the biosphere, especially forest loss, and projects temperature increases when one or both increase.

It shows that even if humanity rapidly draws down greenhouse gas emissions, unless destruction of carbon-absorbing forests is halted at the same time rising global temperatures could tip the planet onto a trajectory of additional warming that would be hard to stop.

All the boundaries can be brought back into the safe operating space, the study concluded.

Hotly debated at first, the planetary boundaries framework quickly became a pillar of Earth system science, with its influence extending today into the realm of policy and even business.

Maria Chami with AFP