Scientists have warned that Earth is exceeding its "safe operating space for humanity" in six of nine key measurements of its health.
Two of the remaining three are also headed in the wrong direction, a new study has found.
This means that Earth's life support systems are being pushed far from the stable state in which they existed from the end of the last ice age 10,000 years ago until the start of the Industrial Revolution.
"We can think of Earth as a human body, and the planetary boundaries as blood pressure," says lead author Katherine Richardson from the University of Copenhagen.
High blood pressure doesn't mean for certain that you are having a heart attack, she explains, but it does increase the risk.
"Therefore, we work to reduce blood pressure."
Which of Earth's boundaries are beyond safe limits?
Earth's climate, biodiversity, land, freshwater, nutrient pollution and 'novel' chemicals - human-made compounds like microplastics and nuclear waste - are all out of whack, a group of international scientists said in Wednesday's journal Science Advances.
Only the acidity of the oceans, the health of the air and the ozone layer are within the boundaries considered safe, and both ocean and air pollution are heading in the wrong direction, the study said.
"We are in very bad shape," says study co-author Johan Rockstrom, director of the Potsdam Institute for Climate Impact Research in Germany.
"We show in this analysis that the planet is losing resilience and the patient is sick."
What are the nine 'planetary boundaries'?
In 2009, Rockstrom and a team of other researchers created nine different broad boundary areas and used scientific measurements to judge Earth's health as a whole.
Wednesday's paper was an update from 2015 which added a sixth factor to the unsafe category.
Water went from barely safe to the out-of-bounds category because of worsening river run-off and better measurements and understanding of the problem, Rockstrom says.
These boundaries "determine the fate of the planet," he adds. The nine factors have been "scientifically well established" by numerous outside studies.
In most cases, the team uses other peer-reviewed science to create measurable thresholds for a safety boundary.
For example, they use 350 parts per million of carbon dioxide in the air, instead of the Paris climate agreement's 1.5 degrees of warming since pre-industrial times. This year carbon in the air peaked at 424 parts per million.
If Earth can manage these nine factors, it could be relatively safe. But, Rockstrom says, it's not.
A simulated stress test for the planet
Each of the nine different boundaries doesn't exist in isolation, however, and they all intermingle.
When the team used computer simulations, they found that making one factor worse, like the climate or biodiversity, made others degrade. Fixing one may also help others.
Rockstrom said this was like a simulated stress test for the planet.
The simulations showed "that one of the most powerful means that humanity has at its disposal to combat climate change" is cleaning up its land and saving forests, according to the study.
Returning forests to what they were in the late 20th century would provide substantial natural sinks to store carbon dioxide instead of the air, where it traps heat, for example.
Biodiversity – the amount and different types of species of life – is in the most troubling shape. It also doesn't get as much attention as other issues, like climate change, Rockstrom says.
"Biodiversity is fundamental to keeping the carbon cycle and the water cycle intact," he adds.
"The biggest headache we have today is the climate crisis and biodiversity crisis."
What happens when we breach planetary boundaries?
The study's authors say that the resilience of Earth goes well beyond climate change.
Their results are a framework that helps scientists track and communicate how different pressures are destabilising its systems.
"Earth is a living planet, so the consequences are impossible to predict," stresses co-author Sarah Cornell also from Stockholm University.
But, University of Michigan environmental studies dean Jonathan Overpeck, who wasn't part of the study, says the findings could have "deeply troubling in its implications for the planet and people should be worried."
"The analysis is balanced in that it clearly sounds a flashing red alarm, but it is not overly alarmist," Overpeck said. "Importantly, there is hope."
The fact that the ozone layer is the sole improving factor shows that when the world and its leaders decide to recognise and act on a problem, it can be fixed.
And "for the most part there are things that we know how to do" to improve the remaining problems, says Carnegie Mellon chemistry and environment professor Neil Donahue.
Some biodiversity scientists have long disputed Rockstrom's methods and measurements, saying they make the results not worth much.
"Experts don't agree on exactly where the limits are, or how much the planet's different systems may interact, but we are getting dangerously close," explains Carnegie Mellon environmental engineering professor Granger Morgan, who wasn't part of the study.
"I've often said if we don't quickly cut back on how we are stressing the Earth, we're toast," Morgan said in an email.
"This paper says it's more likely that we're burnt toast."