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The authors found that safe planetary boundaries had already been crossed for the climate, freshwater, land use, biogeochemical flows, novel entities, and biosphere integrity—in keeping with a study in Science Advances last year. They found a "clear trend towards further transgression"—moving deeper into the danger zone, where irreversible tipping points are more likely to be triggered—in each of the six categories.
"Our updated diagnosis shows that vital organs of the Earth system are weakening, leading to a loss of resilience and rising risks of crossing tipping points," Levke Caesar, a PIK climate physicist lead author of the report, said in a statement that announced a "red alert."
The health check also showed that ocean acidification, a seventh category, has reached a dangerous precipice, putting the foundations of the marine food web at risk. Ocean acidification, which can threaten coral reefs and phytoplankton populations, is caused by the buildup of carbon dioxide from burning fossil fuels and other human activities.
Caesar said a "safe operating space" threshold for acidification could be crossed in the next few years.
"Looking at the current evolution, I'd say it’s really, really difficult to prevent that [boundary] crossing," she toldMongabay.
A graphic shows the status of nine environmental categories, four of which have been broken down into two control variables. Image from Planetary Health Check 2024. Design by Globaïa.
PIK director Johan Rockström, a co-author of the new report, helped develop planetary boundary research in the late 2000s. In a seminal 2009 paper in Nature, he and his co-authors found that three of the nine boundaries had already been crossed. That number has gradually gone up based on a series of studies over the last decade.
The planet boundary framework, which is often connected to the degrowth movement, emphasizes that the categories are interconnected.
"The interconnectedness of [planetary boundary] processes means that addressing one issue, such as limiting global warming to 1.5°C, requires tackling all of them collectively," the new report says.
Boris Sakschewski, a climate scientist who, along with Caesar, is a lead author of the report said that, "We know that all planetary boundary processes act together and each one needs protection to protect the whole system."
The consequences of continued ocean acidification, which is primarily measured by aragonite saturation, would be severe, the report warns.
Ocean acidification is approaching a critical threshold, with significant declines in surface aragonite saturation, particularly in high-latitude regions like the Arctic and Southern Ocean. These areas are vital for the marine carbon pump and global nutrient cycles, which support marine productivity, biodiversity, and global fisheries. The growing acidification poses an increasing threat to marine ecosystems, especially those reliant on calcium carbonate for shell formation.
Some researchers believe that the ocean acidification threshold has already been crossed, especially given regional variability, with cooler polar waters absorbing more carbon dioxide, causing a faster drop in pH levels.
The report was written with a general audience in mind and is not peer-reviewed, though it's based on peer-reviewed studies, the authors said.
The final pages of the report present solutions, especially agricultural. A radical overhaul of the global food system, heavily dependent on fertilizer and other harmful inputs, will be necessary to reverse the disturbing trends documented in the report, the authors wrote.
"Sometimes overlooked compared to the impacts of energy production and consumption—particularly the use of fossil fuels—the food systems we depend on are among the largest drivers of environmental degradation. The global food system is the single largest driver behind the transgression of multiple planetary boundaries," the report says.
As Carbon Brief reported: "The new study develops the idea of 'planetary boundaries,' first set out in an influential 2009 paper. The paper had defined a set of interlinked thresholds that it said would ensure a 'safe operating space for humanity.' Its authors had warned that crossing these thresholds 'could have disastrous consequences.'"
"We cannot have a biophysically safe planet without justice."
The new paper, written by many of the same people, introduces justice considerations into the framework, leading the authors to propose a set of "safe and just" Earth system boundaries (ESBs) at global and sub-global scales, some of which are stricter than the "safe" limits outlined previously.
"For the first time, we present quantifiable numbers and a solid scientific foundation to assess the state of our planetary health not only in terms of Earth system stability and resilience but also in terms of human well-being and equity/justice," said lead author Johan Rockström, director of the Potsdam Institute for Climate Impact Research.
The interdisciplinary team focused on five of the nine planetary systems identified in 2009—climate, biosphere, water, nutrient cycles, and atmosphere. To determine the health of these systems, they relied on the following eight measurable indicators:
As Phys.org reported: "Safe boundaries ensure stable and resilient conditions on Earth, and use an interglacial Holocene-like Earth system functioning as a reference point for a healthy planet. A stable and resilient Earth is dominated by balancing feedbacks that cope with buffer and dampen disturbances. Cutting-edge science on climate tipping points features as one major line of evidence to set safe boundaries."
To establish "just" boundaries for each indicator, the authors assessed the conditions needed to avert "significant harm," which they defined as "widespread severe existential or irreversible negative impacts on countries, communities, and individuals from Earth system change, such as loss of lives, livelihoods, or incomes; displacement; loss of food, water, or nutritional security; and chronic disease, injury, or malnutrition."
As summarized by Carbon Brief, the researchers took into account the following justice criteria:
"The results of our health check are quite concerning: Within the five analyzed domains, several boundaries, on a global and local scale, are already transgressed," Rockström said. "This means that unless a timely transformation occurs, it is most likely that irreversible tipping points and widespread impacts on human well-being will be unavoidable. Avoiding that scenario is crucial if we want to secure a safe and just future for current and future generations."
According to the paper, "Social and economic systems run on unsustainable resource extraction and consumption" have pushed Earth past seven of the eight "safe and just" ESBs.
The paper includes the following image for reference. The Earth icons representing the current state of the planet should be in the green space, which marks where "safe" (red) and "just" (blue) ESBs overlap. Instead, they lie beyond the "safe and just corridor" for every indicator except aerosol loading.
When "safe" ESBs are looked at in isolation, the planet has entered the danger zone for six of the eight indicators. According to the authors, 1.2°C of global warming to date has pushed the world beyond the "just" ESB for climate, which requires mean surface temperature rise to be capped at 1.0°C. For now, the climate still remains in the "safe" threshold, they say, even as the impacts of increasingly frequent and intense extreme weather are already being felt, especially by the poor.
However, Gupta stressed that "justice is a necessity for humanity to live within planetary limits."
"This is a conclusion seen across the scientific community in multiple heavyweight environmental assessments," said Gupta. "It is not a political choice. Overwhelming evidence shows that a just and equitable approach is essential to planetary stability."
"We cannot have a biophysically safe planet without justice," she added. "This includes setting just targets to prevent significant harm and guarantee access to resources to people and for as well as just transformations to achieve those targets."
As Carbon Brief pointed out: "This study is the first to assess Earth-system boundaries at a local scale, rather than analyzing the planet as a whole. This allows the authors to determine which boundaries have been crossed in specific regions and to identify 'hotspots' for breached boundaries."
As a result, researchers were able to produce the following map, which shows that more boundaries have been breached in certain areas, including Eastern Europe, the Middle East, South and Southeast Asia, and substantial parts of Africa, Brazil, Mexico, China, and the U.S. West.
Rockström told reporters that the eight indicators were "carefully chosen" to be "implementable for stakeholders... across the world."
The researchers hope that the "safe and just" ESBs they have put forth "will underpin the setting of new science-based targets for businesses, cities, and governments to address the polycrises of: increasing human exposure to the climate emergency, biodiversity decline, water shortages, ecosystem damage from fertilizer overuse in some parts of the world coupled with lack of access elsewhere, and health damage from air pollution," Phys.org reported.
"Stewardship of the global commons has never been more urgent or important."
Rockström and Gupta are co-chairs of the Earth Commission, founded in 2019 "to advance the planetary boundaries framework," Carbon Brief observed. "The concept has been widely used in academia and policy spaces, but has also attracted criticism from scientists who say it oversimplifies a complex system, or could spread political will too thinly."
Earth Commission executive director Wendy Broadgate, for her part, said that "a safe and just transformation to a manageable planet requires urgent, collective action by multiple actors, especially in government and business to act within Earth system boundaries to keep our life support system of the planet intact."
"Stewardship of the global commons has never been more urgent or important," she added.
In their conclusion, the authors wrote that "nothing less than a just global transformation across all ESBs is required to ensure human well-being."
"Such transformations must be systemic across energy, food, urban, and other sectors, addressing the economic, technological, political, and other drivers of Earth system change, and ensure access for the poor through reductions and reallocation of resource use," they added. "All evidence suggests this will not be a linear journey; it requires a leap in our understanding of how justice, economics, technology, and global cooperation can be furthered in the service of a safe and just future."
