New report finds seven of nine planetary boundaries now transgressed
Ocean acidification enters the danger zone for the first time
Atmospheric CO₂ has reached 423 ppm, nearing the high-risk threshold of 450 ppm
Extinction rates remain 10 times higher than safe levels, biosphere integrity in steep decline
Forests, freshwater and nutrient cycles continue to deteriorate despite slowing deforestation
Humanity has now breached seven of the nine planetary boundaries that keep the Earth habitable, scientists warn, with ocean acidification joining climate change and biodiversity loss in the danger zone for the first time, according to the latest Planetary Health Check (PHC) report. Six boundaries had already been crossed by last year.
The PHC report, which assesses the state of the Earth system, is based on the framework of planetary boundaries (PB). These boundaries are defined as ecological thresholds that keep life on Earth within a “safe operating space” or safe boundaries. In short, planetary boundaries are processes vital to the Earth system.
The nine processes that regulate planetary stability, resilience and life-support functions are: Climate change; biosphere integrity; land system change; freshwater change; modification of biogeochemical flows; introduction of novel entities; ocean acidification; atmospheric aerosol loading; and stratospheric ozone depletion.
Ocean acidification has crossed the safe operating space for the first time, the PHC report has found. The other six breached boundaries are climate change, biosphere integrity, land system change, freshwater change, modification of biogeochemical flows and introduction of novel entities. Only atmospheric aerosol loading and stratospheric ozone depletion remain stable.
“This year’s report brings sobering news: For the first time, we have crossed the Planetary Boundary for Ocean Acidification. This paints a grave picture — not just for marine ecosystems, but for the entire Earth system that depends on a healthy ocean,” Sylvia A Earle, oceanographer, Planetary Guardian, National Geographic Explorer, founder of Mission Blue and Ocean Elder wrote in the report.
The ocean, which covers 70 per cent of the planet, helps stabilise the climate, builds resilience and acts as a life-support system.
The driver of ocean acidification is fossil fuel combustion. As oceans absorb increasing amounts of carbon dioxide (CO₂) from the atmosphere, their chemistry is changing. Surface ocean acidity has increased by around 30-40 per cent since the industrial era.
The PHC’s assessment is based on the global mean surface aragonite saturation state (Ω), which now stands at 2.84, below the boundary of 2.86, confirming that the threshold has been breached. Aragonite saturation state measures the concentration of aragonite, a form of skeletal carbonate material typically present in organisms in seawater, which is influenced by the pH of the surrounding environment.
Rising acidity threatens marine organisms such as corals, molluscs and key plankton species that build calcium carbonate shells or skeletons, putting marine food webs and ecosystem functions and structure at risk, the report warned.
On climate change, the PHC report highlighted two indicators: CO₂ levels and radiative forcing. Atmospheric CO₂ reached 423 parts per million (ppm) in 2025, far above the 350 ppm boundary, and is rapidly approaching the high-risk threshold of 450 ppm. Radiative forcing from human activity is estimated at +2.97 Watts per square meter (W/m²), nearly double the high-risk threshold of +1.5 W/m². These trends increase the likelihood of large-scale, irreversible changes.
Biosphere integrity continues to worsen. The report found no signs of improvement as the extinction rate remains above 100 extinctions per million species years (E/MSY), far beyond the safe threshold of 10 E/MSY.
“This situation has persisted or slightly worsened since 2024, with ongoing loss of genetic diversity and ecosystem function,” read the report.
Land system change, or earth’s forests, is also deteriorating. Although the pace of deforestation has slowed, global forest cover has fallen to about 59 per cent, well below the 75 per cent safe minimum. All major biomes have breached their thresholds.
The state of freshwater is also dire, increasing risk of droughts and floods. More than 20 per cent of global land now shows significant deviations in streamflow (22.6 per cent) and soil moisture (22 per cent), nearly double safe levels. Major river basins, including the Indo-Gangetic Plain and North China, have exceeded safe thresholds, undermining resilience and water security.
Excessive fertiliser use continues to overload ecosystems with nitrogen and phosphorus, worsening biogeochemical imbalances and creating pollution and dead zones. There is no improvement in sight, the report noted.
Novel entities such as plastics, inadequately tested chemicals and synthetic materials remain a growing threat. The planetary boundary for novel entities is zero untested releases, yet the threshold continues to be breached.
In contrast, atmospheric aerosol loading remains in the safe zone due to declining global aerosol emissions. The interhemispheric aerosol optical depth difference stands at 0.063, down from last year and well below the 0.10 threshold. Aerosols — small particles that contribute to smog and air pollution — play a dual climate role, cooling through sulphates but warming through black carbon.
While aerosols remain within the safe operating space, they continue to cause serious health and justice impacts, including reduced life expectancy and higher likelihoods of lung cancer.
Global ozone concentrations, too, remain within the safe operating space, averaging 285–286 Dobson Units, above the safe threshold of roughly 277 DU.
The ozone hole is steadily recovering and has remained below historical levels, though it persists over Antarctica. The report warned that new risks from rocket launches and satellite debris could threaten progress.
The report concluded that human activity has driven the Earth beyond its safe operating space for the first time in 11,000 years. “This transgression is not due to individual single causes, but to a network of interlinked drivers like fossil fuel combustion, land use change, and unsustainable resource use that collectively push control variables, such as atmospheric CO₂ or species extinction rate, past safe thresholds for life on Earth,” it read.