Six of nine planetary boundaries are already breached.

The concept from the 1972 Limits to Growth has stopped being a forecast and become a description: humanity now uses planetary resources faster than they regenerate and emits waste faster than the sinks absorb it. The measurable signature is the Earth's energy imbalance — about 1.36 watts per square metre of extra heat retained at the surface, per Hansen et al. — equivalent to nearly one million Hiroshima-scale bombs of surplus energy added to the system every single day.

That surplus is not stored quietly. It warms the ocean, which drives the storms, floods, heatwaves, and droughts that now fracture supply chains and displace populations. It also accelerates the warming rate itself: tropospheric temperature rose about 0.18°C per decade between 1970 and 2010, and is projected to rise 0.27°C per decade between 2010 and 2040 — a 50 percent acceleration. A faster rate is what makes tipping points closer than the headline temperature suggests, because the system has less time to absorb each increment.

The IPBES Global Assessment found around one million animal and plant species threatened with extinction, many within decades — more than at any point in human history. Average native species abundance in most major land habitats has fallen by at least 20 percent, mostly since 1900. More than 40 percent of amphibian species, almost 33 percent of reef-forming corals, and more than a third of marine mammals are threatened.

The mechanism is not climate alone. Land-use change, overexploitation, pollution, and invasive species do most of the immediate damage; warming then amplifies it. IPBES found 22 of 44 assessed SDG-related targets undermined by negative nature trends. WWF's Living Planet Report 2024 put the decline in monitored wildlife populations at 73 percent between 1970 and 2020. The ecosystem services at stake — pollination, water purification, soil regeneration — are the load-bearing walls of the food system. Their decline converts biodiversity loss into food-price risk, and food-price risk into political risk.

Ocean chemistry is changing on two fronts. Surface pH has dropped about 0.1 units since the pre-industrial era — roughly a 30 percent increase in acidity, per NOAA — with polar waters acidifying fastest. At the same time, the ocean has lost about 2 percent of its dissolved oxygen since the middle of the 20th century, and the volume of completely oxygen-depleted water has quadrupled since the 1960s, per IUCN.

The two stresses travel together: respiration consumes oxygen and releases carbon dioxide, so deoxygenation and acidification compound each other. Around 700 coastal sites were reporting low-oxygen conditions by 2011, up from 45 before the 1960s. Large predatory species — tuna, marlin, swordfish, sharks — are being squeezed into narrowing surface layers. Under a business-as-usual scenario, the ocean is projected to lose another 3–4 percent of its oxygen by 2100, with fisheries and the hundreds of millions of people who depend on them absorbing the cost. The eastern boundary upwelling systems alone support about one-fifth of the world's wild marine fish harvest.

The UNCCD's drying-lands assessment found 77.6 percent of Earth's land became permanently drier over the three decades to 2020 compared with the previous 30 years. Drylands expanded by 4.3 million square kilometres — an area larger than India — and now cover 40.6 percent of all land outside Antarctica. By 2100, up to five billion people could be living in drylands under a high-emissions trajectory.

Aridity is not drought. Drought ends; aridity is a permanent shift in the water balance that does not reverse when the rains return. It degrades soil, cuts crop yields, and drives migration from exactly the regions the exposure dossier identifies as the polycrisis epicentre: Sub-Saharan Africa, the Middle East, and South Asia. IPBES had already estimated that land degradation affects 3.2 billion people. The aridity data shows the trend is structural, not cyclical.

WRI's Aqueduct Water Risk Atlas finds 25 countries — housing one quarter of the global population — face extremely high water stress, using at least 80 percent of their renewable supply every year. At least 50 percent of the world's population, around four billion people, live under highly water-stressed conditions for at least one month a year. In the Middle East and North Africa, 83 percent of the population is exposed to extreme stress; in South Asia, 74 percent.

The projection compounds the problem: by 2050, an additional one billion people are expected to live under extreme water stress even in an optimistic warming scenario, and water demand is projected to rise 20–25 percent. Thirty-one percent of global GDP — about $70 trillion — will be exposed to high water stress by 2050, up from $15 trillion in 2010. Water stress is where the earth-system boundary becomes a balance-sheet event, and where the energy system meets it: thermal power plants need cooling water, and a water-constrained grid is an electricity-constrained economy.

The Global Tipping Points Report 2025 states the new reality plainly: at 1.4°C of warming, warm-water coral reefs are crossing their thermal tipping point, and parts of the polar ice sheets may have crossed thresholds that eventually commit the world to several metres of sea-level rise. Below 2°C, the Amazon rainforest is at risk of widespread dieback and the Atlantic Meridional Overturning Circulation (AMOC) is at risk of collapse.

These are not distant scenarios. Physics-based early-warning analysis published in Science Advances places the AMOC tipping point within 2025–2095 under the current trajectory. The Arctic has warmed nearly four times faster than the global average since 1979. Permafrost stores roughly twice the carbon currently in the atmosphere; as it thaws, it releases CO₂ and methane that accelerate the very warming causing the thaw. The State of the Cryosphere 2024 report concludes that current commitments, which lead toward well over 2°C, would bring irreversible ice loss with costs beyond adaptation limits for billions of people.

Ecology's Regime Shifts Database maps thirty ecosystem critical transitions, and the comparative work of Rocha et al. shows they do not operate in isolation. Coral dieback removes the habitat that sustains reef fisheries, which shifts protein supply onto other systems, which stresses coastal economies. Amazon dieback cuts the moisture the forest itself generates, drying the basin, extending fire seasons, and weakening the rainfall that South American agriculture depends on. One system's regime shift becomes another system's stress.

This is the ecological version of the polycrisis's three pathways: common stresses weaken several ecosystems at once, domino effects pass a collapse from one ecosystem to the next, and inter-systemic feedbacks lock two collapses together. The climate–biodiversity nexus is the clearest case — warming stresses species, species loss degrades the carbon sinks, weaker sinks accelerate the warming. The loop is already measurable.

The planetary-boundaries framework treats "novel entities" — plastics, synthetic chemicals, and other human-made materials — as its own boundary, and the 2023 update found it already breached. The world produces roughly 400 million tonnes of plastic waste a year, about 11 million tonnes of it entering the ocean annually, on track to triple by 2040. Plastic pollution has increased tenfold since 1980, per IPBES.

Chemical and nutrient pollution run on the same compounding logic. Excess nitrogen and phosphorus from agriculture drive the coastal eutrophication that accelerates deoxygenation. The pollution boundary and the ocean boundary are not separate problems; they are two ends of the same pipe.

The window for an orderly transition to net zero has arguably closed. Delayed policy action now means that aggressive, abrupt carbon reduction will eventually be required — disrupting carbon-intensive industries, stranding trillions of dollars in fossil assets, and displacing workers concentrated in the old energy economy. Failing to act guarantees escalating physical climate risk instead. Leaders face a paralyzing choice: accept severe near-term economic pain, or accept compounding long-term existential pain.

In a polarized, short-term election cycle, the political calculus usually favors delay — which deepens the polycrisis and raises the eventual cost of both options. This is not an argument against transition. It is the reason the transition itself has become one of the system's stresses: the longer it is postponed, the more disruptive its arrival will be, and the more the disruption will be blamed on the transition rather than on the delay.