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Planetary boundaries
| Planetary boundaries - 2025 |
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| The nine planetary boundaries and their status
Climate change: Increased greenhouse gases and aerosols in Earth's atmosphere trap heat that would otherwise escape into space. The climate change planetary boundary assesses the change in the ratio of incoming and outgoing energy of the Earth. More carbon dioxide in the atmosphere and more trapped radiation causes global temperatures to rise and alters climate patterns. This boundary is transgressed, and CO2 concentrations are rising. Novel entities: Technological developments introduce novel synthetic chemicals into the environment, mobilize materials in wholly new ways, modify the genetics of living organisms, and otherwise intervene in evolutionary processes and change the functioning of the Earth system. The amount of synthetic substances released into the environment without adequate safety testing places novel entities in the high-risk zone. Stratospheric ozone depletion: Ozone high in the atmosphere protects life on Earth from incoming ultraviolet radiation. The thinning of the ozone layer, primarily due to human-made chemicals, allows more harmful UV radiation to reach Earth's surface. Total ozone is slowly recovering because of the international phasing-out of ozone-depleting substances since the late 1980s. Ozone depletion is therefore currently in the Safe Operating Space. Atmospheric aerosol loading: Changes in airborne particles from human activities and natural sources influence the climate by altering temperature and precipitation patterns. Although large-scale air pollution already causes changes to monsoon systems, forest biomes and marine ecosystems, the global metric used in the planetary boundaries framework – interhemispheric difference in atmospheric aerosol loading – places this process just within the Safe Operating Space. Ocean acidification: The acidity of ocean water increases (its pH decreases) as it absorbs atmospheric CO2. This process harms organisms that need calcium carbonate to make their shells or skeletons, impacting marine ecosystems, and it reduces the ocean's efficiency in acting as a carbon sink. The indicator for ocean acidification, the aragonite saturation state, is currently within the Safe Operating Space but the rising atmospheric CO2 concentration means it is close to crossing the boundary. Modification of biogeochemical flows: Nutrient elements like nitrogen and phosphorus are crucial for supporting life and maintaining ecosystems. Industrial and agricultural processes disrupt natural cycles and modify the nutrient balance for living organisms. This boundary is transgressed, because both the global phosphorus flow into the ocean and the industrial fixation of nitrogen (converting stable nitrogen from the atmosphere into bioreactive forms) have disrupted global biogeochemical flows. Freshwater change: The alteration of freshwater cycles, including rivers and soil moisture, impacts natural functions such as carbon sequestration and biodiversity, and can lead to shifts in precipitation levels. Human-induced disturbances of both blue water (e.g. rivers and lakes) and green water (i.e. soil moisture) have exceeded the planetary boundary. Land system change: The transformation of natural landscapes, such as through deforestation and urbanization, disrupts habitats and biodiversity and diminishes ecological functions like carbon sequestration and moisture recycling. Globally, the remaining forest areas in tropical, boreal, and temperate biomes have fallen below safe levels. Biosphere integrity: The diversity, extent, and health of living organisms and ecosystems affects the state of the planet by co-regulating the energy balance and chemical cycles on Earth. Disrupting biodiversity threatens this co-regulation and dynamic stability. Both the loss of genetic diversity and the decline in the functional integrity of the biosphere are outside safe levels. |
| https://www.stockholmresilience.org/research/planetary-boundaries.html |
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| 60 percent of the world’s land area is in a precarious state - PIK - 2025 |
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| Functional biosphere integrity refers to the plant world’s ability to co-regulate the state of the Earth system. This requires that the plant world is able to acquire enough energy through photosynthesis to maintain the material flows of carbon, water and nitrogen that support the ecosystems and their many networked processes, despite today’s massive human interference. Together with biodiversity loss and climate change, functional integrity forms the core of the Planetary Boundaries analytical framework for a safe operating space for humanity.
“There is an enormous need for civilisation to utilise the biosphere – for food, raw materials and, in future, also for climate protection,” says Fabian Stenzel, lead author of the study and member of the PIK research group Terrestrial Safe Operating Space. “After all, human demand for biomass continues to grow – and on top of that, the cultivation of fast-growing grasses or trees for producing bioenergy with carbon capture and storage is considered by many to be an important supporting strategy for stabilising climate. It is therefore becoming even more important to quantify the strain we’re already putting on the biosphere – in a regionally differentiated manner and over time – to identify overloads. Our research is paving the way for this.” Two indicators to measure the strain and the risk The study builds on the latest update of the Planetary Boundaries framework published in 2023. “The framework now squarely puts energy flows from photosynthesis in the world’s vegetation at the centre of those processes that co-regulate planetary stability”, explains Wolfgang Lucht, head of PIK’s Earth System Analysis department and coordinator of the study. “These energy flows drive all of life – but humans are now diverting a sizeable fraction of them to their own purposes, disturbing nature’s dynamic processes.” The stress this causes in the Earth system can be measured by the proportion of natural biomass productivity that humanity channels into its own uses – through harvested crops, residues and timber – but also the reduction in photosynthetic activity caused by land cultivation and sealing. The study added to this measure a second powerful indicator of biosphere integrity: An indicator of risk of ecosystem destabilisation records complex structural changes in vegetation and in the biosphere’s water, carbon and nitrogen balances. Europe, Asia and North America particularly affected Based on the global biosphere model LPJmL, which simulates water, carbon and nitrogen flows on a daily basis at a resolution of half a degree of longitude/latitude, the study provides a detailed inventory for each individual year since the 1600, based on changes in climate and human land use. The research team not only computed, mapped and compared the two indicators for functional integrity of the biosphere, but also evaluated them by conducting a mathematical comparison with other measures from the literature for which “critical thresholds” are known. This resulted in each area being assigned a status based on local tolerance limits of ecosystem change: Safe Operating Space, Zone of Increasing Risk or High Risk Zone. The model calculation shows that worrying developments began as early as 1600 in the mid- latitudes. By 1900, the proportion of global land area where ecosystem changes went beyond the locally defined safe zone, or were even in the high-risk zone, was 37 and 14 percent respectively, compared to the 60 and 38 percent we see today. Industrialisation was beginning to take its toll; land use affected the state of the Earth system much earlier than climate warming. At present, this biosphere boundary has been transgressed on almost all land surface – primarily in Europe, Asia and North America – that underwent strong land cover conversion, mainly due to agriculture. PIK Director Rockström: Impetus for international climate policy “This first world map showing the overshoot of the boundary for functional integrity of the biosphere, depicting both human appropriation of biomass and ecological disruption, is a breakthrough from a scientific perspective, offering a better overall understanding of planetary boundaries,” says Johan Rockström, PIK Director and one of the co-authors of the study. “It also provides an important impetus for the further development of international climate policy. This is because it points to the link between biomass and natural carbon sinks, and how they can contribute to mitigating climate change. Governments must treat it as a single overarching issue: comprehensive biosphere protection together with strong climate action.” |
| https://www.sciencedirect.com/science/article/pii/S2590332225002192 |
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