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Planetary limits

Saturday 23rd September 2023.

For the first time, an international research team has quantified all nine planetary stress limits, which, taken together, define humanity’s safe margin of manoeuvre. In doing so, the scientists are providing a detailed overview of the dwindling resilience of our planet. Global warming, biosphere, deforestation, pollutants such as plastics, nitrogen cycles and freshwater: six out of the nine planetary limits have already been exceeded as we speak. At the same time, the pressure exerted by global processes is mounting. This is shown by a new study published in the journal Science Advances by scientists working with the Potsdam Institute for Climate Impact Research (PIK, Germany).

„This general update of the Planetary Limits clearly shows: the earth is a sick patient. Pressure on the planet is increasing further, exceeding vital stress limits. We don’t know for how long we can exceed critical limits to a degree where its consequences lead to irreversible changes and damage”, in the words of Johan Rockström, co-author of the study and PIK’s director.

This second update of the Planetary Limits since its inception in 2009 is the first to include a complete verification of all nine processes and systems, which taken together determine the stability and resilience of the planet. While crossing a line might not be synonymous with drastic changes that become immediately visible, it does mark a critical threshold for significantly increased risk. As the main author, Katherine Richardson of Copenhagen University, explains: „We may imagine the Earth as a human body, and the planetary limits as a kind of blood pressure. Blood pressure exceeding 120/80 does not mean that there is an immediate risk of cardiac arrest, but it does increase the risk. Which is why we are working on lowering the blood pressure. For instance the limit for reducing ozone has not been exceeded at global level, yet increasingly at regional level. While this is still the case in the Antarctic, we can already glimpse an improvement – thanks to global initiatives achieved by the Montreal Protocol.“


Beyond Climate: what’s new in the Planetary Limits 2023 update?

This is the first time that the limit for Novel Entities (‚the introduction of new materials’) has been quantified. The evaluation shows that it has been exceeded. Novel Entities comprise the release of all new kinds of chemical compounds introduced into the environment by humankind, including micro plastics, pesticides or nuclear waste. The limit for fresh water now refers both to what is known as „green“ water (contained in agricultural and natural soils and plants), as well as to „blue“ water (the water of rivers, lakes, etc.). Both these limites have been exceeded. A further novelty was the introduction of a new control variable for the biosphere’s ability to function (integrity) in the earth‘s system. Here too, the analysis revealed that the limit has been exceeded, a process that has been noticeable as far back as the late 19th century, when agriculture and forestry were heavily expanded on a global scale. The research team emphasises that the planet’s resilience depends on far more factors than climate change alone.

Alongside climate change the biosphere’s ability to function represents the second pillar supporting the stability of our planet. And just as happens with the climate humanity is currently destabilising this pillar too, by depleting too much biomass, destroying too many habitats, deforesting too many surfaces, and so forth. Research shows that in the future the two have to go hand in hand: limiting global warming and preserving a functioning biosphere.

Considering the earth system as a whole

„Science and society are extremely concerned with the increase in signs pointing to the dwindling resilience of the planet, as shown by the fact that planetary limits are being exceeded. This takes us closer to potential tipping points, lowering the chance we still have to keep to the planetary climate limit of 1.5°C“, concludes PIK director Johan Rockström. „At the same time it’s a real breakthrough that we have now scientifically quantified humanity’s safe room for manoeuvre on this Earth. This gives us a guide to necessary measures, providing the first complete picture of our planet’s capacities to cushion the pressure we put on it. Possessing this knowledge provides an excellent basis for more systematic efforts to protect the resilience of our planet, to allow it to recover and to restore it again – step by step.“

For more information: https://www.science.org/doi/10.1126/sciadv.adh2458

Uwe Heitkamp (62)

trained TV journalist, book author and hobby botanist, father of two grown-up children, knows Portugal for 30 years, founder of ECO123. Translations: Dina Adão, John Elliot, Ruth Correia, Patrícia Lara, Kathleen Becker

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