On the Brink: Exceeding the Seventh Planetary Boundary

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The planetary boundaries framework identifies nine processes crucial to maintaining the stability and health of the planet. These limits represent fundamental elements of the Earth system that are important for global well-being, but strongly influenced by human activities. The Nine Planetary Limits framework approach was proposed in 2009 by an international research team led by Johan Rockström and Will Steffen, to define and measure levels of human impact that, if met, would allow the Earth to remain in a state similar to the Holocene. The Holocene is the era characterised by low climatic variability, predating the Anthropocene, the period in which humans play a major role in modifying natural systems, which is currently underway. Today,all nine planetary boundaries are severely compromised by human activities, leading to a growing imbalance with respect to the new environmental cond

The Potsdam Institute for Climate Impact Research (PIK) is at the forefront of multidisciplinary research with the aim of ensuring global sustainability and a more secure climate future. The PIK is part of the Leibniz Institute for European History, a non-university scientific research centre of global significance. Exploiting high-level research, the PIK offers valuable scientific advice for political decisions. The institute consists of approximately 400 members with an international staff, led by an interdisciplinary team of directors.

The Planetary Boundaries Approach, known as Planetary Boundaries Science, was developed by Johan Rockström, director of the Potsdam Institute for Climate Impact Research (PIK), with the support of the Planetary Guardian and other partners. The PIK introduced the Planetary Health Check (PHC), a report and an innovative scientific tool that integrates Earth sciences, observational data and applies a multidisciplinary approach to assess the health of the planet and to identify solutions that can reduce the impact of human activities. The PHC is published annually, providing up-to-date data on the state of the Earth's health.

The seventh planetary limit is represented by the acidification of the oceans; the exceeding of this limit lies in the excessive anthropogenic emissions of carbon dioxide into the atmosphere. Although atmospheric CO2 contributes to global warming by trapping heat, the oceans play a key ecological role by constantly absorbing this greenhouse gas, thus mitigating the heat-storing effect. In the past, this gas exchange took place ina slow manner, over thousands or even tens of thousands of years. However, with the onset of the Industrial Revolution, humans disrupted this natural process, putting some 400 billion tonnes of carbon into the atmosphere through the use of fossil fuels and deforestation.

The uptake of carbon dioxide by the oceans causes a change in the pH of ocean waters, as CO2, combining with water, forms carbonic acid. The pH is nothing more than an indicator of the acidity of a solution; a lowering of its value means that the water is increasingly acidic. This change in pH alters the balance of the marine ecosystem, posing a serious threat to ocean flora and fauna. The most vulnerable organisms are the corals and those with calcium carbonate skeletons, which weaken with even the slightest changes in the acid-base balance. This process is similar to corrosion and could trigger a domino effect, with serious repercussions on the entire marine food chain.

The seventh planetary limit is now close to being exceeded, according to a new report by the Potsdam Institute for Climate Impact Research (PIK). The remaining two planetary processes, the reduction of stratospheric ozone and the increase of the aerosol load in the atmosphere, i.e. the content of particulate matter harmful to human health, remain in the safe zone and are not expected to exceed their limits in the near future. However, the Earth is under pressure and this translates into a collective impact, involving both nature and humanity.

Currently,human-caused perturbations to the environment are treated as isolated and separate issues, such as climate change, biodiversity loss and pollution. This approach ignores the interactions that exist between these issues and their cumulative effects on the Earth system. The Planetary Limits framework, on the other hand, provides a 360-degree scientific view, which considers the health of the planet as a whole, highlighting the need for an integrated approach to secure the future of humanity. According to Levke Caesar, PIK scientist and co-head of Planetary Boundaries Science, it is essential to adopt a model of development that makes sustainability the guiding principle of all choices and activities. Only in this way can human wellbeing, economic development and the stability of societies be ensured, putting the protection of the planet at the centre.

The Planetary Health Check represents a important advance in our mission to understand and protect the planet. We know that we are weakening the Earth's resilience, and this scientific update emphasises that all actions must consider impacts on a planetary scale. It is critical to manage the planet in all sectors to ensure security, prosperity and equity. According to Johan Rockström, PIK director and co-founder, quantifying the limits of a healthy planet provides crucial tools for policy and business to avoid unmanageable risks. It is in humanity's interest not to disrupt the Earth's system to the point of drastically changing global environmental conditions.