Our planet is in bad shape and the risk is increasing that the stability and resilience of the Earth system could soon be compromised. For this reason, scientists will from now on give “patient Earth” an annual health check in order to keep an eye on the situation, develop treatment options and identify the underlying causes. The findings of the first annual examination were released on September 24th: the Planetary Health Check (PHC), a scientific report compiled by The Planetary Boundaries Science (PBScience), a new initiative led by the Potsdam Institute for Climate Impact Research (PIK). The scientists examined critical Earth system processes that regulate life support systems on Earth in order to determine whether we are still operating in the safe space within which humanity can thrive while keeping the planet stable and resilient. Nine planetary boundaries (PB) were defined: Climate Change, Biosphere Integrity, Land System Change, Freshwater Change, Biogeochemical Flows, the Introduction of Novel Entities, Ocean Acidification, Atmospheric Aerosol Loading and Stratospheric Ozone Depletion. Once a boundary is breached, there is a risk of large-scale abrupt or irreversible environmental changes. “The overall diagnostic is that the patient, Planet Earth, is in critical condition. Six of nine Planetary Boundaries are transgressed. Seven PB processes show a trend of increasing pressure so that we will soon see the majority of the Planetary Health Check parameters in the high-risk zone,” says PIK Director Johan Rockström.

The concept of the planetary boundaries is not new: In 2009, a group of 29 scientists published a ground-breaking article in the journal Nature titled “A safe operating space for humanity”. In 2015, an update was released which came to the conclusion that the safe operating space for four of the nine systems had already been clearly exceeded, namely in the area of climate change, land-system change, human interference with the biogeochemical cycles (phosphorus and nitrogen) and the loss of biodiversity. In 2023, another study was published which, for the first time, provides a complete analysis of all nine processes and systems that determine the stability and resilience of the planet. The „Planetary Health Check” will now take stock each year and combine earth and world data, the latest scientific information and multidisciplinary insights with the aim of bringing our planet back to a safe operating zone. “Six of the nine planetary boundaries are transgressed, put into context in the report by high-resolution spatial maps of local and regional trends for all nine boundaries,” explains Levke Caesar, PIK Scientist, Co-Lead of PBScience, and one of the lead authors of the PHC. “The message is clear, local actions impact the planet, and a planet under pressure can impact everyone, everywhere. Securing human wellbeing, economic development, and stable societies requires a holistic approach where the protection of the planet takes center stage,” she added.

The authors of the PHC evaluate 13 control variables across the nine planetary boundary processes to report on the overall health of our planet. The six processes that have breached safe levels are: Climate Change, Biosphere Integrity, Land System Change, Freshwater Change, Biogeochemical Flows (phosphorus and nitrogen), and the Introduction of Novel Entities. In these areas, the situation is deteriorating, making further transgression in the near future very likely. “Our updated diagnosis shows that vital organs of the Earth system are weakening, leading to a loss of resilience and rising risks of crossing tipping points,” says Caesar. With regard to climate change, the report shows that atmospheric CO2 concentrations have been continuously rising since industrialization and are now higher than at any time in the last 15 million years. A persistent warming trend is observed that has accelerated since the late 20th century. Global mean temperatures are now higher than at any point since human civilizations emerged on Earth. The changes in biosphere integrity are also alarming: The two indicators here, the global loss of genetic diversity and the decline in functional integrity (measured as energy available to ecosystems), have both exceeded safe levels. This trend is accelerating, particularly in regions with intensive land use. As a result, Earth’s biosphere is losing resilience, adaptability, and its capacity to mitigate various pressures, including those from transgressing other planetary boundaries. Land system change, especially due to deforestation and urbanization, is diminishing ecological functions like carbon sequestration, moisture recycling, and habitats for wildlife. Due to land use and increasingly also due to climate change, global and regional forests have declined steadily over the last few decades across all major forest biomes. Most regions are already in the High Risk Zone, well beyond their safe boundaries, while some areas, such as temperate and tropical America, have only recently surpassed them.

There are two indicators to measure the alteration of freshwater cycles: Human-induced disturbance of “blue water” (referring to water in lakes, rivers, and reservoirs) and of “green water” (referring to the stock of soil moisture which is the water available to plants). Local streamflow and soil moisture deviations have significantly increased since the late 19th century, surpassing their respective boundaries in the early 20th century. On around 18% of the global land area, blue water in lakes, rivers and reservoirs is experiencing dry/wet deviations beyond safe levels. And around 16% of the global land area experience soil moisture levels beyond safe levels. “The increasing variability and instability in global freshwater and terrestrial water systems signal growing concerns for water resource management and environmental stability,” according to the executive summary of the report. The biogeochemical flows analysed in the report are the global nutrient cycles of nitrogen and phosphorus. The use of these nutrients in agriculture has exceeded safe boundary levels. This has led to severe environmental impacts such as water pollution, eutrophication, harmful algal blooms, and so-called “dead zones” in freshwater and marine ecosystems. The problem has been prevalent in industrialized countries for a long time and is becoming an growing threat in developing regions as well.

The sixth boundary that has been transgressed is related to the introduction of novel entities worldwide. This includes synthetic chemicals and substances (e.g., microplastics, endocrine disruptors, organic pollutants), radioactive materials (e.g., nuclear waste, nuclear weapons), and human interventions in evolutionary processes, such as genetically modified organisms (GMOs). According to the report, novel entities have been introduced at a large scale, yet a significant portion of these substances remains untested for their environmental impacts: “This indicates that the boundary is likely exceeded, although exact figures are uncertain. Novel entities can disrupt critical Earth system processes (e.g., CFCs notably damaged the ozone layer), harm ecosystems (e.g., pesticides have caused significant declines in insect and pollinator populations), and lead to long-term, possibly irreversible changes in the environment, including the contamination of soil and water bodies and the alteration of natural habitats,” the authors warn. Apart from the six boundaries that have already been breached, another one is close to being transgressed: Ocean acidification - the phenomenon of increasing acidity (decreasing pH) in ocean water due to the absorption of atmospheric CO2 - is approaching a critical threshold. There have been significant declines in surface aragonite saturation, particularly in high-latitude regions like the Arctic and Southern Ocean. Aragonite is a form of calcium carbonate used by many calcifying organisms (e.g., corals and shellfish) to construct their shells or skeletons. This process harms calcifying organisms, impacting marine ecosystems, and reduces the ocean's efficiency in acting as a carbon sink. “When we look at the trends of Earth’s health indicators, we see that soon the majority of them will be in the high-risk zone,” highlights Boris Sakschewski, Co-lead of PBScience and lead author of the report. “We need to reverse this trend. We know that all Planetary Boundary processes act together and each one needs protection to protect the whole system”, he concluded. (ab)