A new study published in the journal Science Advances has revealed that Earth is “well outside the safe operating space for humanity” in six out of nine key measurements of its health. The study, which was led by an international team of scientists, assessed the state of the planet’s climate, biodiversity, land, freshwater, nutrient pollution, novel chemicals, ocean acidification, air pollution and ozone layer. The researchers found that most of these global systems have been pushed far from the stable and healthy state that existed for the past 10,000 years, the period known as the Holocene, in which modern civilization emerged.
Climate change and biodiversity loss pose the greatest threats
The study identified climate change and biodiversity loss as the two most worrying factors that threaten the Earth’s life support systems. The researchers said that the safe boundary for climate change was surpassed in the late 1980s, when the global average temperature exceeded the pre-industrial level by about 0.5°C. Since then, the temperature has risen by another 0.5°C, reaching 1.1°C above the pre-industrial level in 2020. The study warned that if the temperature rises above 1.5°C, the risks of irreversible and catastrophic changes in the Earth’s systems will increase significantly.
Biodiversity loss, which refers to the decline in the variety and abundance of life on Earth, was also found to be beyond the safe boundary. The study estimated that the current rate of species extinction is about 100 to 1,000 times higher than the natural background rate, and that the loss of genetic diversity within species is also accelerating. The researchers said that biodiversity loss reduces the resilience and stability of the Earth’s systems, as well as the benefits that humans derive from nature, such as food, water, medicine and recreation.
Other factors are also out of balance
The study also found that four other factors are outside the safe operating space for humanity: land, freshwater, nutrient pollution and novel chemicals. Land refers to the amount and quality of terrestrial ecosystems, such as forests, grasslands and wetlands, that provide habitats for wildlife and regulate the climate. The study said that about 75% of the Earth’s ice-free land surface has been altered by human activities, such as agriculture, urbanization and deforestation, resulting in habitat loss, soil degradation and carbon emissions.
Freshwater refers to the availability and quality of water resources, such as rivers, lakes and aquifers, that sustain life and human activities. The study said that about 2.5 billion people live in water-scarce regions, and that water pollution from agricultural runoff, industrial waste and sewage is affecting the health of aquatic ecosystems and human well-being.
Nutrient pollution refers to the excess of nitrogen and phosphorus in the environment, which are essential elements for life but can cause harmful effects when they accumulate beyond natural levels. The study said that human activities, such as fertilizer use, fossil fuel combustion and wastewater discharge, have increased the global flows of nitrogen and phosphorus by about two to three times, leading to eutrophication, algal blooms, dead zones and greenhouse gas emissions.
Novel chemicals refer to the human-made compounds that are not naturally occurring, such as pesticides, plastics, pharmaceuticals and radioactive materials, that can have adverse impacts on the environment and human health. The study said that about 350,000 novel chemicals have been registered since the 1950s, and that many of them are persistent, bioaccumulative and toxic, meaning that they do not break down easily, accumulate in living organisms and cause harm to living cells and organs.
Some factors are still within the safe range, but not for long
The study found that three factors are still within the safe operating space for humanity, but two of them are heading in the wrong direction: ocean acidification and air pollution. Ocean acidification refers to the decrease in the pH of seawater, which is caused by the absorption of carbon dioxide from the atmosphere. The study said that ocean acidification affects the growth and survival of marine organisms, such as corals, shellfish and plankton, that form the basis of the marine food web and provide important ecosystem services, such as coastal protection and tourism.
Air pollution refers to the concentration of harmful substances in the atmosphere, such as particulate matter, ozone, nitrogen oxides and sulfur dioxide, that are emitted by human activities, such as transportation, industry and power generation. The study said that air pollution causes respiratory and cardiovascular diseases, premature deaths, crop damage and climate change.
The only factor that is within the safe range and showing improvement is the ozone layer, which is the layer of the atmosphere that protects life from harmful ultraviolet radiation from the sun. The study said that the ozone layer has been recovering since the 1980s, thanks to the global efforts to phase out the use of ozone-depleting substances, such as chlorofluorocarbons (CFCs), under the Montreal Protocol.
The need for urgent and transformative action
The study concluded that the Earth is losing its resilience and stability, and that humanity is facing unprecedented and existential risks from the degradation of its life support systems. The researchers called for urgent and transformative action to restore and protect the Earth’s systems, and to ensure a safe and prosperous future for humanity and nature. They suggested that some of the most effective solutions include restoring and conserving natural habitats, reducing greenhouse gas emissions, improving water and nutrient management, regulating and replacing harmful chemicals, and enhancing international cooperation and governance.