“The Earth is already in danger.” This is the worrying conclusion reached by 40 researchers from around the world in a study published this Wednesday in the journal ‘Nature’ and in which for the first time the “safe and fair limits” for the health of the planet are quantified. The danger does not come only from climate change. The experts responsible for this work, belonging to the so-called ‘Earth Commission’, have identified four other interrelated areas that must also be monitored – biodiversity, freshwater quality, fertilizers and air pollution – and have detected that in most of them the acceptable limits have already been exceeded.
«The results of our health check are quite worrying: several limits have already been transgressed, on a global and local scale. This means that unless a transformation occurs, irreversible tipping points and widespread impacts on human well-being are very likely inevitable. Avoiding this scenario is crucial if we want to ensure a safe and fair future for current and future generations,” explains Professor Johan Rockström, one of the authors of the work and director of the Potsdam Climate Impact Research Institute.
It has been shown that humans are responsible for the global warming experienced in the last 200 years. Greenhouse gases – primarily the burning of fossil fuels such as coal, oil and gas – act like a blanket enveloping the Earth, trapping heat from the sun and raising temperatures at a faster rate than in recent years. two millennia. Specifically, each of the last four decades has been hotter than any other since 1850. Its effects are well known: intense droughts, water shortages, severe fires, rising sea levels, floods, melting ice at the poles, storms catastrophic, decrease in biodiversity…
This problem began to gain notoriety more than a quarter of a century ago, in 1995, with the first of the annual conferences on climate change organized by the UN. That year it took place in Berlin. Two years later, in Kyoto, an agreement was reached for the first time to reduce the emission of the aforementioned gases, although it did not come into force until 2005. Currently the global increase in temperature stands at 1.2 degrees per year, which would exceed the ideal limit that these experts place at one degree.
But researchers stress that for a secure future, the world needs global goals beyond climate. “What we lack are comparable objectives for other key environmental components,” emphasizes Professor Dahe Qin, another of the experts who participated. These are also at risk.
In the case of biodiversity, the variety of living beings on the planet, the objectives are not met by a percentage that they estimate between 40 and 50%. The causes are well identified: “The change in land use, the overexploitation of natural resources, pollution, the spread of invasive species and global warming.” The safe and fair limit would be that between 50 and 60% of the earth’s surface were natural spaces. And in the case of spaces occupied by humans, they should have at least 20-25% semi-natural habitat per square kilometer.
The freshwater situation is equally worrying, both because of its quality and because millions of people do not have access to it. Its scarcity causes direct effects on crops and, consequently, on the food supply. Regarding its healthiness, contaminated water transmits diseases that can be fatal. Equally important are groundwater. Extracting them in excess can affect the flow of rivers, vital for the planet. The limit for surface waters would be to not alter river systems by more than 20%. Currently, that percentage stands at 34%. For underground, the objective would be “not to extract more than the annual replacement rate of the place of origin.”
Fertilizers, especially nitrogen and phosphorus, are used in agriculture to improve crop yields. However, its excessive use can degrade the ecosystem and affect biodiversity. At the opposite extreme, its scarcity in some parts of the world does not ensure a secure food supply. In other words, rich countries abuse them and poor countries would need more. The balance proposed by scientists is 61 million tons of nitrogen per year and between 4.5 and 9 million tons of phosphorus per year.
Air pollution from aerosols
Most of these particles suspended in the air come from nature – volcanoes, for example. It is in populated areas where those of human origin predominate, caused by emissions from cars or industries. According to researchers, in the northern hemisphere, with more land mass and greater population, pollution is greater, which could cause an imbalance with the southern hemisphere. In turn, this could alter rainfall patterns and affect weather phenomena such as monsoons – the seasons of heavy rain that affect some parts of the planet. All these changes could unleash the risk of both floods and droughts. At a global level, experts propose the figure of 0.15 micrograms per cubic centimeter of average annual difference between both hemispheres.
“With this global scientific assessment, we provide all stakeholders with the scientific boundaries that can enable prosperous and equitable global development on a stable planet, a better future for people and the planet,” they conclude.