“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 should 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 most likely inevitable. Avoiding that 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 paper’s authors and director of the Potsdam Climate Impact Research Institute.
Global warming
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 like coal, oil and gas – act like a blanket around 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 warmer than any other since 1850. Its effects are well known: intense droughts, water shortages, severe fires, sea level rise, floods, melting ice, storms catastrophic, biodiversity decline…
This problem began to gain prominence 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 these gases, although it did not enter 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 in one degree.
But the researchers stress that for a secure future, the world needs global goals beyond climate. “What we lack are comparable targets for other key environmental components,” stresses Professor Dahe Qin, another of the experts who have participated. These are also at risk.
Biodiversity
In the case of biodiversity, the variety of living beings on the planet, the objectives are not met in a percentage that they calculate 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 human-occupied spaces, they should have at least 20-25% semi-natural habitat per square kilometer.
Sweet water
The situation of fresh water is equally worrisome, 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 health, 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 for not altering river systems by more than 20%. Currently, that percentage stands at 34%. For the underground, the objective would be “not to extract more than the annual replacement rate of the place of origin”.
fertilizers
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 makes it impossible to ensure a safe supply of food. In other words, rich countries abuse them and poor countries need more. The balance proposed by the scientists is 61 million tons of nitrogen per year and between 4.5 and 9 million tons of phosphorus per year.
Air pollution by 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 the researchers, in the northern hemisphere, with more land mass and a larger population, pollution is higher, which could cause an imbalance with the southern hemisphere. In turn, this could alter rainfall patterns and affect weather events such as monsoons – the heavy rainy seasons that affect some parts of the planet. All of these changes could unleash the risk of both floods and droughts. On a global level, experts propose the figure of 0.15 micrograms per cubic centimeter of average annual difference between the two hemispheres.
“With this global scientific assessment, we provide all stakeholders with the scientific boundaries that can enable prosperous and equitable world development on a stable planet, a better future for people and the planet,” they conclude.
