The biological and physical limits of the planet, the threshold beyond which the Earth ceases to be a safe and habitable place for human life, are being surpassed by the alterations caused by man. The overexploitation of resources and its impacts are putting the Earth’s ability to overcome (resilience) and continue to provide life support and essential environmental services on the ropes, and thus avoid the risk of collapse. The result is that “human beings are incurring colossal risks” that compromise the future of civilization and all beings living on Earth, according to a study published in the journal Nature.
A team of 40 scientists led by Johan Rockström, co-chairman of the Earth Commission, has defined the five great limits of the planet, something like the five red traffic lights that humanity should not skip. And the conclusion is that most of these thresholds are being crossed.
“We are in the Anthropocene, putting the stability and resilience of the entire planet at risk,” says Johan Rockström, lead author and director of the Potsdam Institute for Research on the Impact of Climate Change.
Scientists make the first major attempt to objectify the safe and fair boundaries of the Earth system for various of the biological and physical processes and systems that regulate it.
But they not only evaluate the state of planetary health, but also the dimension of justice; that is to say, the conditions that avoid the consequences and significant damage of this situation on human populations are used as a criterion.
Specifically, the Earth Commission has quantified the limits that are considered safe and fair for the preservation of the climate, biodiversity, fresh water bodies, nutrient cycles and the presence of polluting aerosols in the atmosphere; and concludes that most of these indicators have been transferred.
For example, it has already exceeded the ‘just and safe’ limit for the climate, set at a temperature increase of 1°C above pre-industrial temperature levels, as tens of millions of people are already affected by the change today. climate. The “safe†limit in the strict sense is 1.5ºC, a bar that defines the high probability of multiple climatic hotspots. However, the “fairness” criterion penalizes the “final grade” and therefore it is concluded that the climatic limit has been exceeded.
To achieve the protection of nature, the “safe and fair†limit is that between 50 and 60% of the world contains predominantly natural ecosystems. However, only 45 to 50% of the planet has an intact ecosystem.
In areas disturbed by humans, such as farms, cities and industrial estates, the Commission says that at least 20-25% of the land should be dedicated to semi-natural habitats such as natural parks, wooded areas to maintain the ecosystem, or that provide pollination services. , regulation of water quality, control of pests and diseases and provides access to nature. However, around two-thirds of altered landscapes do not achieve this goal.
The benchmark for surface water is that no more than 20% of the flow of rivers and streams in any catchment area should be disturbed or blocked, as this results in decreased water quality and loss of habitats for freshwater species. This “safe limit†has already been exceeded on a third of the world’s land by hydroelectric dams, drainage systems and construction.
The balance also offers a cliffhanger for groundwater systems, where the safe limit is that aquifers are not depleted faster than they can be replenished. Yet 47% of the world’s river basins are being depleted at an alarming rate. This is a big problem in population centers like Mexico City and areas of intensive agriculture like the North China Plain.
Another target concerns aerosol pollution, which accumulates in the exhaust pipes of cars, factories, and coal, oil, and gas power plants.
At the local level, for example in cities, the criteria of the World Health Organization are followed by establishing a limit of 15 micrograms per cubic meter of average annual exposure to small particles, known as PM2.5, which can damage the lungs. and the heart. This is a social justice issue because the poorest communities, often predominantly black, tend to suffer the worst outcomes, as many are located in vulnerable areas.
Nutrients, ie excess fertilizers (nitrogen and phosphorus) is another focus of concern because farmers in richer countries are applying more nitrogen and phosphorus to the land than the plants and soil can absorb. These practices temporarily increase yields, but cause leaks, spills and water runoff that lead to the contamination of lakes, lagoons and algae proliferation to contaminate water resources.
Poorer nations need more fertilizer, while rich nations need to reduce the surplus. The “safe and fair limit” is a complex balance: for now it contributes a global surplus of 61 million tons of nitrogen and about 6 million tons of phosphorus.
“The results are quite worrying. Unless a transformation occurs in time, it is very likely that the tipping points of irreversible change (tipping points) will be exceeded and, consequently, a widespread impact on human well-being. Avoiding that scenario is crucial if we are to ensure a safe and just future for current and future generations,” adds Rockström.
Experts have so far identified seventeen critical climate elements, nine of which are related to the cryosphere. “The Asia High Mountain Cryosphere is changing rapidly and is on the verge of becoming a new ‘climate hotspot’, which may impact the regional socio-economy,” said Professor Dahe Qin, Co-Chairman of the Asia High Mountain Cryosphere. Earth Commission and director of the Academic Committee of the Chinese Academy of Sciences.
The limits of the Earth system will be the basis for the establishment of new ‘science-based objectives’ (science-based targets) for companies, cities and governments to address the different crises: the increasing human exposure to the climate emergency, the decline of the biodiversity, water scarcity, damage to ecosystems from excessive use of fertilizers in some parts of the world (along with lack of access in others) and damage to health from air pollution.
“A safe and just transformation urgently requires collective action by multiple actors, especially in governments and companies to act within the limits of the Earth system and keep intact the system that supports life on the planet. The proper management of The global commons has never been more urgent or more important,” says Wendy Broadgate, Executive Director of the Earth Commission and Director of Future Earth’s Global Hub Sweden.
The authors believe that this comprehensive scientific assessment provides society with limits within which prosperous and equitable world development can occur on a stable planet.
“‘Science-based targets’ can be adopted by cities, companies and countries to address the global systemic crises of climate change, biodiversity loss, nutrient overload, excessive water use and air pollution” concludes Rockström.
