In 2009, a large group of scientists identified nine thresholds that humans should not exceed if they want the Earth to remain hospitable to civilization. These included the available fresh water, the protected natural area, the level of pollution, the ozone layer and of course climate change. Now, for the first time, a new report, just published in Nature, quantifies the thresholds for each of these issues that should not be crossed in order for the Earth system to be safe and just not only for people today, but also for generations to come. Seven of these have already been exceeded all over the world or in large parts of the planet. The apocalyptic picture is softened by the fact that the hole in the tropospheric ozone layer was removed from the list: humanity was able to solve the problem in time.
The report identified the limits to the sustainability and security of the Earth system, understood as a global ecosystem. It was written at the time that if widely adopted, a series of disastrous changes would follow. But since then another thought has been added to safety: The earth system will not be safe if it is not also fair. It is one of the contributions of this new report, the quantification of justice between humans, the rest of living beings and future generations.
“Humans are part of the earth system. “We are a big part of the problem and we have to be a big part of the solution,” summarizes Noelia Zafra, co-author of the paper. “But the problems and solutions do not affect everyone equally, and there are some people who endure the inconvenience of maintaining the Earth system while others largely benefit. It also happens that a few cause problems for many,” adds this researcher from BC3, the Basque climate change research center.
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This is the case, for example, with the emissions that cause this climate change. Its rise dates back to the beginning of the industrial revolution and is due to its main players, Europe and North America. Even now, as emerging economies like China are beginning to take much of the responsibility, half of greenhouse gas emissions come from the richest 10% of the population. “We will not be able to act together against the climate and biodiversity crisis if we do not all start from the same situation and there are conflicts between us,” adds Zafra.
“It’s not a goal, it’s a limit”
The 2015 Paris Agreement set the acceptable increase in average global temperature at 1.5 degrees to curb climate change. But this need for justice explains why the report’s authors further lowered the limit of additional warming the planet could tolerate, to one degree. The director of the Potsdam Institute for Climate Research (Germany), Johan Rockström, recalled in an online press conference that “1.5 degrees is not a goal, it is not a goal, it is a physical limit.” From this limit, the Risks very high, but even before this limit is exceeded, the warming has profound consequences. Scientists estimate that the temperature has already risen by an average of 1.2 degrees and the effects are being felt in most parts of the planet, affecting millions of people.
“Humans are part of the earth system. We are a big part of the problem and we have to be a big part of the solution.”
Noelia Zafra, BC3 researcher
One of the contributions of this report is that it doesn’t stop at the climate emergency. It is already clear to its authors that climate change is not the only existential problem facing human civilization. Another quantified threshold concerns the part of the planet that still retains its original state. The work, sponsored by the Earth Commission, an alliance of leading scientists, stipulated that between 50 and 60 percent of the land’s surface should be kept free from pastoralism, agriculture, mining or other human interference. “We are currently between 45% and 50%. So just below the limit,” recalls David Obura from the CORDIO organization and co-author of the study. Obura also points out that denatured areas of the planet can still make the Earth system more resilient. The millions of hectares devoted to grazing and cropping – including cities – can be part of the solution, provided that of every square kilometer of modified ecosystem, at least 20% has vegetation, even if not natural.
Other thresholds that have been quantified and already exceeded are the additional nutrients that humans supply to the earth. In particular, they quantify the anthropogenic nitrogen and phosphorus, which are mainly used in agriculture. An excess of these elements alters both the substrate and the water in a process called eutrophication. Examples such as the Mar Menor in Murcia illustrate this very well. The limit values have not yet been exceeded worldwide, but in large parts of the world they are related to the use of water on the surface and underground. According to the report, one-third of the world is already over-exploiting surface water resources, with the limit set at 20%. For groundwater, the replenishment rate is not respected in half of the world. As for air pollution caused by the emission of particles of non-natural origin (engine combustion, heating and cooling, industrial emissions, etc.), the limit is far from being exceeded worldwide, but has already been exceeded in different regions of the planet, such as Southeast Asia.
“Fresh water, air, pollutants such as nitrogen and phosphorus, and the integrity of the biosphere provide resilience and stability to the entire Earth system.”
Johan Rockström, Director of the Potsdam Institute for Climate Research, Germany
The report admits that it ignores problems such as ocean acidification, the accumulation of plastic and microplastics, persistent chemicals or antibiotics. They claim these are threats that have not yet been adequately studied to determine if they pose existential risks. Several of the problems are also related, such as biodiversity loss accelerated by excess nutrients. And others, like climate change, amplify the severity of others.
“When we study freshwater, air, pollutants like nitrogen and phosphorus, or the integrity of the biosphere, both in terms of area and biodiversity, we do it on purpose because when they add up, they provide resilience, buffering capacity, and stability for.” the entire Earth system,” Rockstrom said at the press conference. Exceeding each threshold in these areas reduces “the planet’s power to confront the climate crisis”. And he adds: “Seven of the eight indicators we assessed are outside the fair and safe range. We also see that there is a window, so a transformation that restores that safe space is still possible. But it requires transformations and very, very quick action. And simply decarbonizing the global energy system will not be enough.”
How it goes? BC3’s Zafra recalls the challenge involved: “There can be no human well-being without the Earth System. In order to fairly reconcile the well-being of all people with the limits of the earth system, we have to ask ourselves what well-being really is, what and how much we need to feel well, how much we are willing to help other people and living beings harm what achieve and implement comprehensive societal processes at all levels that enable inclusive and just transformations to tackle the climate and biodiversity crisis.”
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