The theory of planetary limits: sustainability as a weapon against climate risks

The scientific community has spent decades warning of climate change and warning of the red lines that must not be crossed. Those limits were what, in 2009, the scientists Johan Rockstrom, from the Stockholm Resilience Center (SRC), and Will Stefen, from the Australian National University, defined as planetary boundaries.

They found that there were specifically nine processes that made the Earth system stable and that, if bypassed, could endanger the habitability of the Earth.

This conceptual framework was developed in this way to mark a safe space for human performance. In this way, from governments to civil society could thus initiate actions to try to backtrack and return to a point – more or less – initial from which to start from sustainability.

The scientist Mario Molina, winner of a Nobel Prize, together with his partner Frank Sherwood, began to study in the 1970s a very particular group of chemicals: chlorofluorocarbons or CFCs. Understood as miraculous at the time, they seemed to come to stay. They were not toxic and absorbed heat. They were mostly used in sprays.

However, later studies showed that when these chemicals reached the stratosphere and the sun’s radiation destroyed them, chlorine atoms were released with serious consequences. Just one chlorine atom wiped out thousands of ozone molecules.

The idea that the ozone layer could be destroying created great consternation at the time. Was the barrier that prevented large amounts of radiation from seeping through on earth. Ultraviolet rays could cause skin cancer in humans and even damage terrestrial and marine biological systems.

The idea that the ozone layer could be destroying created great consternation in the 1970s

After discovering the hole in the ozone layer in the 1980s, the world panicked and nations began to stop using CFC products. Awareness campaigns at that time focused on aerosols, as a product that made more visible how when squeezing the diffuser, they expelled a substance that evaporated and contaminated. They made the problem more visible.

In 1987, the countries met in Montreal to establish a treaty to control these chemicals. It was the first and only major treaty on the environment of recent history, and managed to return the planet to a safe zone in one of its planetary limits: stratospheric ozone depletion.

Scientists raised the alarm signal and the world translated it into action and policy. Thanks to this protocol, even today we are in a safe zone at this limit.

Today, according to the scientists who established the concept of planetary boundaries, we have exceeded four of the nine boundaries: climate, deforestation, nutrients and biodiversity.

In these aspects, points of no return are being crossed, but – according to experts – we still have time to return to the safe zone. It’s about creating a new growth model around sustainability.

The weather

This year, the United Nations Group of Experts on Climate Change (IPCC) issued a devastating report: human beings are to blame that the planet is warming at an incessant rate. They warned of the importance of maintaining the temperature increase in this century at 1.5 ° C.

Thanks to the Montreal protocol, we are in a safe zone from stratospheric ozone depletion

For this, the immediate priority is reduce carbon emissions to zero, as well as trying to reduce the presence of other gases such as methane which, although they are found in the atmosphere to a lesser extent than CO₂, are much more polluting.

Currently, 40 billion tons of carbon are emitted every year, which suggests that, if it continues in this way, the limit will be reached in seven years. To stay below 1.5 ° C, less than 300 billion more tons of carbon would have to be emitted.

According to the current production rate, scientists propose that they could be reduced by 50% every decade.

Science has repeatedly shown that the way to avoid crossing the climate frontier is bend the emissions curve. According to the scientists, there is still action to be taken to get back to a safe area.

Measures like planting billions of more trees or moving away from fossil fuels would return the planet to a safe zone. In addition, experts argue, it would also reduce air pollution, slow down ocean acidification and reduce pressure on biodiversity.

To stay below 1.5 ° C, less than 300 billion more tons of carbon should be emitted

Deforestation

Trees are essential to capture the carbon that humans emit into the atmosphere, but they also play an important role in issues such as soil fertility, for example, or the existence of rain. They can be the center of sustainable development, because it is about restore the natural system.

The Amazon is one of the areas that is suffering the most from deforestation. So much so that its dry season has lasted six more days per decade since the 1980s. If it lasts more than four months, the trees die and are replaced by the savannah.

Parts of the Amazon, in fact, are already changing. And with global warming it could increase, according to experts, to 60%. So far around 20% of the forest has been lost.

Remember that trees capture carbon and if they die, it will enter the atmosphere. Scientists studying the Amazon have calculated that the rainforest could emit 200 billion tons in the next 30 years. That is, the same thing that the world has broadcast in the last five years.

The Amazon dry season has lasted six more days per decade since the 1980s

Measures against deforestation and repopulation of trees on the planet could therefore help regulate the climate and fresh water, in addition to having great benefits on food production.

The Biodiversity

The biological diversity of the planet is made up of all species of water or land. Rainforests have been cut down, crops have expanded and, therefore, biodiversity has been lost.

This limit of the biosphere is being exceeded. At least one million plant and animal species out of about eight million are in danger of extinction. A negative trend that, according to scientists like Anne Larigauderie, could be reached to a sixth mass extinction.

And it is that in just 50 years about 60% of wildlife has been killed, what many describe as a biodiversity crisis. This has its effects on the diet on which the world’s population depends.

Current high rates of ecosystem damage and extinction can be slowed by efforts to protect the integrity of living systems (the biosphere), improving habitat and connectivity between ecosystems while maintaining the high agricultural productivity that humanity needs.

Excess of nutrients

The flow of nutrients such as nitrogen or phosphorus, typical of fertilizers used in human activities such as agriculture, are causing a serious impact on the health of the planet. In fact, aquifers are the biggest victims of this practice, but also other natural systems of great ecosystem importance such as wetlands.

The greatest example in Spain we have right now in the Mar Menor where, for several years, they have lived pollution processes of its waters which has resulted in the appearance of many floating fish killed by lack of oxygen. The last episode of anoxia occurred, without going any further, last July. Although it is not the only one.

The Baltic Sea is the most polluted in the world by the discharge of nutrients that come from crops and other food production systems. These chemicals end up changing the composition of the water and have serious effects. Something that also occurs in the oceans and that seems to be the origin of the loss of some marine species.

This is one of the most critical limits of the biosphere, according to scientists. So stopping or regulating its use could return this border to a safe point to alleviate the impact it has on the planet.

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