Science for All | Six out of nine planetary boundaries breached
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September 20, 2023 04:47 pm | Updated September 22, 2023 04:33 pm IST

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Our planet is the only home in the vast stretches of the universe. But the health of this blue planet is now in danger, thanks to the very actions of human beings. A recent study published in Science Advances found that human activities have pushed the earth past the ‘safe limits’ in six of nine planetary boundaries, which scientists have used to measure the planet’s health. Crossing the ninth boundary could be altogether disastrous, jeopardising the precarious balance of the earth’s ecosystems.

The lead author of the study, Katherine Richardson, professor at Globe Institute and Leader of the Sustainability Science Centre at the University of Copenhagen, helped create the planetary boundary framework that recognised nine processes vital to the existence of life on the earth as we know it. The framework is like a scale against which human activities that affect the earth can be measured. This week’s newsletter takes a look at these planetary boundaries.

The nine planetary boundaries are climate change, deforestation, biodiversity loss, synthetic chemicals and plastics, freshwater depletion, nitrogen loss, ocean acidification, particle pollution, and dust in the atmosphere and ozone depletion.

The study updates the framework, which Dr. Richardson created 15 years ago, when only climate change, biodiversity loss, and nitrogen loss had surpassed the safe threshold. Now, in 2023, only three boundaries remain within safe limits. Two—ocean acidification and particle pollution and dust in the atmosphere—are on the cusp. Only ozone depletion, where proper action was taken via the Kyoto and Montreal Protocols,remains truly safe. 

According to Johan Rockstrom, one of the authors of the study, the concentration of CO2 in the atmosphere before the Industrial Revolution was 280 parts per million (ppm) for 10,000 years. Now, the level has skyrocketed to 417 ppm, far above the safe limit of 350 ppm.

The Paris Agreement of 2015 set a goal to limit the warming of the earth’s average global surface temperature to well below 2 degrees Celsius above pre-industrial levels. But studies have found that we are for an at least  2.5 degrees Celsius increase –  unheard of for millions of years.

Loss of biodiversity has also worsened. Species are also going extinct  orders of magnitude faster due to global warming. Toxins such as pesticides, nuclear waste, and microplastics have not only leached into ecosystems at levels well in excess of the safe limits. Freshwater sources are dwindling in size and quality.

Dr. Richardson compares these boundaries to monitoring our own health. “Crossing six boundaries in itself does not necessarily imply a disaster will ensue but it is a clear warning signal. We can regard it as we do our own blood pressure. A BP over 120/80 is not a guarantee of a heart attack but it increases the risk of one. For our own -- and our children’s -- sakes we need to reduce the pressure on these six planetary boundaries,” she said in a release.

The new study also  stresses the interconnected nature of the boundaries. That is, to protect our home, just ‘solving’ climate change won’t suffice if humans don’t also hold themselves accountable for their effects on the other boundaries. 

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