Six of 9 planetary boundaries have been breached because of human activities: Study

The world has breached six of the nine planetary boundaries necessary to maintain Earth’s stability and resilience, according to a new study.

The study, published in Science Advances, was carried out by 29 scientists from eight different countries. The findings are an update to the planetary boundaries framework that was launched in 2009 to define the environmental limits within which humanity can safely operate.

So, what are these boundaries and what does breaching them mean for our world? The six boundaries include climate change, biosphere integrity (which includes genetic diversity and energy available to ecosystems), land system change, freshwater change (which includes changes across the entire water cycle over land), biogeochemical flows (nutrient cycles), and novel entities (consisting of microplastics, endocrine disruptors, and organic pollutants).

The researchers first identified the processes in the Earth’s ecosystem that have been important for maintaining favourable conditions for humans in the last 12,000 years.

Then they assessed and identified the level at which human activities raise the risk of potentially dramatic and irreversible changes in the overall conditions on Earth using computer simulations.

The study results show that humans have caused a breach in our planet’s safe climate and land system in 1988 and are now facing a risk of systemic disruption.

For land system change, the global area of forested land as the percentage of the original forest cover boundary has dropped from 75 per cent to 60 per cent, which is beyond safe limits. As for biosphere integrity, the researchers kept a limit of less than 10 extinctions per million species-years.

But the study estimated the extinction rate was greater than 100 extinctions per million species-years. Currently, it is estimated around one million of the 8 million plant and animal species are threatened with extinction, and over 10 per cent of the genetic diversity of plants and animals may have been wiped out over the last 150 years.

The analysis also showed that violations of blue and green water boundaries occurred in 1905 and 1929, respectively. The planetary boundary of novel entities was calculated to be zero.

This means humans have transgressed this limit as well. Stratospheric ozone depletion, aerosol loading and ocean acidification were found to be within the planetary boundary.

Aerosols are minute particles from combustion processes, biomass burning, and plant/microbial materials suspended in the air and are known to impact climate.

The study suggests that the world needs to negotiate and respect the limits to the amount of waste that is dumped into the environment. The study further points to a strong circular economy as a viable solution moving forward.

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