Earth's health is depleting on six of nine parameters

Human intervention right now holds the key.
Sejal Sharma
Representational image
Representational image


How do we assess the health of our planet? In 2009, a group of 28 scientists wanted a definite answer to this question. So, they outlined nine planetary boundaries, which are critical for Earth’s stability. 

A reassessment in 2023 says that six of these nine planetary boundaries have been transgressed, suggesting that Earth is “well outside of the safe operating space for humanity.”

All planetary boundaries are presently heavily perturbed by human activities, note the scientists in their paper published in Science Advances. The nine boundaries represent components of the Earth system critically affected by anthropogenic activities and relevant to our planet’s overall state.

“This update on planetary boundaries clearly depicts a patient that is unwell, as pressure on the planet increases and vital boundaries are being breached. We don’t know how long we can keep transgressing these key boundaries before combined pressures lead to irreversible change and harm,” said Johan Rockström, researcher and co-author of the study.

The six deadly parameters

The planetary boundary, the worst of the lot, is ‘Biosphere Integrity.’ This boundary includes the healthy functioning of ecosystems. The study says that while global warming issues arose in the 1980s, problems arising in functional biosphere integrity due to human land use began a century earlier. Since the 1960s, global population and consumption growth further accelerated land use, driving the system further into the zone of increasing risk. 

The second most impacted boundary is ‘Novel Entities,’ which include synthetic chemicals and substances like microplastics, endocrine disruptors, organic pollutants, radioactive materials, nuclear waste, and nuclear weapons. A contributing factor to the depleting ozone layer, the study says hundreds of thousands of synthetic chemicals like these are now produced and released to the environment. The scientists suggest zero release of these synthetic chemical compounds into the open environment unless they have been certified as harmless and are monitored.

The third boundary to have been impacted is ‘Climate Change,’ primarily brought on by the emission of greenhouse gasses and aerosols. The study reveals that the planetary boundary for atmospheric CO2 concentration is set at 350 parts per million, but currently, it’s at 417 ppm outside the safe operating space.

The fourth boundary in tatters is ‘Freshwater Change,’ which considers changes across the entire water cycle over land. This boundary was crossed in the early 20th century. The boundary addresses green water- the invisible water held in plants - and blue water, which is visible water in rivers and lakes. Assuming that the preindustrial conditions represent near-perfect conditions, there’s been a notable deviation from this state, putting freshwater’s Earth system functions at risk.

The fifth boundary that has been breached is ‘Land System Change,’ which lays its basis on the forest cover remaining on Earth in comparison to the potential area of forest in the Holocene period - the time since the end of the ice age. The study says that the deforestation of the Amazon tropical forests has alone driven the transgression of this planetary boundary. Deforestation has increased since 2015, whereas land-use conversion and fires are causing rapid change in forest areas.

The sixth boundary is ‘Biogeochemical Flows,’ which reflect the disturbance of nitrogen and phosphorus elements in the air, as these two elements constitute fundamental building blocks of life. The planetary boundary of both these elements has been transgressed. 

The safe boundaries

Now, three boundaries haven’t been affected or significantly affected by the human and non-human disturbances to Earth’s ecosystem.

The first of the three boundaries where Earth is saving face is the boundary for ‘Stratospheric Ozone Depletion.’ Since the Montreal Protocol was signed in 1987, the global extent of ozone depletion has recovered slightly. Due to human intervention, the stratospheric ozone depletion has decreased and is now within the safe operating space. 

The second safe boundary is ‘Anthropogenic Aerosol Loading,’ which has increased, and its impacts on tropical monsoon systems are already seen today. The study says that the effect is restricted to rainfall and broadly affects regional climate.

The third and last safe boundary is ‘Ocean acidification,’ which currently lies at the margin of the safe operating space, but the trend is worsening as CO2 emission continues to rise.

The key actions required are phasing out fossil fuel burning and ending destructive farming. The study recommends that by the year 2100, we should bring total global forest cover back to the levels of the late 20th century, which would provide a substantial cumulative sink for atmospheric CO2. But the scientists also note that it is quite unlikely that this will happen.

Study abstract:

This planetary boundaries framework update finds that six of the nine boundaries are transgressed, suggesting that Earth is now well outside of the safe operating space for humanity. Ocean acidification is close to being breached, while aerosol loading regionally exceeds the boundary. Stratospheric ozone levels have slightly recovered. The transgression level has increased for all boundaries earlier identified as overstepped. As primary production drives Earth system biosphere functions, human appropriation of net primary production is proposed as a control variable for functional biosphere integrity. This boundary is also transgressed. Earth system modeling of different levels of the transgression of the climate and land system change boundaries illustrates that these anthropogenic impacts on Earth system must be considered in a systemic context.

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