Planetary Boundaries

Syllabus: GS3/Environment and Biodiversity

In News

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

What are Planetary Boundaries?

• In 2009, 28 internationally renowned researchers identified and quantified a set of nine planetary boundaries within which humanity can continue to develop and feel good in the future.
  • If we cross these limits, abrupt or irreversible environmental changes can occur with serious consequences for humankind.
• The nine planetary boundaries identified are:
  • Climate change
  • Change in biosphere integrity (biodiversity loss and species extinction)
  • Stratospheric ozone depletion
  • Ocean acidification
  • Biogeochemical flows (phosphorus and nitrogen cycles)
  • Land-system change (for example deforestation)
  • Freshwater use
  • Atmospheric aerosol loading (microscopic particles in the atmosphere that affect climate and living organisms)
  • Introduction of novel entities

About the Study

• The findings are an update to the planetary boundaries framework, which was first launched in 2009, to define the environmental limits within which humanity can safely operate.
• 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. This period is known for its stable and warm planetary conditions.
• Next, they assessed how much humans are changing them and identified the level at which human activities raise the risk of potentially dramatic and irreversible changes in the overall conditions on Earth. 
• The breaching of individual boundaries does not imply immediate disaster but raises the risk of setting processes in motion that are likely to dramatically and irreversibly change the overall environmental conditions on Earth to one that no longer supports civilisation as we know it

Findings of the Study

• Humans caused a breach in the planet’s safe climate and land system in 1988 and are now facing a risk of approaching systemic disruption.
• The six boundaries include climate change, biosphere integrity (genetic diversity and energy available to ecosystems), land system change, freshwater change (changes across the entire water cycle over land), biogeochemical flows (nutrient cycles), and novel entities (microplastics, endocrine disruptors, and organic pollutants).

• Atmospheric Carbon Dioxide: The researchers set the planetary boundary for atmospheric carbon dioxide concentration at 350 parts per million (ppm) currently, this has reached 4w17 ppm.
• Land System Change: The current value is beyond the safe limits.
• Biosphere Integrity: The limit was kept at less than 10 extinctions per million species-years but the extinction rate was greater than 100 extinctions per million species-years. This boundary has also been violated.
  • Currently, it is estimated around one million of the 8 million plant and animal species are threatened with extinction, and over 10 percent of the genetic diversity of plants and animals may have been wiped out over the last 150 years. 
  • The second aspect of biosphere integrity is the energy available to the ecosystem or the net primary production (NPP). It is equal to the difference between the amount of carbon produced through photosynthesis and the amount of energy that is used for respiration.
  • Humans are appropriating roughly 30 percent of the energy that was available to support biodiversity before the Industrial Revolution this could drive biodiversity loss.
• Freshwater: Which includes blue water (surface and groundwater) and green water (available water for plants).
  • Human impacts on blue and green water were calculated to be 18.2 percent and 15.8 percent, respectively, which is higher than the boundary of 10.2 percent and 11.1 percent, respectively.
  • The analysis showed that violations of blue and green water boundaries occurred in 1905 and 1929, respectively.
• Nitrogen and Phosphorus: The boundary was fixed at 11 teragrams (Tg) for Phosphorus and 62 Tg for Nitrogen. This is now 22.6 Tg and 190 Tg, respectively. 
• Introduction of novel entities: It 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.
  • However, the risk that aerosol loading and ocean acidification exiting their boundaries is increasing.

Source: DTE