The livable environment we enjoy exists in a relatively narrow margin of Earth's systems in balance. Pushing those systems out of balance may have disastrous consequences. A new study says we've gone beyond the "tipping point" in four of those nine systems.
Photo Credit: via McGill U

Threat to Earth’s basic systems

They are called “planetary boundaries” the range within which several systems operate which make the Earth able to support billions of humans.

A new report looks at the state of these planetary boundaries, and says we have now pushed four of nine, past their limits.

McGill professor Elena Bennett, PhD, contributed to the study. She is an associate Professor in the Department of Natural Resource Sciences and the School of the Environment. She specializes in ecosystem and landscape ecology.

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Professor Elana Bennett PhD, Natural Resource Sciences and McGill School of Environment, McGill University, Montreal Canada © supplied

Humanity exists within a relatively narrow margin on Earth in terms of weather, water, ability to grow food, provide plant and animal life etc. This narrow margin has existed with relative stability for about 10,000 years and allowed humanity to expand greatly following glacial retreat.

The Earth is like a machine with several components which act in balance, and with some ability to repair itself when knocked out of whack.

However, with mankind’s rapid expansion and activities, we have been putting stress on those various components, to the point where some are threatened with going beyond the margins where they can “repair” themselves.

Some 18 scientists in various fields contributed to this study which looks at nine major systems that make the Earth habitable.

The report was published in the online journal Science (abstract here).

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Retreating ice cap on Baffin Island, 2013. A studty of melting ice on Baffin island showed average summertime temperatures in the Eastern Arctic are wamer than they’ve been in 120,000 years and are “well outside the range of natural variability” accoring to scientist Gifford Miller © Gifford Miller/University of Colorado, Boulde

It says we have now pushed four of the nine systems beyond normal boundaries into a red zone or past “tipping points” beyond which unknown consequences may occur. The report suggests that beyond these “tipping points”, the consequences may be irreversible

It notes that two of those systems, climate change and biosphere integrity, are most critical as they have a follow on effect upon the others, and indeed each has the potential on its own to change the whole Earth environment if pushed too far for too lang.

Professor Bennett specifically looked at nutrient cycling, and found that we have passed the safe limit on that system.  She notes that we are adding so much phosphorus and nitrogen to the environment to push our agricultural production, that it is having a negative effect on both fresh and salt water.

She notes that there are now some vast “dead zones” in the oceans, notably in the Gulf of Mexico from agricultural runoff from the Mississippi.   That same runoff is causing toxic algae blooms in fresh water lakes that are used for municipal drinking water.

She says, “This new data shows that our ability both to produce sufficient food in the future and to have clean water to drink and to swim in are at risk.”

She adds, ”This kind of problem is likely to become much more common. We will see more lakes closed, will have to pay more to clean our water, and we will face temporary situations where our water is not cleanable or drinkable more and more frequently. That’s what it means to have crossed this planetary boundary. It’s not a good thing for any of us.”

Nine planetary boundaries

  • **** Climate change (red zone)
  • **** Change in biosphere integrity (biodiversity loss + species extinction) (red)
  • Stratospheric ozone depletion
  • Ocean acidification
  • ****Biogeochemical flows (phosphorus and nitrogen cycles) (red zone)
  • ****Land-system change (for example deforestation)  (red zone)
  • Freshwater use
  • Atmospheric aerosol loading (microscopic particles in the atmosphere that affect climate and living organisms)
  • Introduction of novel entities (e.g. organic pollutants, radioactive materials, nanomaterials, and micro-plastics).
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