(Environmental) Planetary Boundaries: What They Are, & Which Ones We Have Crossed

There’s various concepts that have been developed to measure different aspects of resource depletion, environmental and ecological degradation, and also overall sustainability.

One example is the ecological footprint, another is carrying capacity, whilst another is the concept of the planetary boundaries.

A scientific team has identified nine planetary boundaries, and in this guide we outline what they are, and which ones we are placing pressure on as a result of human activity.

 

Summary – Planetary Boundaries

The planetary boundaries are a set of processes that ‘regulate the stability and resilience of the Earth system’

Said another way – they have global sustainability implications for humanity depending on how close or far away we are to keeping within them, or exceeding them

Crossing the boundaries ‘increases the risk of generating large-scale abrupt or irreversible environmental changes’, whilst staying within them might mean present and future generations are living sustainability

The changes might affect the state of the environment and it’s ecological systems and wildlife (whether they are thriving, or heading towards degradation and extinction), the availability of natural resources, and other key factors

As of right now, there are two boundaries that we have crossed ‘beyond the zone of uncertainty’, and are a ‘high risk’ – those are biochemical flows (of both nitrogen and phosphorus), and biosphere integrity (genetic diversity).

Nitrogen in particular is one of the boundaries that presents the highest risk right now along with generic diversity, and phosphorus slightly behind that

There are another two boundaries we have reached the ‘zone of uncertainty’ for and have an ‘increasing risk’ rating – climate change, and land system change

Some boundaries may be more critical to stay within than others

There are certain control variables for each boundary/earth system process that might be monitored

Some sources even identify an exact value or measurement for where a boundary might lie e.g. the climate change boundary might be that atmospheric concentrations of CO2 are at no more than 350ppm

 

*Note – like other concepts that attempt to measure sustainability and environmental stability or health, the planetary boundaries concept may also have it’s limitations and might be used as a starting point for discussion only (although it is noted that the concept has generated interest in science, policy, and practice)

 

What Is The Planetary Boundaries Concept?

It’s a concept developed in 2009 that presents a set of nine planetary boundaries that are theorised to ‘regulate the stability and resilience of the Earth system’

Crossing these boundaries ‘increases the risk of generating large-scale abrupt or irreversible environmental changes’

– stockholmresilience.org

 

The potential consequences of crossing planetary boundaries are described in a different way by scripps.ucsd.edu:

Transgressing a boundary increases the risk that human activities could inadvertently drive the earth system into a much less hospitable state, damaging efforts to reduce poverty and leading to a deterioration of human well-being in many parts of the world, including wealthy countries

 

What Are The 9 Different Planetary Boundaries? 

You can read in full the 9 planetary boundaries and a description of each of them at stockholmresilience.org

As a summary, they are:

1. Climate Change

Release of greenhouse gases like CO2 into the atmosphere, leading to Earth’s warming

 

2. Release of Novel Entities

Emissions of toxic and long-lived substances such as synthetic organic pollutants, heavy metal compounds and radioactive materials

 

3. Stratospheric Ozone Depletion

Filters out ultraviolet (UV) radiation from the sun. It’s not desirable for the ozone to be depleting

 

4. Atmospheric Aerosol Loading

Aerosols have an impact on the Earth’s climate system

 

5. Ocean Acidification

CO2 emissions are absorbed by the ocean, leading to warming, altering of the ocean’s chemistry and decreasing the pH of the surface water (amongst other impacts)

 

6. Biogeochemical Flows (both of nitrogen and phosphorus separately)

The flow of Nitrogen & Phosphorus into the biosphere and oceans.

This occurs heavily as a result of agriculture (and the use of synthetic fertilizers may have something to do with this), and industrial activity

 

7. Freshwater Use

Human consumption of freshwater and drinking water, and the impact of climate change on the natural hydrological cycle

 

8. Land-System Change

The change in use of land, such as forests, grasslands, wetlands and other vegetation types that have primarily been converted to agricultural land.

There’s many negative impacts to this.

 

9. Biosphere Integrity (both of genetic diversity, and functional diversity separately)

Involves loss of biodiversity, and also extinction.

Biodiversity loss is the extinction of species (plant or animal) worldwide, and also the local reduction or loss of species in a certain habitat.

 

Right Now, Which Boundaries Are Safe, & Which Ones Are At Risk?

You can see the graphic/visual illustration of the risk ratings of each planetary boundary at stockholmresilience.org

As a summary:

The tracking labels for each boundary can be categorised into:

Boundary not yet quantified – grey

Below boundary (safe) – green

In the zone of uncertainty (increasing risk) – yellow

Beyond the zone of uncertainty (high risk) – red

 

As of 2015, the boundaries fitted into these categories:

Climate Change

In the zone of uncertainty (increasing risk)

 

Release Of Novel Entities

Boundary not yet quantified

 

Stratospheric Ozone Depletion

Below boundary (safe)

 

Atmospheric Aerosol Loading

Boundary not yet quantified

 

Ocean Acidification

Below boundary (safe)

 

Biogeochemical Flows

Nitrogen is beyond the zone of uncertainty (high risk), & Phosphorus is also beyond the zone of uncertainty (high risk).

Nitrogen in particular is one of the boundaries that presents the highest risk right now along with generic diversity, and phosphorus slightly behind that

 

Freshwater Use

Below boundary (safe)

 

Land-System Change

In the zone of uncertainty (increasing risk)

 

Biosphere Integrity

Functional Diversity has no global quantification, & Genetic Diversity is beyond the zone of uncertainty (high risk)

 

Core Planetary Boundaries

scripps.ucsd.edu outlines that some of these boundaries could be ‘core boundaries’ that if altered would ‘drive the earth system into a new state.’

 

Control Variables & Exact Boundary Value For Each Of The Planetary Boundaries

This wikipedia.org guide outlines the different control variables for each of the planetary boundaries/earth-system processes

This ideas.ted.com resource also outlines the exact boundary line measurement/value for each boundary (e.g. for climate change, atmospheric concentrations of CO2 might not be at more than 350ppm)

 

Planetary Limits vs Thresholds

This greenbiz.com resource explains the difference between planetary limits and thresholds, and explains how the boundaries might relate to sectors and companies, and what the targets of each sector might be

 

Sources

1. https://www.stockholmresilience.org/research/planetary-boundaries/planetary-boundaries/about-the-research/the-nine-planetary-boundaries.html

2. https://undark.org/article/ted-nordhaus-carrying-capacity-ecology/ 

3. https://www.stockholmresilience.org/research/planetary-boundaries/planetary-boundaries/about-the-research.html

4. https://www.stockholmresilience.org/research/planetary-boundaries.html

5. https://scripps.ucsd.edu/news/earth-has-crossed-several-planetary-boundaries-thresholds-human-induced-environmental-changes

6. https://en.wikipedia.org/wiki/Planetary_boundaries

7. https://ideas.ted.com/the-9-limits-of-our-planet-and-how-weve-raced-past-4-of-them/

8. https://www.greenbiz.com/article/7-steps-take-if-your-company-oversteps-its-planetary-boundaries

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