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The nine boundaries of sustainability

David Hall · Posted on: November 7th 2025 · read

According to Climate Action Tracker, under current policies, global warming is projected to fall woefully short of the Paris Agreement threshold of 1.5⁰C above pre-industrial levels, which are necessary to mitigate the long-term impacts of global warming and associated man-made climate change.

Shockingly the figure Climate Action Tracker cites is 2.7⁰C above pre-industrial levels.

If further proof is needed that we are failing in this critical mission, a simple scan of recent policy announcements across the globe will highlight a move away from the rhetoric of mitigation to that of adaptation.

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At 2.7⁰C above pre-industrial levels, the planetary impacts would be severe, widespread, and in many cases irreversible.

I have no wish to be accused of scaremongering but while that terrifying fact is sinking in, let’s look at the specifics:

Climate and weather extremes
1. Many regions would experience deadly heatwaves regularly, making some areas uninhabitable for parts of the year.
2. Wildfires would increase in intensity, especially in Australia, Southern Europe and the western part of North America.
3. More intense droughts would occur in dry regions such as Africa, Southern Europe and the Middle East.
4. Stronger tropical cyclones and hurricanes would occur due to warmer ocean temperatures.
Oceans and ice
1. Sea levels would likely rise by 0.5m – 1m, displacing hundreds of millions of people in coastal areas such as Bangladesh, the Pacific Islands and parts of the USA.
2. Almost all coral reefs would be lost.
3. Summer sea ice in the Arctic would disappear almost completely, affecting the polar ecosystems and weather patterns globally.
Food and water security
1. Major staples such as wheat, rice and maize could decline by 10-30% in many regions, especially in tropical and sub-tropical zones.
2. Over 2 billion people could face severe water shortages due to drought and glacial melts.
3. Ocean warming and acidification would collapse many fish populations, threatening coastal livelihoods.
Ecosystems and biodiversity
1. Up to 30-50% of species would face extinction due to habitat loss and climate stress.
2. The Amazon and other rainforests could shift to savanna-like ecosystems, releasing enormous amounts of stored carbon.
3. Permafrost thawing would release methane and CO2, further accelerating warming in a feedback loop.
Human health and livelihoods
1. We could see a sharp increase in mortality rates from heat stress, especially amongst elderly and low-income populations.
2. Expanded spread of diseases such as Malaria, Dengue, and Zika, due to warmer, wetter climates.
3. Increased ozone and wildfire smoke would worsen respiratory diseases.
4. Tens to hundreds of millions would be displaced by sea-level rise, drought, and crop failure, increasing global instability and conflict risk.
Economic and social impacts
1. Global GDP could shrink by 10-20% by the end of this century.
2. Infrastructure damage from storms, flooding, and permafrost melt would cost trillions.
3. Insurance markets and supply chains would collapse in high-risk regions.
4. Inequality would deepen with poorer nations facing the worst impacts despite often contributing least to emissions.

At around 2.7⁰C of global warming several climate tipping points are likely to be triggered, including:

The collapse of the West Antarctic and Greenland ice sheets leading to a long-term 10-20m sea-level rise).

Amazon rainforest dieback, turning it from a carbon sink to a carbon source.

Disruption of ocean currents such as the Atlantic Meridional Overturning Circulation, altering weather patterns globally.

This nightmare scenario may appear remote to some, but it is by no means so. Climate Action Tracker forecasts a 66% chance of restricting global warming to 2.3⁰C under binding long-term or net zero targets, with an uptick in commitments potentially realising a median warming estimate of 1.9⁰C, likely below 2.1⁰C – still above the ‘ideal’ 1.5⁰C target of the 2015 Paris Agreement.

Before you breathe an albeit cautious sigh of relief, some recent news may make you think twice.

According to the Potsdam Institute for Climate Impact Research, the seventh breach of the nine planetary boundaries is confirmed as ocean acidification.

Developed by researchers at the Stockholm Resilience Centre (proposed in 2009, and updated in 2015 and 2023), the nine boundaries represent the safe limits, within which humanity can operate without causing irreversible environmental damage to the Earth’s systems. Crossing these boundaries significantly increases the risk of triggering abrupt and potentially catastrophic environmental change. The current status does not look promising:

Boundary	Description	Status
1. Climate Change	Concentration of greenhouse gases and global temperature rise that regulate Earth’s energy balance	Exceeded – global warming circa 1.3⁰C above pre-industrial levels; rising CO2 levels
2. Biosphere Integrity (Biodiversity Loss)	Maintaining genetic and species diversity essential for ecosystem resilience and stability	Exceeded – current extinction rates are 100-1000 times above natural levels
3. Land-System Change	Conversion of forests, grasslands, and wetlands for human use	Exceeded – excessive levels of forest and natural land conversion; loss of carbon sinks
4. Biogeochemical Flows (Nitrogen & Phosphorus Cycles)	Balance of nutrients that regulate soil fertility and water quality	Exceeded – excessive fertiliser use causes water pollution and ocean ‘dead zones’
5. Freshwater Change (Blue & Green Water Use)	Sustainable management of surface water, groundwater, and soil moisture	Exceeded – freshwater systems are under severe stress in many regions
6. Ocean Acidification	CO2 absorption lowers ocean pH, threatening marine life and coral reefs	Exceeded – ocean pH has fallen by more than circa 0.1 since pre-industrial levels; a 30-40% increase in acidity
7. Atmospheric Aerosol Loading	Airborne particles that affect climate and human health (i.e. soot and sulphates)	Uncertain/Regional Exceedance – harmful levels in South and East Asia; global effects complex
8. Stratospheric Ozone Depletion	The ozone layer protects life from harmful UV radiation	Within safe zone (recovering) due to the Montreal Protocol
9. Novel Entities (Chemical Pollution)	Synthetic compounds like plastics, pesticides, and heavy metals that harm living systems	Exceeded – chemical and plastic pollution are far beyond safe limits

"Seven of the nine boundaries have now been breached – climate change, biosphere integrity, land use, nutrient cycles, freshwater change, novel entities and now ocean acidification, with Atmospheric Aerosol Loading being dangerously close to breaching."

David Hall, ESG Advisory Director

Because the boundaries are interconnected, breaching one often worsens others – staying within them is essential to keep Earth in a ‘safe operating space for humanity’.

In the case of the latest breach (ocean acidification), it is estimated that 60% of the ocean (to 200m depth) has crossed safe acidification limits, particularly in polar zones. Life in the world’s oceans is under extreme stress and one of the Earth’s most vital stabilisers is weakening exponentially.

So, how does all of this affect your future business and future life?

According to Allianz, one of the world’s leading insurers:

“The insurance industry has historically managed these risks. But we are fast approaching temperature levels – 1.5⁰C, 2⁰C, 3⁰C – where insurers will no longer be able to offer coverage for many of these risks. The math breaks down: premiums exceed what people or companies can pay. Entire regions are becoming uninsurable.” (The Guardian).

Abject despair is not an option.

Progress in reducing planet-harming actions is being made despite serious setbacks such as the reversal of many climate actions in one of the largest contributing countries – the USA – and despite the proliferation of climate-damaging armed conflicts.

The COP series needs to double own and harden both the commitments of its members and the timeframes for compliance.

In the meantime, instead of asking ‘what is the minimum I need to do to comply’, those companies that do so need to take a hard look at their commercial future and decide to fully commit to climate change and ecological commitments.