Planetary boundaries – The Green Tau

Counting on 2026 … day 2

8th January

How do we protect and preserve fresh water supplies – part 3

Using less water!

This is something for businesses and farmers and domestic consumers to respond too – and feels particularly pertinent as decisions are made about AI and data centres generally (see tomorrow’s blog).

In the UK at our continued rate of water consumption there will be a daily shortfall of 5 billion litres (about a third of current consumption) by 2050. This takes into account the need to extract less water from rivers, aquifers etc where it negatively impacts the natural environment, a growing population, the need to cope with increasingly frequent droughts, the impact of climate change (eg changing rainfall patterns) and increased use by businesses. (1)

Per capita household water consumption in the UK is already falling, from an average of 169.53 litres per day in 2005/2006 to an average of 139.47 litres in 2023/2024. (2) However there is clearly a need for consumption levels to fall further. A survey across Europe in 2020 varied daily domestic consumption varied from 300 litres in Switzerland to 100 litres in Belgium and even less in Estonia and Slovakia. (3) In some instances the difference maybe due to a lower volume toilet flush, or the frequency and duration and rate of flow of showers, or the frequency of use and water efficiency of appliances such as washing machines.

Websites with water saving tips

How to save water

https://friendsoftheearth.uk/sustainable-living/13-best-ways-save-water

This earlier blog is about saving and reusing grey water around the house – https://greentau.org/2025/07/10/counting-on-day-106-3/

And this one about showering less and more efficiently – https://greentau.org/2025/02/13/counting-on-day-31-3/

Counting on … day 1

7th January 2026

How do we protect and preserve fresh water supplies – part 2

Land use changes, especially things such as deforestation and urbanisation, have aggravated the problem –

“Deforestation, agriculture, and urban expansion have greatly changed the way land stores and moves water. When forests are cleared or soils are sealed under concrete, they lose their ability to hold green water — the moisture that plants rely on. This weakens local rainfall, increases runoff, and can intensify both floods and droughts. Changes to land systems also affect regional weather patterns, such as monsoons, and create feedback loops that further influence the climate.” (1)

Reducing or indeed eliminating such land use changes is clearly beneficial for the wellbeing of the planet. We can go further by reversing the changes by both protecting and increasing land uses that capture and store – eg through reforestation, restoring peatlands and wetlands, re-wriggling rivers (ie allowing them to flow freely and more slowly across a greater expanse of the flood plain, re-establishing water meadows, limiting the extraction of water to protect lakes and aquifers etc.

These nature based solutions not only protect supplies of fresh water, they also protect and enhance biodiversity and reduce the risk of flooding, creating a better environment for us to enjoy.

(1) https://www.planetaryhealthcheck.org/boundary/freshwater-change/

Counting on … day 207

18th December 2025

How do we see the impact of exceeding the planetary boundaries for fresh water?

“Climate change has become the main global driver of freshwater disruption. A warmer atmosphere holds more moisture and changes how and where rain falls, leading to more intense floods in some regions and severe droughts in others. These shifts are transforming long-established rainfall and river patterns, creating new and unpredictable hydrological conditions that put pressure on both ecosystems and human societies.” (1)

A disruption in rainfall patterns can mean either more or less rain than usual, or more rainfall but less often so that rainfall is more intense. This can lead to the drying out of wetlands, the lowering of lake and river levels and the disruption of the ecosystems those water features supported. In the Amazon basin we are seeing river levels drop significantly impacting local communities and their livelihoods and destabilisation of the rainforest such that trees, plants and creatures are lost.

Disruption means loss of soil moisture. Not only does this impact plant growth and thus a whole food chains, it also makes landscapes more vulnerable to droughts and wildfires. The UK saw a record number of wildfires this year.

Excessive amounts of rainfall over a prolonged period, or concentrated into a short time frame, causes extreme flooding that disrupts habitats, destroys infrastructure, displaces people, erodes soils and causes devastating landslides. We have seen many examples of this in the recent Asian super typhoons.

Disruption to normal rainfall patterns leads to water scarcity. A lack of rain depletes water supplies, whilst infrequent intense rainfall runs quickly of the land, again failing to restore water stocks in reservoirs and rivers. Warmer winters diminishes the replenishment of glaciers, and increase the rate at which they melt. Together this reduces the flow of water into rivers during summer periods aggravating water scarcity. Both in Iran and in South Africa, whole communities are face a complete lack of drinking water as droughts combine with atypical rainfall patterns.

https://www.planetaryhealthcheck.org/boundary/freshwater-change/

Counting on … day 201

10th December 2025

When planetary boundaries are once crossed, it is still possible to reverse the situation and restore the balance of the Earth’s systems. However the effect of crossing a planetary boundary may irreversibly impact delicate parts of the Earth’s ecosystems such as coral reefs.

These reefs are important because:-

They protect shorelines from strong ocean currents and prevent coastal erosion
They provide sheltered waters for many species of sea life.
They filter polluted water ensuring clean water for marine life and clean beaches
They sustain local fishing based communities and especially those located on low-lying islands
They absorb carbon dioxide

Coral reefs are being damaged by the acidification of the oceans – the depletion of calcium in the structure weakens them. They are also damaged by rising ocean temperatures which stress the corals causing them to expel the symbiotic algae that enable them to feed and which give them their distinctive colours – this is called coral bleaching. (1)

The multiple causes of damage to the world’s coral reefs has destroyed such a proportion that their future is now jeopardised. These reefs are loss of coral reefs on this scale means that we have passed one of the Earth’s systems tipping points. (2)

In the Caribbean, coral reefs have decreased by 48% since 1980. (3)

Info graphic https://oceanservice.noaa.gov/facts/coralreef-climate.html

(1) https://www.wwf.org.uk/coral-reefs-and-climate-change

(2) https://global-tipping-points.org/case-studies/#coral

(3) https://www.theguardian.com/environment/2025/dec/09/caribbean-reefs-have-lost-48-of-hard-coral-since-1980-study-finds?CMP=Share_iOSApp_Other

Counting on … day 200

9th December 2026

Ocean health: acidification

One of the nine planetary boundaries is ocean acidification. If the oceans become too acidic it endangers marine life and therefore the lives of the rest of us who are dependent on healthy oceans.

The 2025 Planetary Health Check showed that this planetary boundary has been breached: since the start of the industrial era, the oceans’ acidity has increased by 30-40% destabilising this important Earth systems. (1)

What is ocean acidification?

“For millions of years, the ocean has acted as Earth’s carbon sponge, quietly absorbing carbon dioxide (CO₂) from the air. But that natural partnership has turned toxic in the age of fossil fuels.

“As humanity has pumped unprecedented levels of CO₂ into the atmosphere, the oceans have taken in more and more of it—now absorbing roughly a quarter of all carbon emissions. But this uptake comes at a cost. When carbon dioxide dissolves in seawater, it undergoes a chemical transformation, forming carbonic acid. That acidification strips the ocean of carbonate ions—essential building blocks for creatures like corals, clams, and countless shell-forming organisms.

“As their calcium carbonate shells thin and weaken, so too do the coral reefs and underwater habitats they support. A weakened foundation means collapsing ecosystems—once-thriving marine gardens reduced to skeletal remains.” (2)

(1) https://www.stockholmresilience.org/research/planetary-boundaries.html

(2) https://www.sciencenewstoday.org/parts-of-earths-oceans-have-quietly-crossed-a-dangerous-threshold

Counting On … 198

3rd December 2025

Phosphorus is another key mineral for the health of plants and animals. It derives from rocks and through erosion finds its way into the soil, where as soluble phosphates (HPO4 and H20P4) it is absorbed by plants, and through eating plants into plant eating creatures and so up through the food chain. Bacteria in the soil aid the absorption of phosphates.

Organic phosphorus is released back into the soil through defecation and the decay of plants and animals. During the process of decomposition the organic form of phosphorus is converted to an inorganic firm such that it can overtime be reformed into sedimentary rocks. This comprises the natural phosphorus cycle.

Because phosphorus improves crop yields it is added as an artificial fertiliser. This input disrupts the cycle. Excess of phosphorus is the primary cause of algal bloom in water sources, reducing the amount of oxygen present and so killing off many plants and creatures. (1)

The following data comes from Planetary Boundaries Science:-

“Before human intervention, phosphorus flows were low ~2.5 Tg P pa (tetragrams of phosphorus per year) from land to freshwater and ~1.3 Tg P pa of export to the ocean. Human activities have increased flows from land to freshwater systems through a global application of mined phosphorus to cropland of around 18.2 Tg P pa and have increased phosphorus flows to the ocean to around 4.4 Tg P pa, largely due to fertiliser use.”

At the same time, the sage planetary boundary for phosphorus flow is between 6.2 and 11 Tg P pa. (2)

Counting on … 197

2nd December 2025

The imbalance of the nitrogen cycle also causes air pollution. Whilst nitrogen based fertilisers in the soil and water are being consumed by various microbes, processing nitrites in to become a nitrates which can be absorbed by the plants, nitrogen oxide (NO) is released as a bi-product. (1)

Nitrogen oxide, like carbon dioxide, is a greenhouse gas, but with 300 times the warming potential.

Nitrogen oxide readily reacts with other gases in the atmosphere to form nitrogen dioxide which is a healthy hazard inflaming airways and increasing susceptibility to respiratory infections and allergens.

Together nitrogen oxide and nitrogen dioxide are nitrous oxides or NOx. (2)

Whilst agriculture is the main source of nitrous oxides, they are also emitted through the burning of fossil fuels – including from petrol and diesel power vehicles, diesel powered shipping and railway engines, and from aviation.

(1) https://www.bbc.co.uk/future/article/20210603-nitrous-oxide-the-worlds-forgotten-greenhouse-gas

(2) https://www.gov.uk/government/statistics/emissions-of-air-pollutants/emissions-of-air-pollutants-in-the-uk-nitrogen-oxides-nox

(3) https://ourworldindata.org/emissions-by-sector

Counting on … 195

26th November 2025

How can the potential harm caused by novel entities be curbed?

Reduce the sheer number of synthetic chemicals produced globally
Where possible substitute naturally occurring alternatives
Ensure novel entities are recycled as a part of a closed circular economy.
Ensure no leakage of novel entities into air, water or soil systems
Continue to evaluate the risks posed by each novel entity.

As consumers we can try and avoid products that utilise novel entities but in reality we will have to accept that they are so engrained into our systems, that we will not always be able to avoid them. Nevertheless doing what we can will help highlight the issue for others.

Counting on … 194

25th November 2025

Returning to a focus on planetary boundaries (see https://greentau.org/2025/10/22/counting-on-170/) one boundary that may not automatically spring to mind is that of ‘novel entities’. A novel entity is a substance created by humans from synthetic chemicals and/or natural chemicals that processed in wholly new ways to produce a new – ‘novel’ – entity. Or it is something created by us by modifying the genetics of living organisms or the like, again producing a completely new entity. (1)

Examples of novel entities includes:

numerous synthetic fertilisers, insecticides and pesticides – whilst these may increase harvests they also pollute soil and water and kill off pollinators and other essential insects. DTD is one such infamous example.
chloroflurocarbons – these were used in fridges and aerosols before being restricted, because they were damaging the ozone layer.
PFAs which are petrol based chemicals that offer amazing properties in resisting heat, oil, water, grease et such that they have been widely used in creating non-stick cooking ware, waterproof clothing, stain resistant and fire retardant fabrics etc. However they also cause infertility and various cancers, and have such a long life (remaining active pollutants) such that they are termed ‘forever chemicals’.
BPA (Bisphenol A) is widely used in hard plastics cups, baby bottles, toys, food boxes, etc and can linings. It too can damage fertility, disrupt hormones, and cause eye damage, skin reaction and respiratory irritation.
Artificial food additives are used to enhance flavour, smell, texture or shelf-life of foods, with the word artificial indicating that these are synthetic rather than natural ingredients. Whilst they are regulated for safety, there is still evidence that they can harm health. For example, the consumption of artificial sweeteners is linked to both cancer and cardiovascular diseases, and nitrates and nitrites (found in products such as bacon) may also have links to these diseases.
Genetically modified organisms includes such things as golden rice (a GM rice that produces Beta-carotene); Bt Crop Maize which is toxic to certain pests; and AquAdvangage salmon that grow at twice the rate of conventional salmon. Again there are concerns around links between GM food and cancer, allergic reactions etc but before they enter the food chain there are safety assessments to be passed. Another concern is that GMO will disrupt the DNA of their natural counterparts. And with F1 hybrid plants we already know that their seeds have a lower germination success rate.
Plastics generally – much has been written about the problems with plastics, that they hang around in the environment for centuries, and that when they break down into micro and nano-particles they enter into every part of our bodies and into every part of the global environment. As yet we don’t know whether the impact on humans is neutral or harmful. We do know that plastic does maim and kill wildlife and damage ecosystems.

Novel entities are widespread in the world – The Chemical Abstracts Service maintains a database of chemical names which has identified 204 million new chemicals! (2) – yet what we don’t know is the extent to which they are damaging the world’s environment. It is therefore instructive to read this from a report by the American Chemical Society:-

“We submit that the safe operating space of the planetary boundary of novel entities is exceeded since annual production and releases are increasing at a pace that outstrips the global capacity for assessment and monitoring.” (3)

Counting on … 179

4th November 2025

Planetary Health Diet

The EAT-LancetCommission is a global, interdisciplinary group of world-leading researchers with expertise in nutrition, health, agriculture, sustainability, social justice, and policy – working together towards a healthy, sustainable, and just food system. (1) In 2019 this group’s research developed the Planetary Health Diet being a diet that is both healthier for us and for the planet. It is a dietary outline that can be adapted to suit different cultural traditions and different social contexts – in other words it is a diet that everyone could follow with out difficulty.

“The PHD is rich in plants: whole grains, fruits, vegetables, nuts, and legumes comprise a large proportion of foods consumed, with only moderate or small amounts of fish, dairy, and meat recommended.” (2)

This year their research was updated producing the 2025 EAT-Lancet Commission Report. This report demonstrates that the PHD could both bring the human behaviour back within safe planetary boundaries as well as cutting greenhouse gas emissions.

This 2025 report outlines eight areas where transformation can lead to positive outcomes. Protect and promote traditional healthy diets –

Create accessible and affordable food environments that increase demand for healthy diets
Implement sustainable production practices that store carbon, create habitat, and improve water quality and availability
Halt agricultural conversion of intact ecosystems
Reduce food loss and waste
Secure decent working conditions across the food system
Ensure meaningful voice and representation for food systems workers
Recognise and protect marginalised groups (3)

https://eatforum.org/eat-lancet

(2) https://eatforum.org/eat-lancet/the-planetary-health-diet/

(3) https://eatforum.org/update/eat-lancet-commission-warns-food-systems-breach-planetary-limits/