human activity and the destruction of the planet


Artificial Light at Night

NASA photo of a composite image of the Earth at night

There is considerable concern amongst biologists that turning night into day has strong effects on the natural world and is yet another stressor on biodiversity. The fact that life has evolved, over millions of years, on a planet that has had periods of darkness for some of the time, might suggest that there would be consequences of the proliferation of Artificial Light at Night (ALAN). New LED lamps are a particular cause for concern as, their spectra tend have a large blue component, and blue light is a strong signal for daytime.

For example, there is evidence for melatonin suppression in vertebrates due to light: 

For billions of years, all life has relied on Earth’s predictable rhythm of day and night. It’s encoded in the DNA of all plants and animals. Humans have radically disrupted this cycle by lighting up the night.

Plants and animals depend on Earth’s daily cycle of light and dark rhythm to govern life-sustaining behaviors such as reproduction, nourishment, sleep and protection from predators.

Scientific evidence suggests that artificial light at night has negative and deadly effects on many creatures including amphibians, birds, mammals, insects and plants.

Artificial Lights Disrupt the World’s Ecosystems

Nocturnal animals sleep during the day and are active at night. Light pollution radically alters their nighttime environment by turning night into day.

According to research scientist Christopher Kyba, for nocturnal animals, “the introduction of artificial light probably represents the most drastic change human beings have made to their environment.”

“Predators use light to hunt, and prey species use darkness as cover,” Kyba explains “Near cities, cloudy skies are now hundreds, or even thousands of times brighter than they were 200 years ago. We are only beginning to learn what a drastic effect this has had on nocturnal ecology.”

Glare from artificial lights can also impact wetland habitats that are home to amphibians such as frogs and toads, whose nighttime croaking is part of the breeding ritual. Artificial lights disrupt this nocturnal activity, interfering with reproduction and reducing populations.

Artificial Lights Can Lead Baby Sea turtles to their Demise

Sea turtles live in the ocean but hatch at night on the beach. Hatchlings find the sea by detecting the bright horizon over the ocean. Artificial lights draw them away from the ocean. In Florida alone, millions of hatchlings die this way every year.

Birds that migrate or hunt at night navigate by moonlight and starlight. Artificial light can cause them to wander off course and toward the dangerous nighttime landscapes of cities. Every year millions of birds die colliding with needlessly illuminated buildings and towers. Migratory birds depend on cues from properly timed seasonal schedules. Artificial lights can cause them to migrate too early or too late and miss ideal climate conditions for nesting, foraging and other behaviors.

Ecosystems: Everything is Connected

Many insects are drawn to light, but artificial lights can create a fatal attraction. Declining insect populations negatively impact all species that rely on insects for food or pollination. Some predators exploit this attraction to their advantage, affecting food webs in unanticipated ways.

And there is a database of other research findings in this context:

There are claims that brighter lighting greatly enhances public safety and these claims have been used to sell lighting but is this just a sales technique?


There is a consultation at the moment by the All Party Parliamentary Group (APPG) on Dark Skies Policy but it closes very shortly – Sunday 27th September 2020. Copied below from the website is further information:

Dark Skies Policy Consultation

The APPG for Dark Skies is seeking proposals and evidence from a range of stakeholders with expertise and experience in the subject of dark sky preservation and light pollution. 

The purpose of this consultation is to collect information, to identify the main threats and challenges that the cause of dark sky preservation faces in the UK, and identify the most effective and actionable ways in which legislators and policy makers can seek to address these challenges – for example but not limited to the compliance and planning policy frameworks. It will explore the environmental, economic, energy and health consequences of light pollution.

The result of this consultation will be to produce the APPG’s first policy plan since being established in January this year. It will provide a basis for the focus of our campaigns, policy briefs and the language that our extensive group of Parliamentary members use. 

Guidelines for making a submission:

  • State clearly who the submission is from, i.e. whether from yourself in a personal capacity or sent on behalf of an organisation, for example the submission could be headed ‘Written evidence submitted by xxxxxx’
  • Be concise – we recommend no more than 1,000 words in length
  • Begin with an executive summary in bullet point form of the main points made in the submission
  • Include a brief introduction about yourself/your organisation and your reason for submitting evidence
  • Include any factual information you have to offer from which the APPG might be able to draw conclusions
  • Identify any legal or quasi-legal frameworks your proposal would impact or modify
  • Include any recommendations for action by the Government or others which you would like the APPG to consider.CLOSING DATE: Sunday 27th September

Please contact the APPG Coordinator Chris Cook ( with any further questions.


Does light pollution affect humans as well as other species?

I think this is still to be proven but my own experience over more than seven decades of life on this planet, is a great sadness at the gradual loss of an ability to see the stars at night. This has been exacerbated by the arrival, thanks to my City Council, of an LED lamp post right outside my home. It was probably placed there for good sustainable reasons but I now find it impossible to see the stars at night and, if I wake in the night, to be able to guess what time it might be, as it is always light now.

In another post on this site, I have written about “climate change grief” and I wonder if what I have described in the previous paragraph could be described as “light pollution grief”. I certainly believe that being able to see the stars at night gives us a sense of who we are as the inhabitants of a planet, which is just a small part of a diverse and beautiful universe. Can light pollution therefore lead to a loss of identity as an important species within this vast universe? And, going further, to a loss of responsibility for the benevolent stewardship of this planet or even to an impact on human mental health?

Related to this, as described in Chapter 3 of my book (Human Inventiveness and the Concepts of Freedom and Responsibility”), is the description of “space junk” currently circulating our planet and being added to on a regular basis.

It is now known that walking under trees can improve mental health – it is called “tree therapy”. Is it possible that standing and gazing up at the stars can be equally therapeutic?

Maybe this is important to me because five decades ago, I travelled by road from Darwin to Sydney, Australia and spent each night sleeping by the side of the road, under the starts. Is that why I miss them so much now? Certainly, I was gobsmacked when, returning to Australia 10 years ago, and staying at a small town with little light pollution, I felt like I was bathed in the Milky Way. It took my breath away. I had forgotten what I was missing.

See also:


Further information about light pollution can be found at:

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CBI says that Britain must become a global leader in tackling climate crisis

Carolyn Fairbairn, the director-general of the CBI, is launching its ‘green recovery roadmap’. She says that Britain needs to step up and become a global leader in climate action, creating a number of green jobs and boosting productivity to help the economy recover from the coronavirus pandemic.

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UK Government’s £40 million Green Recovery Challenge Fund opens for applications

Grants from £50k to £5 million are now available to help the nation build back greener from the coronavirus pandemic, the government announced today [14 September].

The £40 million Green Recovery Challenge Fund, part of the government’s wider green economic recovery, jobs and skills package, brings forward funding for environmental charities and their partners to start work on projects across England to restore nature and tackle climate change.

The fund will help create up to 3,000 jobs and safeguard up to 2,000 others in areas such as protecting species, finding nature-based solutions to tackling climate change, conservation rangers and connecting people with nature. Up to 100% of project costs will be available.

The fund will be delivered by the National Lottery Heritage Fund in partnership with Natural England and the Environment Agency.

All projects must contribute to at least one of the following themes of the Green Recovery Challenge Fund:

  • nature conservation and restoration;
  • nature-based solutions, particularly focused on climate change mitigation and adaptation such as through tree planting and restoring peatland; and,
  • connecting people with nature.

Projects will be favoured that create or retain jobs, creating opportunities and benefits for all ages, including young people. The fund is open to environmental charities and partnerships that include at least one environmental charity, while projects from both rural, urban and inshore marine areas are welcomed.

The fund will create a broad range of jobs such as ecologists, surveyors, nature reserve staff and education workers in environment organisations, and support their suppliers in areas such as agricultural engineering, horticulture, and equipment and seed supply.

Environment Minister Rebecca Pow, said:

The Green Recovery Challenge Fund is funded by the Department for the Environment, Food and Rural Affairs by bringing forward £10 million of money from the Nature Recovery Fund and £30 million of Nature for Climate Funding.

Applicants for over £250k must submit expressions of interest by 24 September and if successful full applications by 26 October. The deadline for applications under £250k is 2 October.

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Primates facing extinction

Night Monkeys - New England Primate Conservancy
South American Night Monkey

More than 60% of primate species are threatened with extinction mainly due to human activities, such as habitat loss, hunting, illegal trade, climate change and disease.

This extinction crisis makes effective conservation actions vital. There are many different possible conservation actions for primates, like anti-poaching patrols, relocating animals, publicising conservation issues and reintroducing primates into their habitats. But a new study shows that very little is known about what actually works to protect primates.

A team of expert primatologists and conservationists from 21 countries examined the evidence for 162 primate conservation actions to see if they actually worked. They found there wasn’t any research published testing the effectiveness of more than half of the actions. So, it is impossible to know whether these actions work or not.

These huge gaps in knowledge are worrying, because without adequate information, researchers can’t learn from experience and can’t prioritise efforts and funding to best protect our primate relatives. Indeed, without access to evidence, conservationists might apply actions that are ineffective or even damaging to the animals they seek to protect.

The studies reviewed only covered about 14% of the more than 500 primate species and just 12% of threatened primate species. And they mainly focused on the great apes and some of the larger monkey species. There are, for example, no studies of the tarsiers of south-east Asia, or of the night monkeys of Central and South America.

South America and Asia are underrepresented in current conservation research on primates. This is particularly worrying because both are home to a high number of threatened primate species.

Academic scientists can also collaborate with conservationists to design appropriate studies. Evidence databases provide easily-understood summaries of actions and their effectiveness, as well as a place to report findings – and partially address the problem of publication.

Conservationists also need to be cautious as it’s clear that in many instances it’s not yet known if an action is effective or not. This is important because primates and their habitats face ominous threats and urgent effective conservation measures are needed to protect them.

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New solar and lighting technology could propel a renewable energy transformation

This article was published in The Conversation on September 1, 2020 and written by Simon Stranks, a lecturer in Energy and Royal Society and University Research Fellow, University of Cambridge. He is also a co-founder of Swift Solar Inc.

The demand for cheaper, greener electricity means that the energy landscape is changing faster than at any other point in history. This is particularly true of solar-powered electricity and battery storage. The cost of both has dropped at unprecedented rates over the past decade and energy efficient technologies such as LED lighting have also expanded.

Access to cheap and ubiquitous solar power and storage will transform the way we produce and use power, allowing electrification of the transport sector. There is potential for new chemical-based economies in which we store renewable energy as fuels, and support new devices making up an “internet of things”.

But our current energy technologies won’t lead us to this future: we will soon hit efficiency and cost limits. The potential for future reductions in the cost of electricity from silicon solar, for example, is limited. The manufacture of each panel demands a fair amount of energy and factories are expensive to build. And although the cost of production can be squeezed a little further, the costs of a solar installation are now dominated by the extras – installation, wiring, the electronics and so on.

This means that current solar power systems are unlikely to meet the required fraction of our 30 TeraWatt (TW) global power requirements (they produce less than 1 TW today) fast enough to address issues such as climate change.

Likewise, our current LED lighting and display technologies are too expensive and not of good enough colour quality to realistically replace traditional lighting in a short enough time frame. This is a problem, as lighting currently accounts for 5% of the world’s carbon emissions. New technologies are needed to fill this gap, and quickly.

The article then goes on to describe a new family of materials being developed in a laboratory in Cambridge. These are called Halide Perovskites, which are semi-conductors, which conduct charges when stimulated with light.

Coloured perovskite light-emitting inks that can be cast down into thin films

There are still challenges to developing this technology commercially but the author sets out the way forward. Please see the article for a full description.


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What happens to recycled plastic?

This article appeared in The Conversation on September 20th 2020:

The UK Government’s statutory guidance is supposed to clarify how recycled plastics should be dealt with but it is far from clear. Research reported by The Conversation indicates that each local authority commissions a different agency and recycling methods vary enormously. They suggest that the secrecy surrounding the disposal of plastics is the next big scandal waiting to be exposed.

A government briefing paper from March 2020 stated that 91% of the five million tonnes of plastics used in the UK each year is “sent towards treatment”. This does not mean it is actually recycled, just that it went to a waste management company. Even so, the World Wide Fund for Nature estimated that the recycling rate for single-use plastics was 29% in 2018.

A 2018 report by the Local Government Association found only one-third of plastics collected from households can be recycled, due to contamination, low-grade and mixed materials and technical difficulties.

The National Audit Office, an independent body responsible for auditing government departments, claimed in 2018 that there was a sixfold increase in exports of packaging material for recycling abroad between 2002 and 2017. Exports accounted for half of all packaging reported as recycled in 2017. So what happened to all of it?

Exporting the problem

According to industry experts, many businesses that call themselves recycling companies actually only sort waste and then sell it on, often via brokers, towards unknown destinations. Few have their own recycling facilities, and many refuse to say where the plastics go, claiming this is commercially sensitive information.

The UK exports large quantities of plastics to other countries, including Turkey, Egypt and Malaysia. These countries lack the facilities to recycle their own plastics, let alone plastics from elsewhere. Little wonder that most plastics Turkey promises to recycle are actually burned or dumped. Turkey’s recycling capacity in 2019 was claimed to be 850,000 tonnes whereas almost 600,000 tonnes were imported from EU countries. The UK alone exported half a million tonnes in 2019, according to the government’s own source. But an independent report in 2019 suggests that figure is closer to 700,000 tonnes.

A dog picks through a plastic waste dump.
A rubbish dump in Çorum, Turkey. Attraction Art/Shutterstock

Even just talking about “plastic waste” obscures how diverse the materials involved are, and how complicated the inevitable recycling process is. For example TetraPaks – the drink cartons you probably buy milk or orange juice in. Some 68% of councils collect them from the kerbside, but there are few facilities worldwide equipped to recycle them. The UK has only one, built in 2013, that can process 25,000 tonnes a year. But the UK produces about 60,000 tonnes of these cartons annually. Yet, the facility is running under capacity, according to an email they sent us. So most drink cartons must either be exported or have only their cardboard recycled, as they also contain low-density polyethylene (about 21%) and aluminium foil (4%) which are difficult to separate.

COVID-19 has made the UK’s recycling problem much worse. The use of single-use plastics, including disposable masks and other PPE, has prompted a steep increase during the pandemic. Online shopping, with all the additional packaging, has risen too, while recycling in developing countries and elsewhere has halted. All of these factors have increased the amount of plastic waste the UK exports, and increased the likelihood that it will be dumped.

What can be done?

Exporting plastic waste should be forbidden without clear proof it will be recycled. The public needs to be alerted to this growing problem, so that the government is forced to create a legal framework, with enforceable regulations, ensuring British plastics are responsibly recycled in Britain.

Plastics recycling comes in many shapes and forms. There are mechanical and chemical processes for recycling the many different types. Most processes require plastics to be clean and separated by type, but there are also processes such as pyrolysis that can process mixed and contaminated plastics, including printed films.

To deal with all of our plastics, the UK needs to build an integrated plastics recycling facility that can deal with all these in every part of the country.

As a last resort, the unrecyclable leftover waste could be burned in an incinerator to generate energy. These are common in continental Europe, but the UK seems to prefer landfill, with incinerator projects regularly rejected.

Though not perfect, incineration in Britain would be a vast improvement on the current situation, where plastics are shipped to the other side of the planet only to be dumped and burned illegally.

  • ____________________________________________________________________________

September 17th 2020:

In an article for The Guardian this week, Arwa Mahdawi, exposes the fact that plastics recycling is a scam anyway, invented by the manufacturers to move the blame to people, rather than themselves:

“According to one analysis, only 9% of all plastic ever made has likely been recycled. Here’s the kicker: the companies making all that plastic have spent millions on advertising campaigns lecturing us about recycling while knowing full well that most plastic will never be recycled.

A new investigation by National Public Radio (NPR) and the Public Broadcasting Service (PBS) reports that the large oil and gas companies that manufacture plastics have known for decades that recycling plastic was unlikely to ever happen on a broad scale because of the high costs involved. “They were not interested in putting any real money or effort into recycling because they wanted to sell virgin material,” Larry Thomas, former president of one of the plastic industry’s most powerful trade groups, told NPR. There is a lot more money to be made in selling new plastic than reusing the old stuff. But, in order to keep selling new plastic, the industry had to clean up its wasteful image. “If the public thinks that recycling is working, then they are not going to be as concerned about the environment,” Thomas noted. And so a huge amount of resources were diverted into intricate “sustainability theatre”.

Multinationals misleading people for profit? Hold the front page! While the plastics industry’s greenwashing will come as no surprise to anyone, the extent of the deception alleged in NPR’s investigation is truly shocking. (I should state for the record that an industry representative interviewed by NPR contested the idea that the public was intentionally misled, although he does “understand the scepticism”.)

The subterfuge around recycling plastic is also an important reminder of just how cynically and successfully big companies have shifted the burden of combating the climate crisis on to individuals. This might be best encapsulated in a famous ad campaign that aired in the US during the 1970s with the slogan “People Start Pollution. People can stop it.” The campaign was created by a non-profit group called Keep America Beautiful, which happened to be heavily funded by beverage and packaging companies with a vested interest in convincing people that they were the ones to blame for a polluted planet, not capitalism.”


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Australian ecologists are having their research findings suppressed

The Australian government is accused of covering up the impact of the climate crisis and suppressing the work of scientists yesterday as it seeks to amend the country’s environmental legislation. A report by the Ecological Society of Australia found that scientists are routinely blocked from publishing results of their studies and warn that changes are made to their findings before their work is released. It found that half the government scientists and nearly 40 per cent of those working in industry had been blocked from releasing or discussing their findings. 

For the full story see:

the abstract of which is as follows:

Suppressing expert knowledge can hide environmentally damaging practices and policies from public scrutiny. We surveyed ecologists and conservation scientists from universities, government, and industry across Australia to understand the prevalence and consequences of suppressing science communication. Government (34%) and industry (30%) respondents reported higher rates of undue interference by employers than did university respondents (5%). Internal communications (29%) and media (28%) were curtailed most, followed by journal articles (11%), and presentations (12%). When university and industry researchers avoided public commentary, this was mainly for fear of media misrepresentation, while government employees were most often constrained by senior management and workplace policy. One third of respondents reported personal suffering related to suppression, including job losses and deteriorating mental health. Substantial reforms are needed, including to codes of practice, and governance of environmental assessments and research, so that scientific advice can be reported
openly, in a timely manner and free from interference.


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New Extinction Rebellion actions largely ignored by the BBC News

This week has been a long-planned Autumn series of demonstrations by XR across the country. Yet the BBC news has chosen to largely ignore the protests, focusing instead on yet more coverage of the Covid-19 pandemic.

The following link, I hope, will take you to photographic evidence of the demos:

Actions against HS2 have also been ignored. Yet many arrests of peaceful demonstrators have taken place.

At Lambeth Bridge we saw the most shocking scenes of this Rebellion so far. During a critical mass bike ride, a swarm of police vans rushed in and kettled over 200 peaceful protestors. The Met held rebels in the rain for hours, searched and arrested everyone (including bystanders, independent legal observers and welfare rebels) and confiscated hundreds of bikes.

The following photographs give an idea of the extent of the demonstrations.

Peaceful demonstration of cyclists
Demonstrators outside the House of Lords
Arrests in Cardiff
Lambeth Bridge, London

Since I first uploaded this post, there has been another BBC News broadcast. This featured Boris Johnson visiting one of the HS2 building sites and stating very strongly how good and important it is for our country to have the HS2 hi-speed rail link. Later in the broadcast there was a very short clip of some anti-HS2 campaigners demonstrating against HS2. This was hardly balanced recording. Nothing was shown of the destruction of ancient woodlands to make way for the rail line, nor the other devastation already occurring on the route, nor was there any mention of the 100s of protesters who were arrested for peacefully demonstrating against HS2. And the ultimate cost per taxpayer head for the hi-speed train was not mentioned. All this at a time when the economy needs to recover after the Covid-19 crisis.

One XR action which did receive a lot of coverage was their blockade of the printing companies who print most of the right wing press, including newspapers controlled by Rupert Murdoch. One of their posters read “5 Crooks Control our News”. This action meant that newspapers, like The Sun and the Daily Mail could not be issued on time.

This action incensed the current government, most of all the Home Secretary, who claimed angrily that XR were terrorists and that the action was preventing freedom of speech. Did she mean “freedom to tell lies”? The message about the media controlling our news (and printing lies, especially at election time) was ignored.

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Nature is telling us to rebuild our economy around inclusive wealth by Pushpam Kumar


A GDP-based approach to measuring well-being focuses on produced or manufactured capital. It pays less attention to natural capital — goods and services such as water, air, soil, biodiversity and scenic beauty that also benefit society. Even if the value of some ecosystem services is embedded in measures of GDP, many are often ignored and unaccounted for.

Inclusive wealth refers to the sum of social worth of manufactured capital (like building and machines), human capital (like health and skills) and natural capital (like biodiversity and ecosystem services). Image courtesy of UNEP

The Inclusive Wealth Index (IWI), first proposed in 2012 by the United Nations Environment Programme (UNEP) and others and guided by legendary environmental economist Sir Partha Dasgupta of Cambridge, on the other hand, includes a holistic assessment not only of produced or manufactured capital, but also human capital and natural capital. It considers not only traditional kinds of wealth but also less tangible ones — such as skill sets, health care and environmental assets — that form the backbone of human progress and ultimately set the parameters for sustainable development.

A country’s inclusive wealth (IW) is the value of its natural capital, human capital and produced capital. By factoring in all three forms of capital, the IWI allows us to more accurately characterize the overall change to well-being. For example, when trees and biodiversity-supporting habitat are destroyed to build a school or hospital, natural capital decreases but human capital increases. This is very important for decision makers to know and critical for guiding efforts to enhance true sustainability.

Just as businesses do asset accounting, nations should do inclusive wealth accounting. And this accounting should include biodiversity and ecosystem health and resilience, which require investment to maintain and preserve. Because GDP does not factor in the benefits of natural capital, it doesn’t incentivize the actions needed to protect biodiversity and the services it provides — including reducing the risk of pandemic. To provide such protection requires accounting of all kinds of assets, especially natural capital. As the Resolution of United Nations Environment Assembly (UNEA) puts it, “natural capital and natural resource valuation and accounting mechanisms can help countries to assess and appreciate the worth and full value of their natural capital and to monitor environmental degradation.” Inclusive wealth accounting can encourage accountability and allow countries to monitor progress toward conservation goals.

The Dasgupta Review for the UK’s Treasury already has started voicing the need for inclusive wealth accounting to keep track of change of natural assets and the emerging trade-offs.

The IWI was not developed with the intention of replacing GDP as an indicator of progress. Indeed, the UNEP-led Inclusive Wealth reports show that it is possible to achieve per capita growth in GDP and inclusive wealth simultaneously.

The Inclusive Wealth Report 2018 estimates the inclusive wealth per capita over the period 1992–2014 in 140 countries. In spite of considerable data limitations, it found that on average natural capital declined. The inclusive wealth per capita (natural, produced and human) rose, but at a slower rate than that of the GDP per capita. This does not bode well for sustainability, because it means that part of the gain in GDP is coming at the expense of natural and human capital.

The Sustainable Development Goals (SDGs) require nations to strike a balance across various types of capitals — produced, human and natural. GDP per capita is inadequate for the task. The notion of inclusive wealth formalizes a way that balance can be struck. If the SDGs are themselves to be sustainable, nations must provide estimates of changes of inclusive wealth per head.

The progress report on the SDGs suggests that, with just 10 years left to achieve them, we are lagging on almost every goal. We have an opportunity to fix this problem by adopting a credible and well-rounded indicator for true sustainability. Now, more than ever, we need to use the IWI as our measure of well-being.

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Sustainable cement: the simple switch that could massively cut global carbon emissions



At the dawn of the industrial revolution approximately 200 years ago, the carbon footprint of humanity was close to zero. Today, humanity’s carbon footprint is more than half of our overall ecological footprint, resulting in humans using far more resources than could be renewed each year – equivalent to the renewable resources of 1.6 Earths.

Decarbonising industry and the economy is essential to improve the balance between our ecological footprint and the planet’s renewable resources. This would provide the best possible chance for humanity to mitigate the effects of climate change. Consequently, we need to rethink the way we build our cities. And to do this, we need to talk about cement.

Cement, the “glue” in concrete, is the durable, waterproof and ubiquitous material upon which modern civilisation is built. Concrete is second only to water in terms of commodity use, and the world produces more than 10 billion tonnes of it each year.

Recent reports have indicated that since the introduction of Portland cement around 200 years ago, our built environment is now outgrowing the natural environment that has existed for millions of years. This is driven primarily by rapid urbanisation. By 2050, 80% of the world’s population is expected to live in cities.

Cement production alone (excluding other aspects of construction) accounts for around 8% of global CO₂ emissions, about half of which results from chemical reactions inherent in the production process. As other industries such as energy and agriculture reduce their share of emissions, cement production may account for nearly a quarter of all human-driven CO₂ emissions by 2050.

Shifting completely to sustainable cement could, depending on technology used, save between 1.72 and 2.75 billion tonnes of CO₂ emissions annually, moving Earth Overshoot Day back by approximately ten days. These are savings that could be achieved today. By 2050, the savings could reach between 7.25 and 11.60 billion tonnes of CO₂ emissions annually, moving Earth Overshoot Day back by approximately 40 days.

This reduction in carbon footprint can be achieved solely by changing the type of cement we use to build cities and infrastructure. Further savings are achievable with more efficient design and the use of sustainable cements with enhanced performance, so that less cement (and hence less carbon) is required to achieve the same outcome.

Making cement more sustainable

Many low-CO₂ cements have emerged as attractive, more sustainable alternatives to traditional Portland cement. Portland cement is produced by heating a mixture of limestone and other minerals to around 1,450°C, a process that results in chemical reactions that release large amounts of CO₂.

But other materials are also widely used in concrete, including those largely generated from industrial waste or by-products such as coal fly ash, blast furnace slag, calcined clays, finely ground limestone or silica fume. They are used either by blending with traditional cement, or as a binder (or “glue”) themselves, without any Portland cement.

Importantly, the way these materials are produced results in far lower CO₂ emissions than Portland cement. This can reduce CO₂ emissions by between 50% and 80%, depending on the technology used.

Using these materials in cement provides enhanced strength and durability, and also improves sustainability by reducing associated CO₂ emissions and recycling industrial wastes. Many of these cements have been highlighted in the United Nations Environment Programme 2016 report as having greatest potential for cement-related CO₂ emissions reduction.

Despite the extensive environmental and technical benefits achievable, the construction industry has been slow to take up sustainable cement technologies, which have instead been focused primarily in smaller niche markets. This has limited the industry’s ability to decarbonise.

One thing has become increasingly clear in recent years. If we are to mitigate the existential crisis in which we find ourselves, action must be taken now. The Paris Agreement commits world leaders to respond to the threat of climate change by keeping the global average temperature rise to below 2°C, and aiming for 1.5°C.

To achieve this, it is essential that we revolutionise the way in which we build our cities, shifting to sustainable cement technologies that reuse industrial wastes and drive a circular economy. The solutions are within reach. And our future depends on it.