Planetary Limits: How can we respond to the global ecological crisis?

by Robert McLachlan

The challenges posed by humanity’s ever-increasing material and energy use and its impacts on planetary systems – most notably climate and biodiversity – are hardly new or unknown. They have been intensely studied in many disciplines for decades. But as we enter a new phase characterised by widespread and obvious impacts and continue rushing headlong into a minefield studded with points of no return, many academics around the world have concluded that current approaches are woefully insufficient and that something new is needed.

This is a story circling around the equation

materials + energy + technology ➞ consumption ➞ impacts

To start with energy, here is a graph of world energy consumption since 1800:

The rapid increase after 1950 is clearly visible, as is the fact that most energy comes from coal, oil, and gas – fossil fuels. The so-called ‘modern renewables’, wind and solar, on which our hopes of a safe future rely, are so small as to be hardly visible. The period from 1950 is the ‘Great Acceleration’, a time when all aspects of human activity sped up to an unprecedented degree.

For a long time, from Thomas Malthus to the successive waves of the Covid-19 pandemic, people have been trying to persuade other people of the extreme importance and awesome power of exponential increase. Charles Darwin in the Origin of Species famously used the example of elephants:

The elephant is reckoned the slowest breeder of all known animals, and I have taken some pains to estimate its probable minimum rate of natural increase; it will be safest to assume that it begins breeding when thirty years old, and goes on breeding till ninety years old, bringing forth six young in the interval, and surviving till one hundred years old; if this be so, after a period of from 740 to 750 years there would be nearly nineteen million elephants alive descended from the first pair.

If we return to the graph of energy consumption and restrict to the period from 1960, we get a different picture:

The growth is linear, not exponential. This is a sign that something is constraining its growth. If we could have gotten our hands on more energy, we would have.

At the moment, solar and wind power are increasing rapidly, contributing 2% of world energy use.

We are essentially very near the start of a monumental effort to transform the world’s energy system.

The EU’s 2030 target was originally 32%. It has been successively raised to 36% and then (in the Green New Deal) 40%, and in response to the war in Ukraine, to 45%.

However, the global picture for material use looks strikingly different.

Source: Jason Hickel. This is all the fossil fuels, minerals, and rocks extracted from the earth, and all harvested biological problems. The black line is Hickel’s estimate of a sustainable limit for extraction.

It shows a continuing acceleration in extraction. The emerging constraints on energy use encouraged energy efficiency, so that more material could be extracted and processed for the same energy. Although some of the materials can last a long time (roads, buildings), eventually all of it ends up as waste.

In recent decades, some advanced economies have shifted from manufacturing to services and become more purely consumer societies. Domestic material use stopped increasing.

Cement emissions, a stand-in for the size of the construction industry, stopped increasing in advanced economies in the last quarter of the 20th century. The population of the US is 2.5x that of Japan, and the EU, 3.5x.

However, this is not the whole story. Manufacturing was shifting to rapidly industrialising countries, mainly China, and production itself was evolving, as managers aimed to “apply the techniques developed for efficient assembly during the twentieth century to the processes of new product innovation” and to apply information technology to “marketing, innovation, production and to exploiting the information seams created by the Internet.”

The new products became wants and then needs, and material use continued to increase, even in countries that were already rich.

Material footprint (MF) per person continues to increase, even in the most developed regions. Domestic Material Consumption (DMC) per person has declined due to the shift in manufacturing to Asia (source).

It’s the same story in other areas of production, such as meat.

All those animals have to eat, mostly grain and soybeans. If global growth continues without limits, could we really see the whole world consuming at the levels now seen in the US? That would mean a further tripling of production. The role of power in driving ever-high meat consumption is discussed in a paper by Doris Fuchs and others: in ensuring cheap land for feed production obtained through agglomeration and forest clearance, in industrialised farming, in ignoring externalities, in processing and marketing, and also by consumers themselves who also want low prices.

All this production creates environmental impacts. The standard approach is to continue with production, but to try to minimise the impacts. Unfortunately, this has proved persistently difficult, particularly where the impacts are cumulative (build up over time), collective (pollution spreads a long way from the source), or suffer cascading consequences into the future.

Climate change suffers from all three phenomena, and as is now well known, it has turned out to be far harder to reduce emissions than was originally imagined when serious efforts began in the 1990s.

Many impacts of climate change were not predicted in advance and some are poorly understood even now. The catastrophic collapse of north pole sea ice in 2007 was a great surprise.

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Source: NASA

Apart from further amplifying warming, this has been speculatively linked to the slowing of the Gulf Stream and to changes in the northern jet stream leading to weather extremes in Europe and the US.

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Rakovec et al, March 2022:
The 2018–2020 multi-year drought sets a new benchmark in Europe. Under moderate emissions scenarios, droughts would last much longer.

In the oceans, coral bleaching was first observed in 1984 and its causes were the subject of dispute for many years. Now it is common and is unequivocally linked to warming seas. Although it was known that a lot of atmospheric CO2 would end up in the oceans, and this was studied intensively for decades, the fact that this would lead to a significantly lowering of global ocean pH did not become well known until 2003.

The instability of the marine glaciers of West Antarctica, although conjectured in the 1970s, was not clearly observed until the 21st century, and its future course is highly uncertain, and may depend sensitively on the degree of warming.

However, even apart from climate change, human activities are squeezing out the natural world. Wild mammals are now just 4% of the global mammal biomass.

This image has an empty alt attribute; its file name is mammals.png

Confirmed extinctions have accelerated rapidly, and 1/3 of all known vertebrate species are threatened (2/3 in New Zealand).

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Source: IPBES, 2019.

Faced with such multiple challenges, Alex Steffen and Johan Rockström introduced in 2009 the concept of “planetary boundaries”, nine categories of global environmental impact. For each category, a safe operating limit was to be determined, followed by a zone of uncertainty and an unsafe zone. In their most recent update, 8 of the 9 boundaries had been quantified, and in 6, we had departed from the safe zone.

It’s noticeable that the most urgent challenges worldwide are also the main environmental issues facing New Zealand.

For example, freshwater quality impacted by nitrogen and phosphorus pollution from farming has been persistently difficult to address. The Canterbury Water Management Plan, praised for its collaborative, trust-building framework, has failed nearly all of its targets, such as “an upward trend in diversity and abundance of native fish populations“: “We have not identified key Canterbury species to monitor nor do we conduct regular fish monitoring… The data we do have show  that the native fish habitat and populations… continue to decline.”

Johan Rockström has worked with New Zealand’s Ministry for the Environment to study the planetary boundaries in our context. Their report is well worth reading.

Let’s return to the equation from the start,

materials + energy + technology ➞ consumption ➞ impacts.

The mainstream solutions to climate change rely heavily on technology. Some of the required technologies definitely exist, such as wind and solar power, although questions remain as to how quickly they can scale up without being impacted by resource limitations.

To pick just one example, solar panels are now using 10% of the world’s silver supply, which is lower than its 2014 peak. The conventional answer is that if supply is limited, the price will rise, which will either lead to more supply or to the use of substitutes or to different technology altogether. That is one possibility, and it’s what has often happened in the past. But should we bet our future on this happening for every single resource, in a timely and orderly way?

Secondly, many pathways rely on technology that is either not yet in commercial use – like wood-based biofuel and synthetic e-fuels – or has consistently struggled to develop at scale, like carbon capture and storage. Aviation is a striking example: airlines are announcing “net zero 2050” targets, but their route to reach that point is filled with nonexistent technology, like hydrogen- and battery-electric planes and vast quantities of very high integrity sustainable fuels.

Meanwhile, new, energy-intensive technologies are coming along all the time, like cryptocurrency mining and flying cars.

Carey King has argued that the modern, fossil-fueled economy is a kind of “superorganism” that resists all attempts to rein it in. He parodied St Augustine’s 4th century AD plea (“Give me chastity and continency, only not yet. For I fear that You would hear me quickly, and that quickly You would heal me of that disease of lust, which I wished to have satisfied rather than extinguished”):

Give me rapid reductions in greenhouse gas emissions, only not yet. For I fear that the economy would hear me quickly, and that quickly it would heal me of that disease of growth, which I wished to have satisfied rather than extinguished.

Carey King, The Economic Superorganism: Beyond the Competing Narratives on Energy, Growth, and Policy, 2021

Echoes of this can be seen throughout New Zealand’s climate change response, which, despite the encouraging-sounding “net zero” goals, is based on prolonging fossil fuel use as long as possible – well into the 22nd century. Our “carbon capture and storage” is based on trees, a notoriously unstable way to store carbon and which, under our carbon budgets, slows down the exit from fossil fuels.

Now despite the misplaced optimism in the early days about how easy it would be to cut emissions, academics have not been idle. Numerous approaches and schools of thought have been developed in response to what is increasingly seen as a complex global ecological crisis:

This image has an empty alt attribute; its file name is degrowth2.png
Source: Google Ngram. Relative frequency of the given phrases in books.

Unfortunately, not only have the problems not been solved, even within the academic world progress has been limited. How much have traditional university economics, engineering, and agriculture taken on these ideas?

But now a new idea is gaining ground – degrowth.

This image has an empty alt attribute; its file name is degrowth1.png

In Jason Hickel’s words, degrowth is the “planned reduction of energy and resource throughput designed to bring the economy back into balance with the living world in a way that reduces inequality and improves human well-being”. Degrowth shines a spotlight directly on the “consumption” part of the equation.

materials + energy + technology ➞ consumption ➞ impacts

Some examples of current research in degrowth:

  • In “Energy demand reduction options for meeting national zero-emission targets in the UK“, John Barrett and colleagues found that the existing activity in the UK could be accomplished with just 11 MWh of energy per person per year, compared to the present 25 MWh. (New Zealand uses 34 MWh per person.)
  • In “Providing decent living with minimum energy: A global scenario“, Joel Millward-Hopkins turns the question around. Instead of looking at present activity, a scenario of “decent living” is developed: good quality housing, transport, healthcare, education and so on. He finds that it could be delivered indefinitely with 4 MWh of energy per person.
  • The “Absolute Zero” study, led by materials engineer Julian Allwood from Cambridge University, argues that “net zero” is not a strong enough target and, further, that new technologies cannot be anticipated and, in any event, do not diffuse quickly enough. In this scenario, existing technologies are used to reach zero emissions in the UK by 2050.

Radical energy conservation makes the renewable transition much, much easier.

On the material footprint side, it is easy to imagine how we might use less materials. If everything used half the material, and lasted twice as long, material use falls by three-quarters. If inessential products were not made, and essential ones used to their maximum potential, the job is done. Who has ever bought something they regretted? Who has bought something they didn’t use much, or in which a tiny plastic part broke and could not be repaired?

Taken together, the challenges look formidable. Are we doing everything we can to address them? Two new groups of academics, the Planetary Limits Academic Network and Faculty for a Future argue that we are not, and that radically new interdisciplinary approaches are needed.

One final word about technology. It really is a two-edged sword. When I first saw “2001: A Space Odyssey” as a teenager, I saw themes like the evolution of consciousness, our place in the universe, our destiny. Now, it looks more like a parable of how technology has brought mankind to a dead end.

In the famous three-million-year flash-forward,

This image has an empty alt attribute; its file name is 2001-bone.png
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the bone and the satellite are not just tools, they are weapons. (The satellite is an orbiting nuclear warhead.) And here is astronaut Frank Poole, running and running in circles and going nowhere. Apparently, Kubrick wanted this scene to be even longer.

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Later on, Frank is killed by the artificial intelligence HAL 9000, famously the most human character in the whole film.

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In the words of Andrew Delbanco,

2001 was a tribute to the collective genius of humanity for having turned this merciless world into a place fit for human habitation. It was also a merciless assault on the delusion that the world is susceptible to human will.


This post is a version of a talk given on 17 August 2022 at the Institute for Governance and Policy Studies, Victoria University of Wellington, which is available to view. Thanks to Mike Joy for setting up and hosting the talk. For further reading, I recommend the 2016 theme issue of the Proceedings of the Royal Society, Series A, on “Material Demand Reduction”. In particular, I have drawn on the following articles.

3 thoughts on “Planetary Limits: How can we respond to the global ecological crisis?

    1. Dennis, we already have enough electricity, with 70%+ of it renewables. We have plenty of storage in hydro dams. The task, as mentioned in the article, is degrowth. If we reduce our consumption of energy from 34MWh per New Zealander to 4MWh per New Zealander, then we can eliminate fossil fuels while staying within the envelope of current renewable energy production.

      No need for thousands of cubic meters of new concrete and thousands of hectares more of the South Island drowned artificial lakes. The point is, if we continue to try to grow, then the needs of energy storage will eventually overwhelm; either the whole of New Zealand will be under hydro lakes, or the world will be swimming dams containing toxic mine tailings from battery production. Or both. Not to mention the all the other planetary boundaries.

      New Zealand, being at the lowest end of per capita incomes in OECD countries and with one of the lowest growth rates is actually ahead of the pack, we just have to realize it. Our task is to maximize our comfort and contentment with the great things we already have. (Like a 70%-80% renewable electricity supply which is more than adequate to supply 100% with a small amount of degrowth.)

    2. There are some academic studies, but the government ones are out of date, e.g. MBIE considered 5 scenarios in 2019 that led to 34-39% of energy being renewable by 2035, and 35-49% renewable by 2050. But now the Emissions Reduction Plan calls for 50% by 2035 and even that is not a 1.5ºC scenario. The plan for that is not due until 2024 unfortunately.
      We will have to wait and see what modelling comes out of the Lake Onslow project.

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