Earth Overshoot Day reminds us how far we are from sustainability

On 2 August, humanity will have used up its quota of renewable resources for 2023, according to Ecological Footprint analyses. But this barely scratches the surface of understanding the overshoot predicament we now face.

By Jane O’Sullivan

Earth Overshoot Day falls on 2 August this year. This is the day on which, according to the Global Footprint Network (GFN), humanity has used up the whole year’s worth of Earth’s biocapacity. After this date, we are living in overshoot, using biocapacity beyond the level that the Earth can renew. According to this analysis, we would need 1.7 Earths for current human consumption to be sustainable.

The world’s richest countries use up their fair share much earlier in the year. Qatar, thanks largely to water desalination, air-con and a lot of oil wealth, reached overshoot day on 10 February (Figure 1). If everyone consumed like Qataris, we would need nearly 10 Earths. In North America, the date was 13 March, and 3 April in Sweden. To be sustainable, everyone would have to consume at the level of people in Kyrgystan or Nicaragua.

Figure 1: Country Overshoot Days: the date at which countries have used their sustainable share of world biocapacity for the year, according to the Global Footprint Network.

Human consumption of natural resources went into overshoot around 1970. As GFN emphasises, world population increased 121% since 1970. If we all consumed like we did in 1970, we should need 2.21 Earths now. But so far, it’s “only” 1.7, partly because agricultural improvements have increased Earth’s total biocapacity, but largely because most of those additional people live in abject poverty. Not an ideal solution to overshoot.

GFN does not emphasise the role population growth plays in overshoot on their website. Promoted solutions include all the usual measures: renewable energy, eating less meat, reducing food waste, etc.

A 2021 study by Lucia Tamburino and Giangiacomo Bravo usefully compared countries’ ecological footprints and population densities (using biocapacity rather than land area to assess density on a comparable basis), to see “whether changes in consumption patterns and technological improvements may alone bring back humanity’s footprint below planetary limits without reducing human well-being to unacceptable levels, or whether the population lever needs to be used as well, at least in the long run.”

They found the vast majority of countries consume more than their national biocapacity. Almost half of these need to increase consumption per person to achieve adequate living standards. Only a handful of countries were achieving decent living standards without exceeding their biocapacity. A few rich countries, like USA and Denmark, could restore sustainability by lowering consumption per person and still afford decent living standards. Most of them, including most of Europe, Japan and China, have insufficient biocapacity to provide adequate living standards for all their people and would have to reduce population as well as per capita consumption to achieve sustainable wellbeing.

Figure 2: A sprawling slum in Mumbai, India.

By focusing on Ecological Footprint per person, Earth Overshoot Day emphasises each person’s relative level of consumption, which is important. But it de-emphasises how population growth reduces the available biocapacity per person, which is equally important.

A country with a stable population living sustainably from the resources within its borders might still be classed as driving overshoot in the current GNF approach, if its per capita consumption was higher than Earth could support for all people everywhere. In contrast, a country like Nigeria is seen as a victim of overconsumption elsewhere, despite quadrupling its population since 1970 and therefore disproportionately contributing to reducing the sustainable standard of living for everyone.

The different perspectives of per capita consumption and population density were explored in our 2020 blog “Earth overshoot day and population.” It would take five Earths if everyone had the ecological footprint of USA residents, but only 2.2 Earths if they also had the same population density as USA. In contrast, the ecological footprint of the average Indian resident is below Earth’s biocapacity of 1.6 global hectares per person, but if all countries had India’s population density, we would need 2.7 Earths even if we all lived like Indians.

Table 1. How many Earths would it take if the whole world had both the per capita ecological footprint and the population density of each country? From Tamburino and Cafaro

These are salutary findings, but how well does Ecological Footprint methodology describe the conditions needed for sustainability? It has been widely criticised for not considering a sufficiently wide range of human impacts (e.g. here and here). For instance, the impression is given that a surplus of national biocapacity over national consumption makes a country ecologically sustainable. There are many countries which have more biocapacity than their population currently uses, but which are nonetheless degrading their ecosystems. Brazil and Australia are two that stand out.

GFN focuses very heavily on the carbon cycle, neglecting most other “planetary boundaries” for sustainable use of the biosphere. GFN places no value on biodiversity or ecosystem functions, and gives virtually no attention to environmental pollutants other than carbon dioxide. It makes no judgement about the conversion of tropical rainforests into oil-palm plantations, other than to assess this as an increase in biocapacity. It does not judge the biodiversity repercussions of fresh water diversions for human use. Soil degradation is only indirectly reflected if it reduces the measured productivity of land.

Misunderstandings arise from the way GFN incorporates fossil fuel use into footprint, by estimating the land needed to draw down the carbon dioxide emitted. As GFN says, 60% of humanity’s Ecological Footprint comes from carbon emissions. This means that most countries are not actually drawing on their own biocapacity to supply the resources they consume to anything like the extent implied by their ecological footprint. They are not even using biocapacity from elsewhere in the world – they are drawing on the stored biocapacity in fossil fuels.

Likewise, even where biocapacity appears to exist in excess, it is not in fact drawing down the carbon dioxide released by burning fossil fuels. For that to be the case, the total biomass would have to increase by that quantity of carbon per year. GFN extrapolates the biocapacity of forests from typical timber yields in managed forests, which is not the same as biomass increase in natural forests. The annual consumption of biomass by non-humans (from fungi to megafauna) is not measured in GFN’s analyses. Nor are wildfires. As a result, Ecological Footprint tells us little about the adequacy of land resources for feeding people and supporting biodiversity, and little about the sustainability of our fossil fuel use.

In the end, Earth Overshoot Day is a useful awareness-raising concept, even if it raises more questions than it answers about the nature of sustainable societies.

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15 thoughts on “Earth Overshoot Day reminds us how far we are from sustainability

  1. O’Sullivan’s usual excellent thinking. This helped clarify what GFN does and doesn’t do. Concerning how much is leaves out and how overly optimistic (despite dire conclusions) GFN probably is. The uncertainties of making major changes in a complex interdependent system are considerable. Humanity has little awareness of the huge risks we are taking. And whatever else happens, clearly population is a multiplier of impacts. Fewer people would make for better futures.

  2. We have such a challenge ahead. I do hope young people around the globe will consider both factors for their setting and cut back on whatever makes appropriate sense. Consume less and also have fewer children, ideally not more than 2.

  3. “Earth Overshoot Day reminds us how near the United Nations is to the corporate sector and organised religion.” There, fixed it.

  4. “It does not judge the biodiversity repercussions of fresh water diversions for human use. ”
    Unfortunately, no one does. I think that freshwater diversion is one of the biggest blind spots in public debate and environmentalism today (with rare exceptions). Almost everyone I speak to, when I mention water, just says there’s a lot of it and that if we don’t take it it goes to waste. No one understands there are ecosystems that need water to exist. (Or that we could also use water for recreation, fishing, transportation, or that rivers mitigate heat locally)
    I live in a very rainy area of Europe, where rivers are integral to our lifestyle and self-identity. And yet, for huge tracts, river beds are empty or almost empty. Just gravel where water used to flow. No one seems to notice. It’s like talking about a person who’s dead as if they were still alive. It’s surreal.

    1. That is a very important point. Overshoot Day is concerned with sustainable living in terms of consumption. It does not address the need of a person for the natural environment. I for example do not have a very large ecological footprint but I have a great need to roam in wilderness areas, where human density is extremely low and fauna and flora prevail.

  5. Thanks to Jane O’ Sullivan for reminding us the link between population and ecoogical footprint. One sentence raises a question to me : “If we all consumed like we did in 1970, we should need 2.21 Earths now. But so far, it’s “only” 1.7, partly because agricultural improvements have increased Earth’s total biocapacity, but largely because most of those additional people live in abject poverty. ”
    When I look at the World Bank statistics on poverty (,SAS,SSA,LAC,MNA,ECA,OHI,WLD&pv=2.15&oc=pop_in_poverty&on=Population%20living%20in%20poverty&os=millions&od=Population%20living%20below%20the%20poverty%20line%20(2011%20PPP)&tab=table&ppp=2017 ) say that the number of poor people has strongly decreased from 1.990 billion in 1981 (there are no data before that) to 659 million in 2019. Who should I believe ? Intuitevely I tend to agree with Jane Sullivan, but why is there such a contradiction ?

    1. It’s two different statistics. I think what she means is that the *extra* people compared to then were mostly added to the population of poor countries, so are poor themselves.
      Also, there’s a difference between saying that the number of poor people have decreased – you draw a poverty line, and you’re either on one side or the other, you’re either poor or not – and saying that the extra people were so much poorer than those who existed before, they brought the average down.

      Let’s take the famous chicken example. There’s three people: one has two chicken, the other one, the last one none. People “consume” a chicken each on average; the poverty line is below one chicken, so you’ve only got one poor person. This poor person now has a baby, which gets an extra chicken from the person who had two. Now, the per capita average is lower than a chicken per person, but you’ve still got the same number of technically poor people, that is one.
      Hope this makes sense…

      I think most of the out-of-poverty statistics were made by China, and the Chinese workers that got better off were competing with mostly Western workers, who saw their standards of living decrease (oversimplifying the issue here). That should also explain it.

    2. Dear Marc, that is a good observation. Perhaps I should not have said “abject”. The answer is that the World Bank’s poverty line is a much lower bar than that needed to pull down the global average footprint. Assuming countries’ consumption levels stayed constant, an increase in population in any country with per capita footprint below the global average will lower the global average. But they haven’t stayed constant: emerging economies have increased per capita fossil fuel and resource use substantially. However, even as they do this, their population growth will lower the average until their footprint is above the average. Now, an increasing number of emerging economies (especially China, but much of Asia and Latin America) have footprints considerably higher than the global average, so it takes a lot of population growth in much poorer countries to prevent the global average rising.
      Note that, while population growth in poor countries and economic growth in middle-income countries cancel each other in terms of the average per capta footprint, both add together to contribute to the total human footprint, which is what matters most.
      Note also that, according to GFN, world biocapaicty has increased about 20% since 1970 due to agricultural productivity increases (‘improved’ technologies, but not necessarily sustainable improvements). This also contributed to the increase in “planets per year” being less than proportional to the increase in global population.

      1. Jane writes: “Note also that, according to GFN, world biocapacity has increased about 20% since 1970 due to agricultural productivity increases.”

        The agricultural improvements have come at an immense cost to biodiversity — a reminder that the GFN approach to sustainability does not incorporate sharing resources equitably with other species.

  6. Lowering population is effective because of the following. It lowers demand for consumables which reduces pressure on the environment. It lowers the supply of labor which increases its value and thus its strength. It all starts with reducing the birth rate.

  7. Population Growth Is Not a Threat to Prosperity
    Letters, July 27, 2023, Wall St. Journal
    Marian Tupy & David Deutsch’s op-ed “We’ll Never Run Out of Resources” (July 21)
    recalls the work of Julian Simon. The late economist famously bet doomsayer
    Paul Ehrlich in 1980 that the prices for five metals wouldn’t increase over a
    decade, even if the world’s population grew. Ten years later, Simon won the wager.
    Prices for the metals declined sharply.

    Simon’s book “The Ultimate Resource” debunked predictions that population growth
    and resource scarcity would make modern civilization unsustainable. Population
    growth is a boon, it argued, since people and markets would innovate out of
    scarcities and environmental problems and improve well-being. The Competitive
    Enterprise Institute gives an annual Julian L. Simon Award to an individual whose
    work continues to promote the vision of man as the ultimate resource.
    —Joel M. Zinberg, Senior fellow, CEI, New York
    Let’s ask Messrs. Tupy & Deutsch to also please consider clean water, breathable
    air and global temperatures within a livable range.
    —Carol Watts, Overland Park, Kansas

  8. Unfortunately, many important organizations, that are critical to the sustaining of LIFE’S (writ large) ability to just simply survive, have been taken over by moneyed interests. I took the test and there are a lot of missing details (live on an island, have a rain harvesting system, am vegan, drive very little and on and on) which are simply not counted. Number of offspring is also not taken into account. It seems all the science and even the clear reality of things, as Climate Change and species loss, are not even considered. Seems we are not only fighting a steep, uphill battle but are wearing leaded boots. When things start to crash, as they are now, people form tribes and look for others to blame. I have been involved in this issue over 29 years and little has improved. What more can people, as myself, do??

    1. Jack, as individuals we can model more restrained consumption and procreation. As citizens, it’s more complicated … But I think that both mainstream environmental activism (focused on decreasing carbon emissions, setting aside particular places for environmental protection, etc.) and more radical challenges to the pro-growth political status quo have value.

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