Earth Overshoot Day reminds us how far we are from sustainability

By Jane O’Sullivan | 1 August 2023
The Overpopulation Project

(Photo: Babak Fakhamzadeh / Flickr / CC BY-NC 2.0)

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.

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.

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.

Reprinted with permission from Frank Götmark – Project leader of The Overpopulation Project (TORP); Professor, Animal ecology and Conservation Biology, University of Gothenburg.

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