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Natural Environment

Today is Earth Overshoot Day 2021

Every year the date for the Overshoot Day comes earlier, but what does it mean?

Fabrizio Varriale, World Built Environment Forum
29 July 2021

Yesterday, the world burned through the last scraps of its environmental budget for the year. For the rest of 2021, our society and economy will pollute and consume more than the planet can absorb and regenerate. We have exceeded our annual credit allowance, and from now until January 1st 2022, we run on debit.

Every year, the Global Footprint Network calculates the date of the Earth Overshoot Day by comparing environmental demand created by human activities with the limited supply offered by ecosystems. Earth Overshoot Day may be largely symbolic, but it is powerfully so. By clearly demonstrating the pressures placed on nature by human consumption, we see just how far we are from bringing our environmental account back into the black. But what is included in the account, and how is the date on which it empties calculated?

The global environmental demand created by human activities is obtained by summing up the ecological footprint of all countries, as calculated in their National Footprint and Biocapacity Accounts.[1] The Ecological Footprint methodology quantifies each nation’s demand for natural resource and polluting activity in terms of ‘global hectares’ (gha), i.e. nominal biologically-productive hectares with world-average productivity. This allows for the translation of the impact of different activities – fishing or manufacturing, for instance – into a single and consistent unit of measurement. Clearly, this methodology is based on a series of assumptions and simplifications, but it is far from a sterile accounting exercise. On the contrary, the measurement is the result of scientifically rigorous and impartial processes[2], and remains trusted by experts around the world. The methodology also allows greenhouse gas (GHG) emissions to be quantified in terms of the amount of productive land needed for their absorption. The share of our ecological footprint attributed to GHG emissions (i.e. our ‘carbon footprint’) has been growing steadily since 1961 – the first year accounted for by the calculation. It reached 57% in 2021.

On the supply side, the global biocapacity to generate resources and absorb pollution is also obtained on the basis of the National Footprint and Biocapacity Accounts. This is done by totalling the world’s biologically-productive hectares – areas of land and water capable of supporting significant photosynthetic activity and accumulated global biomass use. This total is not fixed but depends on factors such as climate and human intervention. Currently, there are around 12 billion hectares of biologically productive land and water across the world. Over the years this supply-side figure has increased but it has been consistently outmatched by demand, which in 2021 reached 21 billion hectares. We are, then, currently in debt to the tune of 9 billion hectares.

This, though, wasn’t always the case; in fact, it was only at the start of the 1970s that demand began to outstrip supply. Fifty years on, and we find ourselves troublingly, committedly overcapacity. One effect of the COVID-19 crisis was to prove that the trends of the last half-century are not irreversible. In 2020, largely as a result of the pandemic’s limiting effect on human activity, Earth Overshoot Day arrived much later than usual, on August 22nd. Not since 2005 have we made it so far into the year before reaching our tipping point.[3] But, as the world has struggled towards uneven economic recovery in 2021, those gains have been rolled back. This year’s Overshoot Day arrives only three days later than it did in 2019. This immediate rebound has been driven by an increase in our carbon footprint (+6.6%) and a decrease in global forest biocapacity (-0.5%).[4] For all the grand talk and good intentions around the Build Back Better movement, policymakers and corporations seem to be grasping for something like business as usual.

It is an interesting exercise to divide global hectares by world population, thus obtaining a calculation of per-person ecological footprints and biocapacity. At an aggregate level, individual environmental demand has remained fairly stable since 1970 – somewhere 2.5 and 3 gha/person.[5] This might suggest that the expansion of our total ecological footprint has been mainly driven by population growth, rather than any net growth in personal consumption. That, though, would be a dangerous oversimplification: the calculation does not account for vast differences in lifestyle across the developed and developing world, nor between economic strata within societies. At the same time, biocapacity per person has been steadily declining from over 3 gha in 1970 to around 1.6 gha in recent years.[6] Thus, while global biocapacity is rising, it is not keeping pace with population numbers. This is a challenge that requires dedicated attention.

Surely nobody wants to relive the traumas of 2020. But the pandemic year did serve to demonstrate that radical action is required if we want to push Overshoot Day 2022 to the later end of the calendar. The protection and expansion of forested land must be a priority. Energy consumption must be reduced, and so too the production of water- and land-intensive foodstuffs. Women and girls must be empowered the world over, and built and natural environment professionals will, of course, have their own role to play.