Understanding Overshoot

This year’s Earth Overshoot Day falls on 2 August. But, what is it? 

When I tell people about Overshoot Day, or ask them about it, I find that very few people know about it, and even less understand the concept – including many concerned about climate change or the state of the Earth’s ecosystems.

Environmental scientists define overshoot as demand exceeding regeneration. What does that mean in layperson’s language?

How about an analogy.

Suppose at the beginning of the year (on 1 January) you have capital of $1,000. During the year you spend $200. Suppose your investments give you a 10% return, giving an income during the year of $100. At the end of the year (31 December) you will have $900 ($1,000 - $200 + $100.)

Now suppose you do exactly the same the following year, only this time you start with $900 (the amount you had left at the end of the previous year.) Again, you spend $200 and get a 10% return on investments. What are you left with at the end of this second year?

$790.

Your investments give you an income of $90 (10% of $900) and you spent $200. Thus, you have $900 - $200 + $90 = $790.

If you continue doing the same thing year after year then you can easily see that your capital base will diminish each year, and eventually you will have none of it left.

This is overshoot. You are spending more each year than you are making.

It is easy to envisage a theoretical date during the year upon which your spending surpasses your income. For the first year this would be 9/10ths of the way through the year – 25 November. All money you spend after this date puts you into “overshoot.”

So, how does this relate to Earth Overshoot Day?

Think of the amount you spend ($200) as being a metaphor for the quantity of materials and resources that humans extract from the Earth plus the volume of waste (pollution) we pump back into the Earth.

Now consider your return (10%) as representing how quickly the Earth can replenish the materials and resources extracted, plus how long it takes for the Earth to repair from the waste and pollution.

In a nutshell, that is what Earth Overshoot is. It is the difference between the extraction and pollution rates of humans and the ability of the Earth to restore and repair. This difference has been negative for more than 50 years.

Just as with the theoretical financial situation it is possible to calculate the extraction and waste production rates; it is also possible to calculate the restoration and repair speeds. Using these figures calculating a symbolic date for Earth Overshoot becomes workable.

This year it is 2 August.

Earth Overshoot Day has been calculated for every year since 1971 when it was calculated to land on December 25^th.

Returning briefly to the financial analogy above: this date would represent having spent as much as was earned by Christmas – leaving just one week to either go without, or dip into your capital.

Sadly, since 1971 we have been experiencing Earth Overshoot Day earlier and earlier in the year.

The importance of Earth Overshoot Day cannot be overstated, as it is our overshoot that is the fundamental driver of all our environmental (and increasingly, our social as well) woes. Climate change is the issue that gets most attention, yet climate change is only one of a myriad symptoms of overshoot. Other symptoms include; species extinction, deforestation, land/soil loss, desertification, plastic pollution, air quality pollution, litter and rubbish, toxic waste issues, and water pollution.

William R Catton, Jr., is recognised as having written the foundational study on overshoot in his classic 1982 book Overshoot:The Ecological Basis for Revolutionary Change.¹ In that book Catton noted that since the European colonisation of the world the world has been living in what he termed the Age of Exuberance.

The Age of Exuberance saw the massive increase in technology which, along with the extraction of fossil fuels, resulted in enormous increases in the ability of humans to exploit the world. The Age of Exuberance also suggested that resources and human innovation were limitless and there was no stopping human “progress.”

Now, the exuberance is fading rapidly, and we are finding that we cannot continue extracting, exploiting, and polluting. As Catton puts it, ‘technology (has) come to enlarge our resource appetites instead of our world’s carrying capacity.’

We cannot keep feeding our appetite at the rate we are doing. We are growing fat and the kitchen cupboard is becoming bare.

Note:

1. William R Catton, Jr., Overshoot:The Ecological Basis for Revolutionary Change, University of Illinois Press, Urbana and Chicago, 1982.