Global overshoot

Back on 3 August 2017, I read an ABC News story that reported:

There is a date every year when the world’s resource bank goes into overdraft.

This year, Earth Overshoot Day is marked globally on August 2. For the rest of the year we’re in the burning red.

It’s the point when the amount of natural resources — think trees, fish and water — humanity takes from the Earth reaches the total that can be regenerated over the entire year.

It’s when the amount of carbon emitted reaches the amount the forests and oceans are able to absorb.

This year it happened in seven months, according to the Global Footprint Network.

That’s the earliest it’s ever been …[1]

Although I wondered how the natural-resource-regeneration limit and the carbon-sink limit could all be reduced to a single date, I still thought this was a compelling way of representing the ecological problem that humanity is creating for itself.

If we consume more of a natural resource in a year than the Earth can replace in a year, we will eventually run out of that natural resource. For each natural resource, the process of resource depletion will be running at an individual rate. You can go to and to read more about how scientists calculate these rates and combine them to produce the concept of ‘Overshoot Day’. As the scientists make clear, this calculation cannot be precise.

This is why, ultimately, the precise Earth Overshoot Day date for each year is less significant than the sheer magnitude of the ecological overshoot, as well as the overall trend of the date progression year over year […] Over the last decades, the date has been creeping up the calendar every year, although at a slowing rate. [2]

Of course, there are some natural resources that are not regenerated at all (think of metals). We have only a certain quantity of these resources — often a very large quantity, but increasingly difficult to find and expensive to access. Then there are resources like oil and coal, which took hundreds of millions of years to generate in the first place, but which we are consuming at a rate that will deplete existing reserves in a few decades or perhaps hundreds of years. Currently the amount of oil we use in a day is more than the Earth can generate in a million years.

The Global Footprint Network site ( is well worth a visit. You can calculate your personal ecological footprint — that is, how much of the world’s resources it takes to support your life, and how many Earths it would take to support all of humanity if everyone used the same number of resources as you do. If you are a typical Australian or American, it would take five Earths to give all people the lifestyle you currently enjoy.

The Global Footprint Network provides open access to the data it uses to make its calculations. This is a good step towards accountability and honesty in science, but is it enough to confirm that the calculations are correct?

For some scepticism about the whole idea, see for instance: Willis Eschenbach. Ecological Footprints – a good idea gone bad. 26 August 2010. . Note that this article is from a climate-change-sceptic website. I wouldn’t recommend an unsceptical acceptance of arguments posed by people who think that climate change induced by human activity isn’t real, but I think this article, and the sometimes-overly-excited comments posted below it, highlight some of the difficulties involved in accurately assessing ecological trends and risks.

At one extreme we have people who say that human ingenuity is the inexhaustible resource that can overcome any natural resource constraints — for instance, that agricultural productivity will always rise, so there is no risk of running out of food regardless of human population growth. At the other extreme there are people who say that our impact on the environment and our population growth have already exceeded a fatal limit, so that catastrophe and collapse are unavoidable — for instance, that agricultural productivity is bound to fall because of climate change, land degradation, water shortage, alienation of land from agriculture, and various disruptions to the ecosystem caused by pollution, species extinction and other consequences of human population growth and economic growth.

The reality is probably somewhere between these extremes, but where exactly? Technological advances and human adaptability to change will overcome some natural resource constraints, but is this really a limitless prospect? One would want to be pretty damn sure before gambling the future of humanity on one’s confidence in human ingenuity. In the absence of certainty, the only rational course is to be cautious and to give weight to the risk that we will run up against finite limits. The consequences of underestimating that risk are potentially devastating: war, famine and the end of the natural world that we admire. The consequences of overestimating that risk are much less scary: we might reduce economic growth; we might leave some natural resources unexploited for longer; we might change our priorities as a species in ways that leave more room for other forms of life.

What’s more, the optimists who think that we have nothing to fear all too often imply that we have nothing to fix. They don’t just dismiss ecological risk, they are similarly sceptical about social inequality and progressive movements generally.

So, I want to recommend the Global Footprint Network as a group with the right priorities and direction. One of the nicest things about its website and its campaigns is that it gives practical suggestions that are likely to reduce the risks of ecological catastrophe — and none of these suggestions has any terrible downside.

That’s why I’m writing about this now, half a year after the news story that inspired me. Good ideas deserve to run for longer than a single news cycle. They need to be shared, over and over again.


©2018 Craig Bingham

[1]      ABC News. We’ve used a year’s worth of Earth’s resources in seven months. 2 August 2017.

[2]      Amanda Diep. Why past Earth Overshoot Day dates keep changing. 13 July 2017.


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