Hello! Today I want to talk to you about Earth Overshoot Day. You may have heard
of Earth Overshoot Day; it's the brainchild of a small American think tank based in California and it's a way really of comparing the demands that we
humans make on the earth with what the earth is capable of producing, or I should say regenerating, in the space of one year. The definition of Earth Overshoot Day is the day on which the demands that we make on renewable ecological resources exceed the Earth's capacity to produce or regenerate those resources and the word biocapacity is
often used to express that idea. Earth Overshoot Day is falling earlier and
earlier every year as we make more and more demands on the earth's resources
and also as calculation methods improve,so this year it falls on August the 20th,
which is a horrifying thought - the idea that by August the 20th we have
basically used up a year's supply of natural resources and after that we're
going overdrawn, we're going into the red.

You can see that I'm using banking analogies, and it really is a little like your own personal finances; let's say that you earn a particular salary, $50,000 a year and during the year you have outgoings: you have to spend on rent, on insurance, on food, on travel, on maintaining your car, which tends to be a bottomless pit of expenditure. And the
idea of Earth Overshoot Day, if you compare it to your personal spending, is on August the 20th you would have spent your entire annual salary. What do you live on for the rest of the year? Well you live on a credit card, but for the earth, for our planet there is no
such thing as a credit card and if we overspend, if we overshoot then
we are depleting natural resources and the result of that depleting of natural resources is very damaging for the environment. For example, if we don't farm sustainably we'll end up with problems of soil erosion, soil depletion, the soil simply won't be fertile enough to produce the same yields in future. If we overfish, some of the fish stocks will collapse; if we cut down too many forests then we won't have enough carbon sinks to absorb the CO2 that we are releasing into the atmosphere. I'm sure you get the idea - that would then lead to climate change or exacerbate global warming.

If you have come across the idea of Earth Overshoot Day in the past, you have probably heard it expressed in terms like 'we are consuming one and a half times the Earth's resources', or 'we would need one-and-a-half Earths to cover our needs'. It's a very visual way of expressing things and I think it's been a good tool in awareness-raising, in trying to get across to people that we are overusing and exhausting the planet's resources, for all that some of them are renewable to some extent.

Obviously you can keep growing crops the following year, and fish will keep reproducing if there are enough of them, but there are some resources that can't be regenerated, for example certain minerals in the soil or rare earths, unless we find better ways of recycling them. So I think it's been quite a good awareness-raising tool, although the impact on people's behaviour is quite debatable. Do you know anybody who has changed their
consumption patterns because of Earth Overshoot Day? I don't know. 

But the problem with Earth Overshoot Day is that the methodology underlying it is deeply
flawed, to the point that it has very little scientific or conceptual value, and I
want to talk briefly about why that is the case. It's because the methodology
used to calculate the day on which Earth Overshoot Day falls is based on
something called the ecological footprint, and to calculate the footprintall the different parameters are brought down to something which is called the global hectare, which is a measurement of land area. And the global hectare expresses the idea of how much land is needed to produce the food, to produce the fish, and here land and sea are put on an exactly equal footing. How much land is needed to absorb the CO2, how much land is needed for timber etc etc. You get the picture. So everything is brought down to this one common
denominator, the global hectare, but this is an incredibly simplistic methodology, and let me give you some examples of the the results that you come up with if you calculate everything based on a global hectare. I want to look first of all at cropland and pastureland, which are two very important parameters under the ecological footprint model. We are in balance for cropland and pasture land; in other words humanity's demands equal the availability of pastureland and cropland. 

Now you might think that's a very peculiar statement. After all, there's malnutrition in the world, there are people starving to death. How can we say that we have enough grazing land and enough cropland to produce what we need? But the statement is is almost a tautology, because what it is actually saying is we use all the cropland that there is, and we use all the pasture land that there is. The model doesn't tell us anything about whether we're trying to create more grazing land, or whether we need more to feed the world. It just tells us that we are in balance, and it also doesn't say anything at all about how farming methods are affecting soil fertility or the environment. The measurement doesn't say anything about soil acidification or soil erosion, or basically about the
sustainability of Agriculture.

Turning now to forestry, the situation is is fairly similar. This ecological footprint model tells us that although trees are being chopped down at a tremendous rate in some parts of the world, in other parts of the world they're growing faster fast enough to offset the loss of forests in those parts of the world where the trees are being felled. So according to the ecological footprint model, we're in balance when it comes to forestry, and again that tells you nothing about the virgin rainforest or the trees that are being chopped down to create huge soya monoculture or graze cattle which emits greenhouse gases, so it seems to me that the model has a real problem there and it's rather similar with fisheries. The model tells us that some fish stocks are being overfished and might be close to collapse, but other fish stocks are thriving, so overall we have a balance. So you can see that it's a very simplistic model that works on a macro level, if it works at all, but it doesn't work on a micro level. It doesn't tell you about
regional disparities disparities between sectors, and it doesn't tell you about the impact of the activities that it looks at, so if there is a balance in agriculture and forestry and Fisheries then where is this massive deficit coming from? Where are we overspending?

Well, it comes down to essentially one thing: that the land we would need in order to absorb the excess CO2 that we produce is much greater than the land that we have, than the carbon sinks that we currently have. In other words, the overshoot is pretty much all to do with CO2 emissions in this particular model, so the ecological footprint because of the way it's calculated is not really an ecological footprint. It's a CO2 footprint. Now the founder of the think-tank and the person behind Earth Overshoot Day would say that that's because we don't have the datasets to investigate the evidence in sufficient depth to say anything more than that, but it seems to me that although Earth Overshoot Day is a concept that has gained widespread currency, and it's very often cited including by UN agencies for example, it's actually nonsense.

At best, I would say it's a kind of publicity stunt, and at worst it's scaremongering, but in a way that doesn't actually get us anywhere. And what we need instead of Earth Overshoot Day is a new set of indicators for decision-makers. We need metrics which actually show trends for critical Natural Resources, for example trends relating to soil or to the availability of fresh water or fish stocks, but looked at in much more detail and more realistically than the ecological footprint manages to do, because it lumps
everything together in an overly simplistic way. Thank you.