Everyone, big or small, has an Ecological Footprint. How much nature people need depends on what they eat, how they dress, what their home is like, how they move around, and how they get rid of their waste. All of that can be measured. The resulting data allows us to determine the area of biologically productive land and water that is required to grow food, produce fiber for clothing, build houses to shelter people, and absorb their waste. We can measure the carbon dioxide from burning coal, gas, and oil. In the end, we all live on what the “global farm” provides, and we can accurately measure what the farm provides, and what people consume.
Everyone understands money. People with money have more options, and possibly fewer worries, at least material ones. Those with enough money can live how and where they like. Everyone welcomes them. As long as they can pay, no one will show them the door. We can do many things with money. For example, we can compare things. Money also tells us how much everything costs. Once we know the prices, we can relate them to our income. How long do I have to work so I can afford this mobile phone? How much do I earn, compared to my expenses? Compared to last year? Or compared to the income of someone in Singapore?
Ecological Footprint accounting is a tool that, like money, asks the core question: How much nature does everything cost? How much biocapacity is required for a glass of orange juice, and how much for a liter of gas? And we can go further: How much nature does a person need? A person’s Footprint is a “currency” which is spent to provide services, to offer space for our buildings, to produce goods and to dispose of them. For a person, their Footprint is the sum total of all they require, including their waste (because waste too draws on nature). What the Euro, Dollar, or Yuan is to money, the hectare — or more precisely the global hectare — is to the Ecological Footprint.
Just as different currencies can be set off against each other, so can the Footprint’s area units. This is the point: that there is a single unit — a tertium comparationis — that everything refers to. Obviously, not every global hectare is identical, only sufficiently similar. But the same is true for money since one dollar for a person with minimum wage means something quite different than one dollar for a billionaire.
Therefore, in the same way one financial figure cannot describe the health of an economic entity, mapping the entire ecological reality with just one number is obviously crude and insufficient. In fact, Ecological Footprint accounting is not suggesting it is mapping the entire ecological reality. Rather it puts emphasis on biological resources (as we will discuss in more detail). The reason is that biological resources are materially more limiting for the human enterprise than the non-renewable resources like oil or minerals. For instance, while the amount of fossil fuel still underground is limited, even more limiting is the biosphere’s ability to cope with the CO2 emitted when burning it. The burning and coping are competing uses of the planet’s biocapacity. Similarly, minerals are limited by the energy available to extract them from underground and concentrate them.