Footprint Data from Global Footprint Network
The Data Resource Platform that is maintained by the Global Footprint Network is a free resource. The image shown above was obtained by clicking on the UK on the global map. In this way you can discover the available footprint data for most countries. This article explains how to calculate a sustainable population size using the information from the image shown above.
For the UK the available biocapacity per person is shown in green as 1 global hectare. The ecological footprint per person is shown in red as 4.2 global hectares. This means that the UK operates with a chronic ecological deficit of 3.2 global hectares. These ecological resources are stolen from the future wellbeing for our children.
Estimating a sustainable population for the UK.
We currently use about 4 gha per capita. Researchers say a fulfilled life should be possible at 2.14 gha per capita. Therefore we should aim to reduce our consumption per capita to around 2 gha per capita. The UK only has about 1 gha per capita available with our current population size. In his book Half Earth, E O Wilson recommends that we allow half the available biocapacity for biodiversity to flourish. Therefore, the available biocapacity can only sustain a population that is about a quarter of the current size. This estimate only applies if the UK can successfully reduce their consumption per capita to half the current levels.
Estimating the sustainable consumption and population for any country
Let us denote x as the available biocapacity per capita in global hectares, y as the ecological footprint per capita in gha, p as the population size. As explained above, 2 gha per capita is a rough guide to achieving a fulfilled lifestyle.
If y is greater then 2 gha then the country is likely to be overconsuming. This will need some adjustment depending on the climate, warmer countries do not require so much shelter and heating for survival. If y is significantly less than 2 gha then the population are likely to be living unfulfilled lifestyles, and their consumption per capita really needs to be increased. If the country is subject to extreme weather conditions then y will need to be greater than 2 GHa per capita, we might need to allow 3GHa for extremely cold countries, and 1 GHa for warm climates. Extreme heat will become an increasingly relevant factor over time. The calculation below assumes a target consumption of 2GHa per capita.
When we estimate the sustainable population for a country it easiest to assume that we can somehow limit consumption to about 2 gha per capita. Bearing in mind that we need to free half the biocapacity for biodiversity to flourish, then we simply divide four into the total biocapacity available to get a rough idea of what a genuinely sustainable population size would be. In the case of the UK the available biocapacity happens to be about 1 gha per capita, so the available biocapacity is the same figure as the population size. Therefore the UK needs to shrink its population to about a quarter of the current level, and its consumption per capita to half the current levels.
The generic formula for the sustainable population is this: x * p / 4. This formula assumes that the consumption per capita (y) is also adjusted to be about 2 gha.
A Global Aspiration to return within the carrying-capacity of Earth
We have been exceeding the carrying capacity of Earth for over a hundred years. We know this from the data in insect decline which informs us that we are in a mass extinction event. Using the same methods described above, the viable size for a human population on Earth is between 2-3 billion.
If you like the idea of a Global Aspiration to return within the carrying capacity of Earth, please sign the petition.
Conversations about Immigration
Please note that no debate about immigration is honest unless it recognises the acute level of overpopulation that we have reached in the UK. Without that element in the discussion, the debate soon develops racist overtones.