How many planets?
Today there are more than twice the number of people alive than there were 50 years ago, and we've breached environmental limits. It's time for a population policy, writes Nick ReevesAround half the people that have ever lived on Earth are alive today. And yet population growth has become the political and environmental issue that dare not speak its name.
Economically rich parts of the world - usually described as "the West" - continue to breach environmental limits and stymie the capacity of the Earth to support them. In the UK, a child born today will generate more than £1M lifetime's expenditure, and require the resources of six planets to support it.
If all countries achieved UK wealth levels, we would need the natural resources of four or more planet earths. This is not the model of a sustainable world that will achieve social justice and harmony. If we carry on as we are - hard-wired to growth at all costs - we will brutalise the Earth and ourselves, fighting each other for scarce resources. This doomsayer scenario is already a grim reality in places like Darfur.
It's not just numbers - it's the ecological impact of each person that's the problem. We all need a piece of the planet to support us. We need land to grow food, to provide us with water, to supply building materials and energy for cooking and keeping warm or cool.
How much we consume determines how much of the planet we need. Ecological footprinting has become de rigueur and websites such as www.footprintnetwork.org let you measure your own consumption - represented by the number of planets that would be needed if everyone lived like you. Typically, if you own a car, live in a three- or four-bed detached house, eat meat, use supermarkets and fly overseas, we would need between three and five planets to support the existing population.
The Church of England is at last becoming more vociferous on this. A recent policy statement promoted changes in our lifestyles, while the Bishop of London, Richard Chartres, went so far as to declare that flying in polluting aircraft is a sin.
But, if everyone reduced the size of their car, didn't fly, became a vegan and shared their well insulated house with ten people, we would still need more than one planet. Why? Because the number of people keeps increasing.
Those who peddle the myth that increasing human population is not a problem say it is war, corruption and greed that prevent resources from being distributed fairly.
These outmoded folk measure human worth in terms of economic output. In secular societies, people have become little more than economic units contributing to gross domestic product, at the expense of gross domestic happiness. To show that they are eco-savvy, and have an eye on changing public moods, politicians now argue for smaller cars, energy efficiency, grow-your-own veggies and wind turbines on your roof. Do these things, they say, and problem solved.
But, however much you reduce your consumption, some resources, such as water, remain essential. We all need water to survive and maintain healthy lives. Water is required for drinking, cooking and sanitation. If people live in communities that consume more water than rainfall can supply, this is unsustainable.
The number of people living in a region is largely governed by the level of natural resources of that region. We know that desert or mountainous countries will support only a sparse population, while more temperate regions are more densely populated.
Drought used to be synonymous with arid parts of the world. In 2006, it is a problem for metropolitan-man in London and southeast England - designated economic growth areas on which we are depending for future development and prosperity. Our latest challenge is to square the circle of economic growth and environmental sustainability. Because, even if every water leak was repaired tomorrow, there would still be water shortages here - maybe not immediately, but very soon. There are plans to build 700,000 new homes but no plans to make it rain more. Scratch the surface of any environmental problem and population growth is the root cause. We should be tackling it, not just its symptoms.
It is a commonly held myth that the UK population is falling. Regionally, this may be true. However, there is still a surplus of births of something like 100,000, over deaths. EU migration and increasing numbers of refugees mean the UK population is rising above the present 60 million. Both Professor James Lovelock, in his book The Revenge of Gaia, and the WWF estimate that the UK can only support a population of 30 million. This means we should not only change the way we live but also have fewer children.
One of our most mind-blowing failings as a species is our inability to learn from history. We can be fairly certain that after the Easter Islanders cut down the last tree, and ate their last scrap of food, they ate each other because they had no choice.
In Rwanda, the Hutus and the Tutsi lived peaceably together until the population grew to the point where neighbours fought for land and water.
We face a stark choice: either we control our population voluntarily or - as history shows us - war, disease and famine will do it for us.