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Planet Earth: Is It Full?

A recent Horizon program: "How many people can live on planet earth?", narrated by David Attenborough, contained some sobering information that I thought it would be interesting to share.

Up to the 1800's, our population here on Earth was largely kept in check by nature. Lack of resources and disease ensured that for thousands of years the population stayed steady - below or around 1 billion. Since then, largely through reducing our death rate by controlling infectious diseases, our population has risen from 1 billion to its current level of about 6.8 billion. There is no doubt that this is a great achievement, leading to a better life for millions of people. However, those extra people, all living healthily and living longer, mean that our population is going to continue to rise even further. The UN projects that by the year 2050, the population of the world will be 9 billion. They can even predict which countries will be most affected and, as you might guess, much of the population growth will occur in those countries least able to provide for them.

Accommodating those extra 2.2 billion people in the space of 40 years isn’t going to be easy as each one is going to need water, food and energy in order to survive.

Up to now we have relied on the natural systems of the earth for our survival – and, by and large, it has provided what we need as we have learnt to exploit its resources more and more effectively. However many of those natural systems are beginning to show signs of strain:

Water: We already use half of the world’s available freshwater for our own needs, yet 1.2 billion currently live with water scarcity. As well as needing water for ourselves, industry and agriculture use water on colossal scales. Prospects for providing drinking water to an extra 2.2 billion people are not good and prospects for providing enough for the increases in industry and agriculture which will be needed are even worse.

Food: Food production is going to need to double as soon as possible if we are going to be able to feed the predicted rise in population. However, there is evidence to suggest that global agriculture is reaching its natural limit. Much of the land available for food production is already in use. The Green Revolution saw agricultural yields increase up to five fold with the result that much of the world is now fed. However global agricultural yields are now levelling off and rich countries are buying up large areas of land capable of producing food from the poorer countries to achieve food security for their own populations.

Energy: Natural energy resources (fossil fuels such as coal, gas and oil) are finite and are getting harder to find. However we are totally reliant on them to provide not only energy, but also the pesticides, fertilisers and mechanisation to allow us to produce the food for our expanding population. Cheap energy has helped to get us where we are today, but we are only just waking up to the consequences - one of the more obvious being increased CO2 levels leading to climate change.

It is possible to calculate the ‘carrying capacity’ (how large a population an environment can sustain) of Earth by dividing the total productive capacity of the planet with the amount each person consumes. If you do this, you find that Earth can support 15 billion at the consumption level of consumers in India, but 2.5 billion at our own level of consumption and only 1.5 billion at the level of US consumers (and these are believed to be conservative estimates).

At our current global levels of consumption we probably need about one and a half Earths to sustain us. Obviously this can’t continue indefinitely. If we don’t all reduce our impact urgently – all of humanity is going to suffer. We are going to have to make some tough choices in the coming decades. We have used our intelligence to get us where we are – can we use it to make the right decisions and choices to allow us to continue to survive?

Phil Le Sueur
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