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6. Crucial perspectives

Helping us grasp timescales and magnitudes - Paper 6

Understanding the nature of the ecological predicament facing humankind today requires full appreciation of the time perspectives and also of the scale and acceleration of human impacts on the natural world.

For some people such appreciation is assisted by the use of analogies. These comments on perspectives therefore include some analogies which are in brown italics.

The history of life on Earth

Life has been in existence on the planet for around 4000 million years. Until around 800 million years ago, bacteria were the most complex form of life on Earth.

The following table summarises some developments in the history of life on Earth since the emergence of multicellular organisms around 800 million years ago. In the right hand column, we are supposing that 800 million years ago was 24 hours ago, and the other times have been appropriately adjusted to this hypothetical time scale.


Development Years ago Hours ago
First multi-cellular organisms 800 million 24 hours
Life invades the land 400 million 12 hours
Dinosaurs at peak – first mammals 200 million 6 hours
End of the dinosaurs 65 million 2 hours
Upright walking primates (Lucy) 4 million 7 minutes
First Homo species (H. habilis) 1.8 million 3 minutes
First Homo sapiens 180 000 15 seconds
Beginning of farming 12 000 1 second


The human population

Life expectancy is 70 to 80 years in many developed countries today. This is about twice what it was a couple of hundred years ago when the mortality rates were exceptionally high, mainly due to infectious disease and malnutrition, particularly among children.

Over the period from 10 000 years ago to the year 1800 AD, the human population increased by about 1000 million (average of around 100 000 per year).

During the past 200 years it has increased by a further 5000 million (average of around 20 million per year – i.e. 200 times faster)

There are now about a 1000 times as many people to be fed as there were before farming began around 450 generations ago. The difference is equivalent to inviting a friend to dinner and having 20 busloads of friends turn up.

The biological history of Homo sapiens

Picture yourself on the stage of a large theatre with room for an audience of 2000 (100 rows with 20 in each row). In your mind’s eye place your mother in the seat at one end of the front row, and then her mother next to her and so on, until you have filled the place with 2000 generations of mothers and daughters.

The great majority of your maternal ancestors in the theatre would have known nothing of agriculture or of the urban way of life. Only the women in the front twenty or so rows would have been alive since the time when people first started farming. And only those in the front six or seven rows would have lived after the earliest cities came into existence, although few, if any, of these women are likely to have actually lived in cities.

Increasing intensity of human impact

During the past few generations there has been an extraordinary intensification of resource and energy use and waste production by humankind. Figures for energy use are a reasonable general indicator of the intensity of the impact of our species on the ecosystems of the planet. The human species is now using about 12 000 times as much energy per day as was the case when farming first started.

Thus, taking energy use as a rough indicator of the scale of human impact on the biosphere - the difference between the impact on the biosphere of humankind at the time when farming began and the present day is equivalent to the difference in weight between a small apple and a tonne of bricks.

About 10 per cent of this increase is due to the fact that there are about 1000 times as many people alive today as there were just before the first introduction of farming. The rest of the increase is due to the relatively recent introduction of technologies depending on the use of extrasomatic energy (mainly provided by fossil fuels).

Humankind is now appropriating 40 per cent or more of the plant material produced by photosynthesis globally.

The following analogy illustrates the accelerating increase in intensity of human activity on Earth – from the beginning of farming to the year 2000 AD.

Let us suppose that:

  • The beginning of farming was 12 hours ago (rather than 12 000 years)
  • At that time humankind jumped into a vehicle it had invented (representing technology)
  • The speed of this vehicle is proportional to the total amount of energy used each day by humankind. This vehicle set off at a speed of 1 km per hour (i.e. 12 000 years, or 12 hours ago)
  • The vehicle’s speed thus reflects the rate of energy use by humankind at different times — this being a reasonable indicator of the overall magnitude of the impact of our species on the natural environment.


The results of this exercise are as follows:

  • 12 hours ago, then, the vehicle was travelling at 1 km/hr
  • 4 hours ago it had picked up speed and was travelling at 25 km/hr
  • 1 hour ago it was going at 85 km/hr
  • 15 minutes ago – at 100 km/hr
  • 6 minutes ago − at 820 km/hr
  • 3 minutes ago – at 2500 km/hr
  • It is now travelling at around 12 000 km/hr

Visibility is not good and we, the passengers, do not have a clear view of where we are going.

But among us there are some individuals who have made a study of the environment and who are warning that we are heading for a precipice. They are calling out to us – urgently – to slow down and change direction.

However, there are others, especially those in power, who are trying to make the vehicle go faster than ever.

One does not have to be an ecologist to appreciate that this accelerating increase in the intensity of human activity in the biosphere cannot go on indefinitely.

Energy use in Australia

The per capita rate of use of energy today in the developed countries is 30 to 40 times what it was during most of human history.

Energy use per capita in Australia (GJ per year) [1]:

1940: 75 GJ per person per year
1960: 114 GJ per person per year
1990: 228 GJ per person per year
1998: 280 GJ per person per year
2005: 310 GJ per person per year

At the present rate of increase, per capita energy use in Australia will increase by another 50 per cent in about 21 years.

The end use of extrasomatic energy in Australia in the year 2005 was distributed as follows (per cent) [2]:

Transport            35.0
Manufacturing     32.6
Residential           11.3
Mining                 8.9
Commercial         5.5
Agriculture          0.7
Other                   2.2

This shows that the transport and manufacturing sectors are by far the biggest users of energy, accounting together for nearly 70 per cent of our total energy end use consumption, and it is in these sectors that most change is necessary. The residential sector accounts for approximately 11 per cent. [3] Therefore if everybody in our society reduced energy use in their home to zero, the total extrasomatic energy use would be reduced by only about 11 per cent.

In February 2007 the Australian Government announced that, to reduce greenhouse gas emissions, incandescent light bulbs will be phased out – to be replaced by the more energy-efficient fluorescent light bulbs. If all Australian homes made this change overnight, total national energy use (and carbon dioxide emissions) would drop by about 0.35 per cent.

This does not mean that we should not bother to take steps at the household level. It simply means that big changes must be made in all sectors of society.

Weapons of mass destruction

The growth in the killing potential of bombs during the twentieth century can be illustrated by the following analogy.

If we imagine the explosive power of the biggest bombs in World War I to be represented by a pea, then the most powerful weapons used in the Second World War (other than the atomic bombs dropped on Hiroshima and Nagasaki) would equal the size of a large plum. The Hiroshima bomb would be equivalent to a sphere of about 0.5 metre across, and the most powerful bombs now ready for use would have a diameter of 5 metres.


Gross disparities exist today in human conditions of life, health and wellbeing. This has been commonplace in urban societies over the past few thousand years, but it was not a feature of hunter-gatherer bands or early farming societies.

There are around 2.2 billion children on the planet today; 1 billion of them live in poverty. According to UNICEF 25 000 children die each day due to poverty. 1.4 million die each year because of lack of safe water and adequate sanitation.

About 15 per cent of children in Australia live in poverty.

About 0.13 per cent of the world’s population control 25 per cent of the world’s financial assets. According to UNDP the combined wealth of the world’s richest 225 people in 1998 was equal to the combined annual income of the world’s 2.5 billion poorest people. The wealth of the three richest individuals in the world was greater than the combined GDP of the 48 least developed nations, and the average citizen of the USA is about 60 times richer than the average Tanzanian.

The wealthiest nation on Earth, the USA, has the widest gap between rich and poor of any industrialised nation.


1. GJ = Gigajoules = 109 Joules. A barrel of oil contains about 6 GJ of chemical energy. Back to text

2. These figures are from the Australian Bureau of Statistics. Government administration and defence are included in the Commercial category. Back to text

3. This figure for the residential sector is energy used in the home (e.g. for heating, cooling or cooking). It does not include energy embodied in the purchases of residents or energy used in their travel. Back to text