"Anyone who believes exponential growth can go on forever in a finite world is either a madman or an economist."
We have developed an economic system over the past two centuries dominated by exponential growth of world domestic product, GDP, and world population, writes GEOFFREY P. GLASBY. Calculating continuing growth rates of GDP and world population through the 20th and 21st centuries shows we have the potential to create between 8 and 26 times more wealth in the 21st century than in the rest of human history. The unprecedented increase in resource consumption that will occur in the next 90 years, compared to the preceding 10,000 years of human history, will result in a massive environmental deficit by 2100. We are on course now in 2008 to overwhelm the natural environment on which we depend for life on Earth, which will cause severe problems for the more populous world of the late 21st century. vigorous steps are needed to curtail resource consumption, world GDP, population growth, and global greenhouse gas emissions to improve human prospects for the 21st century and beyond. Humanity must learn restraint to survive.
1820 is a key date in human history, (1) marking the beginning of a huge increase in world population from about one billion to just over 6.6 billion in 2007. This was accompanied by a 180-fold increase in world GDP, as a result of industrialization and large-scale use of fossil fuels. As a consequence, we are putting increasing stress on the environment and moving steadily away from the ideal of sustainable development as envisaged in the Brundtland Report. (2)
The early 21st century is a critical juncture in human history. There is now clear evidence the lifestyle of the developed world is unsustainable (3) and this trend will increase markedly over the coming decades, unless we make major changes in our consumption patterns and attitudes to the environment. (4) The central role of humanity in recent earth history has been recognised in a newly coined geological epoch, the "Anthropocene" (5) now divided into three phases. (6) The first, beginning between 8,000 and 5,000 years ago, was the result of long-term emissions of carbon dioxide (C[O.sub.2]) and methane (C[H.sub.4]) from forest clearance for agriculture and animal husbandry. (7) The second phase began with the industrial revolution through the invention of the steam engine in 1784. (8) The third phase began around 1950, and marks the period where human activities advanced from influencing the global environment in a few ways to dominating it in many ways.
To calculate the impact of human population on the global environment, I list three parameters, world population, world per capita GDP and world GDP over the last 8,000 years. This period is subdivided as follows: a 5,000-year interval from 8000 B.C. to 3000 B.C., 500-year intervals for the period from 3000 B.C. to 1500 A.D. and then 50-year intervals for the period from 1500 to 2000 (Table 1). Data and methods are described and referenced in paper by J. Bradford DeLong, University of. California. Berkeley. (9) From these data, it's possible to calculate the growth rate of each of the parameters for each of the 5,000, 500 and 50-year intervals. Total wealth created in each interval can then be derived by calculating annual world GDP for each interval. This enables the growth rate of total wealth created to be calculated for the three phases of the Anthropocene.
To make similar calculations for the period from 2000 to 2100, it is assumed world population will grow from 6.272 billion in 2000 to a median peak value of 9.0 billion in 2070 and then slowly decline. (10) This corresponds to an average annual median world population growth rate of 0.3% during the 21st century. Increases in world GDP were calculated based on three scenarios: i) and ii) using Keynes' assumption that world GDP will naturally increase by factors of four and eight per century, (11) and iii) assuming world per capita GDP will continue to grow at the annual rate experienced between 1950 and 2000 of 2.83%.
This gives an overall growth rate for world GDP during the 21st century of 3.12% annually, and can be taken to represent the "business as usual" scenario.
Growth rates in world GDP based on these three scenarios can then be calculated to be 1.4% p.a., 2.1% p.a. and 3.1% p.a. for the entire century, respectively. Total wealth created from 2000 to 2049 and from 2050 to 2099 is found by summing the annual world GDP for each of these two periods based on these three scenarios (Table 1).
Various methods have been devised to quantify adverse environmental impacts on a global scale. One involves the equation:
Environmental Impact = Population x GDP per capita x Environmental Impact per unit of GDP.
This equation provides a crude estimate of the global environmental impact of human activity for any period. The environmental impact per unit of GDP depends on many factors, like amount of waste produced per unit of economic activity, efficiency of economic activity and the production technologies used. (12) As this term is not easily quantifiable, I have defined Environmental Impact solely as total wealth created per unit of time, understanding this to be an approximation and the analysis therefore only semi-quantitative. Others have used a similar approach with some success. (13)
The period from 8000 B.C. to 1500 A.D. covers the dawn of civilization to the beginning of the early modern period of European history. (14) For this period, DeLong assumed a constant world per capita GDP of US$115 (in constant 1990 us$). (9) This value is taken as a measure of per capita agricultural output in pre-industrialized agricultural societies and reflects humanity's inevitable dependence on working the soil.
From 8000 B.C. to 3000 B.C., world population and GDP growth rates were 0.02% yearly. This figure can be considered the natural growth rate of the human population before civilization began. Total wealth created in this period was $3.48 trillion, representing 0.3% of total wealth created in the subsequent 5,000 years of our history.
From 3000 B.C. to 1500 A.D., world population and world GDP growth rates varied between …