Humankind made tremendous advances in science and technology, medicine and health, universal education and general material welfare during the 20th century. World population also ballooned from 1.6 billion in 1900 to six billion by 1999. Over that century we freely helped ourselves to the Earth's limited resources of fossil fuel, we polluted the air and the water and we killed off many living species. We are now at a fork in the road. If we choose the branch that continues our profligate habits, we will.
We must take the alternative pathway of moderation and control. E.O. Wilson describes the situation in the February issue of Scientific American.
The Earth's resources - soil, water, air, etc - must support human activities. The average area required to support each person, for food, housing, transport, energy and waste absorption, is 2.5 acres in developing countries and 24 acres in the US. The worldwide average is 5.2 acres per person. If everyone in the world were to reach American levels of consumption, with present technology, we would need four more planet Earths.
While the latter objective is neither attainable nor desirable, developing countries have every right to pursue decent living standards through economic growth. Unfortunately, in so doing, they are repeating what the developed countries did long ago - destroying natural environments.
Humankind has become a global geophysical force by pumping so much industrial carbon dioxide into the air that we have artificially accelerated global warming. Other gas emissions have weakened the atmospheric ozone layer protecting us from harmful ultraviolet radiation.
Many influential economists are sanguine about future prospects for the environment. They say "doomsdayers" in the past have been wrong and they predict human ingenuity will continue to solve problems as they arise. They point to the steady improvement in the global economy, food production, political democratisation and social progress over the 20th century.
Environmentalists say present economic development rates could only continue indefinitely on a planet with limitless resources, and we have now passed the point of sustainable development. They compare the environment to an aircraft which is held together by thousands of rivets. You can remove some, indeed many, rivets without causing much apparent harm to the aircraft. However, remove too many and the aircraft abruptly falls apart.
World population in 1800 was one billion. In 1900 it had reached 1.6 billion. By 1950, the population had reached 2.5 billion and, in October 1999, it reached six billion. It continues to grow at an annual rate of 1.4 per cent, adding 200,000 people each day. The Earth's resources cannot sustain another 100 years like the past century.
The appropriation of productive land to meet growing population demands is already too much for the planet to sustain. Human population reached the limit of the Earth's sustainable capacity by 1978 and by 2000 had exceeded that capacity by a factor of 1.4. The Earth has lost its ability to regenerate itself.
AT the limit, how many people could the planet support? Grains supply most of humanity's calories and the world currently produces two billion tonnes annually. This would support 10 billion East Indians who eat grains primarily, but only 2.5 billion Americans who convert much grain into livestock and poultry. However, if everyone became vegetarian, the present world stock of arable land would support 10 billion people.
The rate of increase in world population is slowing down. In 1960, the average number of children per woman in the world was 4.3. This had fallen to 2.6 by 2000. The number required for zero population growth (when births balance deaths) is 2.1. So long as the number stays even slightly above 2.1, the population expands exponentially, and given enough time, would grow to a density where the surface of the globe would be covered by people standing shoulder to shoulder.
The slowing rate of global population increase is attributable to three forces, according to Wilson: the globalisation of the economy, the consequent move of rural populations into cities and the consequent empowerment of women. The economic and social freeing of women allowed them to choose to have fewer children - who can then be raised in better health and with better educational opportunities.
If the trend towards smaller families continues, it will eventually halt and then reverse population numbers. The UN estimates that by the year 2050 world population will be nine to 10 billion. At the moment, most population growth is occurring in developing countries. More than half of the developing countries have population policies to control growth.
Wilson contends that evolution has programmed humans not to think forward beyond a generation or two and not to think further afield than the local environment. People who thought like this tended to thrive better and left more offspring than those who thought differently, although this way of thinking had long-term and large-scale negative consequences.
But we now press so hard on the whole Earth that nothing less than developing a global environmental ethic will prevent very severe, even disastrous, future consequences. We must consciously override our natural parochial instincts.
William Reville is a senior lecturer in biochemistry and director of microscopy at UCC.
