Nature and Environmental Book Reviews

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World Population Growth Through History

by David Yarian, Ph.D.

As of 11 am on January 5, 2008, the estimated world population is 6,642,100,544 people – and growing. Net population growth is about 75 million per year, which is declining: during the 1980s, population growth was about 87 million per year. The United Nations estimates that world population will reach 9 billion by 2050. At current growth rates this is equivalent to adding 90 cities the size of New York per decade.

Gloomy population predictions are nothing new. In An Essay on the Principle of Population, published in 1798, economist Thomas Robert Malthus made his famous prediction that world population growth would outrun the food supply. This prediction was based on the assumption that population, if unchecked, increases at a geometric rate, while food supply grows at an arithmetic rate.

Paul R. Ehrlich’s book The Population Bomb, published in 1968, predicted that “in the 1970s and 1980s hundreds of millions of people will starve to death”; that mass famine would occur due to overpopulation and depleting the available food supply.

Many other scientists and economists have made pessimistic predictions about the Earth’s ultimate carrying capacity. Most famously, the Club of Rome published its book Limits to Growth in 1972, which predicted that economic growth could not continue indefinitely because of the finite availability of natural resources, particularly oil. This book has sold over 30 million copies, making it the best-selling environmental book ever.

It has become a cottage industry to debunk those who make “gloomy Malthusian predictions.” Since Malthus was wrong, Ehrlich’s predictions did not come true, and the Club of Rome over-reached its data in making its predictions, these naysayers suggest that we have nothing to worry about. Their implicit assumption seems to be that human creativity and technological advances will open new vistas and continuing opportunity for expansion and growth, whether through genetically engineered crops - or colonizing the Moon. In psychological terms, this is called “denial.”

While these predictions have been incorrect in their details, their premise does hold true. It is not possible to infinitely increase the population of the Earth without at some point depleting its enormous though finite resources. In the process, there are very real consequences of the tremendous population growth that occurred during the 20th century as Earth’s population increased from 1.6 billion to 6.1 billion people.

Chart of Population Growth

Source: www.susps.org

Foremost of these consequences is the tremendous degradation of the environment. The enormous growth of population has caused unprecedented loss of habitat and ever-increasing extinctions of plant and animal species worldwide. This loss of biodiversity leads to ecosystem instability, which ultimately threatens the plant and animal resources upon which we depend. Pollution and emission of greenhouse gases have left toxic residues in every part of the globe, and are causing catastrophic global climate change. (See Global Warming and Climate Change)

Rapid population growth aggravates poverty in developing countries, as a large portion of available resources are expended upon the basic survival needs of food and housing. Only twenty percent of the world’s population enjoys an adequate standard of living; the other eighty percent struggle on a daily basis with substandard living conditions that are often life-threatening.

The Green Revolution of the 1970s enabled many developing countries to grow surpluses of food for the first time. Population growth is overtaking these gains; leading, for example, to a decline worldwide in per capita availability of cereal grains over the last fifteen years. Intensive fertilizer-based agricultural methods are lowering the quality of the soil, and irrigation is depleting water tables and increasing soil salinity. Pests are increasingly resistant to insecticides: some 37% of food and fiber crops are lost to pests worldwide. Agricultural land is being lost due to spreading industrialization and growing need for living space.  (see Sustainable Agriculture)

Some 400 million people currently live in regions with severe water shortages; by 2050 this is projected to increase to approximately two billion people. Water tables worldwide are falling as underground aquifers are being pumped out to provide irrigation for agriculture. Over half of all accessible fresh water on the globe is currently being utilized; we are approaching the limits of our ecosystem’s ability to support our numbers. (see Water Resources and Water Conservation)

As the divide between haves and have-nots is intensified by population growth, there are growing threats to international security. Underemployed labor forces naturally seek to enter areas of economic opportunity; as we are seeing in the current debate over immigration policy in the U.S. there is likely to be significant resistance to opening national borders. High rates of unemployment in developing countries contribute to rising political instability, often with violent outcomes. Refugees from civil wars, natural disasters and economic dislocation add to instability and political unrest. (see Conflict Resolution)

As the world becomes more crowded, we are pressed to find meaningful responses to the issues outlined above. The recommended books in this section on Population Growth offer objective data concerning population growth and resource depletion, and project current trends into the future. They provide reasoned approaches to meeting the challenges of population growth in the years ahead.

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