The consequences of environmental change are of great international concern and have focused attention on the complex interrelationship between population, environment and development.
The United Nations recognises this, and has issued its first wall-chart on population, environment and development. It features new demographic data and reveals some interesting trends:
The world population is now 6.1 billion people and less developed regions account for 80 per cent of the total. World population is growing at 1.2 per cent annually, or at 77 million people per year. The more developed regions are growing at only 0.2 per cent annually whereas the less well developed regions are growing at 1.5 per cent annually.
More developed regions have a population density of 22 persons per square kilometre, whereas in less developed regions it is 59 persons per square kilometre.
The world is becoming continuously more urbanised. In more developed regions, 76 per cent of the population is urbanised, whereas the corresponding figure for less developed regions is 40 per cent. Urban areas in less developed regions are growing much more rapidly (2.7 per cent per year) than in more developed regions (0.5 per cent per year).
The global rural population is growing at a rate of 0.4 per cent annually, while the rural population in more developed regions is shrinking by 0.8 per cent annually. The rural population will shrink after 2010 in all major areas except for Africa and Oceania.
The demand for fresh water has grown steadily with increasing population and socio-economic development. As a result, the availability of fresh water per head globally has fallen to about one third of its 1950 level. During the 20th century water use grew at more than twice the rate of the population increase. About one-third of the world's population lives in countries with serious levels of water stress.
About half of the original forest cover of the earth has been cleared. Forests are important as they are home to indigenous cultures. They service whole ecological systems, protect global biodiversity, store carbon, help economic growth and provide recreational amenity. Between 1990 and 2000, about 90 million hectares of forest were lost, although deforestation rate was lower than during the 1980s.
The amount of land available for crops per capita is declining in all regions as population rises. Farmers traditionally plough new land to service increasing demand, but world opportunities to expand are limited. It has, therefore, become critical to boost productivity in order to increase food production.
The percentage of the population that is undernourished has halved since 1970. However, about 800 million people in developing countries and 34 million people in more developed countries are still undernourished. Almost half the population in central, eastern and southern Africa is undernourished.
The global economy in the latter half of the 20th century grew at an unprecedented rate but growth was distributed very unevenly between countries and regions. Although population increased more rapidly during the 20th century than ever, economic output grew even faster because of the enormous technological progress.
Poverty is related to many factors including income, health, gender, education and ethnicity. The fraction of the global population living in absolute poverty (living on less than one US dollar per day) has shrunk since the 1980s. However, the total number of poor in 1998 was greater than in 1988. There is an international development goal to reduce extreme poverty by one half by 2015.
Energy consumption is very unevenly distributed around the world because it is a function of economic growth and level of development. The developed market economies comprise one-fifth of the world's population, but consume three-fifths of the world's primary energy. A major shift from rail and water to road and air transport occurred during the 20th century.
The number of vehicles on the road has grown from 40 million in the 1940s to 680 million today. The steepest rate of increase in motor vehicles is in less developed regions where automobile ownership is low.
Emissions from motor vehicles contribute greatly to greenhouse gas release, air pollution, urban congestion and health hazards.
The global emission of carbon dioxide from the burning of fossil fuels has steadily risen annually and has quadrupled since 1950. This is a contributing factor to global warming. A continuation of these trends puts the earth at serious risk of climate change, possibly raising sea levels and flooding low lying coastal areas. Other negative effects of global warming would include the spread of vector-borne (usually carried by insects) disease and a reduction in agricultural yields.
Demographic change and socio-economic development are occurring together with environmental degradation in several countries. The global challenge is to improve living standards of the population without environmental damage.
The United Nations wall chart data can be consulted on the internet at http://www.un.org/esa/population
William Reville is a Senior Lecturer in Biochemistry and Director of Microscopy.