POPULATION & ENVIRONMENT

Despite humanity's success in feeding a growing world population, the natural resources on which life depends — fresh water, cropland, fisheries and forests among them — are increasingly depleted or strained. One hopeful sign for the new millennium is that population growth is slowing significantly. Current population protections suggest the possibility that the world population could peak earlier and at a lower level than indicated by the protections of the past. Such an outcome, however, will require that family planning and related services be available to all who seek them, that more girls attend school and remain there longer, and that more women have the same economic opportunities men enjoy. We know that making family planning related reproductive health services increasingly available to those who seek them is one the world's success stories. The challenge in the new century is to make such services available to all who want them.

Having reached 6 billion in 1999, human population continues to grow. UN population projections for the year 2050 range from 7.3 billion to 10.7 billion, suggesting the scope for influencing population's future. More people and higher incomes worldwide are multiplying humanity's impacts on the environment and on the natural resources that are essential to life. The planet's fresh water, fisheries, forests and atmosphere are already strained. Based on this trends, it is clear that the 21st century will witness even greater pressures on natural resources. Current demographic trends offer hope, however. Over the past 40 years the average number of children born to each woman has fallen from five to less than three. Young people increasingly want to wait to have children and to have smaller families. Policymakers have a choice. They can do nothing, or they can help ensure that in the 21st century the world's population peaks with fewer than 8 billion people, simply by committing the financial resources to meet the needs of couples who want to have smaller families, later in life.

Currently, 505 billion people face water scarcity. Depending on the future rates of population growth, between 2.4 billion and 3.2 billion people may be living in either water-scarce or water-stressed conditions by 2025. For tens of millions of people in the Middle East and in much of Africa today, the lack of available fresh water is a chronic concern that is growing more acute and more widespread. The problem is worse than it often appears on the ground, because much of the fresh water now used in water-scarce regions comes from deep aquifers that are not being refreshed by the natural water cycle. In most of the countries where water shortage is severe and worsening, high rates of population growth exacerbate the declining availability of renewable fresh water.

The number of people living in countries where cultivated land is critically scarce is projected to increase to between 557 million and 1.04 billion in 2025. Despite the Green Revolution and other technological advances, agriculture experts continue to debate how long crop yields will keep up with population growth. The food that feeds the future will be raised mostly on today's cropland. The soil on this land must remain fertile to keep food production secure. The minimum amount of land needed to supply a vegetarian diet for one person without any use of artificial chemical inputs or loss of soil and soil nutrients is .07 hectare, or slightly less than a quarter of an acre. An estimated 420 million people already live today in countries that have less than that person. Easing world hunger could become unimaginably difficult if population growth resembles demographers' higher projections.

Most fisheries worldwide are fully exploited or in decline. While the number of individual fishers continues to increase, the amount of fish each one catches is falling steadily. The poor have long depended on fish for complete protein, but population growth is helping to push this important food source out of their reach.

Today about 1.8 billion people live in countries with less than 0.1 hectare of forested land per capita, an indicator of critically low levels of forest cover. Based on the medium population projection and current deforestation trends, by 2025 the number of people living in forest-scarce countries could nearly triple to 4.6 billion. Most of the world's original forests have been lost to the expansion of human activities. In many parts of the developing world, the future availability of forest resources for food, fuel and shelter looks quite discouraging. Future declines in the per capita availability of forests, especially in developing countries, are likely to pose major challenges for both conservation and human well-being.

In 1966, the last year for which global data are available for both population and heat-trapping carbon dioxide emissions, per capita emissions of CO2 continued the upward trend that dominated the middle 1990s. When combined with growing world population, these increased per capita emissions accelerated the accumulation of greenhouse gases in the global atmosphere and, thus, future global warming. With 4.6 percent of world's population, the United States accounted for 22% of all emissions from fossil fuel combustion and cement manufacture, by far the largest CO2 contributor among nations. Emissions remained grossly inequitable, with one fifth of the world's population accounting for 62% of all emissions in 1996 while another — and much poorer — fifth accounted for less than 2 percent.

More than 1.1 billion people live in areas that conservationists consider the most rich in non-human species and the most threatened by human activities. While these areas comprise about 12% of the planet's land surface, they hold nearly 20 percent of its human population. The population in these biodiversity hotspots is growing at a collective rate of 1.8% annually, compared to the world's population's annual growth rate of 1.3 percent.

Robert Engleman with Richard P. Cincotta, Bonnie Dye, Tom Gardner-Outlaw and Jeniffer Wisnewski, People in the Balance : Population and Natural Resources at the Turn of the Millennium (Washington DC : Population Action International, 2000).