Introduction xxv
and for the elderly to live longer. Obviously, human population cannot continue to increase indefinitely,
and it is predicted that sometime in the future, probably within the next 200 years, economic, political,
socio-cultural, and environmental factors will lead to a sufficient decline in the birth rate to bring about
a leveling off of the world’s population.
LAND USE AND PROPERTY RIGHTS
Housing, agriculture, grazing, forestry, mining, industry, transportation, and recreation all take up land,
and the larger the population, the more land each of these purposes usually requires, although modern
technology has made it possible to grow more food, feed more livestock, and build higher-rise housing
per acre than in previous centuries. Since land that is used for one purpose generally cannot be used
simultaneously for another purpose, population growth in a region or community tends to spur disputes
between individuals or groups who want to use the available land for different purposes.
The past several decades have witnessed increasing disagreement between those who want to develop
land (including those who want to “reclaim” wet or arid land) or extract its mineral and energy riches
and those who want to limit development, control urban sprawl, preserve open space and wilderness,
and prevent the removal of land from agricultural use. Conflicts have also arisen when runoff from agri-
cultural land has despoiled rivers and lakes and when the reclaiming of wetlands for farming or home
sites has interfered with the land’s normal ability to absorb waste and water.
As the population increases, there is more need to regulate land use so that the activities of one prop-
erty owner do not have a negative impact on the property of others. Land use regulation, though, raises
objections from libertarians who believe they should be free to use their private property in whatever
way they like.
Land use planning and zoning not only affect the allocation of land for farms, homes, and com-
mercial and industrial establishments and impinge on the kind of accommodation that is made for
cars, bicycles, and pedestrians, but also have wide-ranging ramifications for the nation. For example, by
permitting large swaths of land to be used for roads and highways, public policy has encouraged urban
sprawl and led to dependence on automobiles. Urban sprawl and the use of cars, in turn, have led to
public spending on new automobile friendly infrastructure and the decline of public transportation.
As humans use land, less of it is available to the organisms that have evolved to inhabit it. In some cases,
land can be shared, but only rarely is human intrusion not followed by major disruption, displacement, or
elimination of an area’s native organisms. Human use frequently also brings with it, wittingly or unwit-
tingly, a host of exotic species, which may prosper in their new habitat and drive out native species.
Because so many social, economic, and environmental issues are intertwined with land-use issues,
efforts to find creative solutions to major land-use conflicts have stimulated people to reexamine some
of their fundamental ideas about both property rights and the relationship between humans and the
natural world.
WATER AVAILABILITY AND QUALITY
People, industry, and agriculture all require an adequate supply of water that is sufficiently clean and salt
free. However, since water resources—like land resources—are finite, expanding populations place ever
greater stress on the available water both because of the rising need for water and the increased diversion
and contamination of the water that results from human activity.