Environmental Engineering Reference
In-Depth Information
1.3
THE ENVIRONMENT
The twentieth century, during which industrialization proceeded even faster than population growth,
marked the beginning of an understanding, both popular and scientific, that human activity was
having deleterious effects upon the natural world, including human health and welfare. These
effects included increasing pollution of air, water, and land by the byproducts of industrial activity,
permanent loss of natural species of plants and animals by changes in land and water usage and
human predation, and, more recently, growing indications that the global climate was changing
because of the anthropogenic emissions of so-called greenhouse gases.
At first, attention was focused on recurring episodes of high levels of air pollution in areas
surrounding industrial facilities, such as coal burning power plants, steel mills, and mineral refiner-
ies. These pollution episodes were accompanied by acute human sickness and the exacerbation
of chronic illnesses. After mid-century, when industrialized nations' economies recovered rapidly
from World War II and expanded greatly above their prewar levels, many urban regions without
heavy industrial facilities began to experience persistent, chronic, and harmful levels of photo-
chemical smog, a secondary pollutant created in the atmosphere from invisible volatile organic
compounds and nitrogen oxides produced by burning fuels and the widespread use of manufac-
tured organic materials. Concurrently, the overloading of rivers, lakes, and estuaries with industrial
and municipal wastes threatened both human health and the ecological integrity of these natural
systems. The careless disposal on land of mining, industrial, and municipal solid wastes despoiled
the purity of surface and subsurface water supplies.
As the level of environmental damage grew in proportion to the rate of emission of air and
water pollutants, which themselves reflected the increasing level of industrial activity, national
governments undertook to limit the rate of these emissions by requiring technological improvements
to pollutant sources. As a consequence, by the century's end ambient air and water pollution levels
were decreasing gradually in the most advanced industrialized nations, even though energy and
material consumption was increasing. Nevertheless, troubling evidence of the cumulative effects
of industrial waste disposal became evident, such as acidification of forest soils, contamination of
marine sediments with municipal waste sludge, and poisoning of aquifers with drainage from toxic
waste dumps. Not the least of the impending cumulative waste problems is the disposal of used
nuclear power plant fuel and its reprocessing wastes.
Environmental degradation is not confined to urban regions. In preindustrial times, large areas
of forest and grassland ecosystems were replaced by much less diverse crop land. Subsequently,
industrialized agriculture has expanded the predominance of monocultured crops and intensified
production by copious applications of pesticides, herbicides, and inorganic fertilizers. Valuable
topsoil has eroded at rates above replacement levels. Forests managed for pulp and lumber pro-
duction are less diverse than their natural predecessors, the tree crop being optimized by use of
herbicides and pesticides. In the United States, factory production of poultry and pork have created
severe local animal waste control problems.
The most threatened, and most diverse, natural ecosystems on earth are the tropical rain
forests. Tropical forest destruction for agricultural or silvicultural uses destroys ecosystems of great
complexity and diversity, extinguishing irreversibly an evolutionary natural treasure. It also adds
to the burden of atmospheric carbon dioxide in excess of what can be recovered by reforestation.
The most sobering environmental changes are global ones. The recent appearance of strato-
spheric ozone depletion in polar regions, which could increase harmful ultraviolet radiation at
the earth's surface in mid-latitudes should it increase in intensity, was clearly shown by scientific
