Diagram Flow Of Energy On Earths Subsystems

Electronics Repair Manuals

Schematic Diagrams and Service Manuals

Get Instant Access

Figure 1.2 Schematic diagram of the earth/atmosphere system

Earth Energy Flow

material flow system - closed

Figure 1.3a Schematic diagram of a natural subsystem—a lake basin

Figure 1.3a Schematic diagram of a natural subsystem—a lake basin

Earth Four Subsystems And Energy Flow

Figure 1.3 b Schematic diagram of a subsystem of anthropogenic origin—a thermal electric power plant

is said to be in a steady state. Because of the complexity of the earth/atmosphere system, the great number of pathways available to the energy and the variety of short and long-term storage facilities that exist, it may never actually reach that condition. Major excursions away from a steady state in the past may be represented by such events as the Ice Ages, but in most cases the responses to change are less obvious. Changes in one element in the system, tending to produce instability, are countered by changes in other elements which attempt to restore balance. This tendency for the components of the environment to achieve some degree of balance has long been recognized by geographers, and referred to as environmental equilibrium. The balance is never complete, however. Rather, it is a dynamic equilibrium which involves a continuing series of mutual adjustments among the elements that make up the environment. The rate, nature and extent of the adjustments required will vary with the amount of disequilibrium introduced into the system, but in every environment there will be periods when relative stability can be maintained with only minor adjustments. This inherent stability of the environment tends to dampen the impact of changes even as they happen, and any detrimental effects that they produce may go unnoticed. At other times, the equilibrium is so disturbed that stability is lost, and major responses are required to restore the balance. Many environmentalists view the present environmental deterioration as the result of human interference in the system at a level which has pushed the stabilizing mechanisms to their limits, and perhaps beyond.

Running contrary to this is the much less pessimistic point of view expressed by James Lovelock and his various collaborators in the Gaia hypothesis (Lovelock 1972; Lovelock and Margulis 1973). First developed in 1972, and named after an ancient Greek earth-goddess, the hypothesis views the earth as a single organism in which the individual elements exist together in a symbiotic relationship. Internal control mechanisms maintain an appropriate level of stability. Thus, it has much in common with the concept of environmental equilibrium. It goes further, however, in presenting the biocentric view that the living components of the environment are capable of working actively together to provide and retain optimum conditions for their own survival. Animals, for example, take up oxygen during respiration and return carbon dioxide to the atmosphere. The process is reversed in plants, carbon dioxide being absorbed and oxygen released. Thus, the waste product from each group becomes a resource for the other. Working together over hundreds of thousands of years, these living organisms have combined to maintain oxygen and carbon dioxide at levels capable of supporting their particular forms of life. This is one of the more controversial aspects of Gaia, flying in the face of majority scientific opinion—which, since at least the time of Darwin, has seen life responding to environmental conditions rather than initiating them—and inviting some interesting and possibly dangerous corollaries. It would seem to follow, for example, that existing environmental problems which threaten life—ozone depletion, for example—are transitory, and will eventually be brought under control again by the environment itself. To accept that would be to accept the efficacy of regulatory systems which are as yet unproven, particularly in their ability to deal with large scale human interference. Such acceptance would be irresponsible, and has been referred to by Schneider (1986) as 'environmental brinksmanship'.

Lovelock himself has allowed that Gaia's regulatory mechanisms may well have been weakened by human activity (Lovelock and Epton 1975; Lovelock 1986). Systems cope with change most effectively when they have a number of options by which they can take appropriate action, and this was considered one of the main strengths of Gaia. It is possible, however, that the earth's growing population has created so much stress in the environment, that the options are much reduced, and the regulatory mechanisms may no longer be able to nullify the threats to balance in the system. This reduction in the variety of responses available to Gaia may even have cumulative effects which could threaten the survival of human species. Although the idea of the earth as a living organism is a basic concept in Gaia, the hypothesis is not anthropocentric. Humans are simply one of the many forms of life in the biosphere, and whatever happens life will continue to exist, but it may not be human life. For example, Gaia includes mechanisms capable of bringing about the extinction of those organisms which adversely affect the system (Lovelock 1986). Since the human species is currently the source of most environmental deterioration, the partial or complete removal of mankind might be Gaia's natural answer to the earth's current problems.

The need for coexistence between people and the other elements of the environment, now being advocated by Lovelock as a result of his research into Gaia, has been accepted by several generations of geographers, but historically society has tended to view itself as being in conflict with the environment. Many primitive groups may have enjoyed a considerable rapport with their environment, but, for the most part, the relationship was an antagonistic one (Murphey 1973; Smith 1992). The environment was viewed as hostile, and successful growth or development depended upon fighting it, and winning. In the beginning, human inputs were relatively minor, and the results of victory could easily be accommodated in the system. Gradually, through technological advancement and, sometimes sheer weight of numbers, society became increasingly able to challenge its environment and eventually to dominate it. Natural vegetation was replaced by cultivated crops, rivers were dammed or diverted, natural resources were dug from the earth in such quantity that people began to rival geomorphological processes as agents of landscape change, and, to meet the need for shelter, nature was replaced with the built environment created by urbanization.

The environment can no longer be considered predominantly natural in most of Europe and North America. Technological innovations since the mid-eighteenth century have ensured that. In the less-developed nations of Asia, Africa and South America—where the impact of technology is less strong—pressure from large and rapidly growing populations has placed an obviously human imprint on the landscape. Extensive as it is, however, dominance is far from complete. Even after 200 years of technological development and the exponential growth of population in recent years, some geographical regions continue to resist human domination. The frozen reaches of the Arctic and Antarctic are not unaffected by human activity, but they are largely unpopulated, while habitation in the world's hot deserts is in all senses marginal.

Was this article helpful?

0 0
The Basic Survival Guide

The Basic Survival Guide

Disasters: Why No ones Really 100 Safe. This is common knowledgethat disaster is everywhere. Its in the streets, its inside your campuses, and it can even be found inside your home. The question is not whether we are safe because no one is really THAT secure anymore but whether we can do something to lessen the odds of ever becoming a victim.

Get My Free Ebook

Post a comment