At this point it becomes useful to examine the concept of ecosystem in a general way, to relate the concept of ecosystem to human beings, and then to see how engineering could enhance the functioning of the human ecosystem.

The term ecosystem has been used to describe so wide a variety of ecological conditions that its use could be confusing to the nonecologist. We begin with ecology as the science of living organisms in relationship to their environment. An ecosystem is living organisms and their physical/chemical environment, and the interrelation among all the biological and physiochemical factors that affect them.

An ecosystem must be viewed as a functioning whole, because it operates as a system and not as a group of independent processes. Ecosystems follow thermodynamic laws in exactly the same way physical systems do and consequently they posses the same elements of predictability and control. Ecosystems differ from physical systems in that they contain living organisms which can and do adapt to changing conditions, sometimes in surprising ways. In short, because of their ability to react to environmental circumstances, the living organisms within the system can arrange themselves to optimize or maximize their potential within the system. The ecosystem can be said to be "self-designing" as it comes to equilibrium with the thermodynamic conditions of its being.

The complexity of ecosystems arises not out of some reservoir of innate complexity, but from the number of outcomes that are possible through the interaction of a few simple but greatly replicated parts. Various organisms have given spectra of responses to environment; the conditions which favor some do not favor others and vice versa.

As conditions change, the composition of living organisms within the ecosystem may change and these changes will occur as long as conditions that can support life exist. The group of organisms that best fits the conditions at any time will predominate; as conditions change a new set of organisms better suited to the conditions may take its place.

The essential point is that through the chemistry and physics of life the group of organisms best able to survive and thrive in an environment is the group that will tend to occupy it. This is a positive, forceful event that is driven by primary energy sources; locally it seems to defy the second law of thermodynamics, because it proceeds from disorder and goes to order; it moves for the most part from less complex to more complex arrangements, and it requires a steady input of energy to maintain it. Human ecosystems meet these requirements to the same extent that other biological ecosystems do and they may increase in complexity and order or decrease in complexity and order, depending upon the energy inputs and other ecological factors. The question before us is to understand the nature of the energy inputs, to understand the ecological factors and their relationships, and to engineer our human ecosystems taking this information into account.

The term ecosystem causes some confusion because the word has been applied to a great variety of situations of differing complexity—ranging from the relations of single organisms and their limited environment to the totality of all living things and their complex environment: the earth and its energy source, the sun.

One strong emphasis in the study of ecosystems is that living organisms must be considered in the context of their physiochemical environment and that the continuum of conditions from the nonliving to the living must be understood in order to understand living systems. The other strong concept is the probabilistic nature of ecosystems. In this regard their conceptual origins are presumed to be similar to physical systems and more particularly to the probabilistic notion that any particular ecosystem is one form of many that could just as probably have arisen at that some place. This would indicate that even closely related ecosystems are not carbon copies of each other, but that they are related through the probability of their origin and development in the same way that the views through a kaleidoscope are related—each one different but all composed of the same bits of glass or metal, the gravity pull that acts on them as the tube is turned, and the light which reflects from their surfaces. The resulting designs have great similarity, are generated by the same processes, and contain the same ingredients, yet they are all different—but not so different that the relationships among them cannot readily be seen and alike in that environmental factors affect them the same way.

Prior to coining the word ecosystem, ecologists had an array of terms to describe community and environmental conditions. These terms are still in common usage and are used integrally and synonymously with ecosystem.

The term ecosystem can apply equally well to the simplest and the most complex. It is useful therefore to consider orders of ecosystems based upon their complexity. Such a proposition results in a list of ecosystems arranged in order of complexity:

While it is interesting to consider all eight orders of ecosystems, of immediate concern for us are the first three. Perhaps the most important use of this conceptual design is to see each order of ecosystem providing the building blocks to the next higher order of ecosystem and to become aware of the manner in which more complex ecosystems are formed out of the interrelatedness of the simpler subsidiary units.

It is inconceivable that a member of the species Homo sapiens could arise as a "human being" without direct interaction with other human beings, the Tarzan myth notwithstanding. The most usual context for this process of aculturization is the family. While it is not an absolute requirement that each and every individual be reared and educated as a human being by his/her own biological family, it is necessary through human intervention that the functions, that would have been performed by the family be performed by some person or persons. This is an axiomatic part of our thinking, yet the ramifications of it seem not to be understood or given appropriate consideration at the times when ecological engineering is taking place. If such considerations were given their due, the initial engineering task would be to arrange the first order ecosystem correlates not just to favor the individual, but more specifically to do so in the context of the family.

The problem of engineering the environmental requirements of the family will depend in part on the structure of the family and the perceived relationship between its members. The most current notion of the American family is the so-called nuclear family—parents and their children. The nuclear family is in its present configuration probably because of the high mobility of the population as a whole. Not only is there mobility with respect to means of physical transportation, but with respect to social status as well. A great many young people leave home, go to a distant city to attend school, and literally never return.

Much of the rural-to-urban migration occurs because job opportunities are more prevalent in cities than in rural areas—and this is occurring at a time when farms are becoming more highly mechanized. Many work functions formerly performed on farms are being performed on the same products but in city processing plants.

For whatever reason, therefore, American families tend to be nuclear and tend to lose their younger members to college or distant employment. If one of our objectives is to produce ecologically sound family unity, some of the ecological relationships of families and their environmental requirements must be examined. Ecological communities are characterized by having members of all ages. If the nuclear family were to develop (or revert) to the "extended family" (including once again the entire or larger span of family generation), the all-age attribute would be restored. But economic opportunity may not permit three generations of the same family to live together or close by. The engineering problem is to provide the environmental circumstance to permit community members of the three age groups to live proximally and to provide opportunities to members of these age groups to function as members of an extended family. From the standpoint of engineering and city planning, this calls for a closer look at the way individual dwellings are designed with respect to their interior spatial relations, and the way dwellings of all sizes are arranged with respect to all other community elements.

The highrise apartment building and suburbia share one characteristic in common—they tend to segregate a single age and income group. Suburbs tend to be designed for the family with children and highrises for the family without.

Some notable exceptions such as Cedar-Riverside in Minneapolis have tried to accommodate both divergent income groups and divergent age groups. But this is a self-conscious effort against the mainstream where for the most part, domiciles are segregated by age, income, and lifestyle factors. This tends to increase the required mobility of the population since the dwelling area in question may be efficient only during part of the life cycle.

The situation in some European countries, where individualized transportation has not produced the urban sprawl of the United States but where urban immigrations have produced severe housing shortages, has forced the three generations often to occupy the same crowded quarters—an ecologically destabilizing situation because of lack of space. In Prague, where this condition obtains, city planners are designing domiciles specifically to accommodate the three generations; for while there are distinct disadvantages from the crowding aspect, great economic advantages obtain when space is adequate. These advantages include the possibility for interdependency in task performance among all members of the three generation family and the creation of a learning/living environment in which youngsters grow up interacting with all age groups and consequently absorbing a better idea of the operation of the human community as a totality. They participate in all the ceremonies, rites of passage, funerals, and other events of the community as a whole, and therefore experience firsthand their own humanness in an operational human environment.

From a strict engineering point of view, a great deal has yet to be done to lower the cost of housing and the cost of operating and maintaining individual domiciles. Passive design features for the conservation of energy have scarcely begun, and the design of domiciles to utilize environmental energy sources has made only the smallest beginning.

At present, solar energy is used primarily for light. Windows extend our sense of space and permit the entry of light. In an energy-conscious economy, windows account for energy loss from the heating budget of the house. Solar collectors' either to capture heat energy or to convert the energy of photons to the energy of electricity, have yet to be utilized to any significant degree. The benefits from having domiciles more energy independent include not only long-run energy savings, but the fostering of environmental awareness that the domicile is embedded in its immediate environment.

Second order ecosystems are biological communities. In the human context they are the various different neighborhoods of cities. The neighborhood is the basic community element of the city. To function as a community the neighborhood must first be recognized as such by its inhabitants. Any system that does not function is dead, and cities today are full of dead neighborhoods. We have so preoccupied ourselves with the architecture of buildings that we have rarely looked to the larger problem of the architecture of the community.

Foremost among the biological attributes of communities is the characteristic of diversity. Diversity is one of nature's great devices for achieving stability; in biological communities diversity is achieved either through differences in life forms or differences in species. In the human community, since we are only one species and since our life form variation is only in the growth, maturation, and senescence cycle, it would appear that there could not be much diversity. However, since the city and most human communities are based upon technology, we must look to a different kind of diversity to understand this principle in the human community. Organisms classified according to their genetics are called genotypes. A group of closely related genotypes are called biotypes. Those classified by their ecological requirements are called ecotypes. These classifications allow for the analysis of ecological problems involving the genetics of any species whatever and the ability of two different species to occupy similar ecological niches. These suffice for nonhuman biological communities.

What is required for the human community is an additional classification based upon the technological function of the human organisms. The term technotype is proposed to describe this function of the human community. Genetically an individual may be male or female, caucasoid, mongoloid, capoid, negroid, or australoid (the races of man). These attributes aid in the classification of biotypes. Ecotypically, the individuals may be forest people, prairie people, or mountain people—attributes that relate to people as ecotypes. But when the modern human urban community is examined it is obvious that this is not enough; we want to know if the individual is the butcher, the baker, or the candlestick maker; the doctor, lawyer, chief; or merchant it is in this realm of technological function that we look for the technotypes.>

Man as a species has a rather low diversity when it comes to biotypes or ecotypes. But in the realm of technology, man has proliferated himself into thousands of different technotypes, and it is the attribute of diversity related to technotypes to which we must look to see this important principle of human communities.

As an aside we should note that other species of animals that do have technology such as ants and termites have evolutionarily solved this diversity problem by physiological specialization into the workers, soldiers, queens, etc. Man obviously is not physiologically specialized, but rather is educationally specialized—his specialization is a function of his technology, not of his genetics.

If we look at the diversity of technotypes in the human community, the ecological principle of diversity and stability becomes immediately apparent. Communities in which employment opportunities are restricted, either in numbers or types, are much more prone to sudden drastic change than communities in which a great variety of jobs is available for large numbers of people. The one-industry town that folds when the one industry closes down is a classic case in point. Rural communities that serve only the farmers and farm families of a restricted area fluctuate economically along with the fluctuations of the farm commodities market. Even large industrial areas, such as automotive manufacturing centers, suffer greater than average hardships when the auto industry is in a slump. On the other hand, cities with a wide variety of light, medium, and heavy industry may scarcely feel an economic recession, since the majority of workers will not be concentrated in any one business or industry. Thus, the list of occupations for a given area can be examined and segregated by business enterprise, and it will provide a ready index to the community's economic stability.

From the ecological viewpoint, what can be said about how to engineer communities so as to encompass great technotypic variability and thus achieve economic stability? For one thing, the technological feasibility of altering zoning concepts to safely agglomerate diverse business, commerce, and industrial functions with housing functions could be examined. Control of pollution may well be the key to feasibility of spatially locating diverse business and industrial functions close to each other and to the residential elements of the city.

Not only should it be possible for persons to live close to their place of employment but to many other needed facilities and services as well (doctors, food markets, clothing shops, banks, theaters, etc.).

The growth and development of cities could in all probability be gauged by the flux of technotypes in and out of the city. A study of the disappearance of small towns in Minnesota used the closing of the banks as the final indication of the demise of the town. Undoubtedly other businesses were more sensitive indicators than the banks and left earlier, but the closing of the bank leaves no doubt about the demise of economic viability for business and commercial enterprises. It is to be presumed conversely that when a new bank opens in an area, settlement has reached the status of a viable community. In Grand Canyon National Park, urbanization has reached the point where a shopping center with a bank did open, clearly the visible manifestation of the arrival at the canyon's rim of an economically stable human community, albeit one whose human components are rapidly interchangeable.

Using the concept of the technotype, the analysis of the predictable stability or instability of the city is possible and has the same ecological consequences as analyzing the ecological diversity of biotypes and ecotypes. It is at this level of the third order ecosystem that the ecological engineering of the city will have the greatest impact. Third order ecosystems build up from first and second order ecosystems, but it is the relationship of these units to each other and their replication in the matrix of urban technological business and industrial development that will determine the ecological soundness of the city and ultimately its fitness as a human habitation.

For ecosystems higher than the third order, the overwhelming considerations are communications and transportation factors. Prior to high speed transportation and communication, fourth order human ecosystems tended to be restricted to components that could be managed easily under the constraints of long delays in communication time. Now, however, there appears to be no limit to the administrative potential, since worldwide communication is instantaneous and worldwide physical travel is possible in hours.

The facility with which communication and transportation encourage business and social ties between widely dispersed peoples has given rise to the concept of the "symbolic community." This concept is useful, but it is not the overriding concern for the survival or development of the human community, because the place where the important biological/ecological functions must occur determines the viability of the human community.

What is experienced as a result of high-speed communication is technological accommodation. Most long-distance communication takes place as part of a business, commercial, industrial, or governmental information network that serves primarily technological administration purposes and not human ecological needs. It is easy to confuse technological complexes with human ecological ones, but that is only because the humans in such complexes serve technological, not ecological functions. There is, to be sure, an "ecology of technology" but it takes us away from the biological aspects of human ecology.

The engineering aspects of industrial development on a world scale do have an impact on the biosphere as a whole. The biosphere as a fifth order ecosystem has been virtually insensitive to the activities of man for most of the time man has spent on earth. The biosphere changed only in response to worldwide changes in weather and to tectonic and other geological forces—but for most of man's time on earth, the biosphere was beyond the scale of anything humans could do.

Recently that has changed. With technology increasing at breakneck speed, changes now transcend locality and produce ramifications far beyond those conceived by the humans who trigger the actions. The digging of the Suez Canal connected two water bodies of biospheric dimension that had been isolated for millenia. Livestock grazing in Europe has considerably altered the pattern of vegetation. Pollution has affected all parts of the globe. The testing of atomic weapons in the atmosphere caused widespread dispersion of potentially dangerous radionuclide. As a matter of fact, the distribution of the radionuclide Strontium 90 from point sources (weapons explosions) even to the marrow of unborn babies probably did more than anything else to demonstrate the unity of the atmosphere and the living world's mutual dependence on clean air.

The space age with its miracles of space travel will one day settle down to the comparatively mundane and routine task of gathering information about the earth and relaying information over the entire global surface. Space technology already has revolutionized navigation, has brought events of worldwide interest to the TV screens of hundreds of millions simultaneously, and has made highspeed, reliable communication a possibility between any two spots on earth—no matter how remote from each other. Insofar as mutual understanding of information exchange tends to lessen tensions among nations, our ventures into space technology should stabilize ecological conditions in our fifth order ecosystem; but insofar as the rockets are delivery systems for weapons and the earth-observing satellites are "spies in the sky," they will tend to destabilize it. If past technological development is an indication, the stability factors will prevail simply because they are stability factors.

Having now expanded our horizons to the concept of man in the universe, we should not lose sight of the fact that what we are discussing is man in his physical environment—where he lives, eats, sleeps, plays, where his family lives, and what they do together and with their neighbors, how they operate together to form a human community, and how human communities, with their accompanying technology, make up the city.

It is the application of engineering skills to these problems, from rotating street drainage grates so that bicycle wheels cross them at right angles to forecasting weather from satellite images of the earth, that ultimately will determine the ecological soundness of the human community. We have the knowledge and the skill. We can make cities better than they are. But first we must learn more about what ecological principles apply to cities and devote more of our engineering skills to improving their operation.

—Theodore W. Sudia