A species is defined as individuals and populations that can potentially interbreed and produce fertile offspring. The word ecosystem is a generic term that is used to describe one or more communities of organisms that are interacting with their environment as a defined unit. As such, ecosystems can be organized in a hierarchy – they may range from small units occurring in discrete microhabitats (such as an aquatic ecosystem contained within a pitcher plant or in a garden surrounded by pavement) to much larger scales (such as a landscape or seascape). Even the biosphere can be viewed as being a single ecosystem.
Ecological interpretations of the natural world consider the web-like connections amon4g the many components of ecosystems in a holistic manner. This ecosystem approach does not view the system as a random grouping of individuals, populations, species, communities, and environments. Rather, it confirms all of these as being intrinsically connected and mutually dependent, although in varying degrees, and also as having emergent properties.
An important ecological principle is that all species are sustained by environmental resources: the “goods and services” that are provided by their ecosystem. All organisms require specific necessities of life, such as inorganic nutrients, food, and habitat with particular biological and physical qualities. Green plants, for example, need access to an adequate supply of moisture, inorganic nutrients (such as nitrate and phosphate), sunlight, and space. Animals require suitable foods of plant or animal biomass (organic matter), along with habitat requirements that differ for each species.
It is important to understand that humans are no different in this respect from other species. Although this dependence may not always seem to be immediately apparent as we live our daily lives, we nevertheless depend on environmental resources such as food, energy, shelter, and water to sustain ourselves and our larger economies.
It follows that the development and growth of individual people, their populations, and their societies and cultures are limited to some degree by environmental factors. Examples of such constraints include excessively cold or dry climatic conditions, mountainous or otherwise inhospitable terrain, and other factors that influence food production by agriculture or hunting.
However, humans are often able to favourably manipulate their environmental circumstances. For example, crop productivity may be increased by irrigating agricultural land, by applying fertilizer, or by managing pests. In fact, humans are enormously more capable of overcoming their environmental constraints than any other species. This ability is a distinguishing characteristic of our species.
The human species is labelled by the scientific term Homo sapiens, a two-word name (or binomial) that is Latin for “wise man.” Indeed, humans are the most intelligent of all the species, with an enormous cognitive ability (that is, an aptitude for solving problems). When humans and their societies perceive an environmental constraint, such as a scarcity of resources, they often have been able to understand the limiting factors and to then use insight and tools to manipulate the environment accordingly. The clever solutions have generally involved management of the environment or other species to the benefit of humans, or the development of social systems and technologies that allow a more efficient exploitation of natural resources.
Humans are not the only species that can cope with ecological constraints in clever ways. A few other species have learned to use rudimentary tools to exploit the resources of their environment more efficiently. For example, the woodpecker finch of the Galapagos Islands uses cactus spines to pry its food of insects out of fissures in bark and rotting wood. Chimpanzees modify twigs and use them to extract termites, a favourite food, from termite mounds. Egyptian vultures pick up stones in their beak and drop them on ostrich eggs, breaking them and allowing access to the rich food inside.
A few such innovations or “discoveries” by other species have even been observed. About 60 years ago in England, milk was hand-delivered to homes in glass bottles that had a bulbous compartment at the top to collect the cream as it separated. A few great tits (chickadee-like birds) discovered that they could feed on the cream by tearing a hole in the cardboard cap of the bottle. Other great tits observed this behavioural novelty and adopted it. The feeding tactic became widespread and was even adopted by several other species, such as the blue tit. Cream-eating was a clever innovation, allowing access to a new and valuable food resource.
Although other species have developed behavioural changes that allow more efficient exploitation of their environment, none have approached the number and variety of innovations developed by humans. Moreover, no other species has developed a cumulative expertise for exploiting such a broad range of resources. And no other species has managed to spread these adaptive capabilities as extensively as humans have, in an increasingly global culture. Unfortunately, humans also have developed an unparalleled ability to degrade resources and ecosystems and to cause the extinction of other species. The intense damage caused by humans and our economy is, of course, a major element of the subject matter of environmental science.
The concept of systems is important in the hierarchical organization of environmental science. For this purpose, a system may be defined as a group or combination of regularly interacting and interdependent elements that form a collective entity, but one that is more than the mere sum of its constituents. A system can be isolated for purposes of study. Systems occur in various spheres of life, including the following: • biosystems, which are represented by any of the levels of organization of life, ranging from biochemistry to the biosphere • ecosystems, which are biosystems that consist of ecological communities that interact with their environment as a defined unit • economic systems, or integrated activities that produce goods and services in an economy • socio-cultural systems, which consist of ways that specialized people, information, and technologies are organized to achieve some goal • and numerous others, including musical symphonies, physical art such as paintings, and for that matter, the words and data in this book
Note, however, that these various systems are not mutually exclusive. For example, an agroecosystem includes elements of biosystems, ecosystems, and socio-cultural systems.
Systems have collective properties, which are based on the summation of their parts. One such property might be the total number of organisms present in a defined area, which might be measured as the sum of all of the individual plants, animals, and microorganisms that are estimated to be present.
Systems also have emergent properties, which are revealed only when their components interact to develop functional attributes that do not exist at simpler, lower levels. For example, harmonies and melodies are emergent properties of music, as occurs when vocalists, a drummer, a bass and lead guitarist, and a keyboard player of a rock band all integrate their activities to perform a song. Emergent properties are complex and may be difficult to predict or manage.
Biological systems provide numerous examples of emergent properties (see Chapter 9). For example, certain kinds of fungi and algae join together as a life form known as a lichen, which is an intimate, mutually beneficial relationship (a mutualism). The biological properties of a lichen are different from those of the partner species (which cannot live apart in nature), and they are impossible to predict based only on knowledge of the alga and the fungus.
Similarly, assemblages of various species occurring in the same place and time (an ecological community) develop emergent properties based on such interactions as competition, disease, herbivory, and predation. This complexity makes it difficult to predict changes caused by the introduction of a new disease or predator to a community (including the harvesting of certain species by humans). Assemblages of communities over large areas, known as ecoscapes, also have emergent properties, as does the biosphere as a whole.
Emergent properties are extremely difficult to predict and often emerge as “surprises,” for example, occurring when ecosystems are stressed by some human influence. The interconnections within systems are particularly important: any effects on particular components will inevitably affect all of the others. This extreme complexity is one of the defining attributes of life and ecosystems, in contrast with physical (or non-biological) systems, which are less complex.
Systems analysis is the study of the characteristics of systems, including their components, the relationships among those elements, and their collective and emergent properties. Systems analysis is used to study commercial, industrial, and scientific operations, usually with the goal of improving their efficiency. It can also be applied to improve the management of ecosystems being exploited to provide goods and services for use by the human economy. Ecologists also use systems analysis to better understand the organization and working of natural ecosystems, regardless of any direct relationship to the harvesting of natural resources. A key result of many such analyses is that the complexity of the system often precludes accurate predictions.
NOTE: Take Quiz 2-1 before proceeding to next lesson.