Ecosystems are viewed by ecologists as basic units of the biosphere, much as cells are considered by biologists to be the basic units of an organism. Ecosystems are self-organized and self-regulating entities within which energy flows and resources are cycled in a coordinated, interdependent manner to sustain life.
Disruptions and perturbations to, or within, the unit’s organization or processes may reduce the quality of life there or cause its demise. Ecosystem boundaries are usually defined by the research or management questions being asked.
An entire ocean can be viewed as an ecosystem, as can a single tree, a rotting log, or a drop of pond water. Systems with tangible boundaries—such as forests, grasslands, ponds, lakes, watersheds, seas, or oceans—are especially useful to ecosystem research.
The ecosystem concept was first put to use by American limnologist Raymond L. Lindeman in the classic study he conducted on Cedar Bog Lake, Minnesota, which resulted in his article “The Trophic Dynamic Aspect of Ecology” (1942).
Lindeman’s study, along with the publication of Eugene P. Odum’s Fundamentals of Ecology (1953), converted the ecosystem notion into a guiding paradigm for ecological studies, thus making it a concept of theoretical and applied significance.
Ecologists study ecosystems as integrated components through which energy flows and resources cycle. Although ecosystems can be divided into many components, the four fundamental ones are abiotic (nonliving) resources, producers, consumers, and decomposers.
The ultimate sources of energy come from outside the boundaries of the ecosystem (solar energy or chemothermo energy from deep-ocean hydrothermal vent systems).
Because this energy is captured and transformed into chemical energy by producers and translocated through all biological systems via consumers and decomposers, all organisms are considered as potential sources of energy.
From these, producers utilizing energy synthesize biomolecules, which are transformed, upgraded, and degraded as they cycle through the living systems that comprise the various components. The destiny of these bioresources is to be degraded to their original abiotic forms and recycled.
The ecosystem approach to environmental research is a major endeavor. It requires amassing large amounts of data relevant to the structure and function of each component. These data are then integrated among the components, in an attempt to determine linkages and relationships.
This holistic ecosystem approach to research involves the use of systems information theory, predictive models, and computer application and simulations. As ecosystem ecologist Frank B. Golley stated in his book A History of the Ecosystem Concept in Ecology (1993), the ecosystem approach to the study of ecosystems is “machine theory applied to nature.”
Initially, ecosystem ecologists used the principles of Arthur G. Tansley, Lindeman, and Odum to determine and describe the flow of energy and resources through organisms and their environment.
Fundamental academic questions that plagued ecologists included those concerning controls on ecosystem productivity: What are the connections between animal and plant productivity? How are energy and nutrients transformed and cycled in ecosystems?
Responses of ecosystem components could then be examined by manipulating parameters within the simulation model. Early development of the ecosystem concept culminated, during the 1960’s, in defining the approach of ecosystem studies.
Ecosystem projects were primarily funded under the umbrella of the International Biological Program (IBP). Other funding came from the Atomic Energy Commission and the National Science Foundation.
The intention of the IBP was to integrate data collected by teams of scientists at research sites that were considered typical ofwide regions. Although the IBP was international in scope, studies in the United States received the greatest portion of the funds—approximately $45 million during the life of IBP (1964-1974).
Five major IBP ecosystem studies, involving grasslands, tundra, deserts, coniferous forests, and deciduous forests, were undertaken. The Grasslands Project, directed by George Van Dyne, set the research stage for the other four endeavors.
However, because the research effort was so extensive in scope, the objectives of the IBP were not totally realized. Because of the large number of scientists involved, little coherence in results was obtained even within the same project.
A more pervasive concern, voiced by environmentalists and scientists alike, was that little of the information obtained from the ecosystem simulation models could be applied to the solution of existing environmental problems.
An unconventional project partially funded by the IBP was called the Hubbard Brook Watershed Ecosystem. Located in New Hampshire and studied by F. Herbert Bormann and Gene E. Likens, the project redirected the research approach for studying ecosystems from the IBP computer-model-driven theory to more conventional scientific methods of study. Under the Hubbard Brook approach, an ecosystem phenomenon is observed and noted.
Apattern for the phenomenon’s behavior is then established for observation, and questions are posed about the behavior. Hypotheses are developed to allow experimentation in an attempt to explain the observed behavior. This approach requires detailed scrutiny of the ecosystem’s subsystems and their linkages.
Since each ecosystem functions as a unique entity, this approach has more utility. The end results provide insights specific to the activities observed within particular ecosystems. Explanations for these observed behaviors can then be made in terms of biological, chemical, or physical principles.
Utility of the Concept
Publicity from the massive ecosystem projects and the publication of Rachel Carson’s classic Silent Spring (1962) helped stimulate the environmental movement of the 1960’s.
The public began to realize that human activity was destroying the bioecological matrices that sustained life. By the end of the 1960’s, the applicability of the IBP approach to ecosystem research was proving to be purely academic and provided few solutions to the problems that plagued the environment.
Scientists realized that, because of the lack of fundamental knowledge about many of the systems and their links and because of the technological shortcomings that existed, ecosystems could not be divided into three to five components and analyzed by computer simulation.
The more applied approach taken in the Hubbard Brook project, however, showed that the ecosystem approach to environmental studies could be successful if the principles of the scientific method were used. The Hubbard Brook study area and the protocols used to study itwere clearly defined.
This ecosystem allowed hypotheses to be generated and experimentally tested. Applying the scientific method to the study of ecosystems had practical utility for the management of natural resources and for testing possible solutions to environmental problems.
When perturbations such as diseases, parasites, fires, deforestation, and urban and rural development disrupt ecosystems from within, this approach helps define potential mitigation and management plans. Similarly, external causative agents within airsheds, drainage flows, or watersheds can be considered.
The principles and research approach of the ecosystem concept are being used to define and attack the impact of environmental changes caused by humans.
Such problems as human population growth, apportioning of resources, toxification of biosphere, loss of biodiversity, global warming, acid rain, atmospheric ozone depletion, land-use changes, and eutrophication are being holistically examined.
Management programs related to woodlands (the New Forestry program) and urban and rural centers (the Urban to Rural Gradient Ecology, or URGE, program), as well as other governmental agencies that are investigating water and land use, fisheries, endangered species, and exotic species introductions, have found the ecosystem perspective useful.
Ecosystems are also viewed as systems that provide the services necessary to sustain life on earth. Most people either take these services for granted or do not realize that such natural processes exist.
Ecosystem research has identified seventeen naturally occurring services, including water purification, regulation, and supply, as well as atmospheric gas regulation and pollination.
A 1997 article by Robert Costanza and others, “The Value of the World’s Ecosystem Services and Natural Capital,” placed a monetary cost to humanity should the service, for some disastrous reason, need to be maintained by human technology. The amount is staggering, averaging $33 trillion per year. Humanity could not afford this; the global gross national product is only about $20 trillion.
Academically, ecosystem science has been shown to be a tool to dissect environmental problems, but this has not been effectively demonstrated to the public and private sectors, especially decision makers and policymakers at governmental levels. The idea that healthy ecosystems provide socioeconomic benefits and services remains controversial.
In order to bridge this gap between academia and the public, Scott Collins of the National Science Foundation suggested to the Association of Ecosystem Research Centers that ecosystem scientists be “bilingual”; that is, they should be able speak their scientific language and translate it so that the nonscientist can understand.