When a specific problem is presented, the answers can only be as good as the questions that are asked. Allen (1993) explains that good science is consistent within a defined frame; but the best science has a particularly powerful set of definitions implied by the questions it asks.
Our need to define system boundaries brings up the interesting concept of perspectives within an ecosystem. Allen (1993) discusses in detail the differing perspectives that are present when observing an ecosystem with the ecosystem approach. He cites two specific examples of perspective: the first involves a population-community approach; the second involves a process-functional approach. The former focuses solely on organisms as structures and isolates them from the abiotic environment. The latter emphasizes the transfer and processing of matter and energy.
The distinction between the community as a system of populations, and the ecosystem as a system of matter-energy flows through the biota and environment, is a dichotomy that exists in classrooms and textbooks of ecology around the world (Allen 1993). It can be noted however, that despite the separation of community and ecosystem ecology, their emphasis on interactions within the system is a common denominator (Allen 1993). A population-community based approach can, therefore, be identified as one perspective, while matter-energy flow is simply another way of looking at the same system. As Allen (1993) indicates, our perspective of the system is a matter of choosing what is important at the moment. The questions we ask about a system will shape a perspective from which the system is observed. In turn, this will delineate the system boundaries. Combining different perspectives allow us to distinguish the foreground from the background, as if separating an object from its context (Allen 1993). As such, the boundary surrounding an ecological system is a system description of the interacting biota and the environment of some place at a particular time. These systems are difficult to define because they are conceptual rather than physical entities, with boundaries that are dynamic and permeable. Consequently, different questions will define different boundaries. After all, we only have access to the tools that measure the system, and not the system itself (Allen 1993).
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