Ecosystem integrity is a concept of primary importance to the proposal. It describes the functioning of nature and human relationships with nature. Integrity is as much an ethical question as it is an ecological construct. This point is emphasized by the observation that the notion of integrity is definable only in terms of the physical, social, and cultural features that are specific to the geographical region in question (Kay 1993).
The concept of ecological integrity was first enunciated by Aldo Leopold, in 1939 (Woodley and Theberge 1992). He developed an ethical basis for integrity, but failed to identify quantitative measures. He wrote, "...a thing is right when it tends to preserve integrity, stability and beauty of the biotic community. It is wrong when it tends otherwise" (Leopold 1939). In an attempt to provide a more quantitative definition, Cairns, et al. (1977) stated, "Biological integrity is the maintenance of the community structure and function characteristic of a particular locale or deemed satisfactory to society." Karr (1987), in turn, characterized integrity as "...the capability of supporting and maintaining a balanced, integrated, adaptive community of organisms having species composition, diversity, and functional organization comparable to that of the natural habitat of a region." These definitions emphasize the idea that the ability of an ecosystem to maintain itself in the face of external stresses, is an important aspect of ecological integrity.
The implications of the ability of an ecosystem to maintain itself have been developed using theories from the study of complex systems and physics by those working to understand natural areas. Odum (1969) defines an ecosystem as "a unit of biological organization, with interactions within its system so that a flow of energy leads to characteristic trophic structures and material cycles within the system".
Another important implication of the manner in which ecosystems maintain themselves is that since environmental conditions are continuously changing through time and space, there are a number of developmental pathways a particular ecosystem can follow (Kay 1991). This situation is exacerbated by the fact that ecosystems, being complex, non-linear systems, are inherently non-determinant and can change in unforeseen ways given only slight changes in environmental or system conditions. Ecosystems do not have only one "correct" stable structural and functional organization. Thus, the traditional view that succession moves an ecosystem towards a single stable state is not adequate (Kay 1993). Life is not a stable equilibrium state, but is dynamic and constantly changing (Kay 1993). As such, it is important for ecosystems to be studied and managed as dynamic, changing entities.
Much work has been done on the study of ecosystems as non-equilibrium systems; that is, with a dynamically stabilized set of ecosystem domains whose structure is maintained by variability (Holling 1992). To this end Holling (1992) has provided a synthesis of ecosystem behaviour in terms of the sequential interactions between four ecosystems functions - exploitation, conservation, creative destruction or release, and mobilization/retention or reorganization (Figure 3). The progress of these events is such that each function gains dominance at different times and the overall stability of an ecosystem is a function of the ability of these properties to interact. Since the natural development of ecosystems depends on the interactions between these four functions, it is clear that an ecosystem must be managed as a dynamic ecosystem, which travels between these functions in time and space.
Ironically, the efforts of systems ecologists to provide a sound theoretical basis for understanding ecosystems have also served to reinforce the relevance of the ethical side of the ecosystem integrity concept. Since one cannot scientifically determine a single, "correct" ecosystem state for any one locale, value based judgements must be used to highlight the important ecosystem components and characteristics needed to assess the integrity of the ecosystem. An example provided by Allen (1993) is illustrative of this situation: An ecosystem experiences a decrease in biodiversity with no change in ecosystem function (e.g., primary productivity, energy dissipation). If function is the only characteristic of the ecosystem that is deemed important, then the system is not suffering any decrease in integrity, it is "business as usual". On the other hand, if the change in biodiversity reflects the local extinction of a valued species, or if biodiversity itself is considered important, then there is a deterioration of ecosystem integrity. The difference is the result of varying perspectives as to what is valuable in the ecosystem.
Woodley (1993) recognizes five criteria that are relevant to assessing or managing for ecosystem integrity within the Canadian National Parks. Adapted from Jordan et al. (1987) these criteria are: (1) Is the ecosystem capable of perpetuating itself? (2) Does the ecosystem resist invasions by new species? (3) Is net ecosystem productivity unimpaired? (4) Is ecosystem retention of nutrients unimpaired? and (5) Is the biota, and its interactions, unimpaired?
Based on these criteria, this proposal recognizes that any assessment of ecosystem integrity should incorporate elements from the above definitions. These considerations will be:
1. Ecosystems are inherently dynamic and can change in time and space. Ecosystem boundaries are not fixed entities but are both dynamic and permeable. Any consideration of ecosystem boundaries must take into account their dynamic nature and be aware that flows of energy, nutrients and species are more important than precise boundaries delineation.
2. Processes within an ecological system operate on a variety of levels. Therefore, the idea of grain and extent is a necessary tool for the evaluation of ecological integrity. Any sound definition of ecological integrity must evaluate an ecosystem on a wide enough extent to capture entire processes, as well as on a variety of scales.
3. Any assessment of ecological integrity must recognize that ecosystems are complex systems. That is, they do not exhibit single points of stable equilibrium, but have a multitude of steady states across space and time. Thus, in a specific geographic location, the actual ecosystem present is only one of various possible combinations of communities, and species that could exist (Kay 1993). As ecosystems develop they become more effective at dissipating solar energy (Kay 1991, 1993), while at the same time, environmental fluctuations tend to disorganize the dissipating capacity of the system. Too much or too little of each of these opposing forces create an imbalance which will upset the efficiency of the system. Thus, the point where the disorganizing forces of the environment and the organizing forces of the ecosystem are balanced, an optimum operating point is established (Kay 1991). Thus, our sense of integrity must recognize the ability of an ecosystem to attain and maintain its optimum operating point.
4. Ecosystems that exhibit symptoms of stress must be considered to have their integrity threatened. Symptoms of stress, such as decreased productivity and increased respiration may be indicative of the system moving away from its optimum operating point. Inherent in any discussion of stress and the loss of integrity, is the ability of the system to respond to the stress and return to its optimum operating point. The concept of resilience therefore, is critical in any definition and assessment of ecosystem integrity.
5. The human component in ecosystems is often viewed as a separate entity from the natural component. Yet, humans are inextricably linked to and dependant upon ecosystems for their very survival. Human activities induce stresses on ecosystems which must be monitored.
6. The concept of ecosystem integrity is value laden. What might be considered integrity for one person does not necessarily define integrity for another. Consequently, any definition of integrity must explicitly identify the human value judgements which influence the perspective taken.
For the purpose of assessing the integrity of the Huron Natural Park, the Huron Working Group propose a definition of integrity which includes the elements described above, and is defined as follows:
Ecosystem Integrity is defined as a state of ecosystem development that is optimized for its geographical location. (For the Huron Environmental Area this optimal state implies such terms as natural and naturally developing.) Integrity will imply the continued development of the ecosystem in the face of present and future land use pressures. It implies the assessment of ecosystem structure and function with sufficient grain and extent to accommodate for the dynamic and permeable nature of system boundaries and that the structure and function are not impaired by human-caused stresses. Any stress exhibited by the Huron Park must be considered a sign of impaired integrity that will threaten the overall integrity of the Park if it exceeds the systems ability to maintain a naturally developing ecosystem.
Now that we have a working definition of integrity we will discuss the core ideas inherent in an ecosystem approach. The following section will expand on some of the ideas already introduced and will discuss their application to the assessment of the integrity of the Huron Environmental Area.
Continue Reading - The Ecosystem Approach Applied To The Huron Park Ecosystem
An Ecological Framework for Huron Natural Area