Thompson Rivers University

Environmental Sciences Seminar Series

Dr. Jabed Tomal, of TRU’s math and statistics department, and Dr. J. Cibor of the University of Calgary present Environmental Monitoring – Developing Bioindicators of Environmental Condition and Recovery from Degradation as part of the Environmental Sciences Seminar Series.


Various classification systems have been developed to evaluate and understand the state of the environment.

In streams and increasingly in other systems, the ‘reference condition’ approach is used when one wants to ask whether or not the condition of a ‘test site’ is acceptable.  Best professional judgement is used to identify a suite of reference locations to describe what seems to be the range of ‘acceptable’ habitat (environmental conditions). The variation in composition of biological communities found in these locations determines the limits of what is termed the ‘reference community’.

Whatever bounds are selected become the criteria for distinguishing between ‘reference’ (acceptable) and ‘nonreference’ (‘unacceptable’) conditions.  Biological conditions at the test site are then measured, and the probability that the test site community belongs to the reference suite is determined. This approach works well when ‘test areas’ make up only a small proportion of the geographic region of interest. However, few true reference areas exist in places subject to intensive development or expanding human population. Furthermore, there is no basis for assessing the relative condition of locations that are clearly ‘nonreference’.

Just as we have a concept of ‘reference condition’, we propose the complementary concept of ‘degraded condition’, operationally defined as the range of locations whose physicochemical characteristics are deemed unacceptable by professional consensus. If one can identify the two extremes of environmental condition, any test site can be ordinated along a reference-degraded continuum, and its relative quality summarized by its position along the continuum.

We have applied the reference-degraded continuum conceptual model to assess shoreline habitats across the entire Great Lakes basin on the basis of six classes of human disturbance. The Great Lakes Environmental Indicators consortium then sampled a wide range of biota across the basin to study relationships between the disturbance gradients and biological condition. Biological condition is frequently a nonlinear function of environmental stress that can be better modelled by breakpoint or quantile analyses than by linear or nonlinear models. Threshold responses may be a more common manifestation of environmental degradation than gradual changes in biological condition.

This lecture will illustrate these patterns with examples of fish assemblages at Great Lakes coastal margins, aquatic invertebrate assemblages in the Lake Huron-Lake Erie Corridor, and terrestrial species richness in wetlands of varying areas.