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Thresholds of Potential Concern (TPC's)

The information for each of the completed TPC’s can by found below under the following themes:

Thresholds of Potential Concern - Documentation
Invasive Species Fire in the Landscape River Geomorphology
Threatened Biota Heterogeneity Fish Species
Degradation Bovine Tuberculosis Plant and Animal Dynamics
River Flow and Quality Below-ground Water Landscape Function
Vegetation Homogenization  

What are Thresholds of Potential Concern

TPC’s are a set of operational goals that together define the spatiotemporal heterogeneity conditions for which the Kruger ecosystem is managed. TPC’s are essentially upper and lower limits along a continuum of change in selected environmental indicators. The suite of TPC’s together represents the envelope within which ecosystem changes are considered desirable (see figure below). When the upper or lower TPC levels are reached, or when modeling predicts that they will soon be reached, this prompts an assessment of the cause of the extent of change. This assessment provides the basis for deciding whether management action is needed to moderate the change or whether the TPC should be recalibrated in the light of new knowledge and/or understanding. TPC’s form the basis of an inductive approach to adaptive management because they are hypotheses of limits of acceptable change in ecosystem structure, function and composition. Therefore, their validity and appropriateness are always open to challenge, and they must be adaptively modified as our understanding and experience of the system increases.

With the recent revisions of both the KNP Objectives as well as the TPC’s we tried to move away from the concept of upper and lower limits, and as far as possible reformat the TPC’s in terms of rates of approach of thresholds. These rates of approach provide an indication of how fast we are moving towards a point of undesirable system change and allows us to build in confidence buffers and management action time-lags around these. We believe that these rate-based TPC’s will allow us to take the necessary management action timeously.

How do we decide on TPC’s

TPC’s are derived directly from the KNP management and research objectives. Since thresholds of potential concern define the end-points of the desired set of varying conditions in Kruger and are the basis of our strategic adaptive management approach, TPC’s are of necessity based on a combination of best available knowledge and plausible ecological hypotheses around understanding complex dynamic ecosystems. Each discrete set of TPC’s thus is accompanied by a narrative which includes the hypotheses that we are testing as well as a description of the actual concerns. We believe that these narratives will help readers understand Kruger’s multifaceted ecosystem management dimensions and enable judgment of whether the TPC’s are appropriately addressing these issues. Our revised monitoring programs are directly responsible for providing the data that we need to input into the TPC hypotheses / models and ultimately test for potential exceedances.


Biggs, H.C., and Rogers K.H. 2003. An Adaptive System to Link Science, Monitoring and Management in Practice. Pages 59-80 in J.T du Toit, K.H. Rogers and H.C.Biggs (eds.),The Kruger Experience Ecology and Management of savanna heterogeneity. Washington: Island Press.