Disentangling concepts of status, trend, and trajectory

The terms status and trend are ubiquitous in resource monitoring and management settings. To be useful and robust, however, they require precise (mathematical) definitions. It has been my experience that misunderstanding these terms can lead to misapplication of model predictions and to researchers and managers drawing the wrong conclusions from the data. In this post we show how relatively simple, even intuitive, definitions for each of these terms clarifies their intent, and improves the insights provided by models of monitoring data.

For context, it is helpful to see how these terms have been used previously in the literature

The ‘term “trend” [is] a description of an overall tendency, without regard to fluctuations in the trajectory. The distinction between the terms has important consequences for analysis and interpretation of survey data. Trend describes the change in a population over a specific interval; trajectory describes the manner in which the change occurred.

– Link and Sauer 1998

Trend vs. trajectory ( Citation: Link & Sauer, 1998 Link, W. & Sauer, J. (1998). Estimating population change from count data: Application to the north american breeding bird survey. Ecological applications, 8(2). 258–268. ) .

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