Estimate Population Condition

written by Jason Karl

Method Type

qualitative – population condition or trend

Other Names

none known

Description and Uses

This is a quick, qualitative method for establishing the condition (i.e., “health”) of a population of a species with regard to some reference condition. This can be done by defining condition classes and describing the attributes of each class. Field observers then select the class that most closely matches what they are observing the in the field. Photographs can be useful for helping describe classes. To be used successfully, this method requires a high level of training and calibration (and periodic recalibration) of field observers to minimize inter-observer variability. This type of visual estimation technique for comparing a field site to a set of defined categories is used in a number of different assessment protocols.

Advantages and Limitations

The advantage of this method is that it is a relatively quick way to assess condition of a species’ population in the field. The pitfall of this method is that there is a great deal of subjectivity with defining the condition classes in the first place and then being able to appropriately categorize field sites into those categories based on visual estimates. Careful training and periodic recalibration can help to reduce the subjectivity.


Measuring and Monitoring Plant Populations (Elzinga et al. 2001)

Similar Approaches

The Rangeland Health Assessment (i.e., Indicators of Rangeland Health) protocol uses qualitative assessments of condition for 17 different variables to establish the overall condition of a site. The FireMon protocol also uses visual estimation methods for assessing condition for a number of attributes.

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