The Iowa County CRP model

Citation:  Riley, T. Z.  1995.  Association of the Conservation Reserve Program with ring-necked pheasant survey counts in Iowa.  Wildlife Society Bulletin 23:386-390.

This model resulted from research examining the effects of the Conservation Reserve Program shortly after it was initiated.  County-level land cover, weather, and pheasant abundance data collected during 1986-1991 were analyzed for predictive associations.  Based on the data, the following model was constructed:


By setting snowfall at the statewide average of 76 cm (30 inches), and initial land cover conditions of 0% CRP and 69% cropland (the 1985 county average), the following figure illustrates the model's estimation of pheasant response to adding CRP to a county's landscape.  It further assumes that every increment of additional CRP is paired with a corresponding decline in cropland, which the author noted was often true but not always.


If the above estimates are converted to percentage changes in CRP and pheasant abundance, the curve below results. For example, if percent CRP in a county increases from 0% to 5%, a population increase of 46% is predicted, if CRP further increases from 5% to 10%, an additional population increase of 25% is predicted, etc.