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The Center for Native Grasslands Management

Title: Combining data from state and national monitoring surveys to assess large-scale impacts of agricultural policy
Year: 2004
Author(s): Nusser, S. M., Clark, W. R., Wang, J. Y., Bogenschutz, T. R.
Source Title: Journal of Agricultural Biological and Environmental Statistics
Source Type: Journal
pages: 381-397
Original Publication: http://  
Abstract: An increasing number of state and national databases are available to assess agricultural and environmental trends in natural resource populations. We use a case study approach to consider methodologies for combining state and national data to assess the impact of agricultural policy on state wildlife populations. The scientific question is to assess the impact of the Conservation Reserve Program on pheasant populations in Iowa, using land cover/use data from the National Resources Inventory and count data from an annual state pheasant population survey. Our approach involves identifying a common spatial polygon for linking summaries from each of two datasets, and then estimating parameters that describe temporal trends in land cover and in pheasant populations over a common time period within each polygon. Estimated pheasant population parameters are regressed on land cover summaries to investigate the impact of the Conservation Reserve Program on pheasant populations in regions of the state. Results reveal that the population response to the Conservation Reserve Program varies by region in relation to the physiography and agricultural use of the region, in ways that were not anticipated by policy developers. Statistical considerations for developing appropriate models for combining data are discussed.