Spatially Explicit Modeling of Wetland Conservation Costs in Canadian Agricultural Landscapes

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We developed a spatially explicit wetland conservation cost model to estimate the private economic benefit of wetland drainage in an agricultural landscape in Alberta, Canada. The net private benefit of drainage or wetland conservation cost for this study is defined as the present value of net-returns from producing annual crops on the drained wetland basin (with a canola-spring wheat rotation), less the cost of wetland drainage, over 20 years. The expected spatial heterogeneity in wetland conservation cost is driven mainly by the heterogeneity in crop yield and wetland drainage cost in the study area. A relative soil productivity weight was used to account for the heterogeneity in crop yields across the landscape in the study area. The relative soil productivity weight was derived from the land assessment values and the variability in canola yields in Alberta. A surface drainage cost function was developed to estimate the surface drainage cost per acre for the ith wetland, and it is the sum of the fixed cost and the variable cost of surface drainage. We assumed a surface drainage fixed cost of $200 for the 20-year lifetime of the drainage project. The fixed cost of drainage represents all other costs that could be associated with surface wetland drainage, including administrative costs and maintenance/rehabilitation costs. The variable cost component of the surface drainage cost is the product of the relative distance variable and the distance coefficient. A value of 100 was chosen for the distance coefficient such that the maximum (minimum) drainage cost across the study area will be $600 ($200) (equation 2); since the minimum and maximum relative distances of wetlands to watercourse are 0 and 3.99, respectively. We calculated the relative distance variable as the ratio of the distance of a wetland to a watercourse (meters) to the average distance (meters) of all the wetlands to watercourses in the study area. To estimate the present value of a 20-year crop production planning horizon a 7% private discount rate was used to discount the annual net returns of the Canola and Spring wheat rotation (including the cost of wetland drainage). Moreover, using the Alberta’s Relative Wetland Value (RWV) Spatial Information, which is a measure of the ecosystem benefits of a wetland, we categorize all wetland basins located in a given quarter section in a four-level scale (A, B, C or D) whereby A has the highest ecosystem values and D has the lowest ecosystem values. The ecosystem values are assessed on four characteristics: hydrological health function, water quality function, ecological health function, and human use function of the wetlands. To characterize the range and pattern of wetland conservation costs in the study area we applied the net-present benefit of drainage formula to the natural resource conservation targeting scenarios, which are a) high beneficial wetlands (A and B wetlands), b) least cost (wetlands with low conservation cost), c) low benefit (C and D wetlands) and d) no targeting (randomly conserving 50% of wetlands in a quarter-section. One major output of our model is a supply curve for total wetland area, which shows the potential cumulative area of wetlands that could be conserved in the study area given conservation costs, at the margin, for the different targeting scenarios. We also showed, with a map, the degree of spatial heterogeneity of wetland conservation costs of wetlands in the study area.

We developed a spatially explicit wetland conservation cost model to estimate the private economic benefit of wetland drainage in an agricultural landscape in Alberta, Canada. We use the model to estimate the full wetland supply curve and find that these estimated private economic benefits of wetland drainage are highly heterogeneous within the watershed. We then combine these wetland conservation costs with non-monetary measures of public ecosystem benefits to assess three wetland conservation policy targeting scenarios. We find a positive correlation between low-cost wetlands and wetlands that offer low environmental benefits. Under these conditions and a given conservation budget, the choice of a wetland conservation policy would be important in achieving a wetland conservation goal.

Subbasin 14, Vermilion River Basin in Minburn County (CGNDB Unique Identifier : bc9a3eabc6cd11d892e2080020a0f4c9)