Lab 4: Loss of Prime Farmland in Duxbury, Massachusetts

Description of the application:

The goal of this assignment was to calculate the loss of farmland soils in Duxbury, Massachusetts due to an increase in impervious surfaces by using raster data. With an increase in urban development, there are more impervious surfaces taking over the town of Duxbury, leading to a decrease in farmland soils that are considered “prime farmland,” “farmland of statewide importance,” and “farmland of unique importance.” Calculations were performed to determine how much of these areas are present in Duxbury.

Table 1:

	Count (sq meters)	Square Kilometers
Total study area size	62,326,600	62.33
Prime Farmland	4,702,600	4.703
Farmland of statewide importance	9,076,600	9.08
Farmland of unique importance	2,470,300	2.47

Table 2:

	Count (sq meters)	Square Kilometers
Prime farmland lost	484,600	0.48
Farmland of statewide importance lost	803,300	0.80
Farmland of unique importance lost	62,600	0.06

How it was performed:

This process was performed using ArcMap and raster data provided by the state of Massachusetts. The study area for this process was Duxbury (the town I chose), and shapefiles were created for the study area. The raster data provided were for Massachusetts soils, and a “Map Unit” table was provided that describes the different types of soils, and a field called “MUKEY.” A join was performed between the study area soil raster dataset and the Map Unit table with the shared “MUKEY” field to determine the location of the farmland soils. The statistics tool in the attribute table on ArcMap was used to calculate the “count” of the MUKEY, and the count field was converted to square kilometers from square meters (COUNT * 100 to get square meters). Next, the impervious layer raster was used and extracted to the study area. A combination was performed to determine the amount of farmland lost for the three categories, while another join was performed. This combination and join allowed me to get the COUNT for the farmland lost (Table 2).

Figure 1: A map of study area

Results and Conclusions:

Based on Table 1, Duxbury is 62. 3266 square kilometers. Of the entire area size, 4.7026 square kilometers is considered prime farmland, 9.0766 square kilometers is considered farmland of statewide importance, and 2.4703 square kilometers is considered farmland of unique importance. Based on Table 2, 0.4846 square kilometers of 4.7026 (approximately 10%) of prime farmland was lost, 0.8033 square kilometers of 9.0766 (approximately 8.9%) of statewide important farmland was lost, and 0.0626 square kilometers of 2.4703 (approximately 2.5%) of uniquely important farmland was lost.

We were visited by Maggie Payne who works for the USDA NCRS. According to Payne's presentation, the maps were made at different times, and the data was collected based on ground conditions. This is a limitation for the study because the ground conditions can change every day, and impervious surfaces are constantly being added due to rapid urban development. It would be interesting to determine why these farmland areas are being lost, for example, are condominiums being built, or are new parking areas being paved, etc. Determining how many parking areas and shopping malls are being developed on top of prime farmland can help conservationists to stop the excessive loss of farmland. Although 10% doesn’t seem like a high percentage of farmland lost, it would be better if it could remain less than 2%, in my opinion.