Methodology and Interpretation

Percent pasture
The percentage of pasture land cover is calculated by dividing the number of pasture land cover cells in the reporting unit by the total number of land cover cells in the reporting unit minus those cells classified as water (i.e., total land area). Animals grazing on pastures may decrease vegetation cover, possibly leading to increased runoff and erosional soil loss, which may result in increased stream sedimentation. Livestock may also degrade within-stream and stream-bank ecological functions by defecating in the streams and trampling riparian vegetation, respectively.

Quantile: Each class contains an approximately equal number (count) of features. A quantile classification is well-suited to linearly distributed data. Because features are grouped by the number within each class, the resulting map can be misleading, in that similar features can be separated into adjacent classes, or features with widely different values can be lumped into the same class. This distortion can be minimized by increasing the number of classes.

Metric input GIS data:

• United States Hydrologic Units (8-digit HUCs) - Metadata

• United States Coastal Change Analysis Program (CCAP) - Metadata

• Canada Hydrologic Units (Subsubdivisions) - Metadata

• Ontario Ministry of Natural Resources Data Set - Metadata