Land Cover and Land Use

This map shows simple categories of land cover for the Salish Sea Bioregion. These data are derived from satellite imagery from 2015. Each 30x30 meter cell was assigned a value based on its most predominant land cover type. When interpreting these values, please keep in mind that this is a snapshot in time and necessarily involves heavily simplifying the diversity of conditions that might exist within one 30x30 meter grid cell. You can zoom and pan to explore this dataset up close.

Although the Salish Sea Bioregion has been heavily logged, it is still primarily a temperate rainforest. Just over half (50.7%) of the bioregion is covered with forests. These are primarily coniferous forests (40.5% of the bioregion), with smaller areas of mixed (8.5%) and broadleaf (1.8%) forest. Another 12.5% of the bioregion is covered with other types of natural or semi-natural vegetation, including shrublands (8.2%), grasslands (3.2%), and wetlands (1%).

Water, in both liquid and solid form, covers just under a quarter (22.8%) of the bioregion. The marine waters of the Salish Sea make up 17.2% of the bioregion. Freshwater lakes and rivers occupy 2.2% of the bioregion. Frozen water in snowfields and glaciers covers another 3.4% of the bioregion, though the extent of snow obviously changes seasonally and between years.

Coastal and intertidal land cover types are difficult to accurately map using this type of satellite data because they are intermittently covered with water. This dataset provides a rough estimate of the area covered by intertidal marine vegetation (0.12%) and mudflats and beaches (0.07%). These numbers should be interpreted cautiously, as they likely underestimate the true area of intertidal land cover types in many locations.

Human influence is pervasive throughout the bioregion, but developed lands cover only 8.6% of the bioregion. This includes urban areas and roads (6.1%), as well as actively used agricultural areas (2.4%). Forestry is not included in this agricultural lands estimate. Bare rock and ground make up another 5.4% of the bioregion.

Impervious surfaces associated with urban and developed areas, such roofs and roads, prevent water from soaking into the soil below. This changes the patterns of stormwater runoff and increases the frequency and magnitude of "flashy" high-runoff events. Areas with more impervious surface thus become more vulnerable to erosion, flooding, sewer overflow, and delivery of contaminants to nearby waterways. The expansion of impervious surfaces is concerning because of the negative effects on water quality in streams and in the Salish Sea itself. Impervious surfaces are particularly widespread in industrial areas, commercial zones, and roadways.

The dataset shown on this map divides the Salish Sea Bioregion into 30x30 meter grid cells and shows the percent of each cell that was covered by impervious surfaces in 2010. Based on this analysis, 4% of the non-marine grid cells in the Salish Sea Bioregion had a cover of at least 10% impervious surfaces. Impervious surfaces cover only a small area with the bioregion, yet have disproportionately large effects on water quality and quantity.

This map shows the percent of each 30x30 meter grid cell covered by impervious surfaces. The data are derived from NASA's analysis of 2010 satellite imagery. Data are shown only for areas defined as urban in NASA's Global Human Built-up and Settlement Extent dataset, so small areas of impervious surface outside of urban areas may have been excluded. Zoom and pan to explore the patterns of impervious surfaces for individual cities or areas.

Land zoned for primarily agricultural uses covers 5% of the Salish Sea Bioregion's land. Most of this agricultural land is located in the flat terrain associated with major rivers such as the Fraser and Skagit.

This map shows the area of land zoned as being primarily for agricultural use. Zoom, pan, and click to explore the details. In British Columbia, this represents the provincial-level Agricultural Land Reserve zone in which agriculture is the priority land use. In Washington, this represents county-level zoning classifications related to agricultural uses.

The percent of land used for farms varies across the counties and regional districts of the Salish Sea Bioregion. Overall, farm land is most common on the mainland in the central portion of the bioregion, centered on the US-Canada border region. The northernmost regional districts have the lowest proportion of agricultural land.

This map shows the area of farm land as a percent of the total land area for each county or regional district. Farm data were taken from the US and Canadian agricultural census records for the years 2016/2017. Pan, zoom, and click to access detailed tables and graphs.