Component Level Scores
For the Connectivity Component, the three health index scores are combined to create a mean (average) overall component health score.
Connectivity Component Health Score
What do the Connectivity index scores show?
The combined three connectivity index scores reveal a pattern of low scores in the Minnesota and Red River basins with higher scores in extreme northern Minnesota. Very low Terrestrial Habitat Connectivity scores appear to drive that result.
CREATING THE INDEX
Terrestrial Habitat Connectivity Data Layers:
National Land Cover Dataset (NLCD, 2001)
MN County Biological Survey, Sites of Biodiversity Significance
Roads (MN DOT Roads Database)
National Agricultural Statistics Service (NASS, 2007)
Terrestrial Habitat Quality Index (MN DNR Watershed Assessment, 2010)
Aquatic Connectivity Data Layers:
National Dam Inventory, (Corps of Engineers, 2008)
Bridge and Culvert Inventory (MN DOT, 2009)
MN Streams; Perennial Streams and Ditches (MN DNR, 2009)
Riparian Connectivity Data Layers:
National Land Cover Data (NLCD, 2001)
National Agricultural Statistics Service; Row Crop Classes (NASS, 2007)
MN Streams and Lakes; 200 Meter Buffer of Perennial Streams and Lakes (MN DNR, 2009)
Designated Floodplain (Federal Emergency Management Agency, 2009)
The three connectivity index values were combined into one mean (average) connectivity score for each watershed. Comparing the mean (average) score reveals statewide trends in system health. Although it may mask any extreme values in any one index, it serves to illustrate an overall gradient in results by basin and region. The mean can also be used to compare watersheds, such as watersheds that are upstream or downstream within the same basin.
Most of Minnesota has very low terrestrial and aquatic connectivity scores. Single digit scores are found throughout the south and western border of the state. The lowest scores are found in terrestrial habitat connectivity or aquatic connectivity. The consistently higher riparian connectivity scores indicate that some terrestrial habitat may be buffering water bodies, streams and rivers, even in areas where there is little other terrestrial habitat and the aquatic system is disrupted.
Connectivity Index Inputs:
Terrestrial Habitat Connectivity
The free movement of energy, matter and organisms throughout our watersheds is restricted in many ways. The watersheds in the south, southwest and northwest regions of Minnesota have low scores in all three connectivity areas. In these regions, there is very limited terrestrial habitat with few natural areas to connect what does remain due to very extensive agricultural production. There is also a high density of bridges, culverts and dams; and the riparian areas are often unvegetated. The watersheds along the Mississippi River in the southeast fare slightly better. This is likely due to the steep topography that restricts urban and farm development. The winding valleys hold some intact corridors of terrestrial habitat. However, these same valleys often hold streams that have been crossed many times with bridges and culverts leading to low aquatic connectivity scores.
Northeastern Minnesota scores are consistently higher, particularly in Riparian Connectivity. There are somewhat higher Terrestrial Habitat Connectivity scores as well, but Aquatic Connectivity is low except for the northern most tier of watersheds. Similar to the southeast, this area has many stream crossings that reduce the Aquatic Connectivity scores. The highest aquatic connectivity scores are found in the far northern watersheds of the Rapid, Big Fork and Rainy Rivers; followed by the watersheds that contain the Boundary Water Canoe Area Wilderness.
The Terrestrial Habitat Connectivity model will be refined as the terrestrial habitat model is updated with newer land cover data and additional parameters.
The Riparian Connectivity model could be enhanced by delineating the contributing riparian area, rather than calculating land use within a standard buffer width.
The Aquatic Connectivity model could be refined with more detailed information about structures in streams so that structures could be weighted according to their detrimental effect on aquatic connectivity.