Quality and quantity of terrestrial landscape connectivity in the US Great Lakes Coastal Zone

Context

The Great Lakes Coastal Zone (GLCZ), the world’s longest continuous freshwater coastline, consists of interspersed natural and developed landcover and is inhabited by millions of people. Anthropogenic change fragments the GLCZ, decreasing landscape connectivity.

Objectives

We evaluated functional landscape connectivity of the U.S. GLCZ, assessing regional connectivity, protected areas’ effects on connectivity, and identified pinchpoints where connectivity is most vulnerable.

Methods

We modeled landscape connectivity to describe corridors and redundant pathways for two scenarios: (1) continuous terrestrial habitat patches and (2) protected areas. We compared these two scenarios by total corridor area and quality at two spatial scales (coastal zone and ecoregion). We used random forest analyses to examine how ecological factors influenced the connectivity rank and pinchpoint values. A principal components analysis identified how land cover influenced connectivity among ecoregions.

Results

The GLCZ was 69% connected. Although 91% of the GLCZ’s high-quality habitat was within corridors, less than 50% of the corridor area was high-quality (low resistance to movement). While the northernmost region retained high-quality connectivity, connectivity loss and degradation increased with development further south. Corridors between protected areas provided less connectivity, of worse quality, in areas of development and agriculture. Lower connectivity was associated with higher impervious surface cover.

Conclusions

Protected area placement affected both the quantity and quality of connectivity. Improving and maintaining functional connectivity could be accomplished by strategically restoring and protecting habitats most vulnerable to connectivity loss, predominantly in urban and agricultural regions. Our connectivity improvement index is a useful tool to identify areas where connectivity may be improved.