Maintaining connectivity among discrete habitat patches is a major consideration in biodiversity conservation, but most past research has focused on terrestrial ecosystems. Lakes represent a unique type of patch: lakes are discrete waterbodies surrounded by non-habitat, but unlike terrestrial patches, lakes are connected by both aquatic and semi-aquatic features. For example, fish move among lakes through connected streams and wetlands, whereas semi-aquatic amphibians move among lakes through the aquatic-terrestrial matrix (e.g., wetlands, upland vegetation); thus connectivity for different species must be defined in different ways. We modified the existing patch-matrix framework to accommodate lake connectivity for both aquatic and semi-aquatic species. We asked the following: 1) What is the relationship between aquatic and semi-aquatic connectivity for lakes? And 2) Do existing protected areas include lakes with high connectivity for both aquatic and semi-aquatic species? To answer these questions, we applied our conceptual framework to lakes in Michigan, USA, by developing two composite connectivity scores that quantify connectivity for aquatic and semi-aquatic species and examined relationships between connectivity scores and protected areas using the US Protected Areas Database.
Results/Conclusions
Fewer than 3% of lakes had high scores for either aquatic and semi-aquatic connectivity. Connectivity scores were generally greater in Michigan’s Upper Peninsula, which is heavily forested with greater prevalence of protected areas. Although protection varied widely across connectivity scores, highly connected lakes were generally more protected than poorly connected lakes, particularly when considering multi-use protected lands. Our results suggest that protected areas, which are typically designated for terrestrial features, sometimes protect lakes that facilitate movement of aquatic and semi-aquatic species by protecting other aquatic features (e.g., wetlands, streams). Our connectivity-based framework can be used as a coarse-filter approach to help prioritize lakes for conservation that are likely to have high biodiversity and conservation value. Our framework can also facilitate greater incorporation of fresh waters into conservation planning and stimulate future research on the role of connectivity in the distribution and abundance of aquatic and semi-aquatic species.