Pet Project or Best Project? Online Decision Support Tools for Prioritizing Barrier Removals in the Great Lakes and Beyond

Abstract

Structures that block movement of fish through river networks are built to serve a variety of societal needs, including transportation, hydroelectric power, and exclusion of exotic species. Due to their abundance, road crossings and dams reduce the amount of habitat available to fish that migrate from the sea or lakes into rivers to breed. The benefits to fish of removing any particular barrier depends on its location within the river network, its passability to fish, and the relative position of other barriers within the network. Balancing the trade‐offs between ecological and societal values makes choosing among potential removal projects difficult. To facilitate prioritization of barrier removals, we developed an online decision support tool (DST) with three functions: (1) view existing barriers at various spatial scales; (2) modify information about barriers, including removal costs; and (3) run optimization models to identify portfolios of removals that provide the greatest amount of habitat access for a given budget. A survey of available DSTs addressing barrier removal prioritization indicates that barrier visualization is becoming widespread but few tools allow dynamic calculation of connectivity metrics, scenario analysis, or optimization. Having these additional functions, our DST enables organizations to develop barrier removal priorities based on cost‐effectiveness in restoring aquatic connectivity.

Trade‐offs among road–stream crossing upgrade prioritizations based on connectivity restoration and erosion risk control

“…Then, the length of river segment (i.e., habitat) above this barrier was multiplied by the cumulative passability to produce a value describing the cumulative accessible habitat. The Fishwerks tool identifies passability ratings for fish with strong, moderate, and weak swimming ability (Moody et al, ). Because our primary intent is not to address the influence of fish with different swimming abilities, the passability ratings for moderate swimmers were chosen here to represent a general scenario.…”

“…In contrast, optimization approaches incorporate the spatial interdependence among barriers (King & O'Hanley, ) and can help reveal how management scales influence the cost‐effectiveness of connectivity restoration projects (Milt et al, ; Neeson et al, ). Decision support tools have been developed to reduce the requirements for mathematical and programming expertise for applying optimization models to prioritize dams and crossings for connectivity restoration (e.g., OptiPass, O'Hanley, ; Fishwerks, Moody et al, ) .…”

Growth and recruitment dynamics of young‐of‐year northern pike: Implications for habitat conservation and management

“…The highly fragmented state of Great Lakes tributaries provides ample opportunity to favour such sites when prioritising barrier removals (Moody et al, 2017;Neeson et al, 2015) or planning habitat restoration projects.…”

Conserving rare species can have high opportunity costs for common species

“…The Great Lakes are the largest freshwater ecosystem in the world, and support recreational fisheries and other cultural ecosystem services valued at >$8.3 billion USD per year in the United States alone (NOAA , Allan et al., ). More than three dozen native fish species migrate between the Great Lakes and their tributaries, but access to historical breeding habitats is currently blocked by more than 100,000 dams and road crossings (Januchowski‐Hartley et al., ; Moody et al., ). While there is widespread interest in removing dams and retrofitting road crossings to restore fish migrations and the ecosystem services they provide, migratory species vary widely in their distributions across the thousands of tributary watersheds of these five connected lakes.…”

“…To quantify the opportunity costs associated with directing conservation resources to rare species, we compiled data on the current and historical distributions of 35 species of migratory fishes across the entire Great Lakes basin. We paired this distribution data with estimates of barrier passability, removal costs, and upstream habitat for all documented dams and road crossings (Moody et al., ). We then explored three common conservation strategies for prioritizing barrier removal projects: (1) to maximize total habitat gains summed across the entire fish community, (2) to ensure that all species receive some minimum benefit (i.e., a complementarity approach), and (3) to maximize benefits for each species individually, including the cases where resources are directed toward high‐priority rare species.…”