New tool addresses a big obstacle for overcoming aquatic barriers: Knowing where to start

Open the Northeast Aquatic Connectivity project’s new Aquatic Barrier Prioritization web application, developed by The Nature Conservancy, and you will see a standard base map for the Northeast region: a green and beige landmass depicting state and international boundaries, major cities, major mountain ranges, major rivers, and the blue expanse of the Atlantic Ocean to the right. 

But click on the “Get Started!” button, and your perspective will shift from the overall landscape to the extensive aquatic networks within. All 13 states will suddenly be shrouded by thousands of colorful bubbles of varying sizes, as if a shower of confetti had descended upon the region.

This is no party. Those thousands of bubbles represent thousands of dams and road-stream crossings. Many of those dams and road-stream crossings represent major barriers to movement for aquatic organisms, and risks to communities dependent on this infrastructure. Increased flooding as a result of changing precipitation patterns from climate change will only make matters worse. It’s pretty overwhelming. Even more overwhelming than confronting a floor full of confetti after a New Year’s Eve party.

Don’t panic. This visualization tool is not designed to scare you. If you are an average citizen, it is designed to open your eyes to the degree of fragmentation in aquatic systems across the region. If you work in the realm of fish passage, it is designed to help you figure out how you can help address this fragmentation by showing you which barriers to target for the greatest conservation impact. 

“For each dam and road-stream crossing in the region, we calculated a number of ecologically relevant metrics; together, the metrics provide important information about the potential benefit of removing that barrier,” explained Erik Martin, a spatial ecologist for TNC’s Eastern Division and lead of the project.

For example, metrics include the length of upstream habitat that would be “opened” for aquatic organisms by removal of a barrier, indicators of habitat quality, and known presence of downstream species that would be able to take advantage of an extended stream network.

“We used that menu of metrics (about 40 in total) to develop a barrier removal prioritization,” he said. When you know the best one to target first, suddenly those thousands of barriers seem a little less intimidating. 

The Aquatic Barrier Prioritization tool builds upon the first phase of the Northeast Aquatic Connectivity project, completed by Martin in 2011, which focused on assessing and prioritizing dam removal projects in terms of their potential to benefit anadromous species. After Hurricane Sandy brought attention to the risks that outdated and poorly designed road-stream crossings present to both aquatic and human communities, Martin received Department of Interior funding coordinated by the North Atlantic LCC to update the analysis using survey data from the North Atlantic Aquatic Connectivity Collaborative’s (NAACC) regional road-stream crossings database. 

So what combination of metrics makes for a good barrier removal project? It depends on what you hope to accomplish, but the application is designed to serve users with a range of objectives. In addition to visualizing all of the data in the NAACC road-stream crossing survey database, it encompasses a custom analysis tool and a consensus prioritization for anadromous fish for the entire region.

Developed with input from a subcommittee of the NAACC and other partners involved in the Northeast Connectivity study, the consensus result offers a prioritization scheme driven by the presence of anadromous fish species like salmon, and the length of upstream networks that would be made available by removal. Users can filter these results by the degree of barrier severity, stream size, geography, as well as the prioritization’s tiered result to assess a project’s potential ecological value.

“Whether you are proactively looking for potential projects to help restore anadromous fish runs, allocate funding to proposed projects, or provide justification in support of a grant application, the consensus results allow users to leverage the input of expert stakeholders and provide a baseline, screening-level understanding a project’s significance for benefiting anadromous fish," said Martin.

For those who want to dig deeper, the custom analysis tool allows users to develop a prioritization based on their selection of metrics and metric weights. 

Here are the key features: 

Filter to refine your results: Overwhelmed by all of those barriers? Limit your analysis to a subwatershed, town, or county to focus in on the barriers within your reach.

Weigh your options: You can choose from the menu of about 40 metrics and apply relative weights based on relevance to meeting specific conservation goals. So if the length of upstream networks is all you care about, put all of your chips in that metric basket, and the No. 1 barrier identified for removal in your prioritization will be the one that would open up the longest upstream network. Jack pot.

Barriers: Be gone! Click on “Model barrier removal” to select up to ten barriers to “remove” from the landscape, and then run an analysis as if they no longer exist. More than indulging wishful thinking, this feature allows you to assess the impacts of a proposed removal, and to visualize the potential gains of mitigating multiple barriers in succession.

Sum it up: Run summary statistics on your results by your unit of analysis (e.g., watershed or town) in terms of either tier of significance or final rank in the prioritization, to ascertain average barrier priority. 

A map, and more: Upon completion of your analysis, the results will be added to the map, and colored by priority (red = high, blue = low) based on the metrics and weights you selected. But wait, there’s more! The tool will switch from “Prioritization” to “Results” mode, and the interface will be populated with sliders that allow you to explore the attributes of your prioritization. Neat.

Party time? Almost. The map and prioritization tool are intended to be “screening-level” tools to direct users toward “potential” potential fish passage projects worthy of exploration, as a complement to site-specific knowledge about the feasibility of a project.

So after you’ve completed the online analysis, on-site verification is the crucial next step before taking action. But the prioritization offers invaluable guidance for narrowing down your investigation to the barriers that warrant a closer look, and for building a case to support removal projects based on their big-picture conservation value. Whether you are an aquatic ecologist, a concerned citizen, or a river herring, that’s reason to celebrate.