Have you ever considered how often you cross over moving water in the course of a day? In the Northeast alone, there are an estimated 210,000 bridges, culverts, and dams spanning 280,000 miles of river. That’s an average of one every 1.3 miles.
Although these structures play critical roles in our daily lives — many dams provide low-carbon energy, flood production, and stable water supplies, and culverts channel water under roads so that vehicles can pass above safely — most drivers never give them a second thought, or a first thought for that matter.
That included me until I opened a new web application developed by The Nature Conservancy. Now I know that in my 18-mile commute to work, I drive over 11 culverts. Slightly below average, but hardly disappointing.
As the name suggests, the Northeast Aquatic Connectivity project’s new Aquatic Barrier Prioritization application is more than just a map of road-stream crossings. It is a decision-support tool designed to help address the impacts that poorly designed or outdated structures have on aquatic ecosystems. Because what we consider to be stream “crossings” often amount to stream “barriers” for fish, turtles, and other organisms that move through rivers and streams.
Just imagine the reverse scenario: If humans had a transportation network that was periodically interrupted by flowing water in spots where aquatic organisms had decided to route a stream overtop, with no consideration to how it would affect human traffic patterns. Since it would be impossible to drive through moving water — at least, in my Jetta — well-intentioned aquatic organisms would construct tunnels to allow us to pass beneath streams, or ladders for us to climb over them. But over time, tunnels would collapse, ladders would fall down, and we would increasingly find ourselves at unexpected dead ends.
For me, it would mean a much longer commute. But for fish and wildlife, it’s an even bigger problem. The ability to move up and downstream is not just about getting from point A to B. It’s about accessing food, breeding grounds, and shelter. It’s about survival.
“Even if they are not what we have historically considered migratory species, all fish need to be able to move freely within a given stream,” said Phil Herzig, a fisheries biologist with the U.S. Fish and Wildlife Service. “Entire populations can be segmented through barriers such as road crossings or dams.”
What’s more, he said, “When we get heavy rains and flooding, culverts and road crossings can get completely washed out, and that directly affects human safety and health too.”
In other words, structures that are intended to keep us safe can end up putting us in danger if they are not designed properly. Tropical Storm Irene and Hurricane Sandy made this unseen threat a reality in 2011 and 2013, leaving in their wake communities devastated by flooding and erosion. These storms also brought attention to the potential for changing precipitation patterns from climate change to make matters worse for both people and wildlife.
There’s a bright side: Out of this devastation came a commitment to make natural and human communities more resilient to these kinds of threats.
After Hurricane Sandy, spatial ecologist Erik Martin of the TNC’s Eastern Division received a grant to build upon the first phase of the Northeast Aquatic Connectivity project, which he completed in 2011 focusing on assessing and prioritizing dam removal projects in terms of their potential to benefit anadromous species. With Department of Interior funding coordinated by the North Atlantic Landscape Conservation Cooperative, Martin updated his analysis using survey data from the North Atlantic Aquatic Connectivity Collaborative’s (NAACC) regional road-stream crossings database.
The result is the Aquatic Barrier Prioritization, designed to provide a customizable screening-level tool to help people on the front lines of fish passage, like Herzig, figure out which barriers to target first to meet their organization’s conservation objectives, whether they relate to brook trout, salmon, or river herring.
“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 remediating that barrier,” explained Martin.
Those 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.
As Herzig pointed out, what’s good for fish is good for people too. “There is evidence that properly sized wildlife crossing is less likely to be blown out during a storm.”
It’s also good for the bottom line. “There is never enough money to do the conservation we need to do, so having the ability to look at data in different ways, either by species or structure, in order to set priorities is a huge help,” said Herzig. “I think this tool will help us get away from low-hanging fruit, and instead be more strategic in our planning and execution.”
All of the dams and road-stream crossings in the Aquatic Barrier Prioritization tool are assigned a tier of significance and passibility rating, so I can see just how much of a barrier each of the 11 culverts along my commute represents. One is considered insignificant, eight are minor, and one is moderate. Whether or not that last one represents a high priority for fish biologists, it will give me reason to consider taking an alternate route home on rainy days, and remind me that I’m fortunate to have that option.