By KEVIN PROFT/ecoRI News staff
Until recently, conservationists generally believed that the best way to protect a species from extinction was to preserve a chunk of its habitat, then let it thrive and reproduce in that area undisturbed. Conservationists now realize that such a system of isolated preserves is only one piece of the puzzle. Just as important to the survival of many species is the interconnectedness of different preserves.
From India to Indonesia, conservationists are frantically attempting to protect wildlife corridors, undeveloped strips of land that connect preserves, so that tigers can move freely from one region to another without conflict. The goal is to maintain genetic diversity by preventing populations from becoming isolated. Often, when a population becomes isolated, it tends to decline in number or die out completely. Similar efforts are under way from Mexico to the Amazon in an effort to save the jaguar.
While these two examples focus on habitat conservation for large land mammals with expansive ranges, the same principals also hold true on a much smaller scale.
The Rhode Island River and Stream Continuity Project, a partnership between the USDA’s Natural Resources Conservation Service, the Rhode Island Resource Conservation and Development Council, Trout Unlimited, the Wood-Pawcatuck Watershed Association and the University of Massachusetts Department of Natural Resources Conservation, is working to preserve stream ecosystems and to remediate ecosystems that have already been disrupted.
Streams act as important habitat for Rhode Island native species such as brook trout, turtles, crayfish and salamanders. While the entire range of a brook trout is often a network of streams only a few miles long, it is just as vulnerable to fragmentation as a tiger. One poorly designed road or dam can divide an entire stream habitat. Such a division can result in isolated populations, which often means genetic defects within those populations or localized extinction.
Rhode Island has about 600 dams and, according to the Natural Resources Conservation Service, more than 4,300 road and railroad crossings affecting its streams. The top priority of the Rhode Island River and Stream Continuity Project is to inventory the vast majority of these crossings to determine where restoration projects are feasible and which of those projects will yield the longest stretches of restored waterway.
The partnership, with the help of countless volunteers, has succeeded in inventorying the watersheds in southwest Rhode Island and is currently working to complete its inventory of the state’s northern stream systems.
In most cases, when a road crosses a stream the water passes from one side to the other through a pipe called a culvert. As Kathryn Zuromski, programs associate at Rhode Island Resource Conservation and Development Council, said, “culverts are installed with water in mind, not fish.” Culverts can act as barriers to fish for any number of reasons. Some culverts are simply blocked by debris such as branches and/or trash, and others are designed so that the pipe’s exit is many feet above stream level. Both of these scenarios stop fish from passing under a road; the former scenario is inexpensive to fix, while the latter would require money to redesign and reconstruct the stream/road intersection.
Even culverts that pass water freely and don’t require fish to leap acrobatically upon entry can be troublesome. Narrow culverts encourage swift flow that prohibits weaker swimming fish species from moving upstream. Culverts without pebbly and reedy shorelines stop turtles and other creatures from passing and often result in animals being struck by cars on the road above the culvert.
The best way to avoid disturbing a stream ecosystem when building a road is to use a bridge. An optimal bridge doesn’t change the flow of the stream and provides ample space on either side of the stream for semi-aquatic animals to pass freely. If a culvert must be used, the most effective kinds are wide at the base and maintain the natural streambed.
Based on the stream crossing data it has collected, the Rhode Island River and Stream Continuity Project is beginning to take more concrete action. One example is the volunteer-driven stream remediation of Breakheart Brook in Arcadia Park. At that site, an 18-inch manmade drop in the stream was stopping fish from moving into their upstream habitat. Volunteers redirected the flow of the brook into a stream-like channel that they built for the fish by strategically arranging large rocks within the flowing water.
While many remediation sites have been identified, not all remediation efforts can be completed by a daylong volunteer effort such as the one at Breakheart Brook. Most require funding, and grants are highly competitive and usually are only available for stream crossings on private land. Public stream crossings are the most plentiful and the hardest to obtain funding for.
An additional way the Rhode Island River and Stream Continuity Project intends to improve stream habitat is by developing river and stream crossing standards. Once finalized, these standards will encourage road builders to make new stream crossings and crossings in need of repair or restoration more environmentally friendly. Standards from Massachusetts will likely be used as a model for Rhode Island’s standards, but will be modified based on the input of various individuals and groups, from biologists, policy experts, and engineers to the state Department of Environmental Management and the Department of Transportation. Ideally a draft of the standards will be complete by this winter.