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Riparian Buffers - Arteries of Biodiversity in the West

We learn about the role riparian areas play in supporting biodiversity.

By Amy Nelson

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In the semi-arid west, streams and their adjacent riparian areas wind their way down from the mountains and across the plains as “thin green lines” through the otherwise tan and brown prairie. Although riparian areas make up a fraction of the vast western U.S. landscape (less than 1% or 2% depending on the source), they play a disproportionately large role in supporting biodiversity. For example, some reports suggest up to 80% of vertebrate species rely on these areas for part of their life span. Riparian areas are also instrumental in supporting an area’s hydrology, water quality protection, and aquatic ecosystem food chain. The protection and management of these areas, however, lags behind, belying their ecological significance.

Riparian areas are magnets for human activity of all types, in particular recreational use along greenway trails that parallel the streams. Meanwhile, communities across Colorado, as elsewhere in the country, are wrestling with how to protect river corridors and the quality of life they bring, in the absence of adequate regulatory programs, plans, funding, or enforcement. As a result, a patchwork of local efforts has emerged to try to protect and enhance the riparian landscape. Mechanisms to achieve protection include land acquisition, education, stormwater best management practices, restoration, planning, and regulation and zoning. Among the many ideas, the establishment of protected buffers is a central approach that is gaining ground.

Recommended buffer widths and specific mechanisms for protection vary widely, but in general, the wider the buffer the more ecological functions are maintained. The City of Fort Collins has fixed width buffer zones based on the stream or size of wetland (50-300 ft) in which no development is allowed to occur. Much of the Cache la Poudre river corridor has been acquired by the city and is managed as natural areas providing additional opportunities for cohesive long-term management.

In the City of Boulder, where about a dozen drainages bisect the city from west to east, infill developments near the creeks and a burgeoning community of outdoor enthusiasts are literally bumping up to the edge of the waterways. As a result, the City has implemented overlay regulations that include a multi-zone buffer approach in their ordinance for Streams, Wetlands, and Water Body Protection. Rather than prohibit all activities in a single zone, the ordinance “encourages avoidance and minimization of regulated activities” within the different regulated areas. Various levels of permit review are required depending on the proposed activity, with minor activities and pre-existing activity exemptions. In preparing for the recent update to the ordinance, City of Boulder staff compiled a summary (with assistance from Biohabitats) entitled “Wetland and Stream Buffers : A Review of the Science and Regulatory Approaches to Protection” which is a compendium describing the functions of buffers as well as regulatory examples of the approaches used by dozens of other communities to protect these valuable resources.

Buffers are only the beginning, however, of protecting biodiversity along stream corridors in the Southern Mountain Bioregion. Ongoing stewardship of riparian areas requires management of invasive species, restoration of impaired areas, stormwater quality improvements throughout the watershed, and management of human activities and pets. Revegetation projects, in particular, provide an opportunity to reestablish sufficient structure and species composition. However, bird studies in Front Range communities suggest that the “if you build it they will come” habitat approach will not necessarily work if heavy trail use then occurs nearby. Establishing a range of intensities for human uses with at least some areas designated for conservation (and excluding human activity) has been suggested as one technique to ensure a variety of protected habitat types.

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