by Don Flora (a real scientist)
Do wider buffers work better? Maybe, if they promote greater percolation of stormwater into the ground. But do we want tainted storm water assaulting aquifers? And if not tainted, do we care about water-quality buffering in the first place?
It’s well known that diminishing returns arrive with wider buffers: Each ten-percent increase in buffer width produces a smaller and smaller percentage increase in protection.(1)
Largely unknown outside the research community is the low overall correlation between protection and buffer widths. An EPA review of 46 studies showed that only 14 percent of the variation in protection could be explained by buffer widths.(2) In an analysis of 29 studies I found only 11 percent explained for phosphorus and 10 percent for nitrogen. These figures mean that 85-90 percent of the variation found among buffers’ pollutant protection is related to factors other than buffer width.
I also found that there is no significant upward trend in protection with wider buffers.(3) Remarkably, a 100-foot buffer is not significantly more protective than a 15-foot buffer.
Together these findings indicate that wide buffering is probably not a solution to stormwater-borne stream, wetland and tidewater problems. Wide buffering will be disappointing at best and terribly costly in terms of land-use options foregone.(4) It appears that protection will lie mainly in stopping pollutants at their sources.
What about wildlife-habitat buffers? Should tidewater buffers be widened for the greater welfare of wildlife? What if wildlife-oriented buffers didn’t appear in our updated Shoreline Master Program? Some comments next month.
(1) For instance see Brooks, Kenneth M. 2007. Supplemental best available science supporting recommendations for buffer widths in Jefferson County, Washington. Port Townsend: Aquatic Environmental Sciences. P. 36.
(2) Mayer, Paul M., et al. 2005. Riparian buffer width, vegetative cover, and nitrogen removal effectiveness: A review of current science and regulations. Cincinnati, Ohio: US Environmental Protection Agency, National Risk Management Research Laboratory. P. 9.
(3) Flora, Don. Regression analyses of buffer-performance data arrayed in Desbonnet, Alan, et al. 1994. Vegetated buffers in the coastal zone – a summary review and bibliography. Coastal Resources Center Technical Report 2064. Narragansett, RI: University of Rhode Island, Rhode Island Sea Grant. Table 4.
(4) Pizzimenti, John J. 2005. Efficacy and economics of riparian buffers on agriculture lands – State of Washington. Englewood, CO: GEI Consultants.