How did fixed-width buffers become standard practice for protecting freshwaters and their riparian areas from forest harvest practices?

Riparian buffers provide improved protection for water quality and biota, and narrow, fixed-width buffers of native vegetation along streams have been used to mitigate the effects of forest harvest at least since the 1960s. The practice of leaving unmanaged strips of vegetation along water courses in agricultural lands had been used before the 1960s in southern Europe and in eastern North America, but the scientific basis for leaving riparian buffers on forested lands came from observations in the coastal temperate rainforests of western North America. Those observations often were applied to other forested landscapes without further considerations. Fixed-width buffers are administratively simple to implement and assess, and have come to be the norm for streamside protection from forestry. Most guidelines for streamside protection allow some local modification for site and watershed-scale considerations, but frequently, the option to deviate from fixed-width buffers is not exercised because of uncertainty about outcomes. Few experiments have been done to test the efficacy of buffers of a particular width or of site- or landscape-specific modifications.