摘要：Based on observations on rivers in England over a 30-year period, it was hypothesised that the extent of woody vegetation in riparian areas has increased in many locations. Methods to map and measure changes in vegetation cover from aerial photographs were developed and tested on a 5 km reach of the River Dane in Northwest England. Riparian vegetation was divided into seven classes, and these were mapped from aerial photographs of four dates, 1984, 1996, 2001 and 2007. The results indicate an increase from 9% woody vegetation cover in the river corridor in 1984 to 32% cover in 2007, with a 40-fold increase in areas of mature woody vegetation. The results have implications for river processes, because of effects on bank erosion and sediment supply, and for land management policies, with grazing control hypothesised to be a major cause of the changes.
