Many dike grasslands were extremely species-rich in the past but changes in management have often led to substantial impoverishment. To investigate the effects of species loss, a multi-year research project was carried out at Wageningen University, under the leadership of Frank Berendse.
An artificial dike was set up with 100 test plots containing different numbers of plant species. During the third year of the experiment, researchers measured the amount of washed-out soil accumulating at the base of the dike every two weeks. They found a reduction of 75 per cent in species numbers was accompanied by a doubling in erosion.
Researchers have suggested that a larger number of species may mean if one species disappears, it is more likely to be replaced by another species with an equivalent effect on erosion resistance.
In addition, aboveground and underground biomasses were found to be greater where the species diversity was richer, and this, too, limited erosion.
Dike safety is determined by many factors, including dimensions and materials used. Nevertheless the results suggest species diversity can also play a significant role in fighting erosion.