Delta Life 9

Deltares, MARCH 2018 19 10 9 8 6 7 5 Willows and poplars survive the winter; the Japanese Knotweed dies off, leaving soil vulnerable to erosion. Riverbanks can crumble as a result. In waterways and flood plains, the Japanese Knotweed creates problems because it grows muchmore densely than plants such as willows and poplars, making floodingmore likely in summer and autumn, the growing season. Climate change helps exotics to spread even faster. The rapid changes in temperatures and rainfall causes the local loss of some plant species, while other areas actually become more appealing for non-native plants. More information: mijke.vanoorschot@deltares.nl A national management plan is required to control invasive plant species. In the Netherlands, Deltares is using computer models, monitoring and field trials to investigate the effect of the intruders on local vegetation, water levels and the stability of riverbanks. Researchers can use these data to es- tablish a picture of the long-termconsequences of invasive exotics and to determine the effectiveness of different measures, making it possible to advise management authorities better. Aweed in Europe is actually valued in Japan: the young shoots of the Knotweed are eaten as a snack and as amedicine. It has a rhubard-like taste and it is becoming increasingly popular in the Netherlands for use in salads, muffins and pies. Tip: to stop it taking over your garden, don't throw any remnants onto the compost heap. The Himalayan balsamand the Japanese Knotweed are two of the strongest invasive plants found on the riverbanks of northern Europe. The willow, a native European, is an intruder in New Zealand. Although they are used to stabilise riverbanks, large numbers of willows slow down small rivers and exacerbate the risk of flooding.