Bracken invasion in Scotland

Summary For the first time, estimates of the amount of sparse bracken on open land, the amounts of bracken under tree cover and the amounts in linear features are made. These data were used to predict the areas of Scotland most at risk from invasion from patch edges, from sparse patches becoming dense and from invasion along linear features. Computer models show that if the climate warms over the next 50 yr as predicted, then bracken growth will increase and the amount of hill land suitable for invasion by bracken will increase. On some sites where bracken is being controlled, it is reduced in cover and other ground vegetation is becoming established. However, we cannot ensure that when bracken is controlled that the control is always effective and that appropriate vegetation will become established. Some generalized rules have been derived to help in the selection of sites likely to show the most benefit from control treatment.