Invasive species can become a serious threat to native wildlife. The Trust recognises this threat and has a number of projects aimed at controlling invasive species. On several properties, from Brodick Country Park to Torridon to Inverewe, we are actively controlling the spread of Rhododendron ponticum, which is threatening to swamp many areas, including native woodland and archaeological sites. On Canna, we are putting together proposals to return the seabird populations to their former nationally important numbers through the control of the introduced brown rat population on the island. This work will also involve measures to benefit the distinctive island strain of the field mouse. Should they ever become established there, rats would pose a threat to our most important seabird colony – on St Kilda - and we have put measures in place to ensure that they do not reach the archipelago. We also support the control of mink and, through sensitive woodland design, we are trying to limit the spread of grey squirrels into red squirrel areas on many of our properties.