Alien Species

An invasive/alien species is an introduced, non-native species present in an ecosystem.Intentional introduction - where a species is brought in on purpose e.g. cane toadAccidental introduction - where a species is brought in by accident e.g. rats/spiders travelling in with food importsSuccess of alien species:Alien species are successful in their new environments because; they have enhanced survival rates because they are more efficient competitors than native species as an alien species they lack and native predator they are not susceptible to indigenous diseases

Japanese Knotweed: Introduced to Britain in the 19th century as an ornamental plant Grows up to 1 meter in 4 weeks (3cm a day) pushing through concrete and tarmac Can lie dormant underground for up to 20 years and a root can spread up to 7 meters No natural predator and threatens plants and animals Can ruin house prices - value can half In 2003 the cost of eradicating it was £1.5 billion, in 2009 it was £3 billion Have to use industrial strength herbicides and weed killers Mitten Crabs: 1 of the worlds top 100 invasive species Accidental introduction - came from eastern Asia and Europe to north England They caused damage to fishing gear and competed with native species Destroyed local freshwater species, burrowing nature of crabs damages embankments Management is difficult due to abundance Cane Toads: Introduced to Australia to eat cane grubs and beetles that were damaging crops Females lay 40,000 eggs, a large number of which survive They ate everything except the grubs and beetles Difficult to get rid of because they are poisonous Have to deny them access to water. Many people run them over in their cars