Alien species can cause havoc for native ecosystems. Maddie Moate explains how some of the most invasive species have effected parts of the world. Subscribe to Earth Unplugged for more amazing animal videos – http://bit.ly/SubscribeToEarthUnplugged
From grey squirrels in the UK to red foxes in Australia, humans have actively or passively aided opportunistic species to move around the globe, and in many cases cause havoc to local ecosystems.