What are invasive non-native species?

There are many non-native species in Great Britain, but only a small proportion are invasive.
Warning sign that says "rhododendron control" on a fence in the countryside
When the Ice Age ended over 10,000 years ago the ice that covered most of Britain retreated northwards.  Following behind this retreating ice were waves of plants and animals that slowly colonised Britain as conditions warmed up.   These plants and animals got to Britain under their own steam as there was still a connection (the land bridge) attaching us to the European mainland. 

However, as the ice melted sea levels rose and the connection was flooded.  This effectively stopped any more colonisation by species that couldn’t cross the water.  All these plants and animals – the ones that established themselves in Britain naturally - are called native species.

Some species (like elk and lemmings) died out naturally as the climate continued to warm up other species such as wolves and beavers were eradicated by man only relatively recently – in the last few hundred years.

People first arrived in Britain about 8,000 years ago and virtually all new land animals and plants that have become established since this date have been brought here by people.  These are all non-native species

However, we must not think that all non-native species are bad – indeed it is only a minority that have serious negative impacts on our native British species, our health or our economy.  These species we call invasive non-native species.

Thin strip of image show tree trunk and bark