Invaders and Settlers
Invaders and Settlers
The introduction into Britain of plants and animals from elsewhere in the world has not always been beneficial.
Settlers are introduced species which remain where they are cultivated, whilst invaders spread into the countryside on their own.
Settlers
The natural process of settlers was speeded up by human influence. New crops, trees and domestic animals were all introduced from elsewhere, and with them came (accidentally or otherwise) new weeds and pests.
When Did Common Animals Settle In Britain?
- Sheep came with Neolithic farmers
- Horses arrived in the Bronze Age
- Chickens were brought to Britain during the Iron Age
- Cats were introduced by the Romans to protect their grain stores. (Roman cockspur from 2004 excavation).
- Rabbits, Fallow Deer and the Common Pheasant were brought in by the Normans
When Did Common Trees Settle In Britain?
- Beech trees did not arrive until the Neolithic, and other trees including the Sweet Chestnut, walnut and apple came with the Romans
- Horse chestnut, introduced in the 16th Century, has since become widespread
- Douglas Fir was introduced to Britain in 1827 by the famous plant collector and explorer David Douglas.
Invaders On The Wittenham Clumps
The introductions of new species grew with worldwide trade. Some plants and animals, brought in as curiosities for zoos or botanical gardens, escaped to the wild and became naturalised.
- The grey squirrel and the muntjac deer, both common at Little Wittenham, are examples of species that are invaders.
- Since the introduction of grey squirrels from North America in the late 1800s, they have colonised most of mainland Britain displacing the native red squirrels.
- Squirrels now threaten the regeneration of beech trees in the Wittenham Clumps as they strip the bark off young trees, damaging and even killing them.
- Muntjac deer chew the bark off mature trees in Little Wittenham wood and eat seedlings.
- In recent decades the lily beetle has become established in southern Britain, and in Oxfordshire threatens the attractive snakeshead fritillaries which flower at Iffley Meadow and the Northmoor Trust's Clifton Meadow.
- The lily beetle may have been accidentally introduced with imported lily plants.
| Find out more ... Open University: Invaders CABI: Japanese Knotweed |
