NON-NATIVE INVASVE SPECIES – THE JAPANESE KNOTWEED

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The United Kingdom - as well as almost every other country on the planet - has often suffered from the effects of environmental damage through the proliferation of non-native species. For millennia, mankind has travelled the world, followed quickly by the establishment of trade routes and the movement of valuable animal and plant commodities. Unfortunately these routes have also brought their fair share of problems such as the globalisation of small pox, influenza and the infamous ‘black death’.

Today similar problems exist and while modern medicine had made great strides in the prevention of such epidemics there is still an on-going problem with the deliberate and accidental introduction of non-native plant and animal species into sensitive environments. Recent history has already shown us the terrible destruction that can be reaped through the experiences of Hawaii, Australia and New Zealand.

Invasive non-native plant and animal species are now the second greatest threat to biodiversity worldwide after habitat destruction. This is because they can have a negative impact on native species, as well as for the damage caused to the environment, and as a secondary issue - local economies.

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The Japanese Knotweed in one of the most invasive non-native plant species to have been introduced into this country. With its natural habitat being on the slopes of volcanoes, it is no surprise that the less harsh and more fertile environment of Britain has allowed this plant to flourish to extreme proportions. Furthermore, outside of Asia, the plant has no natural biological enemies to check its spread. In Japan, for example, there are at least 30 species of insect and 6 species of fungi that live off this plant.

It thrives on disturbance. The tiniest piece can re-grow enabling the plant spread across the country by both natural means and human activity. Once established, it can quickly overrun riverbanks, railway embankments, road verges, gardens and hedgerows. This rapid growth and speed of travel makes the Japanese Knotweed a severe threat to the survival of native plant species, insects and therefore other native animal species.

Introduced to Britain between 1825 and 1841 the Japanese knotweed is now recognized as the most invasive and damaging weed in the country, even able to force its way through cracks in walls and pavements. It can grow to 13ft in height and with no natural peats or diseases – combined with a strong resistance to commercial weed killers - it has proved to be almost impossible to control.

Huge sums are being spent in the UK controlling the weed. In 2004, a DEFRA review of non-native species policy stated that a conservative estimate for the costs involved in eradication would be approximately £1.56bn. The aggressive spread of the plant has now resulted in it being listed in the Wildlife and Countryside Act 1981 as a pest species. All parts of the plant are considered as controlled waste under the Waste Regulations.