NTU Undergraduates' research April 2014 - Biosciences | Page 105

Abstract
Alien invaders: Three of a kind?
Samuel David James Cutler
Invasion is as old as evolution of life, from the invasion of the seas, to that of land, to the air,
and more recently as a result of human activity. Biological invasions are second only to loss
of habitat and land fragmentation in terms of how damaging and threatening they are to
global biodiversity. With the globalisation of trade, the risk of invasive species entering
many ecosystems is rising. Therefore, the study of invasive species and their management
and control is extremely critical.
Himalayan balsam (Impatiens glandulifera) was introduced in 1839 as an ornamental plant.
It is now found across the entirety of the UK, having spread along watercourses. This species
can replace native flora on invaded sites and suppress woodland regeneration after
disturbances. Management of I. glandulifera is of high cost and limited effectiveness. The
signal crayfish (P. leniusculus) was introduced in 1976 and is now distributed over large parts
of the UK. The greatest impact of this is on Britain’s native crayfish, A. pallipes, which has
experienced massive declines. Like I. glandulifera, management is of limited effectiveness.
Ash dieback (Hymenoscyphus pseudoalbidus) was found in the UK in late 2012, having been
present in the EU since the early 1990’s. It spreads quickly, killing all ash trees that are
infected. It has the potential to cause great environmental, economic and societal damage
to the UK. A management plan is in place with clear objectives to control the very current
issue. When invasive species are allowed to invade, their spread can often be overwhelming.
Control of invasive species after extensive spread is difficult with most management
techniques being inefficient and costly. In the case of ash dieback, everything possible must
be done to control the threat while it is still affordable and potentially attainable. For future
control, prevention may be superior to eradication and therefore, faster and more efficient
frameworks should be established to react to other potential threats.