Invading our wallets and rivers

Invasive non-native species can be extremely costly to our economy and Floating Pennywort is a particularly menacing example.

Floating Pennywort was introduced to the Europe as an ornamental plant for ponds. However, the plant is an aggressive competitor. Capable of growing up to 20 cm a day, Floating Pennywort can quickly exclude other aquatic vegetation and smother the water body beneath – depleting the aquatic environment of light and oxygen.  It is easy to see how this invasive aquatic is costly to local environments……

However what are the actual costs of this plant to us?

A report by CABI (CAB International) attempts to quantify the cost of several invasive species for the UK– The Economic Cost of Invasive Non-Native Species on Great Britain.

The section on Floating Pennywort cites some concerning statistics:

• Cost of Floating Pennywort removal is estimated to be between £1800 - £2000 per km
• The Environment Agency spent £510, 260 on the control of just 300 km of Floating Pennywort in 2009!

The most recent estimate for the whole of the UK was a staggering £1.93 million in 2008! But worse still, it is suggested that this figure will have likely increase by seven times in just six years.

As well as the direct cost of controlling and managing this aquatic invader, there are also the costs accumulated in the loss of leisure and recreation use of our waterways.

In 2008, British Inland Waterways Survey stated that 3.4 million adults visited one of their waterways across the 3,540 km network every average two week period. The CABI Report works this out to be 2087 visitors per km per month. Given that 200 km of canal are infested for a two month period – Floating Pennywort is affecting 834, 300 visitors every year! And that is just in the UK alone…..

A price tag for this: £23,537,000!!

And a total price tag for recreation losses and management costs combined:

£25,467,000

This plant is one expensive mistake!

References: 

 F. Williams, R. Eschen, A. Harris, D. Djeddour, C. Pratt, R.S. Shaw, S. Varia, J. Lamontagne-Godwin, S.E. Thomas, S.T. Murphy  (2010). The Economic Costof Invasive Non-Native Species onGreat Britain. CABI

GBNNSS - https://secure.fera.defra.gov.uk/nonnativespecies/home/index.cfm

Stiers,I., Crohain, N., Josens, G and Triest, L (2011). Impact of three aquatic invasive species on native plants and macro-invertebrates in temperate ponds. Biological Invasions 13: 2715 – 2726

 Photo Credits:

Floating Pennywort - CCW

Floating Pennywort - Simon Mortimer