Life

Lady killers

Invasion of alien species to Ireland is on the increase with nearly four times more seen in the wild in the last century.

Help is needed to combat their threat to our biodiversity, economy and health, writes Valerie Robinson

W e all have 'what if' moments but in nature a single act can have devastating and costly consequences - particularly when an invasive species threatens native plants and animals.

It is estimated that over the past two decades, it has cost E 12 billion annually to deal with the 12,000-odd invasive species that are thought to live within the european Union's boundaries.

Figures for Ireland are just as startling, with the annual bill in the Republic believed to reach £160 million while the cost to northern Ireland's economy is thought to be £46m.

Imagine if, during the 1700s, whoever introduced the rhododendron into Ireland had seen past its abundant flowers to the damage it would inflict on natural plants and trees by its sheer size.

Similarly, the arrival of the north american grey squirrel to Castle Forbes in Co longford in 1911, when it was considered a decorative addition to the native fauna, took no account of the harm it would do, not just to our home-grown red squirrels, but also to oak trees. And of course there's Japanese knotweed, brought here as an ornamental garden plant in the 19th century, but so devastatingly prolific that it's now illegal to plant it or dump it in Ireland.

The national Invasive Species database provides up-to-date centralised information on the distribution of invasive species throughout the island of Ireland. Its database currently holds 34,800 records on 103 species. And there's also monumental work being done on the ground - often by volunteers. The group Groundwork, set up in 1981 to works towards the preservation of some of Ireland's most precious habitats, works tirelessly on the removal of rhododendron from killarney national Park, Co kerry and Glenveagh national Park, Co donegal. And the Irish Wildlife Trust (IWT) has just launched a new Ireland-wide survey aimed at mapping the distribution of ladybirds on the island but also to monitor the spread of the Harlequin ladybird Harmonia axaridis.

Originally from asia, the Harlequin was introduced to north america from asia in 1988 as a biological control agent because it eats more pest insects than any other ladybirds. However, they also eat non-pest and beneficial insects, including the larvae of other ladybirds and the eggs and larva of butterflies and moths. It is now seen as a serious insect pest.

The species first arrived in the UK in the summer of 2004 and is now found throughout England. It reached Co down in 2009 and was first reported in counties Cork and Wicklow in 2010 and Carlow in 2011. "The Harlequin causes problems in the natural environment in that it has a wide dietary range, outcompeting native ladybirds for their main prey of aphids and even consuming other ladybird species eggs and larvae. They can reproduce up to three generations per year whilst most other native ladybird species will only reproduce once. They are a serious threat to our native species and it is important that we monitor their arrival and impact,'' IWT says.

You are encouraged to visit www.iwt.ie for information on ladybirds and the survey and to submit your sighting via the www.

biology.ie website or by emailing info@ biology.ie.

* For more information on other invasive species see www.invasivespeciesireland.com.

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