In recent years xenophobia has extended to include the whole of life with many countries now employing strict controls on the importation of non native species, both plants and animals.

We are constantly bombarded with stories of killer aliens threatening our native fauna and flora. Similarly we are given the impression that this is a new phenomena, a consequence of our highly mobile society and the growth in international trade and that without us carrying these hitchhikers accidentally or deliberately then they would not migrate and the world would be a better place……..

Historical examples of this include the prickly pear and cane toad introductions to Australia, the American grey squirrel into the UK or the American root aphid into the vineyards of Europe… the list is quite endless and it always has a strong bias towards the malignant…

One recent example is this item from the BBC.. news.bbc.co.uk/1/hi/scotl...7254397.stm

And in the Garden Japanese knot weed, an invasive and all but impossible to kill bush has spread out to invade the countryside and wreak havoc on walls and foundations..

But what about the successes? What about the introductions we have benefited from? Like the little known introduction of trout to the Himalayas by the Colonial British. The immediate assumption is that this would have impacted greatly on the river life and it likely has but in many cases there is a surplus of food… in many lakes the trout are so well fed that not only do they grow to great size (8/9 lb) but they need to be ‘annoyed’ into striking if one wants to catch them. Similarly food is scarce in these regions particularly during the winter months and the trout provide a valuable addition to the local diet. It could be argued to that mosquito larvae are likely controlled to some extent where trout are present… Other colonial introductions include the house sparrow to Argentina, the story goes that the wife of a colonial Brit missed them and so a had a couple of pairs introduced… the house sparrow has become one of the great ornithological victims of modern Britain with numbers having declined in recent years by as much as 65% (news.bbc.co.uk/1/hi/sci/t...686136.stm) .. its possible that if the trend continued that the Argentinean introduction could contribute to saving the native population… but there are actually far more notable introductions..

In the 15/1600’s carrots and onions came to Europe from Asia and later the introduction of the humble turnip revolutionized agriculture.. for the first time in our history we had the means to feed cattle over winter and so ended the St Michael mass slaughter.. this also heralded the switch from Ley to rotational farming.

Later we saw the introduction of potato, tomato and maize from the Americas and in the other direction went wheat, originally from the Middle East and rice from Asia… add to this apples, oranges, banana’s and grapes and we begin to see that without introductions we would still be eating coarse kales and parsnips…

Similarly do these invaders really need us? Many are very adapt at hitching rides with long distant migrants and some, like the monarch, painted lady and red admiral butterflies make highly impressive journeys…

Trade winds too must contribute.. in UK peat bogs pollen analysis of early post glacial ( 5-8000 BP) samples often reveals an abundance of pollen originating from the America’s and its therefore not beyond the possibilities that fungal diseases such as Phytophora infestans (potato blight), the cause of the potato famine got to Europe under its own steam..

Is migration not part of the evolutionary story? One that without which we would be the poorer ?

Similarly given the likely changes to environments as a consequence of climate change is not our ability to assist in migration, thus potentially saving diversity, not an asset….

I would aver that too much emphasis is put on the minority of bad introductions, particularly with respect to Island ecology, and that this is not a balanced view against the successful introductions upon which we all depend. This biased view similarly limits consideration of the potential that introductions into new environments could have in preserving bio-diversity or in mediating climate change.

Any thoughts?

Regards

Gm23