ECOS 40(5): Book Review: Invasive Aliens

The plants and animals from over there that are over here

Dan Eatherley

William Collins, 2019
Pbk £16.99  ISBN 978-0-00-826274-7

Review by Peter Shirley

“That seems to have been a mistake” says the author with regard to the UK removing the necessity for raccoon keepers to have a licence in 2007. Not much evidence is provided as to how much of a mistake it was, just a government official quoted as saying about raccoons in the wild “the northeast got a lot of sightings”. Even so, the same could be said for much else covered in this fascinating book, which looks at the ways in which the spread of plants and animals around the world has been facilitated particularly by human activities. Cue my routine complaint about the use of ‘invasive aliens’ to describe and emphasise the more problematic of the species involved. It is a distinctly unhelpful phrase in reaching a common understanding in today’s world. When will someone entitle such a book ‘Successful Exotics’?

Eatherley casts his eye over a wide range of species in both space and time. He starts many thousands of years ago with the arrival here of one of the most successful of those species, Homo sapiens, before moving through recorded history, linking the movement of plants, animals and microbes, to human developments such as agriculture, empire-building, commerce, and scientific and cultural activities. The last named has been especially significant over the past 300 years, with animal and plant hunters and collectors bringing many species to this country for zoos and gardens. At the same time settlers moving to newly discovered parts of the world took familiar and useful species the other way.

The book is pretty even-handed in assessing the ecological and economic impacts of these movements, although there is some of the usual ‘such and such a species costs so many millions a year to control’. Such statements are usually taken at face value, but the statistical analyses behind them often lack rigour and robustness. It is bang up to date with regard to bluebells in this country, pointing out that the latest indications are that Spanish bluebells, and the hybrid between them and the native species, are not, as once feared, invading woodlands to the detriment of the natives. On the other hand, purple loosestrife’s bad reputation in the USA is perpetuated; it is described as “… (smothering) thousands of hectares of temporal and boreal wetlands….”. This may be true visually, but recent research has suggested that it is doing relatively little ecological harm.

There is a classic reference to what our wonderfully inconsistent attitudes to non-natives. The fact that white-clawed crayfish are not native to Britain is discussed, and a correspondent is quoted as saying “Yes, it could be introduced, but do we have a responsibility to assist in the protection of a species endangered to Europe?”.  Related to this is the account given of the role of Woburn’s Père David’s deer herd in the conservation of the species in its homeland in China.

There is much detailed information as to the context, the how, and the why, species have been spread around, intentionally or not. Fur farms for instance are given a whole chapter to themselves. There is plenty of information about some of the specific individuals responsible and the dates of introductions. For example, in the late 1300s a Dominican friar and herbalist, Henry Daniel, had 100 non-native herbs in his garden in Stepney. Nearer our own time successive Dukes of Bedford have introduced all manner of things to their estate in Woburn. The list includes grey squirrels, but especially deer (muntjac released into the wild in 1901, Chinese water deer and the aforementioned Père David’s deer), as well as fish such as zander in 1878 and wels in 1880.

The pleasure of books like this is often the snippets of new information you may glean from them. Reading this one I learned about the potential but, as yet, not much manifested depredations of the New Zealand mud snail in Britain. I also discovered that the black rat may not have been responsible for spreading the Black Death in the fourteenth century. There is a theory now that it was spread directly by human lice and fleas. Maybe the rat has been falsely maligned.

There may be one area of confusion in the book. There is a reference to the fact that in the Western Cape “… almost 9,000 types of non-native tree, shrub and flowering plant grow wild, of which 161 are classed ‘invasive’’. My information is that the Cape Floral Region, the smallest in the world, is home to about 9,000 plant species in total, of which about 70% are endemic.

Other chapters include the marine and freshwater environments, the fraught processes of biological control (which have indirectly brought the harlequin ladybird to this country), the hitch-hikers and, the final chapter, thoughts about the future.

That final chapter reviews the positive and negative aspects of introduced species. The bias against them for no particular reason is aptly summarised thus: “Many people are instinctively vexed by nature in the ‘wrong place’….”. Also though, the positive benefits of introduced species, including to the natural world, are outlined. We are rightly counselled to understand that what is happening is “… normal, if not invigorating for ecosystems” and to have patience whilst nature adapts. For me, the message is that we must become used to living with the nature we have and which we will continue to shape.  Whatever the mistakes might have been, I leave the last word to Eatherley: “… humans continue to benefit from the cornucopia of deliberate introductions”.


Shirley, Peter “ECOS 40(5): Book Review: Invasive Aliens” ECOS vol. 40(5) 2019, British Association of Nature Conservationists,

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