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Invasive plants and forest ecosystems.
RK Kohli, S Jose, HP Singh, DR Batish. eds. 2008.
Boca Raton, FL: CRC Press. $129.95 (hardback). 456 pp.
This volume has its origins in papers given at a technical session of the IUFRO in Brisbane in 2005, but unfortunately falls between a conference proceedings and a commissioned book. If it were a conference proceedings I would expect an abstract for each paper, if a book I would not expect to see basically the same introduction on the dangers of invasive alien plants and how much Pimental says they cost in chapter after chapter. If indeed it were edited I would have expected more of a consensus on the terminology used to describe these plants, which are variously described as IAS (invasive alien species), NNIPs (non-native invasive plants), WONs (weeds of national significance), invasive pests, non-natives, invasive plant species and exotics. Which only goes to show why there has been much discussion in the European literature of the need for the use of standard terms.
In Europe the subject of invasive alien plants has been well-catered for by the regular publication of the EMAPI and Neobiota meeting proceedings, neither of which have a strong element on forest ecosystems. Whilst this volume certainly gives a non-European perspective, anyone hoping for a comprehensive geographical review of the role of alien invasive plants in forest ecosystems is going to be somewhat disappointed. In spite of its broad title, this is basically North American with contributions from Africa, Australia, Bangladesh, China, Europe and India. Whilst the Chinese contribution may have been highly relevant to the conference at which it was originally given, it sits very uncomfortably here, since much of it is concerned with invertebrate threats to crop plants. Similarly one may query the inclusion of the previously published review on cogongrass; an excellent paper but of only tangential relevance to a volume of this title. Also for a book of this price the black and white photographs are very poorly reproduced. That said, there are plenty of excellent contributions highly relevant to forest ecosystems.
The book is divided into four sections: invasion ecology, ecological impacts, management of invasive plants, and socioeconomic and policy aspects – the latter confined to two chapters. After some introductory chapters on invasions and invasion theory there are good, solid contributions on ground-cover plants, invasive exotic trees, resilience to invasion and the use if GIS to chart the extent of invasions. The next section also has useful contributions on invasions in Asia, Europe, America and Australia. The latter well illustrates some of the dilemmas and unpredictable consequences of invasive plants. In the absence of native shrubs, the alien invasive Lantana has become a key species for endemic animals and birds. In addition, the Bell Miner birds nesting in the Lantana understorey in eucalypt forests drive out bird species that normally predate the psyllids, allowing uncontrolled population growth resulting in the die-back of the eucalyptus crowns. Useful contributions on management of invasive plants follow, rounded up by thought-provoking pieces on the position in Namibia and the USA.
However, few authors imagine these invasions to be reversible and unless adequate resources are channelled into the problem we are left to face, in the prophetic words of Charles Elton (1958) ‘ … one world with the remaining wild species dispersed up to the limits set by their genetic characteristics, not to narrower limits set by mechanical barriers … ’.