Threatened Plants of New Zealand

Threatened Plants of New Zealand by Peter de Lange, Peter Heenan, David Norton, Jeremy Rolfe and John Sawyer. Christchurch, Canterbury University Press. 2010. 472 p. ISBN 978-1-877257-56-8. Price NZ$99.95.

Threats to New Zealand's indigenous biota are arguably the greatest of our many conservation issues and challenges that we currently face. This very attractive and comprehensive book on our nationally threatened vascular plants clearly reinforces the seriousness, the several causes and the urgent need to better address these challenges. The book deals with the plants that have become ‘Extinct’ since human settlement (6) and the 184 deemed to be ‘Nationally Threatened’ through being either Nationally Critical (94), Nationally Endangered (46) or Nationally Vulnerable (44), as defined by the New Zealand Threatened Vascular Plants Panel. It does not included the additional 651 taxa now considered to be ‘At Risk’ (Declining, 83; Recovering, 6; Relict, 20; Naturally Uncommon, 542).

Replacing David Given's two earlier books on threatened plants in the 1980s, this authoritative and lavishly illustrated book should certainly raise the profile of, and increase the concern for, our threatened flora. This book would certainly grace any bookshelf. It is based on the recently published reappraisal of the conservation status of our indigenous vascular plant flora by the New Zealand Vascular Plant Panel (de Lange et al. 2009) which used the latest (2008) version of the threat classification system developed for the Department of Conservation. Not surprisingly, three of the five authors, Peter de Lange of the Department of Conservation, Peter Heenan of Landcare Research and David Norton of the University of Canterbury, were among the eight involved with the earlier publication, while John Sawyer and Jeremy Rolfe, of the Department of Conservation also contributed, with Jeremy providing many of the photographs, together with several others who are named with the photo captions.

The 20-page introduction sets the scene, with sections on the origin of the flora, the nature of rarity, types of threat (habitat loss, predation, competition with invasive plants, reproduction failure, ignorance of and their several interactions), the New Zealand Threat Classification System, the nature of our threatened flora, threatened plant management and future prospects, as well as a guide to using the book. The threat states are defined and each is further categorized on the basis of plant population size and extent, and the current and predicted rates of decline. Sixteen additional qualifiers are also applied, as in the formal Threat Classification System, for example, Conservation dependent, Data poor, One location, Sparse. Under ‘The nature of our threatened flora’ the four plant categories are classified according to 14 ‘life forms’ and 19 ‘major habitats’ (based on the 2009 paper), but these are only listed and not further described in the book. There is a predominance of non-Asteraceae dicot herbs (36%) and dicot shrubs (20%) among the so-called life forms implicated, with cliff (22%) and closed forest (18%) having the highest scores among the 19 major habitats. Under threatened plant management, the issues of specific conservation management are discussed, along with invasive plants, the roles of botanic and other gardens and gene banks, as well as legal protection in relation to six relevant items of legislation. The Native Plants Protection Act of 1934 is realistically considered to be ‘simplistic, outdated and untested, and seems unlikely to provide any real protection.’ I was disappointed, however, given that Australia, Canada and the USA all have legislation which makes it illegal for a native species to become extinct, that comparable legislation was not recommended for this country.

The bulk of the book is taken up with the detailed 2-page treatment of each of the 190 taxa (apart from Lepidium oleraceum which receives twice this allocation to deal with seven informal races or ‘forms’). Plants are arranged alphabetically by their binomial, within each of the four major categories, according to a set format of: scientific name, with authority, family name, conservation status and, where known, common and/or Maori name(s), a formal technical description (with its source reference: any new, modified or updated information is also noted), a user-friendly and very helpful guide to its recognition (in a special box), plus distribution information (including a small dot map), and brief notes on habitat and the threats faced. Up to five good-quality photographs (with source) per taxon usually include a habit shot of the plant, as well as photographs showing useful diagnostic features. Helpful scales are included only in some of Jeremy Rolfe's images. There is a comprehensive glossary and a very helpful index, with separate entries for genera and species, and bold type designating the featured taxon, plus families and common and/or Maori names.

To a plant ecologist who keeps a ‘weather eye’ on the threatened plant situation, both the numbers and patterns revealed in this book are clearly alarming. As expected, there is little difference between the situation described in this book and that in the 2009 formal publication of de Lange et al. (2009) but, when compared with one made just five years earlier (de Lange et al. 2004), the situation looks quite desperate. The total number of Nationally Critical, Endangered and Vulnerable taxa has apparently increased from 122 listed in the 2004 publication to 184 today, and moreover, the most at-risk category (Nationally Critical) has shown the greatest increase, from 47 to 94, over this period. Rather than four in 2004, six taxa are now regarded as extinct with the addition of two forget-me-nots, and some 7.6% of our vascular flora is now regarded as seriously threatened with extinction. The apparent major increases over the last five years clearly represent a seriously worsening trend. However, changes to the criteria defining the various threat categories are largely responsible, as well as some recent taxonomic revisions (the inclusion of synonyms would have been helpful in this context) and improved field information on several taxa.

Having researched the demography of one of the listed taxa (Myosotis cheesemanii: see Dickinson et al. 2007), I was surprised to read that ‘long-term monitoring of one or more populations’ of this species is being called for. I was further surprised to see that another species in our study, M. oreophila, did not qualify even though it seems to fulfil two important criteria: one population presumed extinct and the main extant population occupying less than one hectare. It remains listed only as ‘At Risk: Naturally Uncommon’ in de Lange et al. (2009). Such an assessment is puzzling in an otherwise, seemingly comprehensive book.

The very few errors detected include the frequently confused, but geographically separate, Dunstan Mountains and Dunstan Range in Central Otago, where the latter has been used incorrectly for two entries, Myosotis albosericea (pp. 158–159) and M. cheesemanii (p. 303), and the Eyre Mountains (not Range) in northern Southland for Chaerophyllum basicola (p. 81). Also, the southern limit of Pittosporum obcordatum is stated as Lake Manapouri, but there are some questionable dots shown further south, apart from the Catlins region which clearly is its recorded southern limit (pp. 418–419). Several other maps barely conform with the stated distributions, e.g. Crassula peduncularis (pp. 92–93), while the conventional altitudinal zones (coastal, lowland, montane, subalpine, alpine) are often cited without being defined. These minor criticisms, however, should not detract from this magnificent and very timely publication which clearly fulfils the authors’ stated purpose: ‘to provide a needed and up-to-date treatise of our threatened flora … accessible to people of all ages and knowledge levels … that is technical in its formal plant descriptions and nomenclature, but lavishly illustrated with the best images [obtainable] … and also provide a passive education into the joys of formal botany’. It is hoped that this book will also redress the authors’ stated valid concerns for the public's perception of plant conservation and government support for the Conservation Department's important Threatened Plants programme, which still languishes behind that for most of our threatened vertebrate fauna.

ALAN F. MARK

Emeritus Professor,

University of Otago