Plant Conservation: A Natural History Approach. Gary A. Krupnick and W. John Kress, eds. University of Chicago Press, Chicago, 2005. 344 pp., illus. $75.00 (ISBN 0226455122 cloth).
What is the role of natural history in contemporary conservation science? With the increasing focus on mechanisms of extinction, experimental adaptive management, and restoration, today's students of conservation may be forgiven for not considering the question. Yet that is precisely what we are forced to ponder when reading Plant Conservation: A Natural History Approach, edited by Gary Krupnick and W. John Kress (Department of Botany, National Museum of Natural History, Smithsonian Institution). The book, to which some 48 authors contributed, attempts to address this broad issue and advocate for its importance by exploring the state of our understanding of biological diversity, drawing on the expertise and botanical resources available in herbaria, museums, and botanical gardens.
The theme of natural history reflects the premise that conservation is a truly global concern, and protecting biological diversity or the evolutionary processes on which it depends cannot advance with more models and experimental investigations if we cannot comprehend the magnitude, dynamics, and history of biological diversity itself. The strength of herbaria, museums, and botanical gardens in this regard rests on their collections (living and preserved) of diversity, their skills in interpreting evolutionary history, and their sources of plant material for restoration programs. As this book attests, these institutions are making significant contributions toward reversing the deficit of natural history information. In the foreword, tropical biologist Dan Janzen provides a compelling justification for natural history as an instrument for conservation, and promotes the role of herbaria and gardens in democratizing knowledge of biological diversity through emerging tools such as DNA barcoding. Increasing access to basic natural history information may be the most significant method for building awareness and fostering debate about the need for conservation and the methods for accomplishing it.
The main body of the book is organized into four broad sections, roughly corresponding to (1) large-scale variation in diversity, (2) diversity in specific habitats and taxonomic groups, (3) causes of plant extinction, and (4) conservation implications. Each section is subdivided into three to five chapters, each of which is composed of several short accounts written by various authorities. The target audience is never explicitly identified, so readers may either appreciate or dislike the format depending on their motivations. Readers with only a basic knowledge of conservation or interest in a broad overview will like this structure. I found the short essays well written and surprisingly cohesive, but there is necessarily a trade-off with depth in some topics. With 26 of its 48 contributing authors from the Smithsonian Institution, the book presents a broad but somewhat idiosyncratic perspective on diversity, with heavy emphasis on the neotropics and subtropics.
The first section (“Plant Diversity: Past and Present”) sets the stage with discussions of historical and large-scale patterns of plant diversity and extinction. The first chapter, on the evolution of diversity of plant form in geological time, is succinct and enlightening, although a schematic illustrating the timeline of body plan evolution in plants would have helped to clarify the complex patterns discussed. The remaining chapters are also succinct and provide valuable summaries of patterns of diversity and extinction. I especially appreciated the authors' critical analysis of the methods and reliability of current biodiversity knowledge, which contrasts dramatically with the seemingly absolute estimates often given in the popular media. The essential message communicated is that, even for plants, we are only in the early stages of documenting patterns of biological diversity on a global scale.
The second section (“Plant Diversity: Habitats and Taxonomic Groups”) is a series of case studies, each of which describes plant diversity in select geographic regions and taxonomic groups. Chapter 4 focuses on tropical and subtropical ecosystems, areas that are often rich in plant diversity and have high rates of endemism. Overall, the case studies provide detailed glimpses into specific tropical regions that will not be familiar to most readers. The analyses of individual taxonomic groups (chapter 5) seemed less useful. The specific groups highlighted were rather idiosyncratic, and often there were extensive accounts of the basic biology of a particular group, but with few linkages to conservation issues. At times, the perspective was quite narrow. For example, the description of lichens focused on one particular species, with little discussion of the patterns of diversity and concerns associated with lichens as a whole. In general, this section missed an opportunity to explore ways in which contemporary methods can advance the conservation of certain taxa. It might have been useful to ask “In how many cases of conservation (even in the United States) is recovery hampered by taxonomic confusion?” and “How have studies of systematics and phylogeography helped to resolve the appropriate scale of conservation attention?”
An analysis of the causes of extinction, the topic of the third section (“Contemporary Causes of Plant Extinction”), seemed, at first, peripheral to the natural history theme. However, this section distinguishes itself from ecological references on conservation by focusing, in chapters 6 and 8, on the kinds of extinction pressures unique to different ecosystems and taxa as well as the potential consequences of these pressures. In contrast, chapters 7 and 9 attempt to summarize more general causes of endangerment: invasive species and loss of genetic diversity. While each of these chapters does an admirable job with the space available, these more theoretical topics seemed at odds with the field-based, natural-history observations of other chapters. They are also not as well suited to the short essay format, as they cannot encompass the current expansive literature on such mechanisms, nor compete with the detailed theoretical and empirical summaries covered in other references. Moreover, for a book devoted to natural history, there is an imbalance between attention to genetic diversity and the limited consideration of ecology. This perpetuates a prevalent view that extinction risk can be evaluated or resolved with marker genes, and without consideration of the demographic and ecological context of species.
The fourth section (“The Conservation of Plant Diversity: Assessment, Management Strategies, and Action”) provides a sense of how data on biodiversity are used to make conservation decisions—specifically, to set priorities for conservation action. It makes a compelling argument for the value of herbarium collections in developing maps of species diversity and in collecting and documenting diversity in lesser-known areas. This would have been an ideal place to summarize the challenges of sampling and estimating species diversity, and to offer methods for proceeding when resources are less than adequate. In addition, methods for predicting distributions and diversity using geographic information systems required more than just a passing mention. The chapter on phylogenetic considerations made reference to several topics that could have been expanded considerably. The discussions were thought-provoking and highlighted the complexities of prioritizing conservation targets. However, using phylogeographic criteria for identifying target geographic regions and predicting risks of hybridization are areas in which herbaria and botanical gardens can provide much leadership, and hence was worthy of expanded treatment in the book. A chapter on assessing conservation status summarized current methods for evaluating diversity at the genetic, species, and community levels. While a summary is useful to the novice, more emphasis on the criteria used in these analyses (e.g., in IUCN Red List designations) and critical evaluation of the quality of the data that result would have been a valuable addition. For example, the essay on molecular diversity is mostly a summary of kinds of genetic markers. However, it isn't apparent what the relationship is between molecular diversity and the ecological fate of populations, or when demographic and ecological factors may be of more immediate concern and a better predictor of extinction risk than the rate of heterozygosity at some arbitrary DNA segment.
With the increasing availability of genetic markers and ecological models, one could argue that conservation biology is focused on remedies and is losing sight of the basic knowledge of diversity on which the field is based. This book, although superficial in places, reveals a wealth of information about the organization of biological diversity from a global perspective and demonstrates the important contributions that herbaria, botanical gardens, and museums are making to this effort. In the process, it reveals how little we know about the very problem so many are trying to address, and highlights the importance of scientifically sound information as a baseline and an impetus for future research and conservation action through management, restoration, and policy development.