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Plants at the margin. Ecological limits and climate change.
RMM Crawford. 2008.
Cambridge, UK: Cambridge University Press. £40 (hardback). 494 pp.
Documenting and predicting the biotic impacts of rapid changes in climate are currently receiving much-deserved attention. Plants at the margin. Ecological limits and climate change by Prof. R. M. M. Crawford is a timely publication focusing on vascular plants in the habitats where these impacts are widely expected to be most pronounced. Crawford provides a clear and concise summary of the literature on this broad topic, skillfully synthesizing progress in a diversity of research fields to address two specific issues – how vegetation establishes and survives in areas where environmental conditions are outside the physiological tolerances of most plant species, and how changing environmental conditions might affect this vegetation. The book successfully integrates insights from community ecology, landscape genetics, ecophysiology, palaeobotany and bioegeography. As a result, uniquely, both long-term and more recent changes in vegetation patterns are documented for some case studies, as well as the physiological and genetic mechanisms that have driven these changes and that could be influential in determining plant responses to further changes in climate. The remarkably integrative nature of the book is further enhanced by its global span, examining polar and sub-polar, high altitude, saline and aquatic habitats in detail. The book is particularly focused on northern hemisphere tundra, taiga and coastal habitats, and researchers working in these areas will find this book a very valuable reference. Arid environments do not receive much attention, although adaptations to conserve and acquire moisture in other environments are considered.
The book comprises three sections. Part I documents the different factors that cause areas to be marginal for plant growth (chapter 1) and considers plant diversity in a variety of marginal habitats (chapter 2). Part II examines plant adaptations for resource acquisition (chapter 3), and includes an interesting section on alternative supplies of resources (e.g. fog and dew as sources of precipitation, amino acids as a direct source of nitrogen). Chapter 4 provides an excellent discussion of plant reproduction in marginal habitats, covering many topics ranging from phenology and masting to biased sex ratios and asexual reproduction. Part III contains selected case studies, starting with Arctic treelines and the complex relationship with climatic continentality and paludification (chapter 5). Two other chapters chiefly focus on the Arctic tundra (chapters 6 and 9), while marginal coastal, aquatic and alpine habitats are also considered in detail as case studies (chapters 7, 8 and 10). The book concludes with an interesting account of human habitation and exploitation of marginal habitats. All chapters are lavishly illustrated and, despite the quality of some images being poor, the numerous photographs are an excellent complement to the text.
Despite not providing a detailed background on the mechanisms or patterns of recent changes in climate, the book examines a diversity of weather parameters. Crawford considers the impacts of changes in temperature and rainfall, but also highlights the importance of other (often understudied) components of climate change, including changes in the oceanicity of climates and the frequency of anoxic conditions under ice layers. Scientists studying the impacts of climate change would benefit from this broader perspective of the components of climatic change.
While there are more comprehensive accounts of the ecology and vegetation of each of the specific types of margin habitats (e.g. Körner's Alpine plant life), Crawford has succeeded in producing a broad overview of the ecology of the flora of these extreme habitats, using a style that is accessible to undergraduates and established researchers alike. Overall, I can highly recommend this book to all researchers with an interest in the biological impacts of climate change and/or the ecology of abiotically stressful environments.