The Biology of Deserts. By D. Ward


  • Amat, B. ( Department of Ecology, University of Alicante.
    Carretera San Vicente del Raspeig s/n, 03690
    San Vicente del Raspeig, Alicante, Spain.

2009 ). Oxford University Press , Oxford, UK . 352pp . ISBN13: 9780199211463 (Hbk). ISBN13: 978-0-19-921147-0 (Pbk)

The Biology of Deserts is part of The Biology of Habitats Oxford Series, whose aim is to introduce readers to different types of habitats around the world. In this book, Professor David Ward offers a general overview of desert ecosystems. The author presents an excellent synthesis, which is particularly challenging given the wide range of habitats that we call deserts. In eleven chapters, Ward explores the main abiotic and biotic factors structuring desert ecosystems. The book begins with a brief review of abiotic conditions (chapters 1-2), then provides some information about the physiological ecology of plants and animals (chapters 3-4) as well as analyses interactions between organisms (chapters 5-7). The next chapters describe ecosystem properties of deserts (chapters 8-9), and the book concludes with a section on the relationship between humans and deserts (chapters 10-11).

David Ward is Professor in the School of Biological and Conservation Sciences at the University of KwaZulu-Natal, South Africa. His research focuses on ecology and genetics of plant-animal interactions in South Africa savannas and deserts. He deals with various topics such as bush encroachment, local adaptation, defense strategies and co-evolution. He is also an expert on sustainable ecological management for communal and commercial ranchers. His long experience in desert ecosystems makes him highly qualified to merge his knowledge and experiments in a book that provides a quick overview about ecosystem functioning in desert areas and the type of research carried out in these ecosystems.

Several outstanding reference books on deserts have been published in the last decades, but since Whitford'sEcology of desert systems (2002) this is the most general review on desert ecosystems. It is based on an enormous amount of information, including classic and recent works. The book is targeted at undergraduate and graduate students, and it provides a concise and global overview of desert ecosystems. The book is nicely written, easy to read, with lots of charts, diagrams and pictures. It covers desert ecosystems worldwide, with a slight bias towards the Negev desert. The author provides many examples from this desert, which may be the result of the vast amount of information available from this area and author's own experience in this ecosystem. All chapters are organized in sections that clearly elaborate the main ideas presented in the text. Section headings are informative in most cases, but not always. For example, the section entitled Snails within chapter 4 (Morphological, physiological, and behavioural adaptations of desert animals to the abiotic environment) briefly explains snail adaptation to desert habitats, but it also includes a comprehensive and unexpected explanation about amphibian, insect and rodent adaptations.

The book begins with a brief review of the conditions defining a desert in its broadest sense. It explores the main climatic, geologic, ontogenetic and disturbance factors that characterize a desert. This section pays special attention to the diversity of deserts worldwide and the variability of abiotic conditions that are found in them. Afterwards, it develops a physiological perspective, reviewing different morphological and physiological adaptations of plants and other autotrophic organisms, such as biological soil crusts. This section also includes a short explanation of the different types of photosynthetic pathways with examples of functional groups thriving in deserts. The section ends with a description of key adaptations of desert animals from an evolutionary perspective. In an interesting exercise, the author discusses the relative importance of adaptation and phylogeny in defining morpho-functional traits in deserts.

The next section examines factors affecting the abundance of organisms, and how community structure changes over time. This section pays particular attention to intra- and interspecific interactions between plants and animals, as well as direct and indirect interactions (such as competition and facilitation) controlling the structure of desert communities. It also highlights other interactions that affect community structure. For example, the importance of predation via direct mortality or perceived risk; different types of parasitism that modulate the abundance of species; the effects of herbivory on plant community attributes; mutualistic pollination relationships; seed dispersal and seed predation. The author discusses the co-evolution of organisms involved in mutualistic relationships and gives some examples of these interactions. In my opinion, this section is a bit unbalanced between plants and animals. It gives much more importance to animal interactions, and lacks a more comprehensive explanation of the role of plants in structuring the community directly or indirectly. For example, there is only one short section about plant communities in these three chapters, and only one paragraph on facilitation and nurse plants. This is not proportionate with the vast amount of information available on these topics and the emerging research focus on positive interactions between plants in stressful environments such as deserts.

Next, the author reviews food web models and factors affecting the structure of food webs, focusing on those aspects relevant to desert ecosystems. He also describes the effects of precipitation, nutrient availability, disturbances and decomposition in creating temporal and spatial heterogeneity, and how heterogeneity affects ecosystem responses. Ward analyzes and compares the biodiversity of several groups of organisms across deserts worldwide. He also discusses the origin of convergences, divergences and character displacement of desert communities, and provides insights on large-scale desert plant and animal biogeography. In this section, I missed a comparison between deserts and other biomes, to inform readers on the role of deserts in global biodiversity.

The last section of the book deals with problems facing desert ecosystems, and suggests potential solutions. It emphasizes the role of humans promoting desertification, highlighting pastoralism as the main factor inducing desertification-related processes, such as shrub encroachment and changes in species abundance. In a section called Pastoralism is the most important use of desert lands, the author includes information about invasive species and global climate change. I think these topics are not necessarily related to pastoralism, and, in my opinion, they deserve their own sections in a book about deserts. In his last chapter, the author makes a brief review of several strategies for the conservation of desert ecosystems by means of conservation of individual key species and habitats, species reintroduction, revegetation, and conserving populations with strong genotype-environment interactions. He finally considers institutional means of controlling desert habitats, and provides two contrasting examples of desert management and social perception of desert ecosystems.

Ward concludes and prefaces the book with an emphasis on the importance of deserts as “laboratories of nature to study evolution in progress, given their relatively simplicity and underutilized state”. I do not completely agree with this idea. I do believe that deserts are appropriate systems to evaluate biotic interactions and ecosystem studies, but not because of their simplicity. I think that deserts involve a huge amount of diverse and complex processes, which indeed has promoted a vast amount of past and current research in these areas. Moreover, I would not say deserts are underutilized, when 20% of global population is living in semi-arid, arid and hyper-arid lands. Finally, the author makes a call to conserve deserts, in a desertification threatened world, pointing out at their vulnerability. In general, Ward does an excellent job in this book, synthesizing the main points to easily understand figures, processes, studies and limitations of desert ecosystems, making the book a good source of references to vegetation scientists interested in arid-land ecosystems.