Ecological Methods 4e

southwoodRating: ★★★★★

PA Henderson and TRE Southwood. 2016. Ecological Methods 4e. Wiley. ISBN 978 1 118 89528 3

There are some books which go into numerous editions that are easy to review, in that new material can alter the focus of the text. Then there’s the classic text, such as the one reviewed here, where the content is so well known that it is almost enough to just give the name and hit ‘publish’! This is the fourth edition of the ‘standard’ for ecological sampling. Having used the first edition where the focus was on insects, it’s both comforting and instructive to see many of the ‘old’ techniques still in place along with some updates. Much of the original material still works because the way it samples is still valid. However, given some readers might be new to this work and see only this edition, it’s worth outlining its coverage and value.

The aim of the book is quite simple – find the best ways of sampling a variety of species such that the researcher has confidence in the results. The complexity that follows derives in no small part, from the diversity of organisms being studied. We start with two vital chapters, not on method, but on the prelude – the need to understand what is being sampled and why. The when and how of this are the subject of the remaining chapters, but we need to open with these basic points. A very brief look at types of population estimates (and the confidence you can have in them) is followed by a longer treatment on sampling design. As this early work makes clear – poor design and understanding at this stage only compound issues later on. Given this, it’s not surprising that emphasis is placed on finding the right way to find accurate population numbers. All sampling variables – frequency, size, pattern and timing as well as the ethology of the organisms are discussed.

By this stage, there should be a good understanding of what is being done, how and why. It remains to explore the myriad techniques that could be used to discover population estimates. The first four chapters from this point all cover the need for absolute population numbers, corresponding, approximately, to the four groups of techniques, starting with capture-recapture for larger organisms (typically, but not exclusively, animals). Sometimes, the organisms might be smaller or difficult to capture. In these cases, sampling units of habitat whether it be soil, water or air, or with plants or even animals for parasites etc. will be the only way forward and a series of extraction techniques are described from suction traps to trawls.

Absolute methods are preferable if the organisms and situations permit but often, relative measures are the only possible method. These techniques depend on a strong understanding of the physical and behavioural aspects of the organism under study and a wide range of possible methods will flow from these initial understandings. The book describes a wide variety of techniques ranging from several forms of trapping, thorough to the use of animal waste to estimate population size. If possible, census methods can be used such as point-frames and transects.

Up to this point, techniques have focussed on the population size. Now, techniques look at other demographic features such as birth and death rates, life expectancies, species density and even energy budgets. As might be expected, techniques are a varied as aspects studied. In addition, many of the chapters carry outlines of the theory behind the techniques to allow the researcher a better understanding of limitations. The final chapter moves on to modern techniques by considering the value of aerial surveys and long-term studies.

This is less a book to read by chapters and more a reference work where you dip in as needed. Each chapter has some mention of limitations and appropriateness and each has copious references to allow far deeper study of the techniques. What is more useful form the educational standpoint is that the text is accessible to a wide range of students. Senior school students could easily grasp the ideas of soil extraction (and have the equipment available in many school laboratories) whilst undergraduates and others could find the class of technique needed and explore more detailed and nuanced ideas starting with the references supplied. This is one of those genuinely “classic” texts in driving ecological methodology and fieldwork forward and should be seen as a standard text in any setting where such work is studied.

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