Spatial Analysis
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The advent of relatively low-cost but powerful computational technologies has revolutionised many fields, not least ecology. It has allowed for ideas to be tested might might once only have been thought about. Whilst this is a great advantage, there are also problems, not least that the techniques used need to be clearly understood! The most obvious example would be statistics but as techniques improve in other areas (or, indeed, as other areas develop) there comes a need to improve understanding.
One of the more recent fields in ecology is spatial analysis. The idea that plants and animals are spatially organised is hardly new – the earliest texts recognise different species in different places (so, to that extent, the technique is hundreds if not thousands of years old!). What has changed is not just the technology but the ways of thinking. The authors note this rightly, in the preface: spatial understanding is vital but it requires the right technique to interpret the patterns. It’s this point that is intriguing and which drives the text’s direction. Spatial heterogeneity has been long accepted – zonation is one of the first student field exercises in ecology. However, the actual pattern and what might underlie it are far more sophisticated than might be realised. Statistics assumes some independence amongst variables but this might be far from the case with spatial analysis. It is for this reason that the authors have broadened out the text from pure technique to a broader understanding.
The opening chapter looks at the basic concepts. From the outset it is made very clear that there is no simple or agreed answer to the nature of spatial analysis. A range of examples are given but the authors favour a longer set covering not just structure (pattern?) similar to other typologies, but to extrapolation, regression and similar taking the analysis from a description to something more powerful and predictive. The chapter continues, looking at the spatial nature of ecological data (where some patterns might be closely linked to species, whilst others are not), the impact of sampling design, the construction of the hypothesis and the meaning of data produced. The overall effect is to bring the reader into some of the main complexities of the topic. To some extent, chapter two takes an alternative tack, looking at basic ecological processes and the resultant spatial structures – a brief reminder of the ways in which ecological processes might form patterns.
From this stage, we are taken through a series of ideas and techniques. As an aid to understanding these, readers should make sure they view the two decision trees at the very front: they highlight how aspects of the text are related and they also what questions one should consider asking of data. Back in the text, the authors look at one of the more basic patterns in points and networks. We start with the simple nearest neighbour approach and rapidly look at more complex network models. In each chapter in this part of the text, the same issues are raised. We have a spatial pattern where the points of that pattern e.g. plants are not independent in their relations to other points which influences basic parametric statistics. This does not negate the need to find that pattern but it does make the correct test more difficult. Larger data sets might be easier because they can contain patches which might well be independent of other patches, but smaller areas require different treatment. Such treatments are aimed at distributions but we can also use the same ideas on biodiversity or even changes through time.
A final chapter ties together much of the preceding discussion and looks at the current state of work and where it might usefully go in the future. This is clearly a key area for ecologists in times of changing patterns and conditions. For those based in this analysis, the book will prove a detailed addition to the growing literature on the subject. For those hoping to learn more about the issues of spatial analysis without the detailed statistics, there is also much to learn. Here lies one of the common issues with such texts. In the introduction and concluding comments as well as initial and later chapters, there is a wealth of detail that could usefully be included in less advanced ecological study giving it a real emphasis to cutting edge work. For this reason, the text deserves to be widely noted.
