Agricultural and Forest Meteorology 104 (2000) 251–254
Book reviews
Spatial Modeling of Forest Landscape Change: Approaches and Applications
D.J. Mladenoff and W.L. Baker (Eds.); Cambridge University Press, 1999, 352 pp
Forests surely represent the most spectacular and varied form of the earth’s biomes and changes in the forest landscape affect all its inhabitants and users. We have already seen it altered significantly, and prospects for considerably more change are on the horizon in a world of changing climate and exploding populations. The vast range of scales, both temporal and spatial, involved in the description and evolution of the forest landscape clearly calls for the use of models to sharpen our perceptions and predictive powers, and this book intends to give us, the scientists, teachers, graduate students and landscape managers, a snapshot of the current state of modeling in this rapidly changing field at the interface between science and management. Ob-viously, it is not intended primarily for AFM readers, but given the importance of the forest landscape for our research, it merits a look.
The book grew out of an Ecological Society of America symposium, held in 1997, and contains 11 chapters, copiously referenced, on specific model approaches, framed by the editors’ introduction and outlook summary. It has a Web site attached, http:// forestlandscape.wisc.edu/book/, which is intended to keep the reader up-to-date but, at the time of this review, only contained the Table of Contents and or-der/pricing information. Unlike other such books with multi-author contributions, a fairly uniform writing style and format attest to editorial control. Illustrations abound throughout and there is a central section with colored map illustrations. The writing style is gener-ally clear, with exception of some definitions (what does ‘shade cast 25.7’ mean if no units are given?), some dimensionally questionable, presumably
empir-ical, parameters in analytical expressions, and a few technical terms unfamiliar at least to this reviewer. The authors/editors may be forgiven for finding it difficult at times to decide whether to offer a hands-on manual or an overview text, and for occasional redundancies between chapters dealing with similar models.
As interested outsiders, rather than model users, what do we learn about the bewildering array of cur-rent models, their goals, developments and outlooks? The focus is on processes that produce structure in the landscape and the goal is to permit managers to include an understanding of ecological and biological conse-quences in their decisions. The models come in all shapes and sizes, statistical, process-based or ‘fuzzy’? Some authors distinguish between ‘theoretical’ mod-els (in the sense of ‘abstract’ — not tied to a specific landscape) and ‘physical’ models (based on the con-servation laws). ‘Probabilistic’ models (e.g. based on percolation theory) are distinguished from ‘statistical’ models (using probability distributions derived from historical records), and ‘shape models’ superimposed on GIS-based maps of terrain and fuel availability are used to predict the spread of wildfires. Models are built around stands where each tree may be tracked in its interaction with neighboring trees, and differ in within-stand complexity and sophistication in verti-cal structure. Processes in spatially explicit models include light penetration, water regimes, nutrient cy-cling, competition, herbivory, seed dispersal, growth and mortality. The limits in spatially explicit mod-els may not be imposed so much by computational capacity as by their demand of very extensive field sampling for data input and model calibration. In larger-scale models only age classes and other aggre-gate variables (such as patch sizes and distributions) may be predicted. Models may include random se-lection of weather conditions from specified climate types.
252 Book reviews
Whatever the model, basic questions are raised: Do trees affect the landscape or does the landscape affect the trees? What processes, and at what scale, must be included in the model, and what informa-tion must be collected to describe those processes? Just think of fire spread where atmospheric trans-port of burning embers (‘spotting’) may leapfrog over nearest-neighbor interaction, or of the many feedback mechanisms that connect growth, shading, nutrient uptake, litterfall and moisture regimes. Often our knowledge is at one scale but consequences are manifested at regional and even global scales. Con-siderable discussion focuses on the effect of initial conditions on equilibrium community composition, such as whether variations in initial conditions lead to different compositions or only to differences in the time required to approach ‘equilibrium’ (if there is such a thing in the case of a changing climate). Edge effects are of concern because of the increas-ing fragmentation through natural and man-made disturbances and because forest edges have a dif-ferent microclimate and fauna than interior forests. The status of modeling of some of these questions may be rudimentary, but relevant questions are being addressed.
Many authors point out the potential dangers in error propagation in complex models, and the problem of model validation: Does it make sense to validate point by point against existing landscape patterns when the existing pattern may not be the only possible realization arising out of past conditions? It is gener-ally agreed that a main contribution from models is in sensitivity analysis, in the testing of hypotheses, which sharpens our perception of data needs and of the relevant parameters to be considered.
As for results, we find spontaneous clustering out of random distributions, with surprisingly dynamic species compositions, due to competitive interactions, even without considering climate inputs. Competi-tive displacement, based on light/shade or drought tolerance, appears to be extremely important in natu-ral regeneration. Long-term simulations of temperate forests suggest that it would take hundreds of years for a forest to return to a pre-settlement condition even without continued harvesting, that sustained harvest-ing is not possible at current levels, or that drought effects depend more on the seasonal precipitation av-erage than on the severity of individual episodes. Fire
models appear highly developed in the fuel supply aspects, but deficient in the description of the wind regime. Of course, a high-resolution description of the three-dimensional dynamics of the wind field in-side and above the forest canopy in often complex terrain, for prediction of fire spread both in its local and non-local (‘spotting’) aspects, is a forbidding task in itself. Also, good data are lacking for impor-tant observations such as fire boundaries (where fires stopped and why). It is interesting to note that small changes in climate can produce dramatic differences in fire regimes. Effective integration of fire models into management practices has not yet happened, but the models might allow us to estimate effects such as fire intensity reduction expected from introduction of ‘fuel breaks’ (strips of low fuel availability) in the landscape.
Examples given are mainly from the US, but some interesting illustrations come from Malaysia (border effects in tropical forests) and Brazil (deforestation in Rondônia, with socioeconomic and carbon bud-get components in simulation of different scenarios in immigration policy, road development and land tenure practice). In the latter case, the simulations suggest that the typical and worst-case scenarios in cultivation practices do not differ in ultimate out-come, as far as negative effects on species diversity are concerned, only in the timing of it. Fundamental changes in management practices would be required to prevent a degree of fragmentation which prohibits the existence of most species. A similar conclusion is reached, incidentally, in simulation of timber har-vesting in some US National Forests, which foresee a landscape increasingly fragmented and less suitable for the maintenance of wildlife and biodiversity.
Book reviews 253 recreational use, etc.) hierarchically, and where a
higher goal cannot be compromised by actions de-sired for a lower one. In terms of use, significant progress has been achieved on the first step, the inte-gration of ecology into management models, but the integration of weather and climate, ultimately linking models to atmospheric circulation models at a variety of scales, is still in the future. This is understandable, given the size of the task, but more surprising to this reviewer was the low profile accorded in these dis-cussions to insect pests, effects by and on wildlife, and recreational use of forests (virtually ignored). The role of road construction (itself affected by so-cioeconomic and topographic factors), is alluded to and needs to be more directly considered. Carbon modeling, incidentally, is only explicitly considered in the Rondônia model, in a simplistic form justified by the short duration of model extrapolations, during which time climate conditions and natural perturba-tions are assumed to remain constant, and by the lack of basic information on the biogeochemistry of tropi-cal forests. The question of integration of the various models into complex multi-scale constructions, as opposed to a ‘toolbox’ approach based on more com-patible submodels that could be assembled according to specific needs is raised rather than answered.
The editors express their hope, in the concluding chapter, that models will be increasingly used in environmental impact analysis. The cited challenge to landscape ecology (p. 345), that the real test of these models is measured by the impact they have on managing and planning and that up to now they have had ‘surprisingly little to offer’, is one not unfamil-iar to workers in the environmental vineyard. Maybe the vintage harvests have not yet ripened, but this book offers a guided tour through a fascinating array of wild shoots, the diversity of which holds much promise for the future, especially when viewed against a background of rapidly developing local climate and soil–vegetation–atmosphere transfer schemes. It has been a worthwhile tour.
Peter H. Schuepp
Department of Natural Resource Sciences McGill University, Macdonald Campus
Montreal, Que., Canada
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Climate Revealed
William J. Burroughs; Cambridge University Press, 1999, 192 pp, hard cover, ISBN 0521770815
According to the blurb, Climate Revealed (1999) by William J. Burroughs is written for a broad audience,
... and provides a balanced and accessible analysis of the current debate on climatic change, and its pos-sible past and future impacts on all aspects of human society.
There are many books on weather and climate with a similar title. Is this yet another or does Climate Revealed by Dr. Burroughs stand out in the crowd? I believe that it does. Do I recommend it? It is a colour spectacular that I would recommend to anyone inter-ested in climate and the biosphere, even the expert. Bottom line? Its price too is reasonable — ranging between US$ 24 and 40 (excluding shipping). This is not just another climate book. He has written it in a way that you can get something out of it even if you only have 10 min to spare. It is extremely well written, covering a range of topics, and I congratu-late the author for his contribution in taking science to many people. He has taken (very) complicated material from many disciplines and presented non-technical text for all. His style is a very good balance between the science and the simplicity; I believe he has the exact balance. For good measure, breathtaking colour photographs and graphics have been added. It is a book that will sit on my coffee table. I particu-larly enjoyed the occasional brief historical sketches of groundbreaking scientists. Perhaps there is room for more of these sketches where appropriate? The book is divided into bite-sized chapters — one to two pages with a number of chapters placed under an umbrella topic. The umbrella topics range from Climate in Motion, Climate Records and the Future to topics on the regions of the world: divided into groups such as Mountain Regions, Mediterranean Regions, The Prairies, The Tropics, Desert Regions, Temperate Regions, Polar Regions and Tundra and Taiga.
