Amazonian rain forests: Ecosystem disturbance and recovery

Amazonian rain forests: Ecosystem disturbance and recovery

71 gal framework for environmental questions stemming from public concern about the negative effects of hydraulic projects. This overview of the legi...

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gal framework for environmental questions stemming from public concern about the negative effects of hydraulic projects. This overview of the legislation should perhaps have paid greater attention to EEC directives and standards. This third chapter includes an analysis of the methodologies proposed for considering environmental and aesthetic factors in the evaluation and planning of river channelization projects. The third part of the book, Chapters IV, V and VI, deals with the physical, ecological and downstream effects of channelization. In these chapters one can clearly see Brookes’ synthetic achievement. The reader is introduced to a profusion of examples and data regarding the effect of various watercourse channelization projects, all accompanied by a set of graphics and explanatory tables. Sometimes this abundance of information can divert the reader’s attention from cause and effect relationships. A few outline conclusions at the end of each chapter, pointing out the most important changes and their connection with engineering works, would have helped to focus the main ideas. The chapters on recommendations will be of great interest to professionals concerned with river engineering and projects to restore watercourses and river banks of channelized rivers. Chapter VII develops a series of alternatives to present construction procedures with a view to mitigating adverse environmental effects. Techniques for the improvement and restoration of watercourses, especially the recovery of morphological diversity and the handling of river bank vegetation, are dealt with in Chapter VIII. It must be pointed out that this is not meant to be a textbook; nevertheless, the inclusion of details on construction and design should clearly increase the number of potential readers. The author concludes by calling for an improvement in the planning and design of watercourse projects. This improvement should come about as a result of a multidisciplinary

approach to the subject, in which the environmental impact would be evaluated beforehand and the response of the river anticipated. Brookes considers it essential that professionals from different fields should be represented: geomorphologists, biologists and engineers, together with local interest groups. The author singles out the decisive role played by geomorphology at the planning stage of the project, because if the morphological characteristics of the watercourse are not correctly designed, ecological recovery is impracticable. To sum up, Brookes’ work is of the greatest interest to all professionals concerned with river engineering, the evaluation of environmental effects, and projects for the restoration of watercourses and river banks. This excellent book will serve as a starting point for future research into the integrated management of watercourses. VICTOR CASTILLO Department of Forest Engineering Pol_vtechnical Ckiversity of Madrid Madrid 28040 Spain

AMAZONIAN RAIN FORESTS Carl F. Jordan (Ed. ), Amazonian Rain Forests: Ecosystem Disturbance and Recovery, Springer, New York, 1986 (ISBN 0-38796397-9). 133 pp. Price DM 108.00. This small book includes seven concise reports that describe the effects of disturbance on the Amazonian rain forest. The focus throughout is on nutrient dynamics and availability, system productivity, and the potential for system recovery. The book flows smoothly through the continuum of case studies that use similar methods, descriptors and format. The editor, Carl Jordan, introduces the volume with a succinct discussion of current pressures that are resulting in rain-forest destruction. He believes that the Amazonian rain forest cannot be preserved in a pristine state

but that development could proceed with far less ecological disruption. The book was originally planned to document the results and conclusions of five related studies by Jordan and his associates, and to illustrate the effects of different levels of disturbance and recovery. Additional case-studies were added that help to demonstrate the effects of moderate disturbance and different management objectives. The first case-study describes Jordan’s investigation of shifting cultivation and the results of this traditional practice on mineral nutrient dynamics, biomass changes and crop success. The study continued for three years after decline in crop productivity and abandonment of the site, with the results suggesting that the effects of this type of disturbance do not delay the natural successional process. A subsequent study describes the progress of succession towards mature forest using a sequence of 23 individual slash-and-burn sites ranging from those recently abandoned to others abandoned 80 years earlier. This study, by Juan Saldarriaga, does not resolve the questions as to whether, or how soon, a site can again be considered mature forest but it does provide evidence from nutrient levels, biomass accumulation and changes in species diversity, to suggest that mature forest may possibly result within another 100 or 200 years. A third study by Geoffrey Scott examines the effects of shifting cultivation in a region lacking adequate land suitable for agriculture, with the result that relatively young forest recovering from earlier cultivation is again cut and burned. Fire occurs more frequently than in the areas previously described, and some sites have converted into grasslands. Scott concludes that where fallow time was 15 years or more and fire was absent, the pattern of shifting cultivation was probably sustainable without nutrient addition. With shorter fallow periods and fire, fertilizer additions would be essential for crop production. A disturbance of greater severity is represented by a case study that describes the estab-

lishment of pasture for the purpose of delimiting a national frontier. This study, by Robert Buschbacher, describes the impact on a 40-ha area that was cleared and seeded to pasture for grazing. Lacking adequate fertilization, seed, and other support, the project was unsuccessful. Failure, as indicated by poor animal growth, excess mortality, and lack of reproduction, appears to have resulted largely from inadequate mineral nutrition. Chapter 6 encompasses four case-studies abstracted by the editor to supply information on the results of permanent change from rain forest to small-scale agriculture and forestry. These cases include: the relatively unsuccessful attempts to settle the land along the TransAmazonian highway; agricultural ventures where firstly complete fertilizer, and later micronutrients, were provided to maintain yields and where roads were present to move crops to market; a relatively successful integrated farming community where emphasis on tree species and maintainance of ground cover permitted sustainable production of such crops as tree fruits, pepper and rubber; and finally, small-scale forestry based on a system of selective harvest, natural regeneration and active stand improvement. This last system appears to be ecologically sustainable but, as long as virgin timber is readily available, not economically feasible. In Chapter 7, Charles Russell provides an excellent analysis of the Jari project, an attempt to establish large-scale plantation forestry. Rapid tree growth for pulp production was central to the project. Nutrient limitations compounded by tree diseases and other factors are suggested as primary reasons for the lack of success. A final case-study, by Robert Buschbacher, Christopher Uhl and E.A.S. Serrao, documents attempts in large-scale pasture development, efforts that were generally unsuccessful and resulted in pasture abandonment. Increases in land values, derived from a government-supported road network permitting ex-

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ploitive logging, provided profits for some of those involved. After abandonment the pasture landscape followed the pattern suggested by other studies: those tracts that showed the least depletion of nutrient stocks were most successful in reverting to forest. In the final chapter, Jordan evaluates the several case-studies in respect to productivity and sustainability within the social, political and economic contexts of the region. He clarifies the differences between ecological and economic sustainability, and discusses the social and political pressures and the nature of energy comparisons. As he notes, the major component ignored by large-scale projects is the energetic value of the original forest, i.e. the contribution of natural energy. Jordan concludes with well-reasoned suggestions for future development, among them the need to restrict access to the essentially free resource represented by the virgin forest, to stimulate the practices and cultural energy investment necessary to achieve sustainable agriculture or forestry. Jordan and his co-authors deserve thanks for their coherent and well-reasoned account of the effects of disturbance on the rain-forest system and their documentation of the key role that mineral nutrients play in the Amazonian environment. In addition, the authors provide valuable insight into the importance of other environmental factors as well as indicating the difficult social and political questions that must be resolved if the rain forest is to survive in any form. This book should be required reading for anyone with a serious interest in the rain forest and its future. It seems appropriate to end this review with the concluding paragraph of the book: “ ... the most desirable systems for development of the Amazon, from a variety of viewpoints, are those best able to take advantage of the naturally occurring resources of the rain forest. In the long term such systems function better, are more profitable, more sustainable, and more socially and politically beneficial,

and are less environmentally damaging than systems that have evolved in other regions and under other cultural and environmental conditions.” FOREST STEARNS

Biological Sciences University of Wisconsin Milwaukee, WI, U.S.A.

ECONOMIC THEORY Per-Olov Johansson, The Economic Theory and Measurement of Environmental Benefits, Cambridge University Press, Cambridge, 1987 (ISBN 052 1328772, hardback; 052 1348 102, paperback). Price &27.50/ US$49.50 (hardback), &9.95/US$l6.95 (paperback). In this advanced text the author’s main point of discussion focuses on the theoretical properties of consumer surplus measurements and how they relate to a wide variety of environmental problems. Throughout the author utilizes a variety of mathematical models in an attempt to analyze and understand demand potential in relationship to preferences placed on specific man-induced impacts or changes in the character and/or composition of the environments. As a landscape architect I found that the text dealt with a variety of issues that are of concern to the profession such as: land use decisions; carrying capacity; conservation; development potential; pollution; consumption of resources; public and private good; and externalities. The decision making approach advocated by Professor Johansson would be of interest to a landscape architect, but reasonably good understanding of both basic and advance economic theory would be required. The text is primarily oriented towards an individual with a strong economic background or a resource economist dealing with the economics of environmental decisions. The text can be divided into two broad sec-