ENVIRONMENTAL SCIENCES AND APPLICATIONS Other titles in the series: Volume 1 UNITED NATIONS Desertification: Its Causes and Consequenses Volume 2 FUKUSHIMA, Y. Science for Better Environment Volume 3 UNITED NATIONS Alternative Strategies for Desert INSTITUTE FOR Development and Management TRAINING AND RESEARCH Volume 4 BISWAS, A. K. A Strategy for the Ozone Layer Volume 5 HUSAR, R. B., et al. Sulfur in the Atmosphere Volume 6 J0RGENSEN, S. E. Handbook of Environmental Data and Ecological Parameters STATE-OF-THE-ART IN ECOLOGICAL MODELLING Proceedings of the Conference on Ecological Modelling, Copenhagen, Denmark 28 August - 2 September 1978 Editor S. E. J0RGENSEN International Society for Ecological Modelling Distributed throughout the world for the INTERNATIONAL SOCIETY FOR ECOLOGICAL MODELLING by PERGAMON PRESS OXFORD NEW YORK TORONTO SYDNEY · PARIS FRANKFURT U.K. Pergamon Press Ltd., Headington Hill Hall, Oxford OX3 OBW. England U.S.A. Pergamon Press Inc., Maxwell House, Fairview Park, Elmsford, New York 10523, U.S.A. CANADA Pergamon of Canada, Suite 104, 150 Consumers Road, Willowdale, Ontario M2J.1P9, Canada AUSTRALIA Pergamon Press (Aust.) Pty. Ltd., P.O. Box 544, Potts Point, N.S.W. 2011, Australia! FRANCE Pergamon Press SARL, 24 rue des Ecoles, 75240 Paris, Cedex 05, France FEDERAL REPUBLIC Pergamon Press GmbH, 6242 Kronberg Taunus, OF GERMANY Pferdstrasse 1, Federal Republic of Germany Copyright © 1979 International Society for Ecological Modelling. All Rights Reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means: electronic, electrostatic, magnetic tape, mechanical, photocopying, recording or otherwise, without permission in writing from the copyright holders. First edition 1979 British Library Cataloguing in Publication Data Conference on Ecological Modelling, Copenhagen, 1978 State-of-the-art in ecological modelling. - (Environmental sciences and applications; vol. 7). 1. Ecology - Mathematical models - Congresses. I. Title. II. Jorgensen, S. E. III. International Society of Ecological Modelling. IV. Series 574.5ΌΓ84 QH 541.5.M3 78-41208 ISBN 0-08-023443-7 Preface 28. August-2. September 1.978 was in Copenhagen held ISEM!s 1st International Conference on the S tate-of-the-Art in Ecologi- gal Modelling. The proceedings contain staie-of-the-art or review papers, ori- ginal papers and the result of a working session from this confe- rence · The first part of the book containing the invited state-of- the-art or review presentations, covers the following topics within the field of ecological modelling: river models, appli- cation of graphical methods, application of microcosms in ecolo- gical modelling, prey-predator models, modelling water quality and irrigation in agriculture, modelling the distribution and ef- fect of toxic substances, lake models. The second part consists of 29 original papers presented on the conference. The following topics were touched: 1. Models of Sea and Coastal Areas (3 papers) 2. Modelling the Atmospheric Pollution (l paper) 3· Modelling Ecosystems in the Lithosphθre (l paper) 4. Water Management Models (k papers) 5· Lake Models (6 papers) 6. Primary Production Models (3 papers) 7. Prey-Predator Models (2 papers) 8. Theoretical-mathematica1 Problems (9 papers) A working session was arranged for discussion of the state-of- the-art and the needs for further research within some selected fields of ecological modelling. During the working session, the participants were discussing these problems in small groups. The proceedings summarizes the conclusions, covering the following i terns : Prey-Predator Models Lake and River Models Application of Microcosms Toxic Substances Models Hydrochemical Modelling of Irrigated Agriculture Modelling Sediment-Water Interaction Plankton Models Holistic Approaches to Ecological Modelling State-of-the-Art in Ecological Modelling. Vol. 7. INTERNATIONAL SOCIETY FOR ECOLOGICAL MODELLING AN INTRODUCTION Asit K. Biswas, President, International Society for Ecological Modelling. I would like to take this opportunity to explain to you why this new International Society for Ecological Modelling has been formed, what are its objectives, and what we plan to achieve in the future. We are now living in an era of dramatic changes. It is of course true that the world scenarios have never been static ever since the first form of life appeared on earth. The present life- forms have developed through a continuous evolutionary process, and there is no reason to believe that this process has come to an end and that man is the ultimate animal that has evolved and is here to stay until perpetuity. There is no doubt that mismanagement by man of the environment and various ecosystems, on which ultimately our life-support systems depend, can hasten our own demise from this earth. It is true that the world we live in is dynamic, and events and factors are continually changing with time. For example, world population has been increasing continuously ever since man first appeared on the scene. But the real problem is not so much that 2 everything in this world has been dynamic since time immemorial, as it is the rate and/or magnitude of the changes that have taken place in the twentieth century. Let us consider the scale of the changes we are witnessing or have witnessed in the present century: It took nearly a million years for the first billion people to appear on earth, but the next billion is due in only another 15 years. From the beginning of our civilization to the end of the Second World War all the world1s industry totaled less than the new industrialized capacity that has been produced with- in the last 3 years. The United States alone used more resources in one decade, 1959 to 1968, than did the whole world in all previous history. A century ago, the production of crude petroleum was negligible. By 1966, the production amounted to 1,641 million metric tons per year, having increased sixfold over the preceding 30 years. It has increased significantly more since 1966. The world will consume more metals during the next 3 5 years than it has in the last 2,000. The increase in population and standard of living has meant that we need more food, fibre, raw materials, energy and other resources to sustain human needs. It has also resulted in the generation of increasing volumes of residuals which have to be ultimately disposed of on our land, water and atmosphere in such a fashion so as to create minimum ecological damages. Furthermore, man's economic activities have seldom been uniformly distributed all over the world: they are being increasingly concentrated in a few urban centres. Accelerated urbanization that we are witnessing at present, as we approach the twenty-first century, means that 3 ecosystems in those select urban centres are now under continually increasing pressure which directly stem from human activities. In many cases we have already reached the point of no return, where we have already made irrepairable damages to our environment. Environment in such instances can no longer assimilate the insults: its resiliency has virtually disappeared. Fortunately for the future of man we are aware of some of these problems which we ourselves have created, and there are some indications that we are attempting to change our behaviour. Thus, within the last decade, in many countries, societal values and norms have changed significantly from an automatic acceptance of economic growth for its own sake to a deeper concern and better understanding of the ecological and social implications of such growths. This new orientation of our philosophy is manifested in our search for "alternate styles of development," "ecodevelopment," "new growth," "conserver society," and a host of other similar concepts. This shift in our value system has also begun to permeate the political process, within which most major decisions are taken, and this concern is gradually being reflected in national and international policies. These developments, positive as though they are, have contributed to the further complexification of the planning and decision-making processes, which were not simple to begin with. Even though these processes have become exceedingly complex at present, and will undoubtedly continue to become more complex in the future, it is becoming increasingly evident that the average planner and decision-maker has been provided with very few h fundamentally new tools and concepts in the past several decades to cope with such complexities. One of these few new tools is modelling. The state-of-the-art ecological modelling haö advanced considerably during the past decade. Our knowledge and understanding of ecosystems have improved, and accordingly we are now in a better position to develop ecological models which can be used for operational purposes. It has added a new dimension to our analytical capabilities. Furthermore developments in computer technology during the past two decades have not only reduced the cost of unit operation but also have significantly increased computational capabilities. For example, in 19 52, it cost $1.26 to carry out 100,000 multi- plications. This unit cost has progressively declined to $0.26 by 1958, $0.12 by 1964, and $0.05 by 1970. Today the same computations can be carried out for less than one cent and within a fraction of the time that was necessary to carry out such an operation in 19 52. Hence, the potential benefits of ecological modelling is enormous: we have so far hardly even scratched the surface. Because of this situation many like-minded scientists and policy makers felt the need to form a new society for ecological modellers, where we can discuss the latest developments and applications thereof, research priorities, and training programmes. We also urgently need a forum for information exchange. No longer is it possible to search through thousands of journals hoping one would find some relevant articles on ecological modelling. Globally there are now some 35,000 journals which publish about 2,000,000 articles each year, written by about 750,000 scientists in some 5 50 languages. The situation had clearly become intolerable. The existence of this sad state of affairs has led to the formation of the International Society for Ecological Modelling, popularly known as ISEM. Our main objective is to facilitate the international exchange of ideas and concepts, scientific results, and pertinent knowledge, as well as the application thereof, within the general area of ecological and environmental modelling. ISEM is an interdisciplinary society, and we intend to emphasize this aspect continually. An implicit assumption of many university departments and professions is that branches of science are often interpreted as reality. In other words, it is assumed that nature is organized in the same way as the professions are. Thus, we talk of engineering problems, biological problems, social problems, chemical problems, medical problems, etc. In a real world, of course, nothing can be further from the truth. A problem is a problem, and the addition of the professional adjective only indicates our ways of viewing and analysing the problem. The method of analysis depends on our training and background, and this very often introduces significant biases in the resulting analyses. Individuals trained in different disciplines often look at a common problem to be analyzed and solved in totally different fashions, depending on their education, background, and experience. The point can be best illustrated by the following story. The manager of an old building once received complaints from his tenants regarding the long waiting time for elevators, whereupon he called in his engineers and asked for possible solutions. The engineers suggested three alternatives: add extra elevators, replace old elevators with more efficient new ones, or use a banking 6 system, that is one elevator serving a specific set of floors. The manager rejected the first two because they were too expensive for an old building and thus they were not economical. The third alternative reduced the waiting time only marginally, and hence was not an acceptable solution. The manager, however, had a friend who was a psychologist and who heard of this dilemma. The psy- chologist offered a simple but economic solution: install mirrors in the elevator lobbies. This simple solution surprisingly enough stopped all the complaints. The mirror gave the ladies waiting for the elevator an opportunity to do some adjustments, and the men could look at the ladies in the mirror without any embarrassment 1 Whether the story is true or not is really unimportant: what is important is the fact that the psychologist saw the same problem that was facing the engineers in an entirely different light. The engineers attempted to reduce the actual waiting time by technological means, but that solution did not occur to the psychologist. His solution was not to reduce the waiting time but to make it look like it had been reduced, and this happened to be an acceptable solution in this particular case. The point I am trying to make is that an interdisciplinary group is an absolute necessity for ecological modelling because different disciplines could perceive the same problem in different lights as a result of their training and background. Thus, ISEM plans to be truly interdisciplinary society, and I am happy to report that we have already attracted scientists from various disciplines. ISEM will emphasize research, application of research results and training. We believe that research by itself is a valid objective to expand our frontiers of knowledge. Simultaneously we would also