SCOPE 34 - Practitioner's Handbook on the Modelling of Dynamic Change in Ecosystems

Foreword

There exists a wide range in the impact of man's actions on natural ecosystems. When impact is limited, the ecosystem tends to retain most of its original attributes. When impact is very severe, the natural system is often replaced. In the former category are many areas such as national parks and equivalent reserves, or lands where traditional forest and range management techniques are applied and where there is usually a low energy supplement associated with human activity. In the latter category are intensively used rural and urban lands, in which there is usually a high energy supplement. Between the two extremes is a range of increasing habitat modification usually associated with an increasing amount of energy input and a decreasing dependence on the natural environment and biota.

Broadly speaking, it appears that as the degree of habitat modification increases and as natural communities are altered or replaced by communities composed largely of exotic species, a knowledge of the structural and functional relationships of the original ecosystems becomes less relevant to the management of the modified systems. However, the reverse also appears to be true, and in systems that are utilized essentially as managed natural systems, a knowledge of structural and functional relationships probably provides the soundest basis for effective long-term management, consistent with both conservation and maintenance of productivity. These systems include many terrestrial woodland and forest ecosystems, and many non-woodland systems, such as arid rangeland and alpine and tundra systems, in which environmental conditions are too extreme for forest development.

Ecosystems traditionally utilized for agriculture are being intensively studied by many governmental and nongovernmental organizations, at both national and international levels. By comparison, managed natural systems have received relatively little attention, yet when they are utilized by man they tend to become rapidly destabilized, with associated severe, and sometimes essentially irreversible, changes in their physico-chemical environmental attributes as well as in their biological characteristics.

It was within this context that ICSU's Scientific Committee on Problems of the Environment (SCOPE) and UNESCO's Man and Biosphere (MAB) Programme agreed, in late 1974 to jointly sponsor and convene a technical workshop dealing with dynamic changes in ecological systems, with special reference to contemporary concepts relating to such changes, techniques available for their study, and the degree to which such concepts and techniques could contribute to basic ecological research and to the management of natural and near-natural ecological systems. Professor Ralph Slatyer, of the Department of the Environmental Biology, Australian National University, Canberra, generously agreed to be responsible for the scientific preparation and direction of the workshop, which took place at Santa Barbara, California, from 12 to 16 January 1976. It was attended by the following participants and observers: E. Ames; M. P. Austin; M. Cain; J. B. Connell; G. R. Conway; J. B. Egunjobi; D. W. Goodall; J. M. Hett; R. W. Hilborn; H. S. Horn; J. N. R. Jeffers; R. M. May; C. H. Muller; W. Niering; I. R. Noble; K. L. Reed; M. A. Robinson; H. H. Shugart; R. O. Slatyer; W. Souss; M. B. Usher; R. H. Whittaker.

One written output of the workshop was a short, 30-page report entitled 'Dynamic changes in terrestrial ecosystems: patterns of change, techniques for study and applications to management' .Edited by Ralph Slatyer, this report was published by UNESCO in collaboration with SCOPE in 1977 as MAB Technical Note 4. The Technical Note attempted to review concepts and ideas current at that time regarding environmental succession, to examine the effectiveness of various methods available for modelling and predicting successional patterns, and to consider how these methods can be applied to the management of forests, rangelands and related natural and near-natural ecological systems. The final two substantive sections of the Technical Note provide conclusions and recommendations relating to research on dynamic changes in terrestrial ecosystems and its application to resource use and land management.

The present practitioner's handbook, published as SCOPE 34, comprises another follow-up to the Santa Barbara workshop. It has been prepared in response to one of the specific recommendations of the workshop, which called for the preparation of a practitioner's manual which would outline the techniques available for the modelling of successional processes, the data requirements and limitations of each of the major techniques, and methods of applying them to ecological processes and to the management of semi-natural communities.

Following an agreement between ICSU-SCOPE and UNESCO-MAB, John Jeffers was invited to prepare the handbook. Until his retirement in 1986, John Jeffers was the Director of the Institute of Terrestrial Ecology in the United Kingdom, and has long been interested in the application of systems analysis and other modelling approaches to the organization of ecological research and to the management of natural resources. The Santa Barbara workshop had recommended that the opportunity be taken, in preparing the manual, to increase the biological realism and practical value of the various modelling approaches. Research would clearly be required for the application of existing models and for the development of more effective modelling procedures. The time taken for this research to be undertaken explains in part the period of time that has elapsed between the workshop and the publication of the present handbook.

Franceso di Castri and Malcolm Hadley 
Montpellier and Paris, France