Mathematical models for forest management planning
Forest regulation, harvest scheduling, and planning techniques
. W. A. Leuschner, 1992. New York, John Wiley.
Management activities have always been one of the most important aspects of commercial forestry. In recent years, however, the changing needs of modern society have shifted the focus of these activities to encompass forest uses that are not directly connected to timber production. In addition, the development of improved modelling techniques has led to great changes in the approach to planning. The objective of this book is to provide an overview of traditional forest management approaches while, at the same time, introducing updated techniques. The book was mainly developed as a manual for forestry students but could also be useful for professional foresters wishing to update their knowledge and review the latest developments in planning and modelling.
The early chapters review traditional approaches for scheduling the timber harvests of a forest over time. These approaches are simplified in that they commonly use a single idealized stand to represent the entire forest. The essential question considered is "at what age should the stand be harvested?", with possible variations such as "at what age should the stand be thinned in order to improve the value of the final harvest?". When these questions are framed within the context of a single representative stand, the topic is referred to as "forest regulation". Most forest regulation models predate the computer age and for this reason they are now regarded as oversimplified, unless the forest itself is quite simple in form. The author shows that each of the classical regulation models can be formulated as a mathematical programming model, although doing so is mostly of academic interest.
The second part of the book examines the topic of timber harvest scheduling, which may be thought of as "forest regulation for the computer age". Harvest scheduling models are designed to answer the same questions as forest regulation models but permit much greater flexibility in specifying details that describe the complexity of forest systems. The development of mathematical programming techniques, especially linear programming, has made it possible to formulate harvest scheduling models which are sufficiently complex to serve as reasonable representations of forests and yet still be solved. Not by hand, however: for such problems, the computer becomes an indispensable item of forestry equipment.
Both forest regulation and harvest scheduling are discussed from the perspective of a decision-maker who wants to maximize the volume of timber harvested from a forest over one or several rotations. In a third section of chapters, Leuschner broadens this focus to consider the economic objectives that are important in many public forests and essential in most private forests. These chapters introduce criteria such as present new worth, internal rate of return and land expectation value, all of which are useful for evaluating forest plans. Several important forest planning models that utilize economic criteria are also discussed.
The fourth and final portion of the book explores the topic of comprehensive forest planning, as aided by mathematical programming. The first chapter in this final section discusses the general topic of multiple-objective analysis. Examples are provided that utilize the conceptual full-knowledge model, constrained linear programming, goal programming, composite objective functions and parametric programming. For each of these methods, the author discusses not only the mathematical formulation but also considerations that should be addressed before a particular model is selected for use. He also comments on the relative efficiency of the different approaches and possible pitfalls in their application.
The final chapter is devoted to dynamic programming, a class of mathematical programming models in which the system equations can be used in practically any form: linear, nonlinear or discontinuous. The arithmetic needed for solving the problems is very simple, thus making the computer programming relatively easy. Unfortunately, the number of evaluations needed to find an optimal solution is so large that, even with modern computers, practical applications are limited to small problems. Two appendixes, one on linear programming and another on after-tax cash flows, complete the book.
The book gives a good overview of both traditional and modern planning techniques. All chapters are well organized and quite thorough. However, probably because it was born as a textbook, it sometimes lacks fluidity and chapters appear to be isolated from one another. The fact that a single forest example is used throughout most of the book makes comparisons easy but it does lead to a certain lack of variety. Finally, considering that one of the main objectives, as stated in the introduction, was that of examining new approaches to forest management, multiple-objective formulations could have been examined in more detail.
S. Borelli
New publications from the FAO Community Forestry Case Study Series
The FAO Forests, Trees and People Programme (FTPP) focuses on developing and strengthening people's ability to control the management of local forest resources in a sustainable and beneficial manner. One of the principal activities of the FTPP is information dissemination. The Community Forestry Case Study Series describes projects or programmes in which rural people have developed forest resources to respond to local problems and needs. These studies identify factors of the individual, community and/or national level that contribute to success and could find a broader application.
Social and economic incentives for smallholder tree growing. A case study from Murang'a District, Kenya
. P.A. Dewees. 1993 Community Forestry case Study Series No. 5 Rome, FAO.
This study, by natural resource economist Peter Dewees of the Food Studies Group of Queen Elizabeth House, Oxford University, is the result of research undertaken to explore the rationale for smallholder tree growing in its historical and sociocultural context in Kenya. It aims to address two sets of questions. First, how does tree growing, as a labour-intensive cash cropping activity, complement urban wage employment as a strategy for overcoming problems with capital, land and labour markets? Do trees ease or intensify land-use constraints imposed by labour migration? Second, does tree growing, an activity that requires low levels of capital input, have any particular advantage as a land use in situations where limited credit sources have made it difficult for farmers to plant other more capital-intensive cash crops?
In attempting to answer these question the study summarizes some of the descriptive and historical information available in an attempt to describe the evolution of labour markets and land tenure systems and their impact on tree growing. It also reviews traditional tree cultivation and management practices as well as the pricing and policies that brought about changes in land use which, in turn, affected particular types of tree-growing practices.
The study concludes by examining some of the issues of relevance to planners and developers in their efforts to encourage farmers to grow more trees. First, it suggests that tree-planting innovations must take into account local farmer ability and traditional knowledge; second, it is important to recognize that tree growing is a viable option, especially when labour and capital constraints limit agricultural development; and third, existing controls on tree cultivation and management must involve the local population and be more consistent. If farm production of trees is to be encouraged, farmers must be assured that they - rather than the government or local administration - will reap the benefits. Although much of the study focuses on tree-growing activities in Murang'a District in the Central Province, many of the observations and conclusions are relevant to other parts of Kenya and there are certainly parallels to other parts of Africa as well.
Shifting cultivators of Indonesia: marauders or managers of the forest? Rice production and forest use among the Uma' Jalan of East Kalimantan
. C.J Pierce Colfer and R. G. Dudley. 1993. Community Forestry case Study series No. 6. Rome, FAO.
Shifting cultivation systems and their sustainability as an approach to indigenous forest management have been greatly debated. Many policy-makers worldwide consider all shifting cultivators to be villains, "primitive" remnants in otherwise civilized societies who wreak havoc on valuable forests, in spite of convincing evidence that, at least in some circumstances, shifting cultivation is quite sustainable and can provide a model or base on which "modern scientific" agroforestry techniques can build profitably. This case-study continues the evaluation of these natural resource management systems by examining the process of change and development in the system of shifting cultivation practiced by the Uma' Jalan Kenyah over three decades, tracing them from their homeland in the remote interior of Borneo through to their involvement in a government-sponsored resettlement programme and their ultimate dispersal and formation into three new daughter communities. These four communities are compared with regard to population, land/forest use, productivity and land tenure. The analysis sheds light on the nature of shifting cultivation, including its potential as a model for improving agroforestry development, and can serve as a stimulus for agricultural and forestry scientists to attempt to improve these systems rather than trying to supplant them.
In a concluding section, the study makes a number of policy recommendations, including better control of the timber industry, acknowledgement of local people's claims to their land, incorporation of indigenous knowledge into agroforestry development efforts, cessation of projects which increase Kalimantan's population and financial help from the community of nations to help Indonesia in these efforts.
Peasant participation community reforestation. Four communities in the Department of Cuzco
, Peru. 1993. Community Forestry Case Study Series No. 7. Rome, FAO.
This case-study examines the history of government-sponsored communal afforestation efforts in four communities of the Cuzco Department of Peru. It conveys the village perspective on three decades of afforestation, analysing the differential impacts of tree-planting efforts on various subgroups within the villages. The studies describe the communities and the ways their reforestation ventures developed, demonstrating the way local community requirements, social structures and institutions can affect the development of participatory reforestation efforts. In this manner, the study examines the incentives and disincentives to tree planting for distinct groups of community members, also assessing the constraints to reforestation as well as the problems these communities have faced in the distribution of costs and benefits. Finally, the study provides some general guidance regarding factors that encourage or discourage participation in tree-planting activities.
The case-studies reveal a complex set of factors at play in the process of village reforestation. While communal work was traditional in the communities of the Cuzco uplands, changing patterns of ownership and power as well as a changing relationship with the outside world, made the possibility of long-term communal arrangements much more difficult. Some factors, such as constant shortages of local fuelwood, the promises of tangible benefits and familiarity with communal work, appear to have encouraged rural villagers to engage in community-based forest management. Other factors, however, posed severe obstacles to and caused great dissatisfaction with communal reforestation.
Some factors may even have facilitated reforestation at one time and discouraged it at others. When outside agencies and local communities begin to work together on reforestation, there is no substitute for a sensitive and realistic assessment of local needs, customs, socioeconomic structures and social relations.
FAO Forest Harvesting Case-studies
The Forest Harvesting and Transport Branch of the FAO Forestry Department produces a series of case-studies to assist developing countries in promoting harvesting systems, techniques and methods designed to enhance productivity, reduce waste of resources and make forest operations more environmentally acceptable. Emphasis in selecting techniques for inclusion in the case-study series has been placed on systems that favour local people's participation, increase employment and income opportunities and thus contribute to self-reliance and the development of local communities in rural areas. The series was initiated in 1988 and, with the publication of the two studies discussed here, now numbers seven volumes. Serial numbers have only been introduced with the two current works; thus, they are numbered 1 and 2, respectively. The previously published but unnumbered volumes in the series are listed at the end of this article.
Reduction of wood waste by small-scale log production and conversion in tropical high forest.
Forest Harvesting Case-study No. 1. R. Kilkki. 1993. Rome, FAO. (In English)
Studies by FAO have shown that nearly half of the timber volume felled during commercial harvesting operations in tropical forests remains in the forest as unutilized residue after the loggers have departed. Utilizing even a fraction of this residue would reduce the area of forest that must be harvested to produce the approximately 235 million m³ of industrial roundwood which is removed each year from tropical forests.
The case-study reported in this document covers a portable sawmill developed in Papua New Guinea and installed in the Kui logging area in Morobe province, as part of a multiyear effort by the Government of Papua New Guinea to improve harvesting and primary processing of tropical timber. The purpose of the study was to measure and analyse the productivity, recovery rate and sawn timber quality of the sawmill (which is locally known as the Wokabout Somil) in order to increase possibilities for reducing waste and improving round timber usage in commercial logging operations in Papua New Guinea.
The study found that the quality of the sawn timber from the mobile sawmill, assuming a well-trained crew, was adequate to meet grading rules for construction timber in Papua New Guinea. Moreover, the mobile was found to be of particular value as a means of processing reject logs that do not meet export requirements but are of potential value for local use. The mobile nature and relatively low cost of operations of the Wokabout Somil allow its use by small-scale operators to process timber for local use from trees left standing in the forest after commercial harvesting operations have been completed, as well as from logs rejected at the export harbour. In both cases, it provides a cost-efficient means for local people to become involved in and benefit directly from management of forest resources.
The study also noted, however, that the bulk of the Wokabout Somil is somewhat excessive, and though it is not as rigid as a stationary mill, it is too heavy to be transported manually in the forest.
Thus, the sawmill is mobile only as long as a road exists. Development of two new models, one a village-level stationary sawmill and the other a truly portable mobile sawmill both based on the same basic idea, warrants consideration in the future.
Cosecha de hongos en la VII región de Chile
. 1993. Estudio Monográfico de Explotación Forestal No. 2. Rome, FAO. (In Spanish)
Non-timber forest products, including edible wild mushrooms, are an important element in the development of rural forest areas in many countries. This study examines the collection, processing and marketing of edible wild mushrooms in commercial Pinus radiata plantations in Empedrado, a particularly poor area of Chile.
Based on an exhaustive study of the existing literature and intensive interviews with local people, plantation owners and managers and people involved at all levels of the mushroom harvesting, processing and marketing process, the study presents a-brief yet comprehensive overview of the situation. Particularly significant is the relationship between the factors directly related to mushroom production and the wider socio-economic environment.
Mushroom collectors tend to come from the poorest economic strata of the community but, within this group, the income generated from mushroom collecting has a significant and positive effect on family income. Despite the fact that mushroom collection is a seasonal activity, annual income of mushroom collectors may be more than double that of other families.
In the past, mushroom collectors did their own processing but the two phases are now divided, with specialized processors and marketers responding to the increasing quality demands from the urban national and particularly international markets (more than 70 percent of total production is exported).
The study evidences the rapidly growing, dynamic nature of the mushroom "industry" and notes the possibility for continued increases, both in terms of total volume collected and in terms of value-added processing.
However, the study also notes that there are important uncertainties in the system, particularly at the collection level. Currently, mushrooms are gathered "free" by local people on forest lands that are owned or managed by large commercial forestry plantation operations.
Unless this situation is addressed and institutionalized in some manner, as the value of the mushroom industry continues to increase, local people risk being excluded from the process.
Previously published forestry harvesting case-studies:
Intermediate technology in forest harvesting: agricultural tractor with winch: Tanzania
. P. Alhojärvi. 1988 Rome, FAO. (in English)
Intermediate technology in forest harvesting: agricultural tractor and forest trainer with mechanical crane: Ethiopia. R. Jakobsson. 1988. Rome, FAO. (In English)
Plastic log chute in steep terrain thinning operations: Republic of Korea. L. Leppänen. 1989. Rome, FAO. (In English)
Integrated small-scale forest harvesting and wood processing operations: Zimbabwe. O. Eeronheimo. 1990. Rome, FAO. (In English)
Forest harvesting with small-scale mobile crane system: Republic of Korea. O. Eeronheimo. 1991. Rome, FAO. (In English)
