Satellite remote sensing for forestry planning—A review

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Abstract
This review attempts, from a critical perspective, to put 25 years of satellite remote sensing research into the context of forestry planning. It is limited to temperate and boreal regions and to remote sensing in the visible and near infra-red spectra. It is structured as follows: firstly, the forestry planning problem is defined and information requirements are identified; secondly, the attempts to use satellite remote sensing as an information source for forestry planning are reviewed, divided into the topics inventory and monitoring; and, finally, the methods for extracting forest information from satellite images are re-examined, and their inherent limitations and methodological weaknesses are discussed. It is concluded that satellite images seldom contain enough information to support the decision process in applied forestry. Although regional level applications may be useful, few successful and reliable applications for local forest inventory, planning or damage monitoring have evolved. Stratification for multi-stage sampling and monitoring of clear-cuts are areas in which satellite images have been shown to be feasible. However, it is doubtful whether the costs involved call be justified fur such uses alone. A further conclusion is that many studies have adopted simplistic views of the information needs in the forestry planning process, These studies do not relate the analysis to management decisions, but instead assume that plain and approximate mapping of the forest has a great value. Present developments in the discipline involve complex modelling of reflectance, taking into consideration internal shading, topography and other features, yet without dramatic improvements compared with earlier studies. Furthermore, satellite remote sensing and digital image analysis are no longer technologically spectacular, facts which may affect future research in the discipline. It is, perhaps, time to draw the conclusion that current satellite sensors are not in general suitable for forestry planning, since (a) they contain little relevant information, and (b) for forest management planning purposes there are often more efficient ways of collecting the information required.