Colour infrared aerial photography as a tool for vegetation mapping and change detection in environmental studies of Nordic ecosystems: A review

Abstract

The aim of the paper is to sum up knowledge of colour infrared (CIR) aerial photography as a tool for vegetation data for mapping and monitoring in environmental and biodiversity surveys and change detection surveillance. It compiles thirty years of research of the main ecosystems in Swedish vegetation, where the overall goal was to develop methods for mapping and monitoring vegetation by use of CIR aerial photographs, assess the accuracy compared to field-based mapping and to implement them as a tool in nature conservation and environmental planning. The methods include development of a classification system, identification and analysis of indicators, development of interpretation techniques, and evaluation compared to the data collected in the field. The CIR observable criteria are colour, texture, pattern, size, form, and density, based on spectral reflectance, physiognomy, life forms, ecological conditions, moisture and nutrition, vegetation period and phenology, topography, site conditions, and management methods. The methods have been used to produce vegetation maps of mountains, boreal forests, and mires in northern and central Sweden, in national inventories of wetlands, ancient meadows and pastures, key biotopes in forests and for monitoring agricultural landscapes.

Keywords:

• colour infrared aerial photographs
• interpretation methods
• monitoring biodiversity
• vegetation changes
• vegetation mapping

Acknowledgements

The projects have been supported by grants from the Swedish Environmental Agency, the Swedish Council for Natural Sciences, WWF Sweden, Formas, and Mistra. I thank many of my colleagues and students at the Department of Physical Geography and Quaternary Geology, Stockholm University, who have worked with me for many years on CIR aerial photography, on method development and applications. My thanks are due to Professor L. Wastenson, who long ago initiated me into the secrets of photo interpretation, and many of my students and colleagues, who are continuing to develop our methods, particularly Assistant Professor Helle Skånes, Dr Anna Allard, the late Dr Katarina Löfvenhaft, Fil. lic. Mats Leine, Bo Eknert, Merit Kindström, Siv Runborg, Thomas Rafsted.