Jan 0kland. U.B.S./Dr W. Backhuys, Oegstgeest, Netherlands. ISBN 90-73348-02-1, 1990. 516 pp, 316 figures and 102 tables.
Originally reviewed by Ian Killeen in 1994.
Published in Journal of Conchology (1994), Vol.34
How can one assess a man's lifework in just a few paragraphs? In this elegant monograph Jan 0kland presents the results of research which began as an undergraduate project in 1953, with the objective of studying the distribution and ecology of freshwater snails in southeastern Norway. The fieldwork continued for a further 20 years and the scope of the project expanded to become the most comprehensive study of freshwater molluscs and their habitats ever undertaken.
The results are most impressive. They have been brought together in an A4 hardback book with text entirely in English. There are 13 main sections including methodology, the freshwater environment of Norway, environmental parameters, species distribution. There is a concise abstract and two excellent summary and discussion sections. I feel that a considerable amount of thought has gone into the style and layout of this work. With the vast amount of data it presents it would be very easy to produce a complex, almost unreadable tome. However, there are a great number of sub-sections each with discussions and summaries. This makes for a very readable and accessible work, a feature that is particularly important for such a reference book.
There are 27 species of freshwater gastropod occurring in Norway of which only Valvata sihirica is not found in the British Isles. Thus much of these data and conclusions may be applied to species and environments in this country. A major chapter in the book is devoted to a species approach,
Each species is described and photographed, with comments on its distribution in Norway and surrounding areas and a discussion of its ecology in Norway. Of particular interest and use is the table summarizing the environmental factors that characterize the collection sites for each species. Also included are 4 distribution maps for each showing author's records, all records and 50 km square records for the whole country and a more detailed map for the southeastern study area. Although the focus for the study was southeastern Norway, the national coverage by the author is impressive by any standards and we can be sure that all the maps show real distribution patterns. A significant part of the fauna is restricted to the lowland areas in the southeast, although many extend well into the Arctic Circle. A species that might well catch the attention of the British reader is Gyraulus acronicus. In this country it is rare and possibly heading towards extinction, yet in Norway it is common, geographically widespread and is apparently catholic in its environmental requirements.
It is from the sections on environment and species that many of the most important conclusions are drawn. There are comprehensive analyses and descriptions of parameters such as geology, vegetation, surface water type and water chemistry. From a comparison of these data many relationships have been shown. For example it has been demonstrated that freshwater gastropods are sensitive to low pH, water hardness and the interaction between the two. The environmental implications are clear; freshwater snails are likely to be affected by acid rain and acidification of freshwaters and they are therefore important indicator species for environmental monitoring. On this basis this book will be an invaluable reference work.
This is so much of interest in this book and not just to malacologists and biogeographers. It will be of great value to limnologists, ecologists, conservationists, scientists in the water industry, students and so on. At £68 it is not unreasonably priced. A classic - thoroughly recommended.