Understanding our lakes

Press, Volume CXVI, Issue 34130, 17 April 1976, Page 10

Understanding our lakes

New Zealand Lakes. Edited by V. H. Jolly and J. M. A. Brown. Auckland University Press-Oxford University Press. Bibliography, glossary, three indexes. 388 pp. N.Z. price $17.50. Forest, grassland, and lake, have been used in New Zealand long before they were properly understood. The South Island alone has more than 500 lakes, and many of them have been used since the 1860 s, when trout were introduced, and later when they became hydro-electric reserviors, yet, for years hardly anyone was interested in what was happening. Gradually attitudes changed, more and more people studied lakes and rivers, and in 1968 the New Zealand Limnological Society was formed. Soon afterwards Dr Jollv, a pioneer in the study of New Zealand lakes, and Estuary life The World Of An Estuary. By Heather Angel. Faber and Faber. 128 pp. U.K. price £1.95. Having an estuary on their doorstep, most people in Christchurch know what it looks like but fewer people, especially those among the younger generation who have not studied any biology, will know how adaptable plants and animals must be to thrive where river, land and sea meet and the environment is constantly changing. There seem to be few books devoted exclusively to the study of estuaries, and though “The World of an Estuary” was written for young British students, the principles involved are relevant here. Species may be different but plants and animals in our estuary have the same life-forms as those described in this book. The accounts of visiting fish and birds are relevant, and some of the unpleasant effects of man on estuaries unfortunately apply here too. Finally, there is guidance and advice on how estuaries may be studied by young naturalists. The book is well illuatrated with photographs and linedrawings and should be in school libraries.

Dr Brown, had the vision, ability and courage to plan “New Zealand Lakes”. Tragically, Dr Jolly died before it was published. Appropriately it is dedicated to her memory. Limnology, the study of inland waters, is a composite subject, made up of many parts; it deals with everything in inland waters and their drainage basins, and with the interrelationships between them. “New Zealand Lakes” ■ mentions more than 200 of them, about a quarter of the total number in the country. It begins by describing” their form, and origin, particularly those created by glaciers and volcanic activity. Chapters on the physical and chemical characteristics of the waters refer, among other thing, to the far-reaching effects of wind, the sorry state of Lake Rotorua, and the man-made lakes along the Waikato River. About half the book is devoted to the biology of lakes. There are accounts of microscopical plants, including those which cause serious problems when water is enriched in plant nutrients and become eutrophic. Lakes Forsyth, Hayes and Johnson are now outstanding examples of such enrichment or eutrophication. There are chapters about the larger aquatic plants (some of these are pests) and seven chapters about animals in various parts of lakes, including the birds, fish and sport fisheries. Though “New Zealand Lakes” might have ended with an integrated summary’, it was probably too early to attempt this. There is discrepancy in the use of the word '‘eutrophic” — some lakes in Westland seem to be richer in food for birds than they are for microscopic plants. Confusion may arise where the same name is given to different lakes, for example there is Lake Rotoiti near Rotorua, another near Nelson and a third near Kaikoura. Unfortunately, some lakes are omitted from the maps. This needs correction in later editions. “New Zealand Lakes” is wellproduced, pleasant to handle, and has numerous good illustrations distributed throughout the text; it should be welcomed by limnologists, anglers, bird-watchers and all who value lakes as part of their national heritage.