Lake Biwa as a topical ancient lake

Abstract

Abstract Present knowledge concerning the Japanese ancient Lake Biwa is briefly summarized, and extant and potential threats to its well-being are documented. From this example of Lake Biwa, strengths and weaknesses in our knowledge of other ancient lakes and the problems that they face were identified. Several areas of concern were evident. Knowledge of the geological history of ancient lakes is uneven, as is the accuracy and degree of detail of geochronological information available. This greatly complicates meaningful results from studies of palaeohydrology, palaeobiology and palaeoecology. In all ancient lakes, future research must place greater emphasis on these areas. Such studies can both unravel and facilitate an understanding of the history of the lake and the reconstruction of evolutionary scenarios. Ancient lakes are recognized as hotspots of diversity and centres of endemism, but in no ancient lake has an adequate inventory of biodiversity been compiled to test hypotheses concerning patterns of diversity or its regulation. More effort is needed in this area. The importance of such baseline data is exemplified by the case of Lake Biwa, where the absence of quantitative studies of the native fish communities before, during or after the introduction and subsequent population explosions of largemouth bass and bluegill has prevented any meaningful evaluation of the effects of these alien fishes on the native fauna. Lake Biwa has had more ecological insults inflicted upon it than any of the other ancient lakes of the world; physical, chemical and biotic perturbations, including alien introductions and overfishing, have all taken their toll on the lake ecosystem and continue to do so. Measures to ameliorate some of these perturbations are suggested, some of which will require heightened ecological awareness and brave decision making on the part of the authorities who manage this ecological treasure. It is hoped that the organizations and governments responsible for the well-being of the other ancient lakes of the world will heed the example of Lake Biwa when arriving at management decisions concerning the unique biotas and resources of which they have change.