Cooperative Research Centre for Freshwater Ecology, University of Canberra, Australia E-MAIL: pa@lake.canberra.edu.au

Abstract

Introduction
The conservation of biodiversity is a major area of public concern internationally, and there has been considerable activity to protect biodiversity in both terrestrial and marine ecosystems in Australia. There has been a more limited effort with regard to freshwater conservation (Cullen and Lake, 1995). Despite a major public interest in native fish, water-birds and unique aquatic animals like platypus, there is much less understanding that the maintenance of these icon species requires aquatic systems that have adequate flow regimes, adequate water quality and appropriate stream and connecting floodplain habitat. There is limited appreciation of the fact that we can not manage and maintain icon species without maintaining the ecological communities of which they are part. Similar principles could apply to the widespread concern in Australia about the impacts of invasive species like carp and some of the pest water plants.

The Case for Conserving Some Aquatic Ecosystems
Four reasons can be articulated for the need to maintain biodiversity in Australian aquatic ecosystems:

• to meet international biodiversity obligations (Australia signed the International Convention on Biological Diversity of 1992 in June 1993),
• to provide benchmark reference areas to assess how managed rivers have departed from the natural (Franklin, 1989),
• to provide "seeding" sources to help re-colonise downstream areas that have been damaged,
• to acknowledge that the various aquatic species are of value in themselves, and the communities provide essential and often irreplaceable ecosystem services.

Meeting International obligations is made difficult in Australia since the Federal government has the responsibility for making international agreements but it does not have the Constitutional responsibility for managing natural resources. It can only meet the international obligations through collaboration with the Australian States, which often involves Federal funding. Governments have attempted to develop reasonable terrestrial reserves to meet these obligations, and are also attempting to develop marine protected areas. Obligations to protect freshwater biodiversity have involved limited protection of some wetlands but this remains a serious gap in Australia's international commitment.

Aquatic conservation is not an attempt to restore aquatic systems to some "pristine" state that is assumed to have existed before white colonisation. But it is important to maintain some long-term reference sites to enable understanding of the impacts of human intervention and things like climate change (Strayer et al., 1986; Swanson and Sparks, 1990).

Rivers are linear systems that are seeded with biological material from intact upstream reaches and this is essential to maintain downstream river health. The need for connectivity both upstream - downstream and from the stream to the floodplain is now well recognised.