The accessible parts of the extraordinary and extensive biodiversity of the Park represent a small part of the probable total number of lifeforms there. In the species diversity that makes up our world, insects are the dominant group. There are some 756 known species in the Park, a number that could stretch to as many as 5,000 if it was possible to catalogue all microscopic, but essential, organisms such as bacteria. The mammals, of which we are part, represent less than one percent. We bear a large responsibility for the extraordinary influence our lives have on all those living things around us. The diagram is intended to represent graphically an estimation of how the total global number of species is made up. It is based on data found in E. O Wilson, The Diversity of Life, Harvard Press 1992, rev 1999.
Illustrations by Lyndel Wilson, Graphic George Foster
Introduction to Biodiversity
Andrew Beattie and Wendy Carter
Biodiversity is biological variation at all levels, including the genetic variation between individuals in a population, among the populations that comprise a species, among the species that make up communities and between the communities scattered across the landscape.
Genetic Diversity found in a population enables it to adapt to local conditions. Also, as each population in a species is geneticallyslightly different from the others, populations together form a store of genetic information that allows the species to cope with a variety of conditions.
Species Diversity is the total of all species in a given area, such as the Park. At least 517 flowering plant species have been seen in this area as well as 168 bird, 19 native mammal, 38 reptile and 14 frog species – a total of 756 species.While this total may seem high, it is a small number relative to the total number of invertebrate animal, moss, lichen, fungus and bacterial species in the same area. This total is currently unknown but a conservative guess would be 5000 species. Although most of these organisms are small to microscopic, they are vital to the ecosystem processes such as nutrient recycling, energy flow, pollination, seed dispersal, the disposal of wastes and decomposition that maintain the beauty and the function of the Park.
The Park is home to some very special species that are either rare or threatened (remember, some species are rare naturally and not necessarily threatened). These include the following flowering plant species:
| Acacia bynoeana,|
Persoonia mollis subspecies maxima
as well as the
Red-Crowned Toadlet and the
Giant Burrowing Frog.
By contrast with these figures from the flowering plants and vertebrate animals, the
numbers of rare or endangered species of invertebrates and micro-organisms are unknown. Further exploration of the Park will undoubtedly reveal not only more rare or threatened species, but species completely new to science. Aside from the beauty and ecological function of each species, it is impossible to tell which ones will be useful. Tea tree is the source of important oil products, a local bull ant the source of a patent for a new family of antibiotic substances, and even the humble leech has yielded chemicals of major clinical importance.
Community Diversity is the variety of natural communities in an area such as the Park. Communities are usually defined by the dominant flowering plants and on this basis there are 17 recognised plant communities. However, within each of these there are smaller communities that may be defined by almost any kind of organisms, including, for example, butterflies, beetles or bacteria. Thus, a widespread plant community harbours a great variety of smaller ones. At the other end of the scale, communities cluster together on any patch of landscape to form an ecosystem.
Ecosystem diversity therefore refers to the different assemblages of communities in an area of land (or freshwater or ocean). Two hundred years of settlement by Europeans have generated major threats to local and national biodiversity. Vegetation clearing, pollution, over-harvesting of natural resources and unsustainable development have all contributed. All human activities, including economic ones, take place within a natural ecosystem and therefore potentially affect biodiversity. Recent history shows that when environmental management fails, these effects feed back to us in terms of declines in the quality of water, air, soils and human life. Every ecosystem is populated by many thousands of species, most of which are beneficial because their combined activities maintain the ecosystem services that support us.
Beattie, A.J. (ed.) 1995, Australia’s Biodiversity: Living Wealth, Reed Books, Chatswood, NSW.
Benson, D.H., Howell, J. & McDougall, L. 1996, Mountain. Devil to Mangrove: A Guide to Natural Vegetation in the Hawkesbury-Nepean Catchment, Royal Botanic Gardens, Sydney.
Flannery, T.F. 1994, The Future Eaters: An Ecological History of the Australasian Lands and People, Reed Books, Chatswood
Hornsby Shire Council 1990, Berowra Valley Bushland Park: Draft Plan of Management. Stage 1, Parks and Gardens Branch, Hornsby
Mummery, J. & Hardy, N. 1994, Australia’s Biodiversity: An Overview of Selected Significant Components, Dept. of the Environment, Sport and Territories, Biodiversity Unit, Canberra.
National Parks and Wildlife Service 1997, Draft NSW Biodiversity Strategy, NPWS, Hurstville, NSW.
Smith, P. & Smith, A. 1990, The Vegetation and Fauna of Berowra Valley Bushland Park, Hornsby Shire Council.