Wetland Wildlife 4: Biological Diversity

WETLANDS WILDLIFE 4: Biological Diversity

Magpie geese (Anseranas semipalmata), Elizabeth Valley (Ian Morris)

A billabong contains an amazing variety of life forms which range from microscopic plankton, a host of invertebrate forms to frogs, fishes, reptiles, waterbirds and mammals. However, the diversity of species within each of these groups found in wetlands habitats is one of the reasons that makes the wetlands worth being included in the national estate. The Top End wetlands and bordering woodlands contain thirty-nine species of snakes. There are thirty-five species of frogs, three of them endemic, meaning they are found nowhere else in Australia or the world, and in Kakadu National Park an astounding 289 species of birds have been recorded.

Biological diversity (or biodiversity) is the variety of life. It has been defined as:

• the number of different species of plants, animals and microorganisms
• genetic diversity - the variety of genetic information contained in individual organisms and which occurs within and between distinct populations of the same species
• the variety of ecosystems, of which all plants and animals are part.

A species is a group of organisms genetically so similar that they can breed and produce fertile young. It is not just the number of species in an area, also known as species richness, that is important, but also the relative numbers of individuals per species. On the Mary River an estimated 250,000 fruit bats visit a group of paperbark swamps when the trees are in flower. Over 300,000 Magpie Geese gathered one year on the Daly-Reynolds floodplain to breed; they generally number about 200,000 in a wet season. Up to two and a half million water birds have been estimated to congregate in Kakadu National Park in the dry season between August and September.

What caused biological diversity to play such an important part in our present thinking about the natural environment? A rising tide of concern about species, gene and ecosystem loss around the world inspired the Convention on Biological Diversity in Rio de Janeiro in 1992. The convention has more than 30 countries as members, including Australia. The concept of biological diversity encouraged scientists, conservationists, and the general public to take a fresh look at ecosystems, and their interdependent parts, as key elements of nature. Biological diversity is a focus for assessing the effectiveness of our use of the land, of sustainable development and of the effectiveness of conservation programs.

In Australia, 50% of temperate woodlands and 50% of the rainforests have been cleared in 200 years. One hundred plant species (%) and seventeen mammal species (%) have become extinct in that small time. Three bird species have been lost and many more are now endangered. Nobody knows just how many smaller organisms -  invertebrates, ordinary little plants or microorganisms - have disappeared. By recognising the significance of biological diversity, by understanding that the term means more than just counting species, and through action to maintain biodiversity, it may be possible to halt the needless extinction of more plants and animals and the further degradation of our farmlands and catchment areas.

Figure 8. Some birds of the Top End wetlands