Australia: The Land Where Time Began

A biography of the Australian continent 

Surveys of animals in Kakadu in 1986 and 1993 found a substantial reduction in numbers that was attributed to a run of poor wet seasons. Following a series of good wet seasons the same area was again surveyed, the numbers were found to be continually declining. The decline was found to apply to overall numbers of mammals, as well as for most species of animal. Some of the animals found to be in decline are the northern quoll, fawn antechinus, brushtail possum, northern brown bandicoot, dusky rat, black-footed tree rat and pale-faced rat (White, 2003). The same situation was found to occur in other parts of northern Australia. It is these same kinds of animals that have been found to be susceptible to local extinctions in other parts of Australia. Prior to this research it had been thought that the regional extinction patterns found in southern parts of the continent were not present in the north.

Based on the research findings, it appears the reductions are probably unrelated to seasonal variations, but rather a response to some management practice or other factor. According to White (2003), the most likely cause of the decline is widespread, destructive fires, together with pastoralism (it is the pastoralists who believe they are improving the pasture who light many of the fires just before the wet season). The composition of the understorey is changed by hot, frequent fires. Among the plants affected are the mid-storey trees and shrubs that produce fleshy fruit, the productivity and abundance of which are declining as a result. The reduction in numbers of large, hollow trees, hollow logs and litter affects much of the fauna, as the hollow trees are used for breeding sites by birds and mammals, and the hollow logs are refuges for many many small animals. There are also changes to the diversity and species composition of the grasses. The predictable result of all this habitat destruction is the regional extinction of many small animals. The result of the loss of small mammals from the ecosystem can be predicted by studying the observations made in the Yookamurra Sanctuary.

Across the monsoonal tropics there has been a widespread decline of both seed-eating birds and many mammals species. The effects of frequent fires on invertebrate and microorganisms (the basis of the ecosystems) is completely unknown.

According to Mary White (2003), 'Just a trip across the tropical north in the fire season, just before the monsoon, and you will not need to be told of scientific experiments to prove why Australia's biodiversity is being lost. It is caused by gross fire mismanagement and emphases the need for a complete reassessment of fire management on a continent-wide scale'.

Sources & Further reading

1. Mary E. White, Earth Alive, From Microbes to a Living Planet, Rosenberg Publishing Pty. Ltd., 2003
2. Mary E. White, Listen...Our Land is Crying, Kangaroo Press, 1997