It is increasingly recognised that agricultural systems are dependent upon natural healthy systems of vegetation, animals and birds. Together these components protect soil from erosion and maintain fertility, help regeneration of vegetation, and control insect levels. The loss of trees and shrubs through clearing and dieback inevitably leads to the loss of native birds. Woodland suffering severe dieback has only 10 per cent of the birds of healthy woodland. Open pasture has fewer than 5 per cent.
Grazing often removes the understorey shrubs and grasses, making remnants less suitable for birds.
Birds rely particularly on eucalypt trees, and some 300 bird species live in eucalypt woodlands and forests. But they also need shrubs and grasses to survive. It may seem less obvious that Australian vegetation also need birds. Birds add natural interest, colour and sound to the bush. These costs would be similar in Australia if natural predators of scarabs, like magpies, were lost.