Impacts on mammals and birds
Impacts on vegetation
Changes to the landscape structure have led to a decline in bird and mammal species and local extinctions. Only about one third of the tree cover is thought to remain today and this is now in the form of a diffuse mosaic of scattered trees, woodland and patches of forest.
There has been a decrease in woodland birds due to changes in the population density of shrubs and trees. Most species of birds in New England do not require extensive areas of intact woodland. In fact only 17 species are dependent on woodland areas that are larger than 400 ha but these are marginal in distribution (McIntyre and Lavorel, 1994).
The visible result of human activity in this area over the last 200 years has been the widespread decline of eucalypts.
Overgrazing has induced soil loss and loss of native species which is causing problems of sustainability.
Soil disturbance, fertilisation and intensive grazing have also brought about a loss of some native herbaceous species but some species are very tolerant and thrive under these conditions.
Severe grazing and the associated soil disturbance and water enrichment that are the effects of pastoralism, have led to a decline in native species and an increase in exotic species. Fertiliser use is also associated with a decline in native species richness.
Species richness
Since intensification of agriculture took place in this region, declines in species richness have been recorded.
Higher species richness is associated with structural complexity in the landscape (McIntyre and Lavorel, 1994). The McIntyre and Lavorel study is important because to maintain species richness, it is necessary to maintain habitat diversity.
Variation in species richness was analysed at 30m2 scale in relation to environmental factors and exogenous disturbance at 120 sites.
More details of this study are available on a linked page.
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