Millions of years ago, rainforests covered much of Australia when it was part of the great southern supercontinent, Gondwana. After Australia broke away and began its movement northwards, it became warmer and drier, making conditions for rainforest less favourable.
The burning of bushland by Aboriginal people probably diminished the size of rainforest patches. When the first European settlers arrived, rainforests were largely restricted to many small refuges where favourable conditions existed. Isolated patches occurred from Tasmania, through southern and eastern Victoria, eastern New South Wales and Queensland, and across northern Australia to the Kimberleys.
During the past two centuries, many rainforests have been destroyed or modified, yet within them is found a large proportion of the country's plants, animals and fungi. Some species have become rare or are extinct.
All rainforests in Australia, including small remnants, are of great value to science. From a purely economic viewpoint, there is unknown potential for life-saving medicines and other valuable resources.
There has been an increase in interest in rainforests in Australia recently but much remains to be learnt. The Robertson rainforests are no exception - detailed studies of their nature are yet to be completed. Only the Robertson Nature Reserve is adequately protected. This, however, is insufficient as one of the district's finest trees, the Pinkwood, is not found there. The original forests were far from uniform. More of the remnants should become reserves to ensure that they survive for future study and enjoyment.
Robertson rainforests are home to certain native animals which depend on them for food and shelter. There is much more to learn about invertebrates, other small rainforest animals and fungi. It would be unfortunate if extinctions occurred as a result of poor management.
Soil erosion is a problem on steep land during heavy rains. Not only is soil lost but dams are affected. The Nepean Dam is largely supplied from Robertson and it has lately suffered from siltation. Tree cover is a possible remedy.
Rainforest vegetation in the district is protected by the New South Wales Government's Illawarra Regional Environmental Plan No 1, which states that a person shall not clear vegetation on land supporting rainforest species, or adjacent land, without the consent of Council. Approval cannot be given by Council without consultation with the New South Wales National Parks and Wildlife Service. Heavy fines can follow clearing without consent.
Where the conditions of precipitation, soil fertility, available seed source, and protection from bushfires and drying winds are adequate, rainforests will naturally regenerate. In the Robertson district, such conditions are excellent. Where farming has ceased, new forests are growing. Pioneer trees are Blackwood, a very quick grower, and Sassafras, which will regrow from underground stems even after many years of slashing. The vine, Twining Guinea Flower, and some Daisy Bushes are also early colonizers. On the outer edges of advancing rainforests, Native Mulberry, Sweet Pittosporum, Kangaroo Apple, Rough Treefern and Victorian Christmas Bush are also found. Forests which contain only these pioneer species might be regrown forests. It might take centuries for them to return to something like an original state, with Coachwood, Featherwood, Brown Beech, Black Oliveberry and Pinkwood.
Rainforest regeneration projects often have problems with introduced plant species. Local rainforests are threatened by weeds, which should be persistently removed. A thorough knowledge of plant identification and eradication techniques is vital. Soil disturbance and breaking the canopy can favor weed growth.
Trampling of seedlings and the loss of most, if not all, understorey herbs and ferns results from the use of forest remnants for stock shelter. In cases where this pressure has been removed, the difference observed after only a few years is remarkable. Therefore, landholders who have rainforests should fence them. Fast-growing Blackwood could be grown elsewhere for substitute shelter.
Remnants will best preserve native plants and animals when those remnants are large, with a low perimeter to area ratio. It is advantageous to link remnants with corridors of native plants, as some animals cannot survive when isolated.
Native animal populations are integral to rainforest ecosystems and their survival will be favoured by the destruction of feral cats and foxes. Domestic cats should be kept indoors at night.
Planting native rainforest species for timber production on cleared land promises to be a viable enterprise. Where better to do this than here, where conditions are naturally ideal ? Blackwood, Coachwood, and Scrub Beefwood are some of the valuable timbers that survive at Robertson.
How can a rainforest be re-established ?