ISSUES ARISING FROM MODIFICATION OF ECOSYSTEMS

In striving for utilisation of native species while sustaining Victoria's natural resources, the Committee is mindful that the natural environment is already under stress.¹⁰⁸

Since the arrival of European settlers in Victoria in the early 1800s, many vegetation communities have been cleared, fragmented and degraded; large numbers of grazing animals, both feral and domestic, have been introduced; introduced carnivores (cats, foxes, dogs) have become widely distributed; different fire regimes have been imposed; wetlands have been drained and polluted; fertilisers and pesticides have been spread widely; and extensive areas of pasture and crops have replaced diverse native vegetation communities. Many of these changes have had major effects on populations of native flora and fauna.¹⁰⁹

Total grazing pressure now includes rabbits, with their much faster breeding rate and quicker response to increases in feed than those of kangaroos, wallabies, or (generally) domestic stock. Rabbits considerably complicate interactions between plants, herbivores and predators in southern Australia and increase the risk of unsustainable grazing pressures.

In forests clear-fell logging and managed fire regimes have been added to the natural disturbance of wildfire. Adaptations developed by plant and animal species to cope with wildfire do not necessarily afford them the same protection in the face of these new disturbances.¹¹⁰ Clear-fell also produces young, even-aged forests with few hollows to provide nesting sites for birds and arboreal mammals. This has led to the local population decline of several species, including possums, gliders, bats and some birds.¹¹¹

In the non-arid areas of Australia, of which Victoria forms an important part, it has been estimated that 44 per cent of the land is in need of treatment to reverse some form of degradation caused by intensive land use.¹¹² Such degradation includes wind and water erosion, dryland and irrigation-induced salinity and vegetation degradation.

Aquatic ecosystems have also been modified as a result of soil erosion, salinisation, `regulation' and diversion. Exotic species have also been introduced, placing stress on native-fish populations through competition and predation:

Eight species deliberately introduced from overseas have established self-maintaining populations in Victorian inland waters. These are ... Brown Trout, ... Rainbow Trout, ... European Carp, ... Goldfish, ... Tench, ... Roach, ... Redfin, and Mosquito Fish ... Chinook Salmon is maintained through constant restocking. Aquarium species ... have also escaped or been disposed of in the wild and ... established self-maintaining populations.¹¹³

The Committee's recent Inquiry into Weeds in Victoria highlighted the huge environmental and economic impact of exotic weeds in Victoria.¹¹⁴ Many of these weed species were deliberately introduced. Exotic animal pests create similar imbalances in the ecosystem.

These vast and rapid changes have placed great strain on native ecosystems and species. Victoria's environment is far from being at equilibrium. The Committee recognises that assessing the long-term impacts of any form of utilisation under these circumstances is difficult. However, utilisation which places additional stress on populations could have unforeseen and severely deleterious impacts on some species.