The Australian bush, while relatively hardy, can be undone by introduced species. Cats, in particular, have a disastrous impact on native flora and fauna by hunting native birds and animals, eating an estimated 75 million creatures each night. Taking these creatures out of the delicately balanced system can send other species into overdrive and limit the propagation of native flora that relies on being consumed and released as droppings to spread. Here are some stages to reestablish some balance in your bush land if it has been damaged by the presence of feral cats.
Keep the cats out
The first step is to limit the current damage by erecting fencing to keep the cats out. If you find that the cats are still making it through the fencing, you should call your local wildlife department to arrange 'baiting' (where you leave meat with poison to discourage hunting animals).
Survey the bush land
Take a survey of the species that you can observe in your bush land and get in contact with an environmental consultant to discuss how this compares to nondisturbed bush land. You can start a plan to remove any other species that have gone out of control over this time and reintroduce any species that have been lost over this time. Given the interconnection of flora and fauna, it is important to ensure any reintroduced species have adequate food to eat.
Plan the removal of weeds
With the loss of herbivorous animals, you can often get an overgrowth of plants, both native and introduced. It can be hard to chemically remove weeds without injuring animals that may eat these plants, so it's often more effective, although time consuming, to manually remove weeds. Removing weeds is an important step in allowing native plants and animals to thrive.
Support insects and animals to thrive
As you reintroduce native species, it can be useful to initially do some supplemental feeding such as leaving fruit and grains for the species to initially eat while they are getting used to their location and finding new places. Bee boxes can also be a good way to support the local fauna establishing itself, as well as the animals that eat bees. Bees have a massive impact on the success of bush regeneration, as they are required for the pollination of any flowers.
If you are looking to do some bush regeneration after it has been affected by cat hunting it is useful to get some input from an experienced environmental consultant.