At one time the European rabbit was by far the worst environmental and agricultural pest in Australia. Biological control in the 1950s and 1990s gave the country massive relief. In fact, myxomatosis still kills more than 40% of the rabbits born in the country today, some 57 years after its release.
Rabbit haemorrhagic disease (RHD, formerly called rabbit calicivirus in Australia) gave further relief in the 1990s. The 2001 State of the Environment report noted its importance in restoration of vegetation and there is no doubt had a better starting point for the drought that is still affecting much of the country. These two examples are effectively the only big wins in vertebrate pests for biological control, although it is so important in weed and insect management.
There are two reasons to start looking seriously for new biocontrols now. One is that rabbits still cause massive damage to biodiversity when they are in low numbers. it takes very few rabbits to cause serious damage to plants - see the photos by Dr Brian Cooke that I've just posted. Secondly, we know that rabbit numbers are beginning to build again. It is always better to try for a solution to a problem before it is overwhelming you.