Both anecdotal and scientific evidence show that the scourge of Australia's rangelands – rabbits – are again a threat to the environment and the economy.
Despite the spectacular success of the biological control agents myxomatosis and rabbit haemorrhagic disease (RHD) in checking rabbit populations, the alarm bells are again ringing.
Rabbit control with these two agents has provided economic benefits worth more than $1 billion dollars, and enabled enormous recovery of native flora and fauna.
However, chairman of the Rabbit Management Advisory Group and Broken Hill woolgrower, David Lord, says it is imperative that complacency does not set in.
"Both viruses were released with spectacular results and they remain our most valuable rabbit control tools today," Mr Lord said.
"But, even under the current drought, rabbits have now recovered to the point where they are again threatening the gains that have been made since 1996.
"The environment cannot forgo the enormous native vegetation recovery that has occurred and land managers cannot afford to lose our recent gains in sustainability and productivity."
He says that scientific studies suggest that rabbits are developing resistance to RHD.
"Regrettably, we have not ecologically neutralised the rabbit. We have just had a spell for 12 years," he said.
"Resistance to infection with the original strain of RHD released now appears to be increasingly wide-spread."
Nevertheless, the full significance of the emerging resistance to RHD will not be known until there is information on the present status of current field strains – if these are evolving to at least partially off-set the development of resistance, then the disease could remain a useful rabbit control tool into the future.
If they are not, then options for future control need to be considered.
This includes re-investing in conventional techniques and researching new biological control methods.
Studies show that it takes only one rabbit per hectare to significantly reduce the capacity for many native plant species to regenerate.
Mr Lord says that the likelihood of finding another suitable bio-control agent is not unrealistic and one option to be explored would be the introduction of additional isolates of RHD from Europe.
"We must accept the fact that Australia will always require some degree of rabbit control, and we must again tackle the rabbit knowing that the gains are for industry and the environment," he said.
"While the rabbit remains, biodiversity is at serious risk, particularly in the inland regions."