Eradicating fire ants is still possible, but we have to choose now

Australia needs to spend millions of dollars more to eradicate one of the nation’s worst invasive species, the fire ant, according to recent reports.

Fire ants, first detected in Brisbane in 2001, pose a major health and agricultural risk. A recent independent review of the eradication program recommended that A$380 million be spent over 10 years to eradicate the ants, on top of the A$330 million already spent since 2001.

Improvements in knowledge and control methods mean that eradicating the Australian invasion is challenging, but still potentially feasible. We now face a stark choice.

Lessons from previous attempts

The fire ant eradication program began in September 2001 after the species was detected at two locations in Brisbane. By that time, it may have been present for at least five years or perhaps even longer, and large areas were already infested. Fire ants had never been eradicated from areas this large.

However, improved eradication methods mean we have increased the chances of eradicating larger invasions.

Most of the original funds were spent on pesticides and monitoring areas with likely infestations. Monitoring information was used to estimate how far the invasion had spread (“delimitation”) and management efforts were focused on the delimited area.

The early years of the program showed that large infestations, such as those at the Port of Brisbane and Yarwun, can be eradicated when the geographic range of the infestations is known.

However, when this is not the case, undetected nests beyond the known infested area can spread unchecked. In a published reconstruction of the invasion we estimated that undetected nests existed a relatively short distance beyond the delimited area.

Had those nests been detected by monitoring a larger area over the first few years of the program, the ants may already have been eradicated. However, the initial focus on intensively treating known infestations rather than expanding the monitored area reflected the best available scientific advice at the time.

It also reflected an urgent need to protect people from the potentially serious health consequences of coming into contact with fire ants in areas known to be infested.

Is eradication still possible?

Although the invasion now occupies a larger area than it did when the program began, fire ant numbers have effectively been suppressed and some individual infestations have been eradicated. These facts, and the availability of a cheaper monitoring method involving remote sensing with airborne cameras, have kept alive eradication hopes.

A recent meeting of agricultural ministers agreed with the finding of the independent review that eradication remains technically feasible.

The review’s recommendation that eradication program funding be increased is a logical response to the invasion’s expansion. The expansion not only increased the area that requires management, thus increasing costs, but also showed that the areas previously searched and treated each year were too small to achieve eradication, implying there was insufficient annual funding.

Geographic expansion of the invasion cannot continue much longer without the invasion becoming too large to eradicate. The review panel’s finding that increased funding should be made available soon is therefore timely.

A lack of monitoring during the early years of the program led to the erroneous conclusion in 2004 that eradication was imminent, when in fact the invasion was expanding in area. To avoid this mistake being repeated, substantial monitoring will be required beyond known infestations and monitoring data will need to be assessed with reliable statistical methods.

In a recent report we wrote to help the eradication program, we showed that the invasion boundary can be estimated with a high degree of confidence if adequate monitoring data are available.

Pesticide treatment and monitoring will underpin eradication efforts. We need highly sensitive monitoring methods, including sniffer dogs and trained spotters, to confirm absence of fire ants in and near treated locations.

A large enough area should be monitored to ensure all fire ant colonies are found and removed. We need continued support for community members to report fire ants, particularly in urban areas. Remote sensing will be needed in less developed areas where contact between people and fire ants is less likely.

A stark choice

The choice is to continue eradication efforts or live with fire ants forever. Living with fire ants will incur large costs for agricultural producers and households.

The most recent cost-benefit analysis of the program estimated that if these costs were added up over each of the next 70 years they would exceed A$25 billion in today’s dollars.

Over half these estimated costs arise from damage to agricultural activities, with household losses being of a similar magnitude.

Large numbers of people are likely to come into contact with fire ants if the species is left unchecked. Environmental damages could also be substantial. These losses far exceed estimated eradication costs.

The review panel’s report makes it clear that we face an urgent choice between increased eradication funding or living with fire ants. There is not much time left to make this choice.