How will you get the rodents off the sides of the mountains especially where there are cliffs and caves?
Why eradicate rats and mice now?
Lord Howe Island is not unique in having rats and mice, but it does have a rare opportunity to solve the problem. Most inhabited islands around the world have rats, as does every major city, and some manage them better than others. Lord Howe does a good job of managing them around the settlement but they are still impacting on most of the island and they won’t go away unless we do something to get rid of them.
A window of opportunity
The complete eradication of invasive rodents has now been carried out on over 300 islands around the world. It has been done elsewhere, it can be done here. There are solid precedents for what needs to be done and how to do it. Careful feasibility planning indicates it can be done here, and this has led to the availability of funds and expertise to protect Lord Howe Island now. The window will not stay open for long and if the eradication did not go ahead the funds will go back to the mainland, they are not available for other projects on the island.
Everywhere in the world we are seeing a frightening trend: resistance to once effective treatments including antibiotics and pesticides. This is currently happening with TB where strains are appearing which are resistant to all normal antibiotics. Similarly, many other bacteria are becoming resistant to penicillins (which were far more effective when introduced 70 years ago). The mice on Lord Howe Island are already resistant to Warfarin, one of the earlier rodenticides
Imagine an island without rats and mice
Lord Howe is special in many ways, and its unique wildlife, history and its people are reflected in its World Heritage status. Removing rodents completely and for good will make it even more special and enhance a worldwide reputation as an ecotourist destination. Rodents are currently only being controlled on a small percentage of the island. Elsewhere they are having a major impact on the wildlife and vegetation. Without the rodents, plants and wildlife will flourish. People will no longer have to bait around their homes and businesses. There will be no more risk of the ongoing poisoning of native species that is currently happening or the risk to children or dogs.
Is it safe for humans?
Yes, it is. Provided basic precautions are taken, the risk of brodifacoum poisoning during the proposed eradication is remote.
Current usage of Brodifacoum and Talon
The current practice of using rodenticides (such as Ratsak Plus® and Talon®) containing brodifacoum on an ongoing basis for rodent control on Lord Howe Island poses an ever present risk for residents, their pets and local wildlife. The eradication of rodents will remove the need for the ongoing use of rodenticides and the risks that go with it.
How to approach the baits
For the most part, the risks to human health associated with the proposed eradication operation are similar to those that currently exist through the domestic use of products likeTalon®. In brief, the baits should be treated like any other poison. They should not be eaten or handled. Residents with children already exercise care when using baits domestically. Baits used domestically have a much higher concentration of brodifacoum, 2.5 times greater than the baits that will be used in the eradication. However, there will be more baits on the ground during the eradication and care must be taken with children and those unable to read the signage that is posted.
The only way residents could be exposed to brodifacoum absorption from the skin is by handling baits directly. However, for there to be any adverse effects a person would need to handle large quantities of bait for long periods of time. The risk of such exposure is negligible.
What to do
Swallowing one or two baits seldom requires medical treatment. In the extremely unlikely event that medical treatment is required (involving vitamin K injections), it will be available. Nevertheless, anyone suspecting brodifacoum poisoning should seek medical advice.
Before any bait is distributed on the island, the community and tourists will be informed about the nature and timing of the operation and the need to avoid ingesting or handling baits.
Fact Sheet Community health and well-being PDF 534 KB
What about the water and soil?
To date, brodifacoum residues have not been detected in water bodies following any aerial baiting operations—not surprising, given that brodifacoum has very low solubility in water.
The baiting operation will be conducted to avoid bait going into the lagoon and minimise the entry of baits into the ocean.
What we already know, fresh water
From other aerial baiting operations, we know that there is a very low chance of any streams and other water bodies on Lord Howe Island containing detectable levels of brodifacoum, much less biologically harmful concentrations, as a result of the eradication.
Because brodifacoum has very low solubility in water and binds strongly to soils it is unlikely to get washed into the marine environment. Any baits entering streams or other water bodies sink, and disintegrate, usually within a few hours, depending on turbulence and rate of flow. The minute amount of brodifacoum in the bait (20 parts per million) settles in the sediment where it binds to organic material and breaks down.
Brodifacoum binds strongly to soil particles, where it is broken down by soil micro-organisms to its base components, carbon dioxide and water. While the cereal bait pellets disintegrate and disappear within 100 days or so, the toxin itself takes longer to break down but by this stage the concentration is so low that it poses no risk to humans or wildlife. Laboratory studies have shown that brodifacoum is effectively immobile (i.e. not leached) in the soil.
Nonetheless, water samples will be collected at various intervals after the baiting and analysed by an independent laboratory to reassure residents and tourists that the water (along with locally produced milk and locally caught fish) is not contaminated.
In the marine environment, outside the lagoon
Outside the lagoon, any baits that might enter the ocean will be exposed to wave action and strong currents resulting in rapid breakdown and dispersal. This, together with the high dilution factor, and the fact that brodifacoum has very low solubility in salt water, means that the potential risk to marine organisms is very low.
In the marine environment, within the lagoon
Within the lagoon, the physical breakdown of baits would not be as rapid, so entry of baits into the lagoon will be prevented by hand distribution of bait, rather than aerial distribution, along the accessible shoreline of the lagoon. As there is very low risk of brodifacoum being at detectable levels in the streams, any water entering the ocean or lagoon is unlikely to carry detectable levels of brodifacoum.
What is the impact on birds and plants?
Expect increasing numbers and types of birds and other wildlife
Eradicating rats and mice from LHI is expected to result in marked increases in the abundance of land birds and seabirds. Eradicating these pests from LHI will reduce the risk of extinction of many threatened species and help protect the island’s biodiversity and World Heritage status.
There will be substantial increases in the distribution and abundance of the LHI skink and gecko, all species of land snails, as well as many other creatures. There will be an increase in the abundance of seeds and seedlings, increasing recruitment of many threatened plants and enhancing the process of forest regeneration.
With the rats and mice gone, bird populations will flourish, increasing in abundance to levels not seen for many decades. Nesting colonies of storm-petrel and Kermadec petrel are likely to re-establish on the main island. Also, the opportunity would then exist to return some of the species that have been lost from LHI, such as the, fantail, warbler, pigeon and boobook.
Why do aerial baiting, why not do the whole island with bait stations?
It is simply not possible to effectively and safely distribute the bait on areas such as the Southern Mountains and Northern Hills by any other means. Aerial application of bait has been a key factor in previous successful eradications, because it means that every rat on the island has the opportunity to find and eat enough bait, within a short period of time. Due to the small size of some mouse territories it would require putting bait stations at close intervals over the whole island, including the sides of Mt Gower and Mt Lidgbird which is not feasible.
How will you get the rodents off the sides of the mountains especially where there are cliffs and caves?
Spreading bait from a bucket slung under a helicopter has been very successful in removing all rodents in similar situations such as Campbell Island (11,300 hectares) which has 300m cliffs and sea caves. Raoul Island (2900 hectares) in the Kermadec group – about 2000 km east of Lord Howe is similar topographically to lord Howe although its mountains at 516m are not a high as those on LHI. A project is also underway on 352,800 hectare South Georgia Island in the South Atlantic which includes mountains up to 2900m in height.
What about bait getting into the sea?
To minimize the amount of bait that goes into the sea, as much as possible of the area around the lagoon and other sites such as Ned’s beach will be hand-baited. While it is not possible to guarantee that no bait will go into the sea where aerial broadcasting takes place, as it is important to get bait as close to the high tide line as possible, this will be minimised by the use of a deflector in the bucket which directs the bait just out one side.
How much poison?
While the amount of bait proposed for the eradication sounds large (42 tonnes), it is important to remember that the bait pellets are mostly made of cereal, containing just enough poison for a couple of pellets to kill one rat. The concentration of the poison in each bait pellet is 20 parts per million – so if you could divide up one bait pellet into a million same-sized pieces, only 20 of these pieces would be toxic, this is 2 ½ times lower than the bait that can be bought in shops.
Is there a danger from dust?
Only those working directly with the baits around the helicopter will be exposed to significant dust and they will be wearing protective equipment. Bait will not be spread in high winds to minimise the risk of any dust being widely dispersed.
What about water tanks?
Aerial baiting will not be conducted over the settlement and will not be conducted in high wind. Combined with the fact that brodifacoum has very low solubility in water i.e. would sink to the bottom of a tank and bind with any material there, it means that there is effectively no risk to human health from dust in water tanks.
What about my vegie garden?
Brodifacoum has very low solubility in water, and therefore will not be taken up by plants. No exposure risk is anticipated from plant-based food grown on the island.
As an added precaution there will be no bait put in vegie gardens as these areas will be done by hand broadcast or bait stations as per the Property Management Plan for each site.
How will the eradication affect Lord Howe Island’s World Heritage Status?
Successful eradication would protect and enhance the Island’s World Heritage Status. Tim Badman, the Director of the IUCN World Heritage Programme has written to confirm support for the program.
Why are Islands so important for biodiversity?
- Islands make up less than 5% of the earth’s land area, but are home to an estimated 20% of all bird, reptile, and plant species.
- Islands also contain 40% of all critically endangered species, and extinction rates are disproportionately greater on islands.
- 80% of all known extinctions have occurred on islands.
- Nearly a quarter of the world’s plant species exist only on islands.
- Some individual islands are home to hundreds—or even thousands—of plant and animal species found nowhere else in the world (endemic species). Other islands have a few or even a single unique endemic species.
- Many islands are home to species yet to be described by science. We don’t even know what we might be losing—such as sources of food or medicine.
- On islands, species under threat of extinction have nowhere else to go, so they must be protected on-site.
- Many migratory species breed and raise their young only on a few islands, or sometimes only on one single island.
Source: Island Conservation