Lord Howe Island: endangered species thrive after rodent eradication programme

Eliminating invasive rodents from Lord Howe Island stands as a remarkable success story in biodiversity conservation, and Ramboll’s development and preparation of the first human health risk assessment (HHRA) for a permanently inhabited island attempting rodent eradication was a key step in implementing the programme.

Ramboll’s science-based HHRA shaped with in-person community engagement overcame an important hurdle by documenting how potential risks to residents were considered and addressed. The programme was implemented and the most recent survey of the World Heritage-listed island confirms that the invasive rodents were successfully eradicated and endangered species have made an astounding recovery.

The biodiversity and ecosystems challenge at Lord Howe Island

Rats and mice were introduced on Lord Howe Island, 400 miles off the coast of New South Wales, Australia via arriving ships. The fragile and unique ecosystem was upended by the rodents, which consumed the seeds of previously dominant native palms, feasted on invertebrates, and decimated nests. Rats arrived with a 1918 shipwreck and by 1930 at least five bird species were driven to extinction. Thirteen invertebrate species have also become extinct.

While the potential to protect and boost biodiversity by eliminating the rodents was clear, and successful eradications had been carried out on other small islands, the World Heritage-listed Lord Howe Island was different due to its community of full-time residents. A rodent eradication programme had never been previously attempted on an island with a full-time residential community, and that community was understandably concerned.

Independent HHRA of the Lord Howe Island Rodent Eradication Project

The Lord Howe Island Rodent Eradication Project (LHI REP) was developed to address the challenge and funded by National Landcare Program (federal) and the NSW Environmental Trust (state). The design combined aerial spreading of pesticidal rodent baits in the forested portions of the island and bait stations on the ground in the settlement. Ramboll was appointed by NSW Chief Scientist & Engineer on behalf of the Minister for the Environment to undertake an independent HHRA of the programme, to address and ultimately make recommendations to alleviate residents’ concerns.

Ramboll’s team of health sciences experts assessed potential exposure to the island’s 350 residents, evaluating potential long-term risks from pesticide residues in soil, water and fish, along with acute risks, such as a child ingesting bait pellets. From the assessment, we identified the scenarios most important to potential exposures and made recommendations to mitigate them. Ultimately, the most substantial potential risk was determined to be pellets ending up on roofs and being transported into water tanks. The programme mitigated this risk by incorporating visual monitoring of roofs after the helicopter bait drops, ensuring no stray pellets landed on residential homes.

Importance of community engagement and support

While invasive species pose one of the greatest threats to island biodiversity, mitigating this threat depends on addressing more than just the rodents. A cornerstone of Ramboll’s efforts on the HHRA and the success of the LHI REP was the significant involvement of the local community. Residents needed to weigh up the benefits of eradicating the rodent population with controlling the risks of the pesticide baits needed to achieve it.

In collaboration with local and state authorities, Ramboll's team participated in in-person listening sessions, addressing every concern raised by the residents. This collaborative approach ensured that the community's voices were heard, fostering support and understanding. Such engagement was crucial for the programme's ultimate acceptance and successful implementation, demonstrating that sustainable solutions are achieved through strong stakeholder co-operation.