Lord Howe Island's ecosystem recovery after rodent eradication boosts invertebrate populations
Consensus Summary
Lord Howe Island’s ecosystem is showing significant recovery after the 2019 eradication of 300,000 invasive rats and mice, with invertebrate populations—including native cockroaches and beetles—rising by 60% since pre-eradication surveys. Both sources confirm the rediscovery of a previously extinct cockroach species in 2023 and highlight the island’s unique biodiversity, where half of its 1,600+ invertebrate species are endemic. Researchers from Sydney University and the NSW government collected over 24,000 specimens across 20 sites, noting stronger rebounds in larger invertebrates (>13 mm), which serve as key food sources for geckos and birds. While the ABC emphasizes long-term ecological shifts and DNA sequencing for conservation, the Guardian focuses on visible changes like stag beetle sightings and understorey regeneration. Both agree the ecosystem is reorganizing but acknowledge some species remain extinct, and full recovery may take decades.
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Key details reported by multiple sources:
- Lord Howe Island eradicated over 300,000 invasive rats and mice in 2019
- Invertebrate populations on Lord Howe Island increased by 60% since the 2019 rodent eradication
- The study comparing invertebrate populations was published in *Biological Invasions* and involved 20 forest sites across the island
- The native Lord Howe Island cockroach species *Panesthia lata* is one of the species rebounding after rodent removal
- A previously believed extinct cockroach species was rediscovered in 2023, signaling invertebrate recovery
- Lord Howe Island is a World Heritage-listed site located 600 km off the coast of Port Macquarie, NSW
- Rodents were first introduced to the island in the mid-19th century (mice) and 1918 (rats via a grounded ship)
- The study involved collecting 9,000 invertebrate specimens in 2016–17 and 15,000 in 2023–24 (total 24,000 specimens across both surveys)
- The island has over 1,600 known invertebrate species, with about half found nowhere else on Earth
- The next phase of research will focus on studying 'higher-order predators' like geckos and birds
Points of Difference
Details reported by only one source:
- Maxim Adams is a Sydney University honours student and co-lead of the study with the NSW Department of Climate Change, Energy, the Environment and Water (DCCEEW).
- Professor Nathan Lo leads the Molecular Ecology, Evolution and Phylogenomics laboratory at Sydney University and noted that geckos were 'all over the place' in recent fieldwork.
- The first study (2016–17) collected 9,000 specimens, while the second (2023) collected 15,000, with the strongest increases observed among larger invertebrates (>13 mm).
- The ecosystem will reach a 'new equilibrium' different from pre-rodent introduction conditions, with some invertebrate species already extinct.
- DNA sequencing of all invertebrate samples is underway to track biodiversity and biosecurity over the last decade.
- Ian Hutton, a naturalist and nature guide, rediscovered an extinct weevil species during a camping trip in 2024.
- The island’s unique stag beetle, with iridescent green wing cases, is now more visible in summer months.
- The understorey vegetation is regenerating due to reduced seed predation by rodents, with hundreds of seedlings appearing.
- The food web is unusual because Lord Howe has no native mammals, so bugs are primarily eaten by birds and reptiles.
- The study used 'cockroach hotels' (layers of cardboard) to attract and collect specimens.
Contradictions
Conflicting information between sources:
- The ABC states the second survey was conducted 'seven years later' (2023), while the Guardian does not specify the exact year but implies a 5-year gap since 2019.
- The ABC mentions a '60% increase in invertebrates' with a focus on larger species (>13 mm), while the Guardian emphasizes broader ecological reorganization without specifying size-based trends.
Source Articles
Booming cockroach numbers welcome news on island 'paradise of creatures'
Researchers say the removal of invasive rodents on Lord Howe Island has sparked a rebound of invertebrate life, including native cockroaches and other insects, vital to the broader ecosystem.
Lord Howe Island got rid of its rats and mice – now cockroaches and bugs are bouncing back
Rodents arrived on the subtropical island more than a century ago, decimating its native flora and fauna – but its invertebrates are once again booming In the summer months, Lord Howe Island’s unique stag beetle, with wing cases that appear forged from iridescent green metal, fly around the ancient tree tops looking for a mate. “That’s really something wonderful,” said Ian Hutton, a naturalist and nature guide on the World Heritage-listed island. Continue reading...