Invasive Rodent Removal Triggers Insect Rebound on New South Wales Island

The eradication of invasive black rats and house mice from a small island off the coast of New South Wales in 2019 has triggered a significant rebound in invertebrate populations, according to a new study by University of Sydney researchers in collaboration with the NSW Department of Climate Change, Energy, the Environment and Water. The research documents sharp increases in insect abundance as a measurable ecosystem recovery signal.

Researchers from the Molecular Ecology, Evolution and Phylogenomics laboratory and NSW government partners examined how invertebrate communities changed following the 2019 island-wide rodent eradication programme. The study found that total invertebrate abundance increased significantly after the removal of black rats and house mice, with particularly pronounced recoveries among larger-bodied invertebrate species that are more vulnerable to predation. These larger invertebrates are typically keystone species in island food webs, performing pollination, seed dispersal and decomposition functions.

The findings provide empirical evidence for the ecological trophic cascade that follows invasive predator removal. Invasive rodents have been responsible for a significant proportion of island species extinctions globally, and eradication programmes have become a cornerstone of island biodiversity restoration. The New South Wales result adds to a growing evidence base showing that ecological recovery after rodent removal can be rapid and measurable at the invertebrate level, which is harder to document than vertebrate population changes.

The research has broader implications for island conservation management in the Indo-Pacific region, including Australian territories and island systems in the Indian Ocean. For India, which manages several island ecosystems in the Andaman and Nicobar archipelago and the Lakshadweep group, the study provides a methodological model for assessing ecosystem recovery after invasive species interventions. Island biodiversity is increasingly recognised under the Kunming-Montreal framework as requiring targeted conservation investment given the disproportionate extinction risk facing island species.

Key figure — Rodent eradication in 2019 followed by significant invertebrate population rebound