Quantifying biodiversity outcomes of weed control

A major research aim was to explore whether, where and when weed control efforts lead to native plant biodiversity recovery and enhancement in the ACT. The intensive long-term data collection efforts by the ACT Government provided an ideal research environment. By harmonising and integrating multiple such datasets during the ACT proof-of-concept collaboration, CSIRO was able to conduct robust analyses to answer this question.

This research is currently written up for publication in a scientific journal and briefly summarised below.

Weed control was not assessed in isolation. Instead, its effects were examined in tandem with plot condition (a measure of ecological quality encompassing factors such as native species dominance, weed cover, and disturbance history). This dual lens allowed us to tease apart how management actions interacted with site-specific ecological baselines to shape native plant diversity patterns.

We found that both weed control and plot condition significantly affected native plant metrics, including cover, species richness, Shannon diversity, and floristic value scores. Importantly, these effects were not uniform across all sites. The strongest effects were found in low- and moderate-quality grasslands when comparing plots with and without any weed control. Weed control was associated with higher native species richness and diversity, indicating that weed control was likely facilitating some passive recovery of floristic value in these degraded sites.

We also found that native plant community composition was significantly influenced by weed control and plot condition. For example, moderate-quality plots with control contained a different composition of species than where no control had occurred, and that were more similar to high-quality plots. This pattern of control areas supporting a unique and more diverse assemblage was strongest in grasslands. This finding underscores that weed management strategies do more than suppress invasive species and may indeed shape the ecological trajectories of invaded ecosystems.