Guidelines for offset population sizes

Modelling for viable populations of rare plant species

This research will improve the understanding of how ecological and biological traits of rare species of plants, commonly encountered in restoration projects, and different environmental factors determine viable population sizes by using computer models.

Producing evidence-based guidelines for the size of plant populations needed to maximise establishment and persistence of rare plant species.

Reports and papers

Guidelines for plant population offsetting: Improving the effectiveness of biodiversity offsetting

Final report, June 2018.

A science-based population offsetting guidelines for four different plant groups (eucalypts, Acacia, forbs and grasses) from the Brigalow area based on their life-history and ecology. Guidelines taking biological differences into account can help to improve current population offsetting practices by making them more cost-effective as well as increasing the chances of success of plant population offsetting.

The main outcomes from this study are:

Estimated offset ratios (this ratio varies between plant groups), specific recommendations and associated management actions for each plant group to maximise long-term population viability and reduce the possibility of over- or underestimating offset sizes.
Mitigating mortality factors (e.g. fire, inbreeding depression, weed competition) is as important as choosing appropriate offset sizes to increase offset success.
For all plant groups, maintaining population connectivity and gene flow is essential to decrease extinction risk.
Combined management actions to increase spatial availability and genetic diversity increases up to 50 % population viability and population persistence. This is particularly important in short-lived species with self-incompatibility mating systems.

Guidelines for plant population offsetting: Improving the effectiveness of biodiversity offsettingPDF2 MB