Abstract | From random meander to stratified meander: using a quantifiable method to elucidate survey effort and detectability for threatened flora surveys

Environmental impact assessments of proposed roads usually require targeted flora and fauna surveys; however, inconsistent standards and guidelines across jurisdictions can result in varying quality and expectations of survey effort. Survey effort is intrinsically linked to the probability that a target species will be detected (its ‘detectability’) if it is present. Failure to acknowledge imperfect detectability and implement minimum survey guidelines can result in poor decision making and potentially adverse impacts on biodiversity, yet detectability estimates are still rarely required in survey guidelines.

The ‘random meander’ is a widespread and prosaic method for targeted flora surveys, but typically delivers data which does not enable practitioners and regulators to transparently assess the adequacy of survey effort for detecting target species. As a part of studies for the Beaufort Bypass Environmental Effects Statement in Victoria, we trialled a method to undertake flora surveys for the nationally vulnerable shrub Ben Major Grevillea Grevillea floripendula, in a more structured and accountable manner.

The approach involved dividing the landscape into 100 x 100m (1ha) grids, classified a priori based on location of previous records, species distribution model values and preferred habitat. Within each grid, a ‘stratified meander’ method was used, with search intensity prioritised into grids in which the species was most likely to occur, based on initial classification.

In this study, survey effort was transparently documented by recording GPS tracks and time spent surveying in each grid. When combined with species detectability estimates and prior belief about where the species occurs, this information can be used to transparently assess whether the survey effort was sufficient to reduce the chance of a false absence to an acceptable level.

This will have broad application to a number of flora species in a forest or woodland context to provide more certainty on survey effort, particularly in areas where plants have not been found.

Bio | Nic McCaffrey

Nic is a Principal Ecologist with WSP Australia Pty Limited where he is a project manager and coordinates a team of Victorian-based ecologists on a range of small to major projects including Environment Effects Statements (EES), flora and fauna surveys, biodiversity offsets, ecological impact assessments and ecological monitoring. He also holds an Honorary Fellow position at Centre for Mined Land Rehabilitation, The University of Queensland where his research interests revolve around themes of improving ecological monitoring, flora survey effort and mine rehabilitation.

Bio | Dr Georgia Garrard

Georgia is a senior research fellow in RMIT’s Interdisciplinary Conservation Science Research Group, and works as part of the Australian Government’s National Environmental Science Program Threatened Species Recovery Hub. Her research interests include biodiversity sensitive urban design, the interactions between people and nature, and planning for biodiversity conservation in cities. Her work on plant detectability has informed survey effort guidelines for nationally-endangered flora species and invasive weeds.