A plant that was once rare but not any more

Acacia oswaldii is a dense, medium to large shrub of woodlands in low rainfall areas of Victoria.  In summer it is covered with clusters of pale yellow flowers which usually produce large numbers of hard, black seeds.  It is found in all mainland states but is particularly widespread in South Australia and NSW.  Acacia oswaldii is not currently classified as rare or threatened in Victoria or Australia but in the recent past it was classified as vulnerable in Victoria.

The ambiguity of conservation classification for Acacia oswaldii dates back to 1990 when the first systematic assessment of rare or threatened categories was applied to Victorian plants and published by the (then) Department of Conservation and Environment.  In that original list there was a category defined as depleted, which was erected to cover species that were not currently rare but had most of their populations removed since European settlement.  Acacia oswaldii fitted well into this category as most of the vegetation in which it was found (80-90%) has been converted to pasture or crops.  The majority of populations are now on roadsides, edges of agricultural land or small areas of public land.

In 2000 the (then) Department of Natural Resources and Environment abandoned the use of the depleted category so each species classified as such was reassessed.  Acacia oswaldii was reclassified as vulnerable on the basis that its natural habit was the most arable land in the mallee (and hence mostly cleared for agricultural), that there were relatively few current records (about 200), and that nearly all of these were on disturbed sites or small isolated fragments on roadsides.  Over the next few years some local botanists questioned this classification saying that the species was much more common than was originally thought and that it reproduced well on disturbed sites so the populations in some areas were increasing.  In the light of these arguments, and the knowledge that the number of records for Acacia oswaldii had risen to nearly 600, DSE botanists removed Acacia oswaldii from its list of rare and threatened plants in 2007.

Acacia oswaldii wasn't the only species listed as depleted in 1990, there were fourteen others and all but one are plants of low rainfall areas in the north-west.  By 2000 eight of these had been removed from the Victorian rare or threatened plant list while five had been classified as vulnerable and two as rare.  The current assessment is that only three of the original fifteen warrant a classification all of which are listed as vulnerable (Melaleuca halmaturorum subsp. halmaturorum, Templetonia egena and Pomaderris paniculosa subsp. paniculosa).   Curiously one of the species which was not assigned a Victorian rare or threatened category, Allocasuarina luehmannii, has been listed under the Flora and Fauna Guarantee Act (FFG) using the same logic as that for listing Acacia oswaldii as vulnerable.

Reassessment from the depleted category has not been the only circumstance under which species have been removed from the rare or threatened list.  There are at least 20 other cases one of which (the grassland herb Ptilotus erubsescens) is listed under the FFG and another (the ground orchid Calochilus therophilus) has been recorded from only 13 localities.  The reason for the reclassification of the latter is that it is thought to have been mistaken for a much more widespread species Calochilus robertsonii.  While this assumption is not unreasonable, and may turn out to be true, there is still no clear evidence from the data to back it up.