A plant that has become rare without anyone noticing

Spiranthes australis is a slender ground orchid with small pink and white flowers arranged in a spiral along the top half of the stem.  It is found in a broad range of sites where the drainage is poor and the rainfall is above 600 mm a year.  The typical habitat is woodland or forest with an understorey dominated by sedges, rushes, grasses and herbs.  Many of the sites are disturbed, with non-native species constituting up to 20% or more of the ground cover, and about 75% of the known records are from outside the state's reserve system.

Spiranthes is not listed as rare or threatened within Victoria and consequently isn't listed nationally either.  The main reason for this is undoubtedly because the species is so widespread (as indicated by the map below).  It has been recorded from 151 sites across Victoria in 17 of the state's 28 bioregions, and the standard view is that it is quite common.  Nevertheless, a closer examination of the source of the data records for Spiranthes raises some doubt as to the veracity of this view.

Systematic, site-specific, ecological surveys, carried out by professional botanists over the past 30 years, account for over 60% of botanical distribution data in Victoria, yet only 16% of Spiranthes records come from these surveys.  Spiranthes australis has been recorded only 25 times from nearly 45,000 survey sites, even though most surveys would have been carried out at a time of year when it would have been visible an easily identified.  In addition, nearly half the records for Spiranthes in Victoria are more than 20 years old and the species has been recorded only three times in western Victoria during those two decades. 

There are clear indications that Spiranthes australis is in decline in Victoria and that many of the locations in which it is still found are subject to disturbance and are not managed principally for conservation purposes.  Some orchidologists have noted that there is anecdotal evidence that Spiranthes is becoming less common due to the steady decrease in the number and extent of suitable wetlands.  In addition the data we do have on the species shows that it is seldom found in large numbers so relatively small disturbances can have a significant impact on local populations.   All this has happened with few botanists noticing the changes that area taking place.

Obviously Spiranthes australis is not the only species that has escaped the above sort of close scrutiny but it is not always clear where to look for others.  Some species, like Spiranthes, are not listed at any level yet might be worthy of further consideration.  For example, the small shrubs Asterolasia asteriscophora, Olearia floribunda and Comesperma retusum are all widespread species which are unlisted but, as the majority of the records for each species (65-80%) are from 20 years ago or more, and these areas have been subject to more recent surveys, it is likely that all three are less common than they appear.  The same could also be said of the saltmarsh herb, Sarcocornia blackiana, the woodland herb Scaevola aemula and the small ground orchid Corybas unguiculatum (which has been recorded at only four locations from ecological surveys).

Other species which are currently classified as rare in Victoria, for example, the herbs Ammobium alatum and Argentipallium dealbatum, the orchid Burnettia cuneata, the aquatic herb Nymphoides geminatum and the ground ferm Pteris comans, are almost entirely known in Victoria from general species lists or Herbarium collections, and most of these records are two or three decades old.  There are virtually (in some cases, literally) no ecological survey records for any of them.  This is not to suggest that a failure to record a species during a survey is an indication that the species cannot be present, but given that the procedures for the surveys are to exhaustively document all species within any survey plot, it is a suggestive that they are at least very uncommon and thence probably deserve a higher conservation rating.