A Typical Rare Plant

Trochocarpa clarkei is a low, sprawling shrub which usually grows near the bases of snow gums in sub-alpine woodlands.  It produces pea-sized, fleshy fruit in autumn, which form an important source of food for small mammals and frugivorous birds during the weeks leading into winter. 

Sub-alpine woodlands cover only a small area of Victoria and Trochocarpa is never abundant wherever it grows, so the plant has been classified as rare in this state.  Most of the vegetation in which Trochocarpa is found, is relatively undisturbed and weed-free, and the majority of records for the species are within the boundaries of national parks.  All of which means that despite its rarity the species is probably in no immediate danger.

Trochocarpa clarkei - Lilac Berry : Rare in Victoria : Found only in Victoria
Trochocarpa clarkei
© Paul Gullan/Viridans Images

About 20% of Victoria's native plants can be similarly classified as rare but secure for the time being.  Unlike Trochocarpa, most of them are also found in other states, but in general they are uncommon, occupy ecosystems which are uncommon, and have a significant proportion of their populations on secure areas of public land. 

There is no strict definition for uncommon in the classification of rare plant species but, true to the term, species classified as rare do tend to be found in fewer localities than those which aren't.  The map above shows a grid-based distribution of Trochocarpa in Victoria.  These grids are the basic unit for recording species localities in Illustrated Flora of Victoria and there are nearly 1000 of them which cover the state.  The average number of grid records for species that are classified as rare is 15, while the average number of grids for unclassified native species is 135.

Although the term rare is still in common use when describing the conservation status of species some agencies, such as the International Union for Conservation of Nature (IUCN) and Environment Australia (EA), have dispensed with it altogether.  The IUCN Red List and Environment Australia's EPBC list are concerned with threats to species survival and although rarity may be one of the determining criteria, it is often not a significant one.  Only if a species is very rare - for example, there is only a few known populations and these are small - will rarity alone be the principal criterion for inclusion on these lists.

A curious side effect of the threat-based approach is that there can be a degree of inconsistency in its application. For example, Trochocarpa clarkei is not in the IUCN Red List nor is it listed under the Australian EPBC Act, presumably because, under the current Victorian standards, it is not considered to be threatened within Victoria, the only place it is found.  Nevertheless, a strict application of IUCN and EPBC criteria B1 (geographic occurrence is less than 5000 km2) and B2 (area of occupancy less than 500 km2), both of which are true for Trochocarpa, along with the small, fragmented and declining populations, would probably place it on both lists as endangered.  This would result in the odd circumstance that Trochocarpa clarkei is listed as threatened both nationally and internationally but not locally. 

© Paul Gullan, Viridans Biological Databases