Translocation of threatened terrestrial orchids into non-mined and post-mined lands in the Hunter Valley of New South Wales, Australia

Re-introduction of threatened plants is an emerging tool in biodiversity conservation; however, the efficacy and success of translocations vary. This study documents translocation of two threatened terrestrial orchid species (Diuris tricolor,Prasophyllum petilum) over 8 years within coal mining areas in the Hunter Valley of NSW, Australia. In the largest scale orchid translocation known (and the only one translocating into mine rehabilitation), six events have progressively re-located 3,030 mature orchids (1,206D. tricolor, 1,824P. petilum) into biodiversity offsets (non-mined: 1,099D. tricolor, 1,493P. petilum) and mine rehabilitation (post-mined: 127D. tricolor, 311P. petilum), and 300 salvaged tubers into non-mined (20D. tricolor, 180P. petilum) and post-mined (10D. tricolor, 90P. petilum) lands. Monitoring of orchids for 3-8 years revealed significant relationships between winter rainfall (July forP. petilum, August forD. tricolor) and orchid detection. Both species survived significantly better in non-mined and post-mined land when translocated in soil cores than as salvaged tubers.Diuris tricolorwas more detectable overall, with rates 3-8 years post-translocation as high as 53-67% in good years and 16-47% during drought.Prasophyllum petilumwas less detectable, returning 4-12% in drought but rising to 52-63% during wetter seasons. Diligent searching prior to flowering doubled detection forD. tricolorand increased it by one third forP. petilum. Two monitoring inspections per season increased detection by up to 12%. After 3-8 years post-translocation, orchids have persisted and are well established. Staged translocation over 8 years with adaptive management to operational procedures and monitoring has increased orchid detectability, and can be applied to future orchid translocations.