A continental scale analysis of threats to orchids

Abstract

Thousands of plants are at risk of extinction globally due to human activities, including many species of orchids. In Australia alone there are 184 orchids identified as threatened by the Australian Government, but what threatens them and where are they threatened? Using data derived from listing documents for these orchids, threats were allocated to 28 categories. Then, the distributions of the orchids and hence likely geographic patterns of threats were mapped using 14,651 location records from the Atlas of Living Australia. The most common threats were changes in fire regimes (74% of threatened Australian orchids), invasive species (65%), habitat modification (64%), grazing (63%), tourism and recreation (47%) and illegal collection (46%), which often co-occurred as threat syndromes. Most threatened orchids are terrestrial (165 species), and many occur in temperate forests (96) and temperate shrubland (36). When generalised linear models were used to assess geographic patterns in threats, bioregions with less cover of native vegetation were more likely to have orchids threatened by habitat modification, grazing or weeds (p < 0.05). Bioregions with higher protected area coverage were more likely to contain orchids threatened by tourism and recreation, but less likely to have orchids threatened by habitat modification (p < 0.05). Understanding drivers of threats and their distribution is crucial for successful management as they highlight key areas for conservation. The results also highlight the need for updating orchid listings nationally and internationally to better reflect the diversity of orchids threatened and threats to them, including the increasing impact of climate change.