Slipper orchids are closer to the edge than we thought

Slipper orchids are members of Cypripedioideae, one of five subfamilies of orchids, and there are currently 182 recognised species. Instantly recognisable because of the characteristic slipper-shaped lip of the flower, these iconic orchids are increasingly popular in cultivation, and many species and hybrids are available in the horticultural trade for the garden or the house. Despite this popularity, many species are threatened with extinction in the wild - and Kew is working with colleagues around the world to try to prevent them from disappearing. 

The Global Strategy for Plant Conservation and Red Listing

Target 2 of the Global Strategy for Plant Conservation calls for “an assessment of the conservation status of all known plant species, as far as possible, to guide conservation action” by 2020. The IUCN (International Union for Conservation of Nature) Red List of Threatened Species™, which celebrates its 50th anniversary this year, is the product of a globally-recognised methodology for achieving this.

The process of Red Listing involves a rigorous assessment of the trends in population size and threats to species, providing assessments of species that are comparable across different groups of organisms. The Royal Botanic Gardens, Kew is a member of the IUCN Red List Partnership and various Kew staff members and associates are involved in Specialist Groups of the Species Survival Commission of IUCN. These groups are making a major contribution to meeting the 2020 target. For example, Bill Baker (Chair of the Palm Specialist Group) and colleagues have just published a paper on Red List assessments for all Madagascan palm species.

As part of our activities relating to the Orchid Specialist Group, Kew is leading on Red List assessments for all species of slipper orchids. Orchids are currently under-represented on the IUCN Red List of Threatened Species, with only about 2% of species having been assessed - for comparison, all conifers, all carnivorous plants and more than 20% of palms have been assessed. Part of the problem has been deciding where to start with such a large group of plants (Orchidaceae is one of the largest plant families, with about 27,800 species). We decided that the time had come to address this imbalance by focusing on slipper orchids, as agreed with Simon Stuart, Chair of the Species Survival Commission.

Red Listing slipper orchids

Hassan Rankou, from Kew's Jodrell Laboratory, is the Red List Focal Point for orchids, and he is pulling together all the information necessary to make the assessments, in collaboration with colleagues in the countries where slipper orchids grow. The first batch of these (the assessments for all 52 currently recognised Cypripedium species) has now been published on the Global IUCN Red List. Similar assessments for the other four genera will follow in due course.

The Cypripedium assessments make shocking reading - 79% fall in one of the categories of threat [8% critically endangered (CR), 46% endangered (EN) and 25% vulnerable (VU)] and a further 9% are considered near threatened (NT). In the same update, 90% of all lemur species (all endemic to Madagascar) were shown to be threatened - these slipper orchids thus rank among some of the most threatened organisms assessed so far. Several species (including the UK native C. calceolus which occurs from England to eastern Asia, photo above) have wide distributions, and these are the species that were assessed as “least concern” (LC), meaning they are not currently facing a threat of extinction.

I was in Yunnan in western China this year and visited a site (shown in the photo at the start of this post) where C. flavum (VU; western China) and C. tibeticum (LC; Sikkim, Bhutan and western China) grow together. It was thrilling to see these beautiful species in flower in large numbers, but the future for these populations is clearly uncertain.

Can slipper orchids be saved?

What can be done to save these charismatic slipper orchids from extinction? Due to improved propagation methods, a range of species and hybrids is now available in the trade. Hopefully, this will lead to a reduction in collecting pressure on wild populations by unscrupulous collectors. In the meantime, Kew and other organisations are working on a suite of conservation activities, including ex situ storage, propagation, reintroduction and conservation genetics. These activities mean that we are learning more about the biology of these species and how they can be best conserved.