Conservation status of Buddlejas
(threat classification 5.3.1; IUCN, 2023b) and road construc- tion (4.1). Of 57 B. colvilei plants originally recorded in Goruwale, Ilam, Nepal, we observed that 15 were cut and did not regenerate (Plate 1e). Only 26 were observed in Yadong, Tibet, China, with a 64% decline compared to the number of plants recorded in the original survey. Although the combined records of B. delavayi demon-
strate a large extent of occurrence, during our fieldwork in 2017 we found the species to be facing significant threats. It has a limited area of occupancy of 0.14 km2, with only 29 individuals. Its habitat, which lies alongside a village road- side in Jianchuan County, Dali, appears to be at significant risk from housing and urban areas (threat 1.1) and road con- struction (4.1). The small number of mature individuals also poses a further severe risk of extinction. Our findings suggest that ex situ conservation is necessary to safeguard this species, and we have already implemented this: after 11 years of cultivation following their initial introduction in 2012, two individuals are thriving in Kunming Botanical Garden (Plate 1h). The distribution of B. sessilifolia onGaoligong Mountain
reflects the fragmentation and isolated nature of its habitat. We recorded .768 B. sessilifolia in total during our initial field surveys in 2010, 2015 and 2021. On returning to the sites in 2015, 2018 and 2022, respectively, although three po- pulations remained stable, four had decreased, by 145 (91% decline), 23 (17%), 22 (24%) and 18 (90%) individuals. In addition, the population of 28 individuals in Fugong county had disappeared as a result of road construction (threat 4.1) and debris flow (10.3; Plate 1f). Despite our attempts, ex situ conservation of this species has so far failed because of the difficulty of establishing seedlings (Plate 1g). Our field assessment of B. yunnanensis revealed that its
distribution spans various habitats. However, these habitats are threatened by the development of housing and urban areas (threat 1.1) and shifting agriculture (2.1.1), posing a sig- nificant risk of extinction to this species from habitat loss and fragmentation. In Zhenyuan and Ninger counties, Yunnan, we found a small population of 18 individual plants with an area of occupancy of 14.86 km2. This population lies outside any protected areas, in a region potentially prone to threats that would significantly impact survival. Despite our ex situ conservation efforts, the single individual that we had in cultivation died after 5 years. Both the automated and field study assessments suggest
B. colvilei should be categorized as Vulnerable. The auto- mated assessments suggest classification under criteria B1a +B2a because of an extent of occurrence of ,20,000 km2 (B1), area of occupancy of,2,000 km2 (B2) and documen- tation in ,10 localities (a). The field assessment further suggests classification under criteria B2ab(iii)c(iv); C2a(i)b, with observed declines (B2b) in area, extent and quality of habitat (iii), extreme fluctuations (c), the presence
of,1,000 mature individuals in locations (iv) and continu- ing decline (C2a) in the number ofmature individuals with- in each subpopulation (i) along with extreme fluctuations in their numbers (b). From our field studies, we propose that both B. yun-
nanensis and B. delavayi are categorized as Critically Endangered based on criteria B2ab(iii)c(iv) because their area of occupancy is,10km2 (B2), with a severely fragmen- ted habitat (a), continuous decline observed (b) in area, ex- tent and quality of habitat (iii), and significant fluctuations (c) in the number of locations (iv), with only 29 mature individuals of B. delavayi and 18 of B. yunnanensis recorded. Also from our field studies, we propose that B. sessilifolia
is categorized as Endangered based on criteria B2ab(ii)c(iv) because of its area of occupancy ,500 km2 (B2), fragmen- ted distribution occurring at no more than five locations (Gongshan, Yunnan and Kachin, Myanmar) (a), continu- ous decline (b) in its area of occupancy (ii), and significant fluctuations (c) in the number of mature individuals (iv) due to multiple threats (4.1 and 10.3).
Discussion
Of the 36 globally significant biodiversity hotspots, three (Eastern Himalayas, Indo-Burma, and the Mountains of Southwest China) are in the Himalayan region (CEPF, 2023) and have a high conservation priority. Circa 45.1% of the world’s angiosperm species are potentially under threat (Bachman et al., 2024). Therefore, conservation assessments are critical for the identification of threatened species and for the development of conservation plans, but different assessment methods can provide varying degrees of accuracy and reliability. Automated assessments are based solely on georeferenced data, whereas field studies incorporate additional parameters such as habitat status, number of mature individuals and threats. However, both methods highlighted the precarious status of these four species of Himalayan Buddleja. The Threatened Species List of China’s Higher Plants
(Qin et al., 2017) is an expert-driven assessment that covers a large number of species. Although it can be informative, the categorizations may not consider all nuances of the ecology and behaviour of a species and can also be subject to bias. Three of the four Buddleja species we assessed have been categorized on the Threatened Species List, but two of these categorizations, for B. delavayi and B. yunnanensis,are markedly different from our field assessment (Vulnerable as opposed to Critically Endangered). This could be attributed to the limited availability of long-term investigations and the reliance on checklist data from various databases. Conversely, automated assessment tools are fast, efficient
and cost-effective, can provide preliminary conservation as- sessments for large numbers of species, and can minimize
Oryx, 2024, 58(5), 618–626 © The Author(s), 2024. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605323001503
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