Biological and cultural diversity are integrally linked, yet understanding how culture impacts biological extinction is limited. The orchid richness of Southwest China’s Sichuan Province is the second highest in China, but price speculation and overharvest have resulted in significant recent orchid population collapses. Due to the importance of Cymbidium orchids to Han Chinese traditional culture, this study sought to test how the decline of these populations related to four different orchid knowledge domains and various socio-demographic variables on the local scale. Interviews were conducted in eight villages in rural Liangshan Yi Autonomous Prefecture: four Han-majority and four Yi-majority. Using photographic-cue-cards of nine Cymbidium taxa, aggregate- and specific-knowledge were assessed of 15 randomly selected individuals per village (120 total), in three age groups. Results showed that species decline negatively impacted culturally important knowledge of orchids across all knowledge domains, regardless of pre-extinction orchid rarity, and regardless of socio-demographic variables. Following population collapse, the decline in perceived economic value of orchid knowledge outweighed the influence of cultural veneration that traditionally drove Cymbidium knowledge acquisition. These findings highlight how biodiversity loss not only negatively affects the ecology and environment, but also culture, with profound implications for cultural resilience and biocultural diversity conservation efforts.