A MaxEnt–Based Assessment of Climate–Suitable Habitat for the Rare Orchid Cymbidium insigne in Hainan Under Climate Change

Cymbidium insigne is a tropical rare orchid and a Grade I protected wild plant in China, highly sensitive to understory microclimate. Based on 9 occurrence records from Hainan Island and 9 core environmental variables, we used a maximum entropy (MaxEnt) model with leave–one–out cross–validation to predict its current and future suitable habitats across four 20–year periods (2021–2040s, 2041–2060s, 2061–2080s, 2081–2100s) under three shared socioeconomic pathway (SSP) scenarios. The model showed high apparent discrimination under leave–one–out cross–validation, with a mean area under the receiver operating characteristic curve (AUC) of 0.99; however, given only nine presence–only occurrence records, all quantitative predictions should be interpreted with caution. Elevation was the dominant factor, contributing 82%, followed by the wettest–quarter mean temperature of 8.6% and annual temperature range of 8.0%. Current suitable area totaled 2054 km2, with high suitable areas concentrated in mid–to–high elevation valleys at the junction of Wuzhishan, Baoting, Qiongzhong, Ledong, and Baisha. Suitable habitat shrank significantly under all future scenarios by 2081–2100s: only about 48% (983 km2), 1% (24 km2), and none (0 km2) of the present 2054 km2 were projected to remain under SSP1–2.6, SSP2–4.5, and SSP5–8.5, respectively. Climate warming is projected to cause substantial loss of suitable habitat for C. insigne. We recommend constructing conservation corridors within Hainan Tropical Rainforest National Park, centered on stable central–mountain core zones, combined with ex–situ conservation and microclimate monitoring for adaptive management.