Expanding Ranges Yet Shrinking Refugia: Protected-Area Mismatch with Early-Spring Ephemerals Under Climate Change Scenarios in Xinjiang, China

Early-spring ephemeral plants constitute a dominant photosynthetic functional group during the critical early-spring moisture window (March–April) in the desert ecosystems of Xinjiang. They provide the primary energy base for pollinators and granivores and stabilize soils before perennial vegetation is activated. Despite this foundational role, their conservation status within protected areas (PAs) under changing climatic scenarios remains unquantified. This study aims to assess the current and future distribution of Brassicaceae early-spring ephemeral plants and evaluate the effectiveness of the current nature-reserve network in Xinjiang. Using 91 occurrence records and five environmental variables, we applied MaxEnt species distribution modeling (AUC = 0.917 ± 0.023) combined with spatial overlap analysis to quantify suitable habitats within PAs under current and future (2050s and 2070s) climate scenarios. Precipitation during the driest month (Bio14, 83.8%) was the most influential predictor in the model, followed by mean annual temperature (Bio1, 5.7%) and annual precipitation (Bio12, 5.4%). Under current climatic conditions, the total suitable area was 423,500 km2 (25.4% of Xinjiang), with high-suitability habitats (125,571 km2) concentrated along the northern Tian Shan piedmont. However, only 28,349 km2 (6.7%) of the total suitable area and 5640 km2 (4.5%) of the high-suitability zone fall within the 18 analyzed nature reserves. Under climate scenarios for the 2050s and 2070s, the total suitable area was projected to expand by 11.6–15.8%, but the high-suitability habitat within the analyzed nature reserves was predicted to collapse by 88–92%, as newly emerging suitable areas are projected to occur almost entirely outside their boundaries. Based on spatial overlap analysis, the current PA network is structurally incompatible with both current core habitats and future climate refugia of early-spring ephemeral plants, as it was designed for flagship vertebrates and landscape-scale ecosystems. As these irreplaceable early-spring energy conduits possess limited dispersal capacity to autonomously track shifting climates, their exclusion from PA planning represents a critical conservation gap. Thus, a climate-adaptive reorientation of conservation planning, including PA boundary expansion along the northern Tian Shan piedmont, dynamic buffer zoning to capture migrating moisture corridors, and the establishment of ecological corridors, is required to maintain connectivity between current and emerging suitable habitats.