Mountain fog serves as a critical water source for Taiwan’s high-altitude tea plantations and unique cloud forest ecosystems. Our research reveals that climate warming and intensifying urbanization are reshaping this misty landscape in a dramatically asymmetric manner, amplifying hydrological stress across the island’s two flanks. By using high-resolution climate modeling, we confirmed that two primary drivers behind this East-West imbalance:

1.The West: Urbanization Pushes Fog Upward. Intense Urban Heat Island effects from dense western cities act like a large heater, pushing the existing fog layer to significantly higher altitudes. This drastically reduces the frequency of fog at traditional low-to-mid elevations, posing a serious drought threat to agriculture and forest ecology.

2.The East: Warming Intensifies Fog. Climate change alters regional wind circulation patterns. On the windward eastern slopes, enhanced atmospheric flow drives more moisture-laden marine air toward the mountains, leading to an increase in fog formation frequency.

Overall, this striking "drier West, foggier East" contrast is compelling fog-dependent habitats and species to migrate toward higher mid-elevations (roughly 1,500–2,500 meters a.s.l.) for survival. Our findings provide a critical warning for Taiwan’s future conservation strategies, water resource management, and high-mountain agricultural planning.