Mountains serve as critical biodiversity observatories, offering unique insights into the ecological impacts of climate change. Among the most striking transformations in these environments is the retreat of glaciers, which is reshaping species distributions, forcing new biotic interactions, and restructuring ecological networks. However, how these emerging networks develop and respond to environmental change and in turn influence ecosystem functions remains poorly understood. In this presentation, I will synthesize recent studies examining how glacier retreat directly and indirectly alters biodiversity and ecosystem functions in mountain ecosystems. We observed sharp shifts in plant, animal, and soil microorganism communities, plant–pollinator and plant–soil microbe networks with glacier retreat. Plant facilitation and symbiotic interactions enhance biodiversity in recently deglaciated terrains, while plant competition driven by shrub encroachment and soil acidification in later successional stages reduced species persistence. Our findings reveal an initial increase in interaction diversity following glacier retreat, followed by an ultimate decline with glacier extinction. These cascading effects undermine key ecosystem functions and services, including regulating and material contribution from pioneer, threatened species. These results highlight the value of ecological network approaches in biodiversity assessment and underscore the need for integrated, long-term monitoring strategies that enhance biodiversity maintenance, sustain ecosystem services, and support human welfare in mountain regions.