Fungi play an outsized role in climate mitigation, with mycorrhizal networks contributing roughly 13% of global soil carbon inputs and fungal biomass storing carbon at scales comparable to plant roots. The review also highlights mushrooms turning agricultural waste into soil amendments, replacing petro-based materials with mycelium composites, and producing protein with a fraction of the land and emissions of animal agriculture. Rather than a single solution, mushrooms show up repeatedly as low-energy tools that quietly reinforce carbon storage, circular systems, and climate-resilient land use.