Contribution of lakes to global greenhouse gas emissions: Mechanisms, quantification and mitigation strategies.

Lakes cover only 1.8 % of Earth's land yet emit 0.35-0.55 Pg C yr-1 as CO2, 60-120 Tg CH4, and 60-150 Gg N2O, about 5 % of global fossil-fuel emissions. This review synthesizes recent advances in lake GHG mechanisms, measurement, and mitigation, and outlines key research directions. Net respiration generally exceeds primary production, maintaining CO2 supersaturation, while anaerobic methanogenesis dominates CH4 release; oxic pathways linked to methyl-phosphonate cleavage and cyanobacterial leakage add up to 28 % of CH4 in warm, P-limited, dissolved organic carbon (DOC)-rich waters. Roughly 60 % of N2O originates from nitrifier-denitrification. Multi-scale monitoring now combines satellite retrievals, eddy covariance, and buoy sensors, yet global budgets still vary ten-fold because small ponds, littoral "hot spots", and winter ice-outs are under-sampled and gas-transfer coefficients are inconsistent. A range of mitigation measures offers substantial climate-related benefits: (i) enhanced wastewater treatment, urine-diverting sanitation, and vegetated buffers cut CH4 + N2O by 15-25 %, while generating climate and water quality co-benefits can value at billions of USD globally; (ii) biomass harvesting and floating macrophytes lower CH4 + CO2 by up to 57 %; (iii) micro-bubble destratification or moderate sulfate dosing trim residual CH4 by 25-60 %. Together, these measures can abate 0.01-0.08 Mt CO2-eq yr-1 per 100 ha of intensively managed urban lake, enough to achieve 6-10 % of the Global Methane Pledge. Future priorities are resolving the oxic-methane paradox, standardising monitoring, and applying AI-driven up-scaling to embed lake mitigation within SDGs, turning lakes from overlooked emitters into actionable components of climate and water-quality policy.