Nitrous Oxide Emissions from Urban Green Spaces Substantially Offset Their Carbon Sequestration Benefits

However, their net climate benefit remains uncertain due to the poorly quantified release of nitrous oxide (N₂O), a potent greenhouse gas and ozone-depleting substance. Here, we present the national-scale assessment of N₂O fluxes from China’s rapidly expanding UGS, based on high-frequency continuous monitoring and machine-learning extrapolation.

We reveal that UGS function as intensive N₂O sources, with a mean emission intensity of 12.5 kg·N·ha^–1·yr^–1, even though most monitored plots received no direct fertilizer application. These emissions are driven by a unique urban synergy where anthropogenic nitrogen enrichment interacts with irrigation pulses and the urban heat island effect to trigger explosive hot moments of denitrification.