Net Zero land-use change impact on ammonia emissions: a spatial mapping case study in England

Land-use measures to tackle climate change are being established across the globe that will have implications beyond their net-zero objectives. The most suitable land for these measures is likely to be in agricultural use which means their implementation will affect ammonia emissions and have onward impacts on health, ecosystems and food production. Existing ammonia emissions modelling does not consider how national scale net zero land-use targets are spatially distributed which means these onward impacts may not be adequately assessed. Using England as a case study area, we employed spatial land allocation (LA) modelling to apply these measures on suitable land. We then used emissions modelling to estimate the resulting changes to livestock and chemical fertiliser ammonia emissions at a 5 km grid resolution. To assess the effect of LA modelling on results, we also carried out non-land allocation (NLA) modelling which did not consider the suitability of land, instead distributing the measures uniformly across all agricultural land. The resulting total reductions due to LA modelling of measures was 15.9 kt-NH₃, or 10.5 % of total livestock and chemical fertiliser emissions in England. The NLA approach resulted in similar total reductions, but their distribution was markedly different, particularly for peatland restoration and afforestation measures. We conclude that spatial land allocation modelling of net zero land-use measures is needed to inform policies and strategies to ensure suitable land is targeted and wider environmental and health impacts are considered.