Climate warming from managed grasslands cancels the cooling effect of carbon sinks in sparsely grazed and natural grasslands

Summary

This global modelling study quantified the full greenhouse gas balance (CO₂, CH₄, N₂O) of grasslands from 1750 to 2012, using a spatially explicit land surface model to distinguish direct human management effects from indirect climate change and CO₂ enrichment effects. Direct human activities—increased livestock numbers and conversion of natural land to pasture—have shifted managed grasslands from carbon sinks to net sources of greenhouse gases. However, climate change drivers (rising CO₂ and nitrogen deposition) have enhanced grassland productivity and soil carbon sequestration. The net result is that warming from managed grasslands currently cancels the climate cooling potential of carbon sinks in natural and extensively grazed grasslands, highlighting the need for sustainable management to enhance soil carbon storage and reduce emissions from managed systems.

UK applicability

The findings are relevant to UK policy on grassland management and livestock emissions, particularly given the UK's climate commitments and reliance on pastoral systems. UK grazing management practices and pasture intensification decisions will influence whether grasslands function as net sinks or sources, making the study's emphasis on sustainable management directly applicable to national climate and agricultural strategy.

Key measures

Radiative forcing (W m⁻²) from combined greenhouse gas fluxes; trends in net greenhouse gas balance by grassland type; separation of management effects from climate and CO₂ fertilisation effects

Outcomes reported

The study quantified trends in CO₂, CH₄, and N₂O fluxes from managed and natural grasslands from 1750 to 2012, separating direct human management effects from indirect climate change effects. It demonstrated that managed grasslands currently offset the climate cooling benefit of carbon sinks in sparsely grazed and natural grasslands.

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