Summary
Chang et al. applied a spatially explicit land surface model to quantify global grassland greenhouse gas balances from 1750–2012, distinguishing direct human management impacts from indirect climate and CO₂ fertilisation effects. Direct human activities (livestock intensification and pasture conversion) shifted grasslands from carbon sinks to sources, whilst climate change drivers paradoxically increased soil carbon accumulation through enhanced productivity. The analysis reveals that net warming from managed grasslands currently negates the net cooling benefit of carbon sinks in natural and sparsely grazed grasslands, emphasising the need for sustainable management to preserve soil carbon and reduce livestock emissions.
UK applicability
UK grasslands, predominantly managed pastures for dairy and sheep production, are likely subject to similar management intensification pressures and would benefit from the study's evidence that sustainable practices can preserve soil carbon sinks. The findings support UK policy objectives around agricultural greenhouse gas reduction and soil health but do not address UK-specific pasture productivity, soil types, or climate conditions.
Key measures
Radiative forcing (W m⁻²), greenhouse gas fluxes (CO₂, CH₄, N₂O), soil organic matter carbon stocks, net climate warming/cooling contribution by grassland type and time period
Outcomes reported
The study quantified the full greenhouse gas balance (CO₂, CH₄, N₂O) of managed and natural grasslands from 1750 to 2012, separating direct human management effects from indirect climate change drivers. It found that net radiative forcing from all grasslands is currently near neutral but increasing since the 1960s, with managed grassland warming offsetting cooling effects from carbon sinks in sparsely grazed and natural grasslands.
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