Carbon stocks and sequestration in hedgerows by Dr. Lilian O’Sullivan, Teagasc Johnstown Castle.
Hedgerows have important benefits in agricultural landscapes. Along with acting as field boundaries, hedgerows provide animals with shelter, can support flood control, and are widely known for their importance for biodiversity. Increasingly though, farmers are interested in the carbon stock and sequestration potential of hedgerows and to see hedgerows accounted for in national inventories for greenhouse gases.
To account for hedgerows in inventories, it is necessary to know the extent of hedgerows, the size of the hedgerows and the type with respect to management. In addition, a mechanism to assess carbon stock change over time is needed. Since 2010, Teagasc have been researching hedgerows to estimate national hedgerow stock and the carbon sequestration figure. The BRIAR project estimated 689,000km hedgerow or 186,000ha taking an average width. In the Farm Carbon project, direct hedgerow measurements were taken so that remote measurements can now be related to biomass and carbon stock.
What did we find?
Hedgerow management directly affects the amount of carbon that is sequestered or stored over time. Two main hedgerows types can be found. Intensively managed hedgerows that have limited benefits for carbon or biodiversity and less intensively managed, wider, taller hedgerows that are managed on a cycle that contain significantly higher amount of carbon. An average across all hedgerows assessed indicated average aboveground biomass stocks of ~58 tonnes carbon per hectare.
What does this mean?
At national scale, if hedgerow removals exceed the carbon accumulated in newly established or growing hedgerows, then hedgerows can be reflected as a source of emissions. While new hedgerow planting offers the best carbon sequestration potential, allowing hedgerows to grow out 1m either side and upward increases sequestration by 1-2 t carbon per ha per year.
What is the opportunity?
Hedgerow management that promotes rejuvenation of older hedges, less intensive management or planting of new hedgerows can enhance the sequestration of hedgerows on your farm.
Less intensively managed hedgerow
Over-managed older gappy hedgerow