A new study has highlighted that hedgerow biomass is in decline in Ireland in terms of area, due to removals and intensive management.
The research by Teagasc, prepared by the Environmental Protection Agency (EPA), was done to advance understanding of the contribution of hedgerows and non-forest woodland (NFW) patches to carbon stocks in agricultural landscapes.
The study stated that in order to enhance carbon sinks to mitigate climate change, “greater horizontal integration” of policy objectives is needed.
A field survey was completed to establish the relationship between hedgerow biomass and corresponding measurements of hedgerows.
The approach was successfully applied to a scaled-up approach across two counties on “average” dairy, beef and tillage farming systems.
Results
The highest increase in mean biomass was found for emergent hedgerows followed by unmanaged irregular hedgerows.
The largest biomass losses occurred when irregular hedgerows were permanently removed.
There was also a review of existing biodiversity scorecards, which indicated that current scorecards used in hedgerow assessments overlook the carbon benefits.
The study also showed that assuming full coverage of regular managed hedgerows, the carbon sequestered by regular hedgerows could be equivalent to 7% on the average dairy farm, compared with 43% on the average tillage farm.
The study stated: “This is a reflection of the high level of emissions associated with the average dairy farm and heightens the importance of hedgerow retention, reduced hedgerow management intensity and increasing the area of new hedgerows at farm scale.”
Hedgerow goals
Current national greenhouse gas emission inventory submissions to the United Nations Framework Convention on Climate Change show that the land use, land use change and forestry (LULUCF) sector is a net source of emissions in Ireland.
The LULUCF sector now has a target of enhancing carbon sinks to 310MT of carbon dioxide by 2030 under revised regulations, which are expected to come into force in 2024.
The study stated: “Although the research indicates that current management of hedgerows may result in net emissions from the biomass pool, alternative, less intensive, hedgerow management can result in significant removals of carbon dioxide within the LULUCF sector.”
In Ireland, hedgerows are estimated to cover 689,000km, according to Teagasc.
It recommended further policy incentives to allow less intensive management of existing hedges, establishment of new hedges and regeneration of older hedges.
The study stated that this would increase both carbon sequestration and biodiversity ecosystem service potential for hedgerows.