Hedgerows and carbon storage
From a carbon storage perspective, the removal of hedgerows is one of the worst actions farmers can undertake on their farms.
That’s according to Dr. Stuart Green, a Remote Sensing Specialist in Teagasc’s Department of Agribusiness and Spatial Analysis, who’s part of a project using cutting-edge technology to assess the biodiversity and the carbon stored within its biomass on Signpost Programme farms.
Delivering a message to the Teagasc Signpost Conference and General Assembly on November 21, Dr. Green explained how LIDAR technology is being used, detailing work completed over winter 2022/2023 and 2023/2024.
He explained: “Carbon stored in biomass and the distribution of on-farm habitats are suitable to be assessed using remote sensing technology. A total of 92 Signpost farms were surveyed using drone-mounted cameras and LIDAR.
“The colour imagery taken by the drone gives a snapshot of the farm land cover and habitats. The LIDAR is a scanning technology the sends out laser pulses and measures the time it takes for the pulse to be reflected from the surface back to the drone, allowing a 3D picture of the farm to be built up of millions of points.” As visible in figure 1 below
Early indications from this work show that habitat values are lower on the Signpost Programme farms than those found on farms nationally, but this will be an area of work where advisors and the participating farmers will endeavour to improve.
On how this will occur, Dr. Green explained: “These maps provide a baseline for the farmer and advisor. They show the distribution of the habitats on the farm and help direct discussion about where and how to improve.”
Figure 1: A 3D model of a signpost farm block, with accompanying habitat map. The figure shown is actual above ground carbon estimates for those two hedgerows (both the same length).
Carbon and hedgerows
Dr. Green also detailed how the exact volume of a hedgerow is calculated and converted to biomass, using equations developed at Teagasc, to provide an estimate of the tonnes of carbon stored within.
“It is important to think of volume when assessing how much carbon a hedgerow contains, not its length” he commented.
Dr. Green explained: “The Signpost farms assessed have stored within their woody biomass hundreds of tonnes of carbon. But it’s important to note that this is carbon stored over the life of the farm, it is not the carbon sequestered annually by the farm biomass.”
“Hedgerows only store extra carbon if they are allowed to grow. Allowing a hedgerow to grow will make significant changes to the carbon sequestered, as well as providing major biodiversity and habitat benefits to your farm.”
“Taking away a hedgerow is one of the worst things you can do to the carbon budget on your farm. If you were to remove for example a short, topped hedgerow, even when following the rules and replacing it with twice the length of hedge beforehand, it will take 12-15 years to get back to the carbon you have lost from removal, that’s before you even start to add extra carbon,” he explained.