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08 December 2021

The state of Ireland’s hedgerows

The state of Ireland’s hedgerows

Catherine Keena Teagasc Countryside Management Specialist covers The state of Ireland’s hedgerows, as talked about in the Teagasc Hedgerow Week Panel Discussion on Monday's webinar. Watch back on the webinar here and tune in all this week to Hedgerow Week events

Hedgerows are the most common habitat on lowland farms in Ireland - a characteristic feature of the Irish countryside. They encompass many different forms, shapes and sizes. The state of Ireland’s hedgerows was discussed during Teagasc Hedgerow Week by a panel including researchers, county council staff and non-governmental hedgerow organisation representatives. The discussion covered quantity and quality of Irish hedgerows.

Some 689,000 kms of hedgerows in Ireland

A report from Stuart Green , Teagasc Remote Sensing Specialist detailed an estimated 689,000 kms of hedgerows in the country using a very broad definition of hedgerow which includes all woody vegetation growing on a boundary from stockproof hedgerows to relict hedgerows. Hedgerow length varies across the country.

  • Counties around the midlands and the border tend to have the highest density of hedgerows with smaller fields.
  • Cavan has the highest length of hedgerows per hectare.
  • Counties on the western seaboard have the lowest percentage because they have areas of open upland that isn’t enclosed.
  • Counties like Donegal and Galway have a lot of stonewalls rather than hedgerows.

Mapping hedgerows

Earth observation technologies such as satellites, drones and Geographic Information Systems or GIS are used to map the Irish agri-environment including hedgerows. The extent and condition of hedgerows is mapped using satellites and aerial photographs. Technologies like laser scanning and drones are used to get characteristics of individual hedgerows.

Technologies used to map hedgerows including satellites and aerial photography look down from above, giving the footprint and extent. Hedgerow volume is also of interest. As hedgerows are three dimensional (3D), height and width are needed in addition to length. Technologies like laser scanning and drones give a 3D model, from which biomass can be determined and used for assessing hedgerows for the sequestration of carbon.

Teagasc Research

During her PhD research with Teagasc which started in 2014, Julie Larkin surveyed 119 intensively managed farms across three farming enterprises (tillage, beef and dairy) primarily in the south and south east of Ireland with many of the farms in Cork, Kildare and Wexford. Hedges were the most abundant and frequently occurring wildlife habitat, they were present on all farms surveyed and accounted for almost 3% of the total area of every farm. Beef farms had 2.93%, dairy farms had 2.73% with 2.67% on tillage farms.

On 92 of these farms Julie looked at the quality of their hedges (537 hedges in total), using the Hedgerow Appraisal System (Foulkes et al. (2012)) to get a quality parameter.

A startling 90% of these hedges were classed as low quality and only 1% classed as high quality.

The reason why these hedges were failing on quality was primarily because of their impoverished ground flora with very low species diversity in the ground flora and within the hedgerow woody species. Herbicide use was very obvious within the hedgerow edge. There was a dominance of weeds such as thistles, nettles and cleavers in some of the hedgerows. Cattle poaching at the base of the hedge causing bank or wall degradation was another problem. Gappiness was another reason for low quality.

Monaghan Hedgerow Appraisal Survey 2021

County specific hedgerow results were presented for Monaghan described by Shirley Clerkin, Heritage Officer, Monaghan County Council as a drumlin, wetland, hedged county.  A survey was carried by Flynn Furney for Monaghan County Council with financial assistance of The Heritage Council out during the months of July and August in 2021 on hedges previously surveyed in 2010. The aim and intent were to assess these hedges a decade on to review the state of hedgerow in the county. The methodology used during surveying has been set out by Foulkes et al. (2012) in the Hedgerow Appraisal Survey (HAS) methodology, which was first piloted in Monaghan’s 2010 survey. The study was split into two phases in 2010; baseline hedges which were randomly chosen from twelve 1km2 squares; and hedges which were perceived to be of High Ecological value, namely townland boundary hedges and those connected to native woodland. Both sets of hedges were re-surveyed and results outlined in this report.

With the results showing a decade of change, the news is very poor according to Shirley. Extent, floristic composition, physical structure and management of hedges were assessed. In 2010, there was an estimated 12,845 kms of hedges with over 1,000 kms removed in the following decade – based on a survey of 108 hedges. In the 12 sample squares surveyed, over 10 kms were removed. This equates to 0.9% may have be removed annually in County Monaghan, far higher than the EPA estimate of 0.3%. The main reason was agriculture - in three-quarters of the cases

In 2021 in the shrub layer there were 30 species, 5 less species than in 2010 with whitethorn being the most frequent, followed by blackthorn and holly. Numbers of climbers such as brambles, roses and honeysuckle were similar over the decade. For species diversity, in 2010 37% of the hedges were species rich (4 or more woody species), now down to 23% in 2021. There were 20 tree species in hedges with 71% of the tree species being ash. Of hedges where ash was noted, 90% displayed signs of dieback. A high percentage of ivy in the canopy is often linked to trees in a natural state of decline and hedges which contained over 25% ivy in the canopy have increased from 10.2% in 2010 to 36.4% in 2021.

Species diversity of the herb species in the ground flora has decreased in nutrient-rich hedges with a lot of nutrient run-off from agriculture, resulting in a lot more nutrient rich species such as nettles, cleavers. Slurry was found close to the base of hedges – even spread on some hedges. 64% of the adjacent land use is now improved agricultural land, an increase of ten per cent since 2010. Almost 88% of hedges in Monaghan are in unfavourable condition with only 12% in favourable condition.

Shirley explained how the gradual decrease in the quality of our landscape over time means a loss of flood control capacities of our hedges and a loss of nutrient absorption capacity because they can no longer function. There is a need for a results-based payment scheme for hedgerows to incentivise best practice management.

Farm Carbon

Teagasc are currently leading Farm-Carbon , a research project co-funded by the Environmental Protection Agency and Department of Agriculture, Food & The Marine (DAFM). Lilian O’Sullivan gave an update on the Farm Carbon project with results expected in 2022.

The aim is to quantify the carbon stock of selected hedgerows by measuring the different carbon pools. A biomass function will be based on volume measurement captured using remote technologies, through the development of a 3D digital surface model. An integrated scorecard for hedgerow assessment will be developed along with a best practice management advice for the delivery of ecosystem services such as carbon and biodiversity.

Hedgerows are a prevalent feature in the Irish landscape and best practice management is important to maximise the delivery of important ecosystem services such as biodiversity and carbon. Up to now most research on hedgerows has focused on the role of hedgerows in terms of biodiversity and how they function as landscape features in terms of biodiversity provision. There is less research on the role of hedgerows in relation to carbon storage and sequestration. 

Research is needed on carbon stocks and the impact of management on biomass accumulation in hedgerows but also how carbon and biodiversity are related. Very often the indicators or attributes that are good for biodiversity are also important for carbon. For example the structure, in particular width, density and connectivity of hedges are attributes that are important for biodiversity, but also important for the carbon profile.

Biomass is an important part of the global carbon cycle because dried wood biomass weight is estimated to contain about fifty percent carbon (Houghton et al., 2009). Biomass density which refers to the amount of biomass in a unit area is a good indicator of carbon. Hedgerows can contain a relatively high biomass per unit area and so they potentially represent a considerable carbon stock. Research in the UK indicates that species like whitethorn (hawthorn) and blackthorn, which are common in Irish hedges contain about 48.3% carbon on average (Axe, 2015).

To estimate the carbon contained in hedges different carbon pools must be considered. Carbon that is contained in the biomass includes above ground biomass which is visible along with below ground biomass. Consideration must be given to different organic matter returns into the system so if there is deadwood or if leaf litter is being lost seasonally – how much is going back into the system and cycled into the carbon pool. Regarding soil organic matter, consideration must be given to the amount of carbon that is being contained in the soil under hedgerows relative to adjacent land use. Also there is a need to understand how management impacts biomass accumulation and the sequestration difference between managed and unmanaged hedgerows.

Hedge Laying Association of Ireland (HLAI)

Mark McDowell spoke on behalf of the Hedge Laying Association of Ireland which was founded in 2004 by a group of people who realized that there were serious issues with hedgerow management in Ireland. The main objectives of the association are to encourage and facilitate the conservation protection and appropriate management of hedgerows and to facilitate landowners in the management of hedgerows by hedge laying, also to establish maintain and promote recognized standards of craftsmanship in hedgelaying also to provide training. This has been an issue over the years.

Agri-environment schemes have been in place now for over 20 years. Mark feels they were well intentioned at the start with REPS, but overall the state of our hedges has disimproved. Applying standards and promoting standards in hedgerow management is crucial. There is a basic lack of understanding in the schemes with over-simplification but they have that they've been a disaster for our hedgerows according to Mark. On a farm, hedge laying is not something that you sign up for a couple years and then your hedges are laid and then you never bother with them again. If you have a thousand meters of hedge on a farm, ideally you will lay 50 to 100 meters annually. This preserves the habitats in the remaining 900 metres of hedge and provides space for the birds to continue nesting because hedgelaying is quite invasive. It reduces the volume of the hedge considerably initially but it extends the life of the hedge indefinitely. Where approximately ten percent of hedges are laid every year, by the time the final section is laid, the first section is ready to be laid again. 

Hedges are top of everyone's agenda, but Mark stressed the basic need that all hedges have is management. Hedges want to become and will become a row of trees unless it is managed by people who know what they are doing.

Hedgerows Ireland

Alan Moore represented Hedgerows Ireland which is a fairly new national lobby group comprising landowners and people interested in the environment, whose position on the current situation is a mixture of real hope for the future of hedgerows countered by the reality of the continuing vulnerability of our existing hedgerows.

Hedges are really important for our wildlife and for addressing climate change and their importance cannot be overestimated according to Alan. They are ’alive inside’ home to a birds, plants and a huge range of insects and pollinators that depend on both the flowering hedge with shrubs like whitethorn as well as the flowering plants that grow alongside the hedge itself. Hedgerows Ireland sometimes refer to our hedges as being the Irish equivalent of the Amazonian rainforests and they are just as vulnerable to destruction in the last few years. It's no coincidence that during Covid and the lockdown there's been an explosion of public interest in our countryside with people walking the roads, foraging for blackberries, elderflower and elderberries, bird watching, plant spotting and so on. People really like hedges and this has been matched by a growing scientific appreciation of what hedgerows can do for carbon both above and below ground. The science is telling us - not surprisingly, that when it comes to carbon bigger taller wider hedges are better just as these kind of hedges are better for wildlife. Alan thinks we should be using this knowledge wisely now. Hedgerows Ireland is submitting a detailed proposal to the CAP consultation process to suggest some measure of hedgerow quality and size is included in the new eco schemes relating to existing hedgerows. There's lots of good stuff in the draft proposals about planting new hedges and trees but nothing yet about the management of our existing 700,000 kms of hedge which according to Alan is a real lost opportunity. The technique in recent years for very severe annual cutting means that a lot of the potential of our hedgerows for both carbon and wildlife is being lost. Hedgerows Ireland think that changing this needs to be incentivized in the new cap and also think that the reintroduction of regional hedge cutting and hedge management courses. Certification will be really important too. Knowledge is key here. It it's a potential growth area with jobs.

‘Regulations around hedgerow removal are crazy’ according to Alan in that you can remove up to 500 meters of hedgerow without needing to alert the DAFM and if you intend to remove more than that length or create a field bigger than five hectares there's a 95% chance that DAFM will give you the go ahead (up to 98% in the southeast). This means that hundreds or thousands of kilometers have been removed legally in recent years and that only accounts for hedge removal where permission is sought. In the UK it's illegal to remove over twenty meters of hedge without approval. As a result we are seeing more and more 100 acre fields appearing in our countryside with all the loss of habitat that goes with that. When it comes to tillage - big machines need big fields but surely not 100 acre prairies - is that really necessary? As well as loosing habitat for wildlife, there is a loss of shade and shelter for livestock, flood control, water filtration and of course the sheer beauty that the network of connected hedges gives to a landscape as opposed to a bleak desert.

Take-away messages

The big message from Hedgerows Ireland is this huge potential we still have in the network of hedges largely intact despite all the removal and we need to make the most of it. Hedges tick all the boxes for carbon, biodiversity and so on – Alan would like to see the new Common Agricultural Policy doing much more. It should be much more ambitious and harness the potential that is waiting to be harnessed

The take home message from Lilian is that there are a lot of positives here and there's a lot of opportunity that could be exploited and there are ways that we should be better supporting farmers and not only for biodiversity but carbon and the other multiple benefits. There's lots of hedgerows and farmers should not be penalized for managing hedgerows and perhaps even letting them grow a little wider than they currently are.

The Hedge Laying Association of Ireland want the application of standards in professional hedgerow management and that hedges identified for laying or coppicing in schemes are chosen by people who understand hedges and that rejuvenation work is carried out and inspected by people who have expertise.

Julie wanted to highlight our valuable hedgerow network and the importance of our hedgerows around the country because of the low level of native woodland in Ireland.

Shirley believes hedgerows connect us and our landscape. They are culturally important as well as ecologically important and while we heard stark facts about the current quality of hedgerows, the infrastructure is there in place and can be improved. She would really encourage farmers to come together and think about how we could actually operate a results-based payment schemes for hedges.  ‘Let's not say things are positive and rosy in the garden because it's not – a lot of work needs to be done and I think we should do it’ says Shirley.

Overall the conclusion was we are lucky to have the network of hedges in Ireland with huge potential for the future but lots to do and we need to work together. 

The state of Ireland’s hedgerows - Monday December 6th

On Monday, 6th December, the state of Ireland’s hedgerows both quantity and quality was discussed. Catherine Keena, Countryside Management Specialist, Teagasc was joined by a panel including: Lilian O’Sullivan, Teagasc Johnstown Castle Researcher; Julie Larkin, RPS (former Teagasc PhD student); Shirley Clerkin, Heritage Officer, Monaghan County Council; Mark McDowell, Hedge Laying Association of Ireland; and Alan Moore, Hedgerows Ireland. A questions and answers session took place at the end of the webinar which was facilitated by Padraig Foley, Teagasc.

Watch webinar recording below

Further Information:

Follow Teagasc Daily all this week for a daily update on the articles and webinars from Hedgerow Week 2021