Species-rich hedgerows are hedges which are contain five or more native woody species in a 30 metre length (UK HAP, 1995). These often form linear boundaries of planted shrubs.
- Site: Less intensively farmed areas
- Soil: Nutrient-poor soils
- Main species: 5 or more native woody spp.
- UK: 190,000 km
- NI: 44,000 km (includes bramble)
- Species-rich hedgerows typically contain five or more native woody species such as oak, ash, hazel, beech, elm, sycamore & elder.
- Those with fewer woody species but rich basal flora of herbaceous plants, such as wood anemone, primrose, bluebell, are also regarded as species-rich hedgerows.
- Hedgerows associated with semi-natural vegetation such as rivers or wooded ground are often very species-rich (Hegarty, 1992; NIEA, 2003)
Current Status in UK & Northern Ireland
- The UK HAP (1995) estimates that the UK total is 450,000 km.
- Northern Ireland has the highest density of field boundaries in the UK, with an average of 17 km per km2 (Copper et al., 2002).
- The NICS (2000) estimated 119,000 km of hedgerows in NI, showing a decline of 4% between the 1992 & 2000 NICS (125,000 km to 119,000 km).
- The NICS (2000) estimated that 37% (44,000 km) of hedges in NI are species-rich. However, this included bramble Rubus fruticosus which are not included on the UK HAP definition.
- In NI hedges that are unmanaged & close together (with <10% gaps) have the highest species richness. Those associated with semi-natural vegetation are also species-rich. This contrasts to species-poor hedges which are associated with intensively managed farmland (NIEA, 2003). Over half of the hedgerows in NI are species-poor, dominated by Hawthorn Crataegus monogyna & Ash Fraxinus excelsior.
- Hedgerows in NI are threatened by neglect, inappropriate machinery (resulting in poor structure & gap development), use of chemicals, complete removal & increased stocking rates, resulting in hedgerow damage & replacement with fences.
- Species-rich hedgerows are concentrated in Fermanagh but also occur in the Antrim Coast & Glens AONB
- (2181km) and Binevenagh AONB (237km) (NICS, 2000)