Threats to UK Upland Habitats

 

UK upland habitats and their associated species are threatened by a range of factors. Over the last century, all semi-natural upland habitats have been reduced in extent and suffered degradation due to a combination of afforestation, air pollution, built development, improvement for agriculture/game rearing, inappropriate grazing or burning, peat extraction, quarrying, recreation and other factors. Encouragingly, the impact of many of these has been reduced in recent times.

 

The table below provides a summary of major pressures and threats to UK upland habitats – details are given beneath. These are based on information in the 3rd UK Report on Implementation of the Habitats Directive, the UK Biodiversity Habitat Action Plans, and Common Standards Monitoring for Designated Sites: First Six Year Report.

 

 

Blanket bog

Upland heathland

Upland flushes, fens and swamps

Inland rock outcrop and scree habitats

Mountain heaths and willow scrub

Limestone pavements

Upland calcareous grassland

Calamin-arian grassland

Air pollution

*

*

*

*

*

*

*

*

Grazing

*

*

*

*

*

*

*

*

Burning

*

*

*

*

*

 

 

 

Invasive non-native species

*

*

*

*

 

*

*

 

Improvement for agriculture/game rearing

* *

*

 

 

*

 

 

Afforestation

*

*

 

 

 

*

 

 

Built development

*

*

 

 

 

 

 

 

Recreation

*

 

 

*

*

 

 

 

Erosion

*

 

 

 

 

 

 

 

Peat extraction

*

 

 

 

 

 

 

 

Quarrying

 

 

 

 

 

*

 

 

Land reclamation & mineral re-working

 

 

 

 

 

 

 

*

 

Afforestation

Large areas of blanket bog and upland heath have been lost due to afforestation, mainly with non-native conifers and including site drainage. This practice has been greatly reduced in recent times, and some areas of afforested bog and heathland are undergoing restoration after the first rotation of conifers. Some maturing plantations are, nevertheless, having an impact on the hydrology and species composition of adjacent blanket bogs, and full restoration is a problematic and long-term process. In addition, some wooded limestone pavements have been adversely affected by planting of conifers or beech. As these mature, they can heavily shade the ground and create an inhospitable deep, slowly decaying layer of needles or leaves.

 

Air pollution

Air pollution is a widespread threat affecting upland habitats. Many of the key species and ecological conditions are highly sensitive to nitrogen and acid deposition and to direct exposure to high concentrations of ammonia and ozone. Major areas of blanket bog, upland heathland and mountain heath exceed the critical loads for nutrient nitrogen and/or acid deposition. Such pollution alters the composition of the vegetation by encouraging the growth of certain species, whilst other ‘sensitive’ species decline or are out-competed. For further info: UK Air Pollution Information System (APIS)..

 

Built development

Drumderg windfarm. @Lorne Gill, SNH

Wind farms, communication masts and their associated infrastructure (e.g. access tracks) have increasing become a significant threat to upland heathland and blanket bog, especially at high altitude. There are also threats from hydro-electric schemes in Scotland.

 

Burning

Burning is a traditional management technique that is used to modify the vegetation mainly for the benefit of livestock, grouse and deer. It is a common practice on upland heathland, but also affects other upland habitat types. Inappropriate burning is a widespread problem in the uplands. This can arise due to wildfires or from deliberate or accidental burning. It can be very damaging to wildlife habitats, especially if it is combined with over-grazing. The effects are comparable to over-grazing and recovery can also be slow and incomplete. Burning of blanket bog is, in many situations, considered inappropriate. Accidental spread of fires upslope onto mountain heaths is a widespread damaging factor. Burning can also damage the regeneration potential of rocky habitats with skeletal soils and certain kinds of flushes, fens and swamps.

 

Erosion

High altitude blanket bogs in particular, and especially those in the Pennines and South Wales, are suffering from erosion of the underlying peat mass. Some of this may be due to natural processes, but it is exacerbated by factors such as drainage, over-grazing, drying of the climate, and recreation.

 

Grazing

Like many wildlife habitats in the UK, upland habitats usually benefit from a moderate, but not excessive, level of grazing. This may involve cattle, sheep, deer and/or rabbits, and helps maximise vegetation structure and floristic diversity.

Over-grazing (by livestock or wild deer) is, however, a widespread problem in the uplands. This reduces the vegetation, leads to a loss of structure, characteristic species and floristic diversity, encourages the spread of unpalatable plant species, and impoverishes the associated fauna. In extreme cases, trampling can expose the underlying soil and cause instability in screes and soil erosion. Recovery after heavy grazing can be slow and incomplete.

In contrast, some upland habitats suffer from under-grazing, most notably upland flushes, fens and swamps and Calaminarian grassland. Without grazing, rank and scrubby species will invade and spread, leading to a loss of floristic diversity. Calaminarian grassland require more or less continuous grazing by rabbits or sheep, without which soil organic material builds up, with a gradual dilution of the effect of heavy metal contaminants, often resulting in scrub invasion. In this case some form of disturbance may be necessary to maintain soil toxicity.

 

Improvement for agriculture/game rearing

Extensive tracts of blanket bog, as well as some areas of upland wet heath and flush, fen and swamp habitat, have been drained in an attempt to improve their grazing quality (for livestock, grouse or deer). This has been achieved by creating artificial drainage channels known as ‘grips’. Gripping is a major cause of unfavourable condition on blanket bogs. It results in the vegetation changing towards drier forms of heathland and degradation of the underlying peat. In places, new grips continue to be dug and existing grips cleaned. Even without maintenance, most grips continue to lower the water table and some initiate erosion. There is a widespread need to reinstate the natural hydrology of many blanket bogs by blocking grips.

Other forms of agricultural improvement, notably conversion of semi-natural vegetation to simple pasture and application of fertilisers and herbicides, have occurred frequently in the past on various upland habitats. This and associated practices, such as intensive winter livestock feeding, remain as locally significant threats to blanket bog, limestone pavements, upland heathland and upland flushes, fens and swamps.

 

Invasive non-native species

There are a number of non-native plant species with the propensity to invade upland habitats. These include:

  • Australian swamp stonecrop and Parrot’s feather, which can rapidly colonise and change the ecology of small standing water and wetland habitats;
  • New Zealand willow herb, which favours moist, skeletal screes and grassland sites, especially where grazing has favoured open ground;
  • Cotoneaster and Buddleja, which are a local problem on limestone pavements.

The impacts of the non-native heather beetle on upland heathland appear to be increasing and may become a bigger problem, possibly linked with climate and atmospheric pollution.

 

Mineral re-working and land reclamation

Re-working of abandoned mineral veins is a significant threat to some Calaminarian grassland sites. At other sites, such grassland is deliberately ‘reclaimed’ to remove a source of contamination to livestock or simply to improve the aesthetic appearance of former mining land.

 

Peat extraction

Peat extraction on blanket bogs has had important local effects. Domestic cutting, most of which has occurred on common land, is locally extensive. Elsewhere, mechanical extraction has been employed for commercial purposes, notably in Northern Ireland. Not only does this directly damage the habitat, but it drains and disrupts the natural hydrological regime.

 

Footpath erosion on N. Goat Fell, Isle of Arran. @Lorne Gill, SNH

Quarrying

Removal of surface stone from limestone pavement badly impacted on this habitat in the past. Since the mid-1990s, however, such activity has largely been stopped, save for a small-scale illegal extraction and loss due to built development. Although pressure remains to extend deep quarries onto surviving pavements, this has been prevented by strong development control policies.

 

Recreation

Many popular walking routes, some of which are also used by cyclists and horse-riders, traverse blanket bog and mountain heath areas, which are very sensitive to such pressure. The increased use of all-terrain vehicles for recreational, agricultural and sporting activities has also resulted in local erosion. Recreational disturbance, such as rock climbing and scree running, has resulted in accelerated erosion on a number of inland rock outcrop and scree habitat sites.