National Character Area 110

Chilterns - Natural Capital and Key Ecosystem Services


The Chilterns NCA provides a wide range of benefits to society. Each is derived from the attributes and processes (both natural and cultural features) within the area. These benefits are known collectively as ‘ecosystem services’. The predominant services are summarised below. Further information on ecosystem services provided in the Chilterns NCA is contained in the ‘Analysis’ section of this website.

Note: The natural capital in this NCA is mapped below. This displays more recent national and publicly available data sets as used within Natural England’s 2020 Natural Capital Atlas Profiles.

The predominant ecosystem services in this NCA are also summarised below. The text contained in this section is based on the previous NCA profiles in 2014, and so is not entirely current. Further information on ecosystem services provided in the North Northumberland Coastal Plain NCA is contained in the Analysis: Ecosystem Services page of this website.

What is Natural Capital?

Natural capital means “the elements of nature that directly or indirectly produce value to people, including ecosystems, species, freshwater, land, minerals, the air and oceans, as well as natural processes and functions” (Natural Capital Committee, 2017).

It is helpful to consider natural capital in the form of a logic chain that represents the links between ecosystem assets, services, benefits and value to people. The figure below displays that logic chain. The quantity and quality of ecosystem assets (woodland, bogs, etc) support different types of ecosystem services, such as carbon sequestration or water filtration. These ecosystem services then provide different benefits to society, providing value for people. The figure also shows how management interventions, as well as pressures and drivers of change, influence this chain. Other capital inputs are also often needed for people to obtain the benefits from ecosystem services (a simple example is the processing of trees to produce wood products).

As an example, an area of woodland (ecosystem asset) may reduce air pollution created by traffic on a nearby road. This woodland is therefore improving air quality (ecosystem service) in the local area which results in cleaner air and improved health in the adjacent residential street (benefit). This cleaner air has a value because we know it impacts the health and wellbeing of communities.

Sometimes for ease of understanding, economic framing is used to give these benefits a monetary value. The figure below shows how natural capital assets support the provision of ecosystem services, benefits and value. The roots of the tree show how aspects of asset quality are critical to the provision of ecosystem services. The roots also show that geodiversity underpins the ecosystem assets and therefore the ecosystem services and benefits they can provide. It is important to remember that this diagram, and natural capital frameworks more generally, are a simplification of how nature works in practice.

Natural Capital within this NCA

In 2018, Natural England published ‘Natural Capital Indicators: for defining and measuring change in natural capital’ (Lusardi et al., 2018). This report identified key properties of the natural environment vital for the long-term sustainability of benefits, which can act as indicators of change.

These indicators are designed to inform our understanding of the state of our natural assets. The indicators highlight the importance of our natural assets for delivering which ecosystem service and the benefits they provide for society. The indicators and datasets identified in Natural England’s Natural Capital Indicators Project provide the foundation for the Natural Capital Atlas Profiles.

Natural England’s Natural Capital Atlas Profiles provide an “off the shelf” natural capital evidence base for each county or city region. They have a wide variety of uses with more information in the How to Start Using Your Natural Capital Atlas.

The Natural Capital indicators are presented on the map below by broad asset theme, displaying the natural capital within the NCA.

It is noted that not all indicators listed within the Natural Capital Atlas Profiles are included within the map as data is not yet available to measure them. Refer to the “Indicator Gaps and Limitations” of the Natural Capital Atlas Profiles for further information.

Note that numbers and figures in the body of the text are based on the 2014 profiles, unless otherwise stated.

Provisioning services (food, fibre and water supply)

Food provision: As a result of the predominance of Grade 3 agricultural land, farming is mixed, with average levels of productivity. There is a concentration of arable production on Grade 1 and 2 land along the Thames Valley, beneath the hills in the north and along the scarp foot. Cereals dominate arable production, with wheat being a predominant crop. There are limited but well-established sheep farms and localised areas of dairy and beef production.

Water availability: The Chalk is the most significant aquifer of southern England and is of national importance in terms of abstracted volume and development for Groundwater abstraction volumes far outweigh those from surface waters in the Chilterns, with much of it being for public water supply. A large and growing population combined with high consumption rates per person put significant demands on the resource.

Chilterns water resources also support London’s groundwater supplies in the confined aquifer and the Thames river system downstream of the Chilterns. Unsustainable abstraction currently takes place in the north of the Chilterns, where the rivers Ver, Misbourne, Mimram and Lee are considered to be over-abstracted and hence experience low flows exacerbated by abstraction pressures. There is hydraulic continuity between the aquifer and watercourses, which means that changes in groundwater levels directly affect surface water levels. The Thames is relatively resilient to abstraction but alleviation schemes and monitoring have been required for the Chilterns’ small chalk streams to address negative impacts of low flows on valued biodiversity.For information regarding the current state of water availability within this NCA, refer to the Environment Agency (Abstraction Licensing Strategy).

Biomass energy: The extensive woodland cover represents a source of wood fuel, particularly since timber quality is limited in the immediate The market for firewood is growing significantly in parts of the Chilterns. The potential for miscanthus is limited and there have been very few plantings. Short rotation coppice coverage is minimal and is discouraged in areas such as the Chilterns where there are water availability concerns.

Regulating services (water purification, air quality maintenance and climate regulation)

Climate regulation: Across most of the NCA, carbon stored in the topsoil horizon is typically in the range of 0-5 per cent, which is good for mineral soils in agricultural use. The considerable area of undisturbed soils beneath remnant historic land uses such as ancient woodlands and downland represents a large, longstanding carbon store with maximised storage capacity. The extensive tree cover also sequesters carbon, although trees make a greater contribution to carbon reduction by providing alternatives to fossil fuels.

Regulating water quality: For information regarding the current state of water quality within this NCA, refer to the Environment Agency (Draft river basin management plan maps).

Regulating water flow (flooding): The Thames Valley has a fairly high risk of flooding, with riverside settlements including Reading, Henley and Marlow The Thames Valley also offers potential floodwater storage areas. Smaller-scale flooding may also affect those settlements adjacent to chalk streams in the dip slope valleys but, historically, low flows have been a more significant issue, with natural flows needing to be artificially supplemented in many cases. Natural river processes are often constrained by channel modifications in urban and developed areas, for example canalisation in Luton and High Wycombe.

Regulating soil quality: Agricultural opportunities are optimal across the Grade 1 and 2 land found in valley bottoms, along the scarp foot and in other lower-lying Historic land uses with a long history of low or zero chemical input and limited or no cultivation, including traditionally managed downland, parkland and ancient woodland, represent areas of soil that have benefited from a long continuity of conservation practices and natural soil processes. Soil quality is at risk across much of the NCA due to compaction. The role of soil quality in water filtration to the aquifer and water pollution is of significance to groundwater quality in the Chilterns’ principal aquifer and to the biodiversity of chalk streams.

Cultural services (inspiration, education and wellbeing)

Sense of place/inspiration: Landscape character ranges from enclosed and intimate folded valley landforms to the exposed plateau tops and scarp that afford extensive views, with the separate character of the Thames flood plain to the The unifying elements include sunken lanes, woodland, downland, chalk streams, parkland and a distinctive vernacular architecture. Red kites are now a common sight adding to sense of place. Prominent landmarks include grand houses and follies (as at West Wycombe), chalk figures (such as Whiteleaf Cross) and monuments (such as Coombe Hill Monument). The undeveloped commons and dry valleys evoke a sense of rural endurance, particularly when contrasted with nearby London and its fringe. The Chilterns landscape inspired John Milton, Stanley Spencer, John Nash and Roald Dahl. Properties owned by key historic figures include Benjamin Disraeli’s country estate, Hughenden Manor, and the Rothschild family’s Natural History Museum at Tring.

Sense of history: Extensive flint-working sites and finds date from the early Palaeolithic The prehistoric routeways of the Ridgeway and the Icknield Way and associated prehistoric monuments create a particularly strong sense of prehistory along the escarpment. Roman influence on the landscape is still evident, primarily through the communications network and settlement pattern. Many villages, farmsteads and field patterns are of medieval origin, including rare co-axial fields. Commons and woodlands rich with archaeology are widespread. Historic buildings and more recent constructions make use of traditional materials such as flint, brick, and tiles and, in places, weatherboard and thatch. Designed parklands and large gardens are prominent, covering 3 per cent of the area, and many are included on the national Register of Historic Parks and Gardens. There are examples by key landscape designers such as Brown and Repton. More recent heritage features include the Grand Union Canal and the ‘Metroland’ towns along the London Underground Metropolitan Line.

Tranquillity: Contrasting with nearby London, this area offers relative Tranquillity is found along parts of the escarpment but the largest area is found in the remote and sparsely settled dip slope in Oxfordshire. Transport corridors, such as the motorways, and aircraft impact negatively on tranquillity in localised areas.

Recreation: A variety of green spaces and an extensive rights of way network offer a range of recreation opportunities suitable for walkers, horse riders and cyclists, as well as for those who enjoy less common pursuits, such as carriage drivers and Improvements have also been made to increase accessibility for disabled users. Long-distance trails include the Ridgeway and the Thames Path National Trails, and the Chiltern Way. There are more than 3,500 ha of open access land, around 2.5 per cent of the NCA, including significant tracts of common land close to settlement. There are three National Nature Reserves (NNRs) that provide access to some of the best examples of semi-natural habitats in the country and a particularly large area of accessible woodlands. Green space is well distributed except in the north, where Luton, for example, is noticeably lacking.

Biodiversity: The approximate area of priority habitat amounts to just over 16,000 ha, of which the huge majority is woodland and includes the Chilterns Beechwoods Fragments of lowland calcareous grassland total more than 700 ha (Chilterns Area of Outstanding Natural Beauty: Management Plan 2008 – 2013 – A Framework for Action, Chilterns Conservation Board, undated)  and include Barton Hills and Knocking Hoe NNRs. Chiltern chalk grasslands are distinctive for their large number of rare and scarce vascular plant species such as the Chiltern gentian. At Hartslock Wood SAC and Aston Rowant SAC, there are important examples of the Chilterns’ mosaic of chalk grassland, scrub and woodland. Site of Special Scientific Interest (SSSI) designation protects more than 3,600 ha of habitat and Local Wildlife Sites a further 12,647 ha. In addition, there are undesignated chalk streams and parklands. The area is popularly known for its numerous red kites.

Geodiversity: The Chalk outcrop of the Chilterns filters and stores large quantities of high-quality potable water, making it a principal The Chalk produces water that is naturally mineral rich, sediment free and of a stable temperature and as such supports specialised chalk stream ecology. In the Thames Valley, large flood plain terraces create a distinct landform and comprise a valuable aggregate resource. Buildings have made use of Chiltern flint; a particular form of hard chalk called ‘clunch’ or Totternhoe; a conglomeration of flint and pebble called puddingstone; and red brick made from local clays (Chilterns Building Design Guide, Chilterns Area of Outstanding Natural Beauty, February 2010, second edition). Of the 14 SSSI designated for their geological interest, many are small-scale historical sites of mineral extraction, including brickworks, sand pits, gravel pits and chalk pits. There are 33 Local Geological Sites.