135 - Dorset Heaths : Natural Capital and Key Ecosystem Services

Introduction

The Dorset Heaths 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 Dorset Heaths NCA is contained in the ‘Analysis’ section 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.

Natural Capital Atlas Profiles

The following Natural Capital Atlas Profiles cover counties within this NCA:
 

• 10: Dorset
• 17: Hampshire and the Isle of Wight

Provisioning services (food, fibre and water supply)

Food provision: Cattle farming is the dominant agricultural activity, often with associated forage crops such as maize grown on the flatter ground. In recent decades many smaller dairies have closed and switched to beef. Since the 1990s, extensive grazing of beef cattle (and ponies) has again become a feature of many of the larger heathland blocks. Even more recently, salad vegetable production has emerged as a significant land use in the middle Frome catchment. Poole Harbour supports a regionally important shellfish industry as well as a small inshore fleet. The harbour is also an important nursery area for commercial fish stocks. A sika deer population, which is often excessively high bearing in mind the welfare of the habitats in which it lives, supplies a local venison market.

Timber provision: The bulk of commercial timber comes from plantations, mainly of Corsican and Scots pine, established by the Forestry Commission, the Ministry of Defence and some private estates in the first half of the 20th century. Corsican pine is presently subject to significant disease challenge by red band needle blight and is no longer considered commercially viable for restocking.

Biomass energy: In addition to the ‘lop and top’ from the commercial plantations, locally significant amounts of biomass are generated as a result of heathland management activities. It remains a challenge to find a way of making this material commercially useful.

Water availability: The Dorset Heaths are underlain by a chalk aquifer contiguous with the adjacent NCAs from which much of the public water supply is drawn. For information regarding the current state of water availability within this NCA, refer to the Environment Agency (Abstraction Licensing Strategy).

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

Climate regulation: Salt marsh is a very effective carbon store, and both of the harbours will be important in this respect. Heathland retains much carbon in both its above-ground dwarf shrub community and in the undisturbed humus that forms in the soil below. In wetter areas the heathland vegetation has accumulated and formed peat, creating widely distributed mires, which will be a locally significant carbon store – as will areas of permanent grassland on the deeper alluvial soils.

Regulating soil erosion: Soil erosion is evident from arable areas on the light sandy soils during high rainfall events. This problem is largely avoided under the permanent cover of semi-natural vegetation.

Regulating soil quality: Soil quality is likely to be stable under the permanent vegetation cover that predominates in this NCA.

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 of non-agricultural land is only an occasional problem in this NCA and is confined to a relatively small number of properties. Particular issues occur when high river flows coincide with high tides and the lower reaches of several of the rivers become tidally locked. The semi-natural vegetation of the heathland, and in particular
its wetter areas and bogs, is an important water-retaining and regulating system for the area. Where this has been removed or compromised it has sometimes been necessary to invest in flood prevention measures, for example on the Moors River below Verwood. The Bourne stream collects surface water flows from a large area of developed and impermeable land and tends to flood in its lower reaches during high rainfall events.

Regulating coastal flooding and erosion: The dune system at Studland is naturally mobile and changed dramatically during historical times but has now protected Poole Harbour for centuries. This mobility is part of the geomorphological interest of the NNR. The northern and much of the western parts of Poole Harbour are ‘defended’ by traditional hard-engineered solutions. In most locations these defences are fronted by narrow beaches or salt marshes that help to protect the defences against erosion. The coastline, mainly cliffs, from Poole to Hengistbury Head, is heavily defended in places and this has greatly slowed the natural rate of erosion, reducing significantly the supply of sediment from the coastal system in the process. For information regarding current shoreline management within this NCA, refer to the Environment Agency (Shoreline management plans).

Cultural services (inspiration, education and wellbeing)

Sense of place/inspiration: The most famous figure associated with this NCA is the author Thomas Hardy, who was born and lived until his death in the western end of the area and wrote evocatively about both its landscape and its people. Other literary and creative figures including J.M.W. Turner, Alfred Russel Wallace and T.E. Lawrence have been drawn to the area.

Sense of history: A landscape that human intervention started to forge many millennia ago now demonstrates how different waves of economic pressure and societal demand can wash over it, sometimes resulting in temporary change, sometimes permanently transforming it. There are rich historical associations and remains from the Bronze and Iron Ages, through the Roman and Saxon occupations to the rise of the British Empire and Britain’s emergence as a trading nation and world military power.

Tranquillity: Pockets of tranquillity exist within the larger heathland and forest blocks and, especially when intrusive uses are absent, within Poole Harbour. However, this NCA does contain a major conurbation and a military live firing range and is a honeypot for tourism.

Recreation: The easternmost 7 km of the 1,000-kilometre South West Coast Path are within this NCA, extending along Studland Beach. The principal recreational opportunities are on the beaches at Studland, Sandbanks and Bournemouth, within the harbours at Poole and Christchurch and on the gravel tracks in the commercial forests (increasingly a venue for mountain biking). The location of the heathlands near to the centre of population also provides valuable recreation opportunities and the potential to engage visitors to develop an understanding of this precious resource. However, some recreational uses of the heathland are acknowledged to be damaging to its special interest. There are three country parks, at Upton, Moors Valley and Avon Heath. The conurbation has a range of parks and other greenspaces of varying formality.

Biodiversity: The Dorset Heaths have several international conservation designations and, outside of the New Forest, are arguably some of the best examples of this habitat in the world. Representative species include Dartford warbler, nightjar, woodlark, sand lizard, smooth snake, ladybird spider, Purbeck mason wasp, southern damselfly, marsh gentian and Dorset heath. Poole Harbour is also a wetland of international importance and hosts an internationally important assemblage of winter wildfowl, including spectacular flocks of avocet and black-tailed godwit. The NCA has been an early host to several continental species as they spread northwards, notably little egret and Mediterranean gull.

Geodiversity: The surface geology for this NCA is relatively recent, predominantly Palaeogene sands. The cliffs at Studland show evidence of the Cretaceous/Palaeogene unconformity, as well as good exposures of Palaeocene and Lower Eocene deposits. Limited cliff exposures within Poole Harbour, for example at Ham Common, demonstrate early Eocene deposits, with mid-Eocene exposed at Poole Bay Cliffs and even more recent strata further east at Hengistbury Head. Slightly inland, late Eocene exposures are visible in now disused pits at St Catherine’s Hill. Creech Barrow, on the southern edge of the area, is the highest Palaeogene hill in England, with a unique early Eocene limestone capping featuring fossil plants found nowhere else.

Dolines – large craters caused by sub-surface solution of the underlying Chalk by acidic water from above – are visible at Cull-peppers Dish and Rinsmoor Pond. The more familiar geology is both much older (Jurassic) and much deeper (750 to 1,600 m) where the oil for the UK’s largest onshore oil field is trapped.

Coastal geomorphology and the geomorphological processes within Poole Harbour, including Studland dunes just west of Poole Harbour entrance, are of note. This is an accumulating dune system showing the relationship between geomorphological processes and ecological succession.