137 - Isle of Portland : Natural Capital and Key Ecosystem Services

Introduction

The Isle of Portland 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 Isle of Portland NCA is contained in the ‘Analysis’ section of this website.

The complexity of interactions across these ecosystem services and across adjoining NCAs means that the summary provided here requires further refinement and analysis of evidence at a more local scale.

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

Provisioning services (food, fibre and water supply)

Water availability: Rainfall percolates through the Purbeck and Portland Bed limestones, forming an unconfined aquifer underlain by Kimmeridge Clay. The limestones are isolated to the island by erosion and thus the aquifer is also isolated to the island. Portland therefore does not supply adjacent NCAs with potable water, and there is insufficient groundwater to use domestically on the island. There are springs on Portland, which are important in that they support SAC vegetation assemblages. For information regarding the current state of water availability within this NCA, refer to the Environment Agency (Abstraction Licensing Strategy).

Genetic diversity: A rare breed of sheep originates from Portland, and a wild relative of the cabbage is found here.

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

Climate regulation: Biological carbon storage in this NCA is very limited because of the general lack of mature woodland and wetlands and because of the thin soils that cover this limestone plateau. The carbonate rocks of which Portland is composed locked up large quantities of carbon during their formation.

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 coastal erosion and flooding: Portland shelters Weymouth Bay and land to the east from westerly storms and waves. This is probably the most important service the NCA performs. Chesil Beach performs a natural flood defence against storm waves, protecting the low-lying village of Chiswell. This offers only a low standard of protection, with manmade defences providing some improvement. 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: A sense of place is provided by rugged cliffs, which are designated as part of the Jurassic Coast; by active and disused quarries; by drystone walls; and by the vernacular building stone. There are inspiring views across to the mainland along the Jurassic Coast World Heritage Site and along the cliffs of the island and across Fortuneswell to Chesil Beach and the Fleet. Seascapes from the island can be imposing, especially during stormy weather, and the seascape of the Portland Race can be spectacular in high winds, as can the swell waves generated in the Atlantic running up Chesil Beach during a storm.

Sense of history: Portland has a strong sense of history from the Mesolithic to the late 20th century. There are important Mesolithic sites near Portland Bill. The Romans occupied the island. The castle was commissioned by Henry VIII. Agricultural history is recorded in the relict field systems at the south of the island. The prison, an imposing presence on the island, was a Victorian fortress and presents a number of military features, for example the moat and gun emplacements. More recent history has seen the building of the harbour in the 1800s, and there are important military installations dating from that point onwards.

Tranquillity: Some of the relatively remote spots on the island, mainly in East and West Weares, can be tranquil in calm weather.

Recreation: More than 13 per cent of the island is classified as being publicly accessible, and the South West Coast Path National Trail extends around the perimeter. Visitors and residents benefit from the many rights of way. Access has recently been increased by the definition of coastal access.Watersports such as windsurfing and kitesurfing take place in the harbour. Portland is famous for its geology and is part of the Jurassic Coast World Heritage Site. Tout Sculpture Park includes The Falling Man rock carving by Antony Gormley. Birdwatching is popular, with Portland Bill being very important for migrant birds. Portland is a significant site for people interested in natural history, most notably for botanists and entomologists. There are opportunities to involve local people in access and wildlife management.

Biodiversity: International and national nature conservation designations currently cover the coastal cliffs and part of the inland area. One of the two SAC, most of the coast and part of the inland area are also designated as SSSI. There is a mosaic of local wildlife sites on the island.

Geodiversity: The steep, rugged cliffs and landslips expose an outstanding geology (including rich stratigraphy and fossil assemblages) and support important wildlife habitats (such as rare lichen communities and migrating birds). The area also features the South Coast’s most important raised beach, which provides valuable information about past climates and sea-level change.

Chesil Beach is vitally important in protecting communications and infrastructure connections to the island by shielding the lower part of the island on the north side from storm wave flooding, and in providing an internationally important nature conservation resource.

The entire island is also part of the large structures, created during the Alpine Orogeny, that act as a dominant controlling factor in the landscape character of much of the Dorset Coast. Fossil flora include the tree now standing outside the Portland Heights Hotel and the stromatolites that formed around fossil tree trunks in what is now King Barrow Quarries. The ‘roach stone’ is rich in fossil fauna, including the Portland Screw. Portland is part of the Jurassic Coast World Heritage Site, and provides opportunities for study and research. Portland stone has been used for building many of the most important and best-known buildings in England, including St Paul’s Cathedral and many of the government buildings in London. Many buildings on the Isle are also built from this material. Portland Museum holds an internationally important collection of fossil cycads found on Portland, as well as a rare freshwater turtle fossil from the Portland stone. It also holds a representative collection of fossils from Portland.