B: Ancient woodland information

What information does the survey provide and why does it matter?

Native Woodland Survey of Scotland has surveyed all native woods and near-native woods currently present on ancient woodland sites, as well as all otherplanted woods on ancient woodland sites (PAWS).

Ancient woodlands usually have ahigh value for natural and cultural heritage because of their long history of continuous woodland cover. Ancient and semi-natural woods (i.e. those where the current stands appear to be naturally regenerated rather than planted) are the woodland category that generally has the highest biodiversity value.

Area changes compared to the existing ancient woodland inventory

In the local authority reports the NWSS data has been compared with maps of ancient woodlands from the Scottish Ancient Woodlands Inventory (SAWI) link to an external site) carried out in the 1980s, in order to identify the current status of woodlands on these sites. The results are shown in tables in the reports.

All woods that are currently native or nearly-native in composition, plus all other woodlands on areas classed as planted woods on ancient woodland sites, will have received afull survey. Some other areas, that were marked as ancient and semi-natural woods on the SAWI, will not have been surveyed in full under NWSS.

This may be because, at the time the aerial photographs were taken, these areas were not woodland, or they were felled or awaiting replanting. Alternatively some may have been visited and found by surveyors to be wooded, but with less than 40% native species.

The SAWI was published as a provisional inventory, as it was based mainly on map records and photographs and was not verified by field survey. The NWSS therefore gives usthe first national update and picture of the current status of ancient woodlands. And it will provide insights into what has changed in the quarter century since the SAWI was compiled, as well as correcting errors in the original SAWI maps.

There will be cases where apparent changes are due to mapping errors in the SAWI data and others where genuine changes have occurred, e.g. loss of ancient woodland.

NWSS has also collected data on sites where recent woodland loss has occurred between the date when aerial photographs were taken and the survey visit. Surveyors have recorded a view on likely cause of any loss eg from various forms of development. This will help us understand the extent and causes of recent loss of ancient and native woods.

Ancient and semi-natural woodlands (ASNW)

NWSS provides current information on Ancient and semi-natural woodlands and so updates the information in the SAWI. ASNW are often described as the most important single category of woods for nature conservation or biodiversity.

The NWSS data on semi-naturalness relates to current stand structure and composition. A wood scores highly for ‘semi-naturalness’ if it has a diverse structure and composition and an absence of indicators of planting such as cultivation, straight lines of trees or geometric shaped stand boundaries.

Woods like these are likely to have ahigher biodiversity value than more uniform planted woods.

A high semi-naturalness value in NWSS also suggests that a wood has been largely or entirely naturally regenerated, but this cannot be said with certainty without documentary evidence. It is possible to create an irregular structure in a planted wood by management such as irregular thinnings, or by chance events (e.g. windthrow) and prolonged low intensity management.

The reports show what proportion of ASNW areas that were identified in the SAWI are currently native or nearly native woodland. And for the native ancient woods the NWSS reports show a breakdown of semi-naturalness classes (0-20%, 20-40% etc). Users could also analyse data to generate reports on other aspects of polygons within selected semi-naturalness classes.

Planted woods an ancient woodlands sites (PAWS)

The survey provides full information on the composition and structure of ancient native woods (and nearly-native woods), and also for other areas of planted ancient woods that were identified in SAWI. This information is valuable to help planning of work both to improve the condition of current ancient native woods for biodiversity, and to restore PAWS areas that are now mainly composed of non-native species back towards native woodland.

For example, PAWS with a high proportion of shade-casting species like Sitka spruce might be suitable priorities for work to increase the proportion of native species and reduce shade to benefit remaining woodland ground flora.

Policy relevance

Conservation of ASNW and restoration of the biodiversity of planted woods on ancient woodland sites are priorities in theScottish Forestry Strategy andScottish Biodiversity Strategy, and both have adopted UK Biodiversity Action Plan (UKBAP) targets for restoring PAWS to native woodland. Scottish Planning Policy recognises the high value of ancient woods and semi-natural woodlands for nature conservation.

How can the NWSS data be used?

Type of useNationalRegional/local authorityLandscape/site scale
Assessing the area of native woodland on ancient woodland sites and its composition and condition Yes Yes Yes
Assessing change from 1980s in the area, type and composition of ancient woodlands Yes Yes Yes
Updating the SAWI Yes n/a n/a
Planning action strategically or locally Yes Yes Yes