So what is an ancient woodland? Ancient woodland is designated as being land which has been continuously wooded since AD1600 in England and Wales, or AD1750 in Scotland. These dates mark the beginning of reasonably accurate historical information on local land use, often in the form of estate maps.
Ancient woodland is divided into ancient semi-natural woodland and plantations on ancient woodland sites. Ancient Semi-Natural Woodland sites are composed predominantly of trees and shrubs native to the site, which do not obviously originate from planting. Ancient Replanted Woodland sites are areas of ancient woodland where the original native tree cover has been felled and replaced by planted stock.
Not all ancient woodlands will have historical records, and so we need another method in order to try and determine whether a particular woodland is ancient.
Ecologists have compiled lists of plant species that favour ancient woodland sites. These lists were complied by surveying a number of these ‘proven’ ancient woodlands, i.e. those with historical records. Species which are usually confined to this type of habitat are identified and, by assessing the number of these indicator species present in a particular wood an educated guess can be made as to whether it is an ancient woodland site or not.
The indicator species chosen are more commonly plants rather than animals. This is because plants are usually conspicuous, relatively easy to identify and do not hide themselves! However, an example of an indicator species which not a plant is the Lemon Slug. This slug feeds on fungi that break down dead and rotting wood, which is something an ancient woodland should be full of.
Lists of indicator species vary according to geographical location. This means that a list specifically worked out for North East England must be consulted if the survey is being carried out in Durham. A list compiled in South East England, for example, may give completely erroneous results in other areas of the country. This is because local geology, soils, climate and history of land use will all influence the plant species present and their ecological distribution.
In addition, the presence of a few relevant indicator species does not mean that the woodland should be designated as ‘ancient’. In general, the greater the number of Ancient Woodland Indicator species occurring together in a wood, the greater the probability that a woodland can be accorded this status. Most ancient woodlands surveyed to compile the list for Durham contained 20 or more indicator species.
So what should you be looking out for next time you walk through a woodland in Durham? More common indicator species include Ramsons (wild garlic), Wood Anemone, Dogs Mercury, Wood Sorrel and Bluebell. Most of these will carpet the woodland floor and are difficult to miss. Wood Sorrel has heart-shaped clover-like leaves and small white flowers, which close and droop when it is wet. Ramsons smell strongly of garlic, and you can often smell this ancient woodland indicator before you actually see it. Take care when using Bluebells as an indicator species because our native plant can be easily confused with the Spanish variety and these two varieties can also interbreed.
A rare indicator species is Herb Paris, which is found in only 6 areas in County Durham including Teesdale and Coastal Denes. This plant is incredibly slow growing and does not set seed easily. Both of these factors mean that it does not colonise new woodlands easily so can only be found in some of the oldest woodlands in our area.
Every single ancient woodland is unique and over flowing with wildlife. Each one has taken hundreds of years to develop and each one is irreplaceable.