In England and Wales ancient woodland is defined as an area which has been wooded continuously since 1600 and in Scotland since 1750. Ancient woodlands have been mostly undisturbed for many years and have a high ecological value. Reasons for this stem from the slow changes that have occurred over many years. Leaf litter falling and building up on the forest floor over a long period of time creates special conditions, holding communities of fungi, bacteria and dormant seeds. These components of ancient woodland are unseen to the human eye but play a vital part within a complex food chain. Mature trees have the ability to hold a huge amount biodiversity. As trees get bigger they get a larger surface area which can then be colonised by other plants. As the tree ages it also gets more fissured bark and caverns in the trunk and some parts of it may die which create rot and deadwood habitats. As a tree gets older the amount of these types of characteristics increase which in turn increases the numbers of species it supports.
A vast array of invertebrates are supported by the stable conditions and variety of habitats within ancient woodland which then become food for birds, bats, reptiles, amphibians and mammals. As a result meso-predators and apex predators also have a food source. As a result ancient woodlands support whole ecosystems and they support more threatened species that any other habitat.
One way of identifying ancient woodland is by looking at the ground flora. There are over 200 plants which are known as ancient woodland indicator species. Depending on geographical location the presence of these species and their abundance are a sign that the woodland is likely to be ancient.
Species including; ramsons Allium ursinum, opposite-leaved golden-saxifrage Chrysosplenium oppositifolium, wood anemone Anemone nemorosa and native bluebell Hyacinthoides non-scripta are among those classed as ancient woodland indicator species.
These easily identifiable species are used as indicator species as they are much slower to colonise and therefore, less likely to be in a new woodland. They are less likely to grow outside of woodlands where they are more exposed as they require the shade and stable conditions inside of woodland. However, looking at plant species which are present isn’t the only way to distinguish new woodland from ancient woodland and indicator species are also not confined to growing within ancient woodland.
Historical evidence of human activity such as wood banks and old maps can be a good way of finding out how old the woodland is. Another useful tool is the ancient woodland inventories which have been created for Scotland, Wales, Northern Ireland and England; these can be viewed online. This shows information about where semi-natural ancient woodland exists and where ancient woodland sites historically existed but have subsequently been re-planted with non-native species.
Our ecologists recently visited a site in south Wales where there were ancient woodland indicator species within the ground flora. Upon checking the ancient woodland inventory for Wales it was confirmed that there was ancient woodland at the site. The team are now working towards methods for mitigating woodland which could be lost during a road widening scheme. This may include the following; woodland creation, planting native species, translocation of some trees, coppicing, translocation of topsoil, translocating deadwood and collecting seeds from trees to be used in woodland creation.