Definition

These habitats are derived from medieval forests, wooded commons, parks and pastures with trees in them. Subsequently, some had a designed landscape superimposed; usually during the 19th century. A range of native species usually predominates amongst the old trees, together with non-native species that have usually been planted. The Royal Parks are classic examples.

Defunct wood pasture is found where the traditional management of stock grazing is no longer practiced and where the trees are no longer pollarded to provide timber or fodder. They may include a landscape history of commoners’ rights and forest rights. A typical example is Epping Forest.

Parklands are the typical open landscapes with scattered trees. They may include a history of having been enclosed and managed as deer parks, Royal hunting grounds or formal public and private open landscapes.

There have been no previous comprehensive surveys of this resource. There are many difficulties in trying to establish the extent of this habitat type due to it’s complex composition. It has, therefore, been very difficult to identify discrete areas of open landscape with ancient/old trees. Many areas of former wood pasture, for example, have developed into closed canopy woodland since the cessation of grazing and the natural character of some former wood pasture or deer park has been lost as a result of subsequent landscape planting or conversion to more formal urban parks. On the rural fringes of London some of this habitat may have been lost via conversion to farmland. Table 1 and the Map summarise the extent of this resource within the limitations outlined above.

Although not included within this audit, the city squares in the City of London and boroughs such as Islington, Kensington and Chelsea and Westminster support significant numbers of mature trees, particularly London Plane Platanus x hispanica. This species is not noted for its nature conservation value.

It is important to stress that this audit deals specifically with ancient/old trees found within open landscapes as opposed to an audit of individual ancient/old trees. Clearly ancient/old trees occur within several other habitats, particularly within the more formal parks and open spaces which are not covered by this audit; in woodlands, old hedgerows and within larger gardens of low-density suburban housing.

The old trees and dead wood components of wood-pasture have some similarities to the original ‘wildwood’. These sites are frequently of national, cultural and landscape importance. The great number and continuity of ancient/old trees and associated dead wood habitats within these areas are outstanding at a European scale and this habitat is most common in southern Britain. Pedunculate oak Quercus robur is the most common tree associated with this habitat although others, particularly sweet chesnut Castanea sativa, are associated with this resource in London. However, in former deer parks and wood pastures, which have subsequently been, landscaped, exotic tree species (particularly London plane) often greatly outnumber the native oaks.

Parkland and wood-pasture habitats are particularly of value for the fungi, lichens, and insects associated with ancient/old trees and decaying timber. Several species of insect such as the click beetle Ampedus cardinalis and the cranefly Ctenophora pectinicornis which are confined to the deadwood habitat in the trees. Isolated oak trees may also support colonies of the purple hairstreak butterfly.

Open landscapes with ancient/old trees support a wide variety of bird species that are typical of both woodland and grassland habitats. However, green woodpecker, kestrel and nuthatch are species with a particular affinity for this habitat type. Mature trees and open habitats may also be of significance to bats, which may utilise them as roosts sites and as flight line features in the landscape.

Threats
The major threat to open landscapes with ancient/old trees is the cessation of traditional management, particularly grazing. Most sites in London are no longer managed in this way although deer still graze Richmond Park and Bushy Park. The remainder of this habitat in London is maintained by mowing, which is a much less sympathetic management regime. In addition to the lack of grazing, many mature parkland trees are managed inappropriately from a nature conservation point of view, by the removal dead and decaying limbs and the clearance of fallen or standing dead wood.

Open landscapes with ancient/old trees are, by definition, habitats with a well-established presence in the landscape. This is itself a threat to their survival as it is often forgotten that they are essentially human-created landscapes that need to be maintained by human intervention. New generations of trees need to be planted (or naturally regenerating saplings protected from mowing or grazing) as long-term replacements for extant mature specimens.

A less obvious threat, but one which may adversely affect the diversity of sensitive species such as lichens and fungi living on the mature trees, is air pollution. It is well known that many lichen species are sensitive to air pollution and their loss, or failure to re-establish themselves, may have unforeseen consequences for a wider range of species which may be dependent upon the lichen communities.

Poor management of these sites is linked with a poor understanding of their nature conservation value and a concern for public safety. There is a widespread and mistaken belief that dead wood is bad for the tree and a public hazard.

Opportunities
Most of the resource in London lies within areas of protected open space. However, this does not necessarily ensure effective nature conservation management, as the protection is aimed mainly at maintaining the recreational and aesthetic attributes of habitat. However, under the auspices of the Veteran Trees Initiative, better management of ancient and old trees for nature conservation is being promoted. A number of sites around London provide examples of successful re-introduction of pollarding, planting of replacement trees, and resumption of grazing management. These techniques could be readily translated to sites within London.

The old parklands in London are among the most popular places visited by Londoners and tourists alike. Most informal recreational activity is compatible with maintaining the nature conservation of these sites and, therefore, there are opportunities for raising awareness about park management that integrates biodiversity conservation, landscape maintenance and recreational demand. Awareness-raising programmes could focus on the conservation work for some high-profile species such as the stag beetle, bats and woodpeckers.

Local communities could become involved with the conservation of this habitat by collecting and propagating local seed (from oaks and other appropriate trees) for eventual planting out to provide future generations of parkland trees.

The moss and lichen communities on ancient and old parkland trees may provide a useful biological indicator for air quality in the city. Recovery of fungi, mosses and lichens on the trees is related directly to reductions in nitrogen dioxide and sulphur dioxide in the air. As a better understanding develops of the potentially damaging effects of climate change on trees (for example drought stress), people may develop a better appreciation of their own responsibilities in terms of air pollution and water consumption. This would provide a link between the London Biodiversity Action Plan and other environmental initiatives.