Threats to wood pasture and parkland
These habitats and their features are increasingly rare and face many threats. They are suffering from landscape fragmentation becoming disconnected from other woody habitats, conversion to commercial forestry or ploughed agriculture, development, and neglect. Also a threat from increasing numbers of Festivals and big money raising events. On top of this the impact of climate change, pollution and tree diseases, threaten the core features at the heart of this habitat; the veteran trees.
Direct loss through conversion
pasture sites are prone to being partially, or sometimes wholly converted to
other land uses, all of which change the essential characteristics of the site
and reduce their value to the wildlife wood pasture supports.
Common among these are conversion to forestry, the closely planted trees of which shades out the open habitat (could be grass or heathland) making it unsuitable for the higher/vascular plant, scrub and fungal communities that thrive in more open setting. It also shades the trunks of the veteran and ancient trees putting them and the wildlife communities which depend on the unique habitat niches which they support, for example lichens and bryophytes, under stress.
Arable farming disrupts the soil structure, which in some wood pasture sites will have been undisturbed for centuries. This alongside the addition of extra nutrients and other chemicals (fertilisers, pesticides, herbicides) can kill off the soil fungi typical of old undisturbed ground, such as wax caps and mycorrhizal fungi on which tree health depends. Even where old trees are retained, often the lower limbs -essential for the survival of the trees in its later stages of a trees life- are removed for vehicle access, and they tend to be ploughed far too close to the tree which damages the roots and again reduces the life span of the tree.
As wood pasture and parkland sites are lost, converted, developed or neglected, the remaining sites become more and more isolated.
Unfortunately, many of the specialist species that live in these ancient trees are poor at dispersing over long distances, meaning they are not only losing vital habitat but becoming isolated populations, unable to travel or breed with other populations. This puts them at even greater risk of extinction as isolated populations are more vulnerable.
Poor tree care
Open grown trees tend to have large limbs low down on the tree trunk. This structure provides a variety of important niches for wildlife. These lower limbs are sometimes removed for agricultural reasons or machinery access. Removal of these limbs not only takes away a great habitat, but can reduce the life of the tree; without without them the trees can be more top heavy and prone to windfall, and may reduce their capacity to survive into ancientness, where their crowns retrench and they rely on branches lower and closer to the trunk.
In many sites open to the public, deadwood is tidied away, even whole trees of great character and interest are removed, often thought of as unsafe. This can remove a substantial amount of the rare deadwood habitat that these trees are so valuable for.
Lack of management
Without management, sites are at risk of
becoming overgrown and turning into secondary woodland, losing their
characteristic open structure. This can quickly lead to the demise of the veteran
trees which are less able to tolerate being shaded.
Open grown trees develop an entirely different shape and structure than those growing in a woodland. This structure and veteran features makes them better at supporting wildlife.
Trees grown in open habitats (such as wood pasture or parkland) are more likely than forest trees to reach their full life potential. Longer lived trees means more decaying wood which is one of the rarest and most cherished micro-habitats that ancient trees in wood pastures support. With the help of some fungi, the heart of old trees slowly decay. This decay happens in stages, with each and every stage having different species depending on it. The last stages of this decay process are so uncommon that many of the species that rely on this micro-habitat are now at risk of extinction.
The presence of grazing animals is a fundamental aspect of wood pasture maintenance, but the balance of stock needs to be carefully struck so as not to over or under graze a site. When over grazed, or grazed with the wrong type of animal for the site, this can cause damage to the trees, the soil and can also affect the scrub levels as well as removing essential invertebrate nectar sources. Scrub is not only vital for much of the invertebrate life that wood pasture is home to, but also can act as tree nurserys for the natural regeneration of trees.
If grazing levels and timings are right providing supplementary food should be unnecessary, which is good because it adds nutrients to the grassland, damaging both fungal and plant diversity.
Lack of re-planting or natural regeneration
wood pasture and parkland sites have been providing an incredibly rich habitat,
often for hundreds of years, offering exactly the continuity that specialised,
rare, low dispersing species require. If this continuity is broken for any
reason and the deadwood and lichen species are lost, it is difficult to recreate
the same diversity of fauna that is lost. In Britain, there are concentrated
pockets of these of rare deadwood-dependent communities living in historic parkland
and open wood pasture where the continuity of their habitat has remained
unbroken for centuries.
Key to this continuity is having trees of all ages on a site, so that when the ancient ones inevitably die, there is an appropriately old tree with the requisite veteran features nearby to take its place. In reality this means trees of all ages are required to ensure this continuity hundreds of years into the future.
Lack of public recognition
Unlike other habitats such as ancient woodlands and meadows, wood pasture and parkland is difficult to describe and is poorly recognised by the general public, and the vital contribution to sustaining our wildlife they provide. Our conservation task is a greater challenge as a result.
On top of this there are, more wide-scale and unpredictable threats from climate change, pollution and tree diseases.
Visit the Woodland Trust website to learn more about tree disease