TREES – IN HABITAT – AS HABITAT

1. TREES – IN HABITAT – AS HABITAT Issues, considerations, suggestions Brian Crane, November 2006

2. Contents • Tree habitats • Trees as habitat • Management considerations and options Marble Hill Park, London Brian Crane, November 2006

3. Aims • To examine the factors which should inform any prescription for tree management • To suggest outline guidance for determining management objectives and implementation Marble Hill Park, London Brian Crane, November 2006

4. Tree habitats Trees grow in different habitats. It is important to recognise this as the place where a tree is growing will have a major influence on its future management. Tree habitats divide into two main groupings: • Urban i.e. built-up, developed areas • Rural areas Brian Crane, November 2006

5. Urban areas - towns and cities • Highways and transport infrastructure areas • Housing areas • Parks and gardens • Commercial and industrial areas • Schools • Settings for historic buildings Champs Elysee, Arc de Triomphe, Paris, 1944 Brian Crane, November 2006

6. Urban areas bring man and tree into closest conflict (1) • Safety • Need for management increases with intensity and sensitivity of site use (e.g. children’s playgrounds) • Will increase with age of tree • Will increase according to past tree management (e.g. pollarding) • Interference with services • Overhead • Underground • Highways - sight-lines, sign clearance, street lights Champs Elysee, Arc de Triomphe, Paris, 2005 Brian Crane, November 2006

7. Failed Aesculus hippocastanum High Wycombe, Buckinghamshire, England Brian Crane, November 2006

8. Failed Aesculus hippocastanum • Tree growing adjacent to a public car park • Inspected a few weeks earlier by contractor who failed to realise urgency of need for work • Embedded branch junction failed, damaging car and injuring driver • Tree owner completely at fault High Wycombe Brian Crane, November 2006

9. Urban areas - conflicts (2) • Inhospitable growing conditions: • Soils • Pollution – air, water • Mechanical damage • Poor management/lack of management • Management costs • Difficulties of managing a large and changing resource, some of which is not in public control La Defence, Paris Brian Crane, November 2006

10. Urban areas - conflicts (3) • Pressure for more space – development • Above and below ground pressures • One tree may be a habitat in itself, rather than forming part of a grouping Notting Hill, London Brian Crane, November 2006

11. The urban situation • Managed trees • High maintenance input • Multiple problems • Historic considerations Brian Crane, November 2006

12. Trees in urban areas are often the most highly prized • They soften the built environment • They add relevance to development • They provide visual links between differing landscape types and uses • They provide a scale to which humans can relate • They contribute to a ‘sense of place’ • They influence local micro-climate Nottingham, England Brian Crane, November 2006

13. Urban areas - clear conflict……… • Highly prized trees • In areas where they are under pressure HOLD THIS THOUGHT!!!!! Brian Crane, November 2006

14. Rural areas – tree habitats • Forests (economic) • Woodlands (amenity and multi-use) • Farmland • Hedgerows • Transport systems • Roads • Rail • Waterways Suffolk, England Brian Crane, November 2006

15. Rural areas • Pressures on trees generally less severe • Land use for people less intensive • Environmental conditions usually less degraded • Trees can form part of a habitat grouping, rather than being the sole habitat THE INDIVIDUAL TREE MAY BECOME LESS IMPORTANT Brian Crane, November 2006

16. Tree habitats - summary • Urban areas – • fewer trees, each individually prized for its landscape, social and wildlife conservation values • need to maintain trees in a safer condition • greater potential for conflict • Rural areas- • more trees, each less valuable individually • safety parameters expanded • value as part of a grouping rather than as individuals Brian Crane, November 2006

17. Trees as habitat A tree may be regarded as a large volume of ‘greenspace’ held conveniently above head level. It has the potential to contain a number of varied (and in some cases, rare, habitat types). • Leaves • Fruit • Buds • Flowers • New growth • Bark • Conducting tissue • Rooting zone • Cast detritus • DEAD WOOD Brian Crane, November 2006

18. Trees have a number of features which make them particularly valuable as habitat They live to considerable age They achieve very large sizes They have a large surface area to volume ratio They offer a range of differing shelter and food sites These change………… Trees as habitat Brian Crane, November 2006

19. Trees change…..as they age, they provide different, specialised habitat sites • Holes in branches • Cavities, • Dead wood • Crevices in bark • Fungal fruiting bodies • Water pools • Sites for ephiphytic plants • Loose bark • Cast dead wood • Sap runs Photo Roy Finch Brian Crane, November 2006

20. Burnham Beeches, Buckinghamshire, England. Photo Roy Finch Brian Crane, November 2006

21. Old, apparently dilapidated trees are very valuable in wildlife terms An important feature is the presence of dead or dying wood – this provides the habitat for some very specialised invertbrates which cannot survive elsewhere – they are called saproxylic organisms. Some species of beetle are particularly important and are threatened because of the absence of dead wood. Brian Crane, November 2006

22. We are now faced with a dilemma (1) • Man requires that trees are kept: • Safe • In pleasing aesthetic condition • That landscape features such as avenues are maintained • That infrastructures work • That risk of disease insect colonisation is minimised • That everything is TIDY!!!!! Brian Crane, November 2006

23. We are now faced with a dilemma (2) Wildlife conservation (biodiversity) and the conservation of many threatened species requires: • That we allow things to decay and become potentially dangerous • That we leave untidy detritus • POSSIBLY, that we CREATE conditions for colonisation by organisms WE HAVE CONFLICT !!!!!! Brian Crane, November 2006

24. Dangerous branches over house SE, 2006, photo De Gouret Brian Crane, November 2006

25. Suspect, dead pollard close to railway line (DG) SE, 2006, photo De Gouret Brian Crane, November 2006

26. Stumps in conifer plantation SE – responsible for infestation of bark beetle in standing crop (DG) SE, 2006, photo De Gouret Brian Crane, November 2006

27. Creating ’old’ trees (1) There is a current ’trend’ towards creating habitat niches in healthy trees which would otherwise not be there until they aged. This can be done by deliberate injury: • Spiking live trunks • Deliberate tearing of branches when pruning • Creating pollards from established trees Brian Crane, November 2006

28. Creating ’old’ trees (2) This may be justified BUT we must consider the situation: Aesthetics • Landscape • Historical implications Safety • Position • Liability Brian Crane, November 2006

29. Photo DG, 2006 Brian Crane, November 2006

30. Creating ’old’ trees (3) Will the process be effective? • Will the protected organisms colonise the tree? • Use of native species • Is the protected species sufficiently threatened? • Will the wrong species colonise the tree • Is there a risk that diseases or pests will proliferate? Ethics – • is it right to damage a healthy organism? • Is it right to shorten the life of a tree which might give pleasure to future generations? Brian Crane, November 2006

31. Need for an assessment methodology • Unconsidered retention or creation of dangerous trees is irresponsible • There is a clear need for specialised habitats for the protection of endangered species • A methodology for assessment should consider: • The tree • The landscape • The people • The wildlife Brian Crane, November 2006

32. THE END Thanks for your attention Brian Crane, November 2006