HARRAWAY TREE SERVICES
Tree Management and Training VAT 620 9197 42
John Harraway F Arbor A, MICFor, Dip Arb (RFS)
33 Freshbrook Road, Lancing, West Sussex, BN15 8DF
tel/fax: 01903 756153 mobile: 07831 651090
e-mail: [email protected]
Member of the Expert Witness Institute
An Overview of the Use of Trees on Go Ape! Ropes Courses
1. Scope:
Go Ape has operated ‘tree-top adventures courses’ in the UK since 2002; currently a total of
28 sites are in operation across the UK and a total of some 500,000 people attended these
sites during the 2012 season. Of central importance to the success of these sites is the
continuing management of all trees within them. Go Ape pioneered the use of trees for
adventure ropes courses in the UK and for over ten years has provided healthy activity in a
natural environment for millions of people. This document provides an overview of how trees
are used and how construction methods and operating systems are designed especially to
minimise the impact on their long term retention.
At present, fourteen sites are with Forestry Commission England, 1 with Forestry
Commission Wales, 2 with Forestry Commission Scotland, 4 with Councils, 4 with private
landowners (including a well known Safari Park), 1 with National Trust Scotland, 1 with
United Utilities and 1 on Crown Estate land. The majority of these sites (19) comprise
coniferous woodland, four sites are mixed broadleaf and conifer woodland, three are mostly
conifer but with some broadleaf trees and two comprise all broadleaf trees. Typically a total
of 40-50 trees are utilised to construct each site and thus represent a very small percentage of
the number of trees and area used at each location.
3. Installation methods:
Each set of aerial crossings on a Go Ape site comprises a secured rope ladder to a platform on
the stem of the tree and a variety of crossings constructed around cables between each tree;
each course terminates in a ‘zip slide’, usually along a cable anchored to a tree. Methods of
attachment to the tree must be secure, capable of ongoing inspection and maintenance and of
course minimise any long term effects to the tree. Historically, similar sites have often used
invasive methods of attachment with metal fixings screwed into the stem or inserted through
drilled holes. From the onset, these methods were rejected because they involve physical
damage to the fabric of the tree (and conceivably offer a conduit for colonisation by harmful
organisms, such as bacteria and fungi) and severely limit the opportunity for continuing
inspection of components. Additionally, such fixings could foster an impression of
exploitation of trees and a lack of concern for their individual integrity. Accordingly, Go Ape
has opted for non-invasive fixings, capable of visual inspection and adjustment.
Platform construction comprises planks placed on the upper side of wooden cross-beams
clamped to either side of the stem and held in place by threaded rod that is tensioned from
either side by washers and hexagonal nuts. Planks laid adjacent to the stem are sawn to
provide a gap all around the stem, thereby avoiding constriction.
Cable fixings involve wraps made around the stem that are secured with a system of rope
clamps (WRG’s wire rope grips or swaging). Protection of the stem is provided by inserting
full-round wooden battens underneath the cable wraps. Cable tension may result in some
flattening and distortion of the battens but constriction of the stem is prevented. During
construction battens are held in place with nails into the stem while cables are installed.
However, no loading is placed on the nails and penetration is kept to a minimum.
Living trees are constantly enlarging in a radial direction as well as axially and incremental
growth can cause clearances around platforms and cable wraps to be reduced. Accordingly
continuing inspection is used to identify areas of constriction and timely remedial action can
then be taken. This can involve any of the following; re-laying planks on platforms, reclamping platforms, re-tensioning and re-positioning cable wraps and replacement of wooden
battens.
Inevitably some distortion of incremental stem growth can occur in the immediate vicinity of
cross-beams and battens. In some instances this has become quite pronounced but no trees
have been noted as suffering any decline in physiological health or have developed structural
defects as a result of localised distortion; this includes some trees that have been in continual
use for ten years. Some coniferous species (such as Spruce and Douglas Fir) are prone to
resin production in response to the surface pressure produced by cross-beams and battens but
this often occurs soon after installation and ceases thereafter.
As part of continuing research into the possible effects of course installation on individual
trees, a number of ‘retired’ trees have been retained on sites to monitor their health. All
appear to thrive, despite some exhibiting significant localised distortion. A number of large
Douglas Firs recently retired from use on the original Go Ape site at Thetford, Norfolk, were
felled and dissected by our arboricultural advisers (Harraway Tree Services) to examine
possible internal dysfunction. It was apparent that even after ten years’ service no dead or
decaying tissue was present and growth processes, such as callus repair tissue, were vigorous
around areas of previous constriction. Some localised disruption of phloem tissue within the
bark layer (and hence the flow of nutrients from the foliage) was inevitable but this appeared
to have no general effect on the trees’ continuing health and development.
Methods of crossing construction are constantly reviewed and compared to systems used by
other service providers in the UK and across Europe and beyond. If alternative methods that
further reduce the long term impact of courses on trees become apparent, they will certainly
be considered in future construction.
Course construction involves linking up 5 or 6 sets of typically ten trees; this obviously alters
their individual bending response to wind. However, no detrimental effects, such as stem
fracture above the point of attachment or combined wind-throw have occurred. At one site
course trees actually remained stable whilst those around them blew down. One site was
severely damaged but the severity of the storm was such that all trees in the vicinity were
destroyed.
4. General Woodland Impact:
Construction methods and siting of other course features, such as footpaths and cabins, are
designed to minimise their impact on individual trees and the general environment. Footpaths
are typically constructed with brushwood chippings or other porous materials such as crushed
stone. Natural material on site, such as brushwood from clearance operations, may be used to
hinder access to environmentally sensitive or potentially hazardous areas.
Development of each new site is subject to local authority and national planning legislation
and control; tree surveys and reports (to BS5837: 2012 Trees in relation to design, demolition
and construction – Recommendations) are produced if required. Work to trees on site is
carried out in accordance with the BS 3998: 2010 Tree work – Recommendations.
Each of the sites used by Go Ape is the location of other established outdoor pursuits, such as
walking, running and cycling. The general effects of increased footfall are mitigated by
designated parking areas and footpaths, as well as other facilities such as toilets and cafes.
5. Tree inspection regimes:
Trees are natural structures and in addition to continuing growth processes they can be
subject to pest and disease colonisation and physical damage from the natural environment or
sudden physical impact. To ensure their healthy and safe condition a regime of continual
routine and specialist inspection is in operation. Site staff monitor trees as part of daily site
inspection procedures; in addition, site managers undertake a monthly recorded inspection of
all course features including trees. Any queries or observations arising are forwarded to area
mangers and a designated member of management with arboricultural experience.
Go Ape also uses the services of an independent arboricultural consultancy practice to
provide expert advice on tree health and safety as well as annual inspections of all sites across
the UK. The use of a single source of arboricultural input since 2005 has resulted in a buildup of specialist knowledge and experience in the use of trees on ropes courses. The company
also provides initial advice on tree selection and suitability at course construction stage, in
line with the recommendations contained in the European Standard for Ropes Course EN
15667 Part 1 (Construction) and Part 2 (Operation) Go Ape have contributed to the
formulation of these standards, including a recent comprehensive revision of arboricultural
inspection guidelines.
6. Statement summary:
Since the first site was opened in March 2002, a total of 3.2 million customers (as at
December 2012) have used Go Ape ropes courses; none has been injured as a result of trees
on site. The facilities offered have obviously been a beneficial influence in drawing a wide
range of people from urban areas into more natural environments. In addition to healthy
exercise and a feeling of well-being and achievement, participants also get an opportunity to
see and feel trees at very close quarters; this must increase an appreciation of the natural
environment and trees in particular.
No trees have died or suffered significant decline as a result of use within a site but some
localised constriction has occurred as a result of course fixings. However, the majority of
trees used form a very small component of wider woodland landscapes that, in the main, were
originally planted as a timber crop. It can be postulated that the presence of Go Ape courses
helps justify the retention of parts of the nation’s woodland areas for recreational use that
may otherwise have been cleared for timber.
Go Ape considers itself people friendly and tree friendly; it will continue to reduce where
possible the impact of courses on the environment; any localised impact on a small number of
trees is more than outweighed by the benefits of the healthy recreation provided by the
facilities.