The missing link

Canopy bridge building in Sumatra

Andy Pinder

The mountains of northwest Sumatra.

Packed and ready to go! Andy Pinder (left) and Tony Darbyshire en route to Sumatra. The orange bags were full of kit donated by supporters.

It all began for me at the 2025 ARB Show. I’d gone looking for Tony Darbyshire of Sawpod fame to ask about his past experiences in Indonesia because my wife and I were thinking of going there on holiday. I found him mid-burger, and before I’d even sat down, he said, ‘We’re going again in August. Do you want to come?’

Blimey. Without hesitation, I replied, ‘Why not?’ And just like that, the adventure began.

Tony and his team had last travelled to northern Sumatra more than a decade ago. This time the mission was to train a new generation of conservation volunteers to install canopy bridges – pathways that help orangutans and other wildlife safely cross fragmented forest. We’d also be supporting the installation and monitoring of camera traps which are used to assess wildlife movement patterns and the threats to them.

The project partnered with the Sumatran Orangutan Society (SOS) and TaHuKah (Tangguh Hutan Khatulistiwa Foundation), a local NGO dedicated to conservation and community-led forest protection. Their team included ecologists, guides, anthropologists, and local rangers who knew every bird and animal call, path and patch of forest like the back of their hand – thankfully for us.

The team flew into Medan and the project area is indicated in yellow. (base map: www.commons.wikimedia.org)

Getting familiar with the terrain.

Andy, Geoff, Tony and Marcus with Fong, their guide at Singapore Botanic Gardens.

A fragile forest, a critical cause

So where is Sumatra? Well, I didn’t really know either. It is the world’s sixth biggest island and is part of the Sunda Islands group in western Indonesia. It is renowned for its rugged tropical terrain, active volcanoes, and exceptional biodiversity, being one of only two places on Earth where orangutans can be found in the wild. The Barisan Mountains run the length of the island, featuring Mount Kerinci (the highest peak at 3,805 m) and the massive Lake Toba, the world’s largest volcanic lake.

The Tropical Rainforest Heritage of Sumatra, a UNESCO World Heritage site, consists of three national parks: Gunung Leuser, Kerinci Seblat, and Bukit Barisan Selatan. It is home to critically endangered species including the orangutan and the Sumatran tiger, rhinoceros, and elephant.

Sumatra has over 50 languages and numerous ethnic groups, including the Acehnese (north), the Batak (around Lake Toba), and the Minangkabau (west), known for their matrilinear society and spicy cuisine.

The Sumatran orangutan’s numbers have plummeted due to palm oil expansion, logging, and forest fires. Only seven of nine known populations are expected to survive in the long term.

These great apes rarely descend to the forest floor due to the dangers from tigers, clouded leopards, pythons, and eagles. Their world is the canopy, and forest fragmentation leaves them stranded as they forage following their instinctive migration routes, which are based on the fruiting times (masting) of various tree species. The key tree species are camphor, shorea, and fig. That’s why canopy bridges matter.

An orangutan nest – rangers can tell how recently a nest was built by how green it is.

Rope bridge warning signs.

Simple rope bridge.

Rope bridge with improved foot grips.

Attachment to a tree.

The people who made it possible

Before any of us set foot in Sumatra, months of planning were already underway. Securing gear, transport and resources for such a remote conservation project required a huge amount of help from a wide community of supporters.

Suppliers

Sawpod • Petzl • Sorbus International • ISC • Honey Brothers • Oakleaf Tree Services • LRV8 Rescue • Arbor Pride • Arbsystem • Gustharts • Arbor-Venture. These suppliers contributed essential climbing, rigging, and safety equipment – all of which was donated permanently to the trainees and conservation groups in Sumatra.

Sponsors

Arboricultural Association • The Toby and Regina Wyles Charitable Trust • Sawpod • website donors. Their vital financial support made the journey, gear transport, and training possible.

Personal thanks

A shout-out to The Rekerz for single-rope technique (SRT) training (and patience!), and to Di Darbyshire, whose organising, planning, and resilience formed the backbone of the entire operation. With their support, the team arrived in Sumatra fully equipped, fully supported, and ready to train the next wave of forest guardians.

Preparation and departure

Tony, Di, and our supporters had already coordinated much of the groundwork. Our job was to bring ourselves – and our arboricultural knowledge. Tony and I met the rest of the international crew in Singapore: Geoff Pugsley from British Columbia and Marcus Nicholson from Sydney. Their enthusiasm and youth added to my growing awareness that I might be the ‘older one’.

We enjoyed a private tour of the Singapore Botanic Gardens courtesy of Fong, the Senior Arboricultural Manager. Her knowledge was extraordinary, and the visit gave us a sense of what awaited us in the Sumatran forests:

• Trees grow very quickly in this region of the world.
• There are two typical seasons: wet and hot, and hot and hotter
• Many trees are reduced in height to avoid failure by mechanical stresses and lightning strikes.
• There are many branch failures.
• Root systems tend to be shallow and widely spreading.

We quickly realised that we did not have a scooby about tropical tree species. Many thanks to colleagues at Royal Botanic Gardens Kew for arranging this visit.

Into Sumatra

After landing in Medan – the economic capital of Sumatra – we were met at the airport by the event organisers from SOS and then embarked on a 7.5-hour drive to our base in Salak, northwest Sumatra.

During this journey we witnessed the somewhat chaotic traffic systems, beautiful landscapes, subsistence farming, convoys of lorries full of cut palm trees and timber, and a Dutch windmill: from the 1700s until 1949 the majority of Sumatra was a Dutch colony. We were also fortunate to be in Sumatra to witness the decoration of numerous villages in preparation for celebrations marking the country’s Independence Day on 12th August.

We finally arrived at Sidikalang. The accommodation was basic but the best available in the local area. This was never going to be a luxury holiday; at best it could be described as a 1970s holiday camp, and, as this is a predominantly Muslim country, the bar only served cola.

That evening we met the trainees – a vibrant mix of volunteers from across Sumatra. Their roles extended far beyond learning to climb: they were also cooks, guides, drivers, photographers, storytellers, translators, drone pilots, and even Tony’s dedicated coffee provider.

The next day, we were shown previous bridge projects – some successful, some destroyed by storms or lightning – as well as the strict requirements for future designs: natural materials, minimal scent transfer (animals are deterred from using the bridges if they are tainted by human scent), strength, adjustability, low weight, and no damage to trees. No small challenge.

We also saw orangutan ‘nests’ within the tree canopies. The rangers look for these structures to monitor the animals’ movements across the jungle canopy. A nest is made every evening, and therefore the greenness of the vegetation indicates an orangutan’s proximity.

Rope bridge span.

Trying to find suitable trees for training.

An evening training session.

Training in the jungle

The next challenge for the team was to find trees that 20 inexperienced climbers could take on; they ideally had to be close to the road so the equipment could be transported relatively straightforwardly, isolated so that we could easily see the trainees, and on reasonably flat ground. The main problem was that the road carved its way through mountainous terrain with steep slopes and heavy vegetation, so although there were thousands of trees, most were unsuitable. Other challenges included the fact that the tree species were alien to us (so we had no knowledge of the strength of their wood or branch attachment), the height of the trees and their canopy architecture, wildlife within the canopy, and epiphytes, plus the length of ropes that we had available. We eventually identified an appropriate site, but it was an hour or so’s drive from the base. Even these trees had their challenges. Evenings were spent covering the basics: harnesses, helmets, karabiners, knots, climbing devices. Our translator did heroic work handling everything from Tony’s Yorkshire expletives to the variety of English accents.

The next four days were spent in full-on training sessions with early starts and late finishes, starting with the basics. By the end of the first day most had accomplished rope throwing and first changeover. Each evening was spent reviewing the day’s progress. Tony was conscious of the time constraints and the number of trainees, so we decided to fast track the better climbers and train the others as effective support crew.

Geoff and Marcus worked their magic, tirelessly demonstrating, encouraging, and guiding the trainees, and by the end of day 3 they successfully had eight trainees to top anchor point with numerous changeovers in between. Meanwhile, Tony and I coached the support teams and battled with the local invertebrate population.

I must add here that the trainees were truly remarkable. It is hard enough learning new skills in one’s native tongue, but what they accomplished in five days in a second language is truly unbelievable – and they also did the catering, took photographs and made recordings, dealt with blisters and aching limbs, loaded and unloaded gear and equipment, drove gear and people to the training site, uploaded recordings, and then practised new skills in the evenings and cooked again. Always with a smile.

We spent every evening in their company, running through bits they did not quite understand, but always ending with a karaoke session around the campfire.

Running through the systems.

Into the canopy.

Trainees teaching each other.

Confidence growing!

Happy climbers.

Translator at work.

Preparing the ground crew./span>

Food, heat and sweat bees

Meals were prepared by the catering crew each day, and we often ate while sitting in the cool river. Regional Sumatran dishes appeared daily – fish heads, chicken claws, giblets, unidentified brown meat, sticky rice, and fresh fruit. Eventually, most of us adopted the local custom of eating with our hands. Tony, steadfastly stubborn, stuck to using his cutlery.

Sweat bees became our constant companions – crawling across our faces, arms, and kit; buzzing around drinks; and swarming in clouds whenever we stopped. You learn to ignore them. Mostly.

Moments money cannot buy

We were blessed with two orangutan encounters during our time in the forest. To put this into perspective, some of the volunteers we met have worked for SOS for over two years and it was also their first sighting of these extraordinary animals.

On the way to our first training day site, we saw a mother and juvenile feeding quietly in the canopy just 30 metres away. Tony and I exchanged a glance – both in tears and speechless. The second sighting came on the final day: a huge male preparing his night nest only 10 metres from the road. He observed us briefly before melting back into the forest. Seeing these magnificent animals in the wild was amazing: a reminder of why the work matters.

Tony being irritated by bees.

The secret is to just ignore them.

If you can!!

A mother and a juvenile orangutan.

Lunch preparation.

Screenshot from the first recording of an orangutan using a rope bridge.

Future challenges

The training continues, and rope bridges are being monitored with camera traps installed by the volunteers. But designing the perfect bridge remains an engineering and ecological challenge.

Future bridges must be:

• made from natural materials
• scent-neutral
• colour-neutral
• adjustable for fast-growing trees
• strong enough to sway with motion
• light enough to haul
• easy for volunteers to install
• completely non-damaging to trees

If you have ideas or innovations that could help, the team welcomes input via www.sawpod.co.uk.

Footnote

Since we returned to our normal lives, SOS has sent us footage of the volunteers installing camera traps in trees at potential crossing points using the equipment and training that we supplied, AND a video of the FIRST recorded orangutan crossing on a bridge!! You can find it here: www.orangutans-sos.org/sumatran-orangutan-explores-our-canopy-bridge-for-the-first-time.

Photos by Sawpod and TaHuKah team members.

Andy Pinder is a retired arboriculturist.

This article was taken from Issue 213 Summer 2026 of the ARB Magazine, which is available to view free to members by simply logging in to the website and viewing your profile area.