science in the tree tops
...Mitchell. “We then added components relating to conservation, education and poverty alleviation of those people who depend upon these forests.” Launched with funding from the Rufford and Maurice Laing foundations, the GCP now has 15 major member institutions and its lobbying has secured a canopy element to the UN Convention on Biological Diversity. The GCP is also working to bring economic help and autonomy to forest communities in order to reduce their dependence on their environment. Ecotourism, and more specifically tourism that features canopy walkways, is seen as the best way to do this. Using the forest walkway in Ghana’s Kakum National Park as a model (it raised park visitor numbers from 2,000 to 70,000 a year, and produces a direct annual revenue of US$1million [£600,000]), the GCP is building a 300-metre walkway in Madagascar’s Ranomafana National Park with walkway-design specialists Greenheart Conservation. “It’s part of a fully integrated project, with scientific, tourism, forest restoration and management, and training components,” explains Katherine Secoy, GCP programme coordinator. “The difference with our approach is that we’re not a company looking to exploit tourism. We’re coming from a conservation point of view. The idea is to have local support for such a project.” Dizzying heights Given that many rainforest trees can grow as tall as Nelson’s Column, with little between the roots and the flourishing crown other than bare trunk, it’s hardly surprising that so few people have explored the canopy. “Make no mistake, going up into the canopy is terrifying,” says Mitchell. “The trees are designed to sway with the wind, so when you get up there and walk about, 40 to 50 metres up, it’s very frightening. You must have a safety rope – otherwise, if you fall, you will die.” Many early naturalists working in the tropics used local climbers to col-lect their specimens. Indigenous forest dwellers have been getting into the canopy for thousands of years, usually to collect fruits or honey, but they were limited in their mobility. The early collectors would also rely on a trusty axe – using the ‘mountains to Mohammed’ approach, trees were felled, although any creatures that survived the fall usually escaped – or a less trustworthy pig-tailed macaque, which couldn’t always be relied upon not to eat its quarry instead of handing it over. Since the late 1970s, fogging – gassing the canopy with a cloud of typically pyrethrum-based insecticide – has been used as an effective ground-based technique to ‘knock down’ the insect life in a section of the canopy. Its early use led Terry Erwin of the Smithsonian Institution to revise the estimate of the world’s total biodiversity from one million species to more than 30 million (a figure now thought to be closer to six million). Just two weeks of fogging 15 trees in Borneo left one group of researchers with a decade’s worth of material to identify. “There’s more life up there than any other place,” asserts Mitchell. “Finding new species is dead easy. Finding the ones you know is harder.” The first Briton to actually get into the canopy may have been Sir Francis Drake who, in 1573, gained his first glimpse of the Pacific Ocean from a tall tree in Darien, Panama. However, the first serious effort to reach and study the canopy didn’t begin until 1929. The Oxford University Expedition to British Guiana (now Guyana), led by Major RWG Hingston, managed to acquire every potentially useful device available to the British military, but still ended up requiring the help of locals when it came to building an observation platform. It was a successful expedition all the same, despite the colony’s acting governor getting stuck high up on a winched seat during a visit. From 1929, little took place in the way of canopy exploration until the construction of the Haddow Tower in the Mpanga Forest Reserve, Uganda, in the 1950s. Funded by the East Africa Virus Research Institute, it was used to revolutionise understanding of insect life in the canopy and biting-insect studies. Then, in 1960, Dutchman Adriaan Kortlandt enlisted local pygmies to help him build a tree platform from which to study chimpanzees. Once the platform was enlarged to accommodate him – the pygmies had built it to cater to their smaller frames – it allowed for some of the first continuous observations of chimpanzees in the wild. Lightweight materials developed during the Second World War were behind the next two innovations – a 50-metre aluminium ladder built by Elliot McClure and a suspended walkway designed by US Army engineers for the Institute of Medical Research at Bukit Lanjan, Malaysia. At the end of the 1970s, multiple walkways of more than 300 metres in length were built at sites in Panama, Papua New Guinea and Sulawesi in Indonesia as part of the Scientific Exploration Society’s Operation Drake, commemorating Sir Francis’s circumnavigation of the globe. However, there still remained no general commitment to canopy study, while the expense and lack of mobility offered by the various available techniques for getting into the canopy remained problematic. These difficulties were eventually overcome by borrowing cavers’ single rope technique (SRT), which allowed individual (and brave) researchers much greater freedom, even if using a crossbow to fire a rope over a distant bough was a hit-and-miss affair. “It’s still the best method for a single scientist to get up into the trees,” says Mitchell. However, as Stephen Sutton of the Tropical Biology and Conservation Research Institute at the University of Malaysia, Sabah, points out, researchers are still restricted to a single tree. “The value of SRT, on its own, can be over-emphasised,” he says. “Gaining access to a substantial bough in the lower part of the tree crown is not in itself a passport to a successful piece of research.” Flying visits In terms of canopy access, the French have proved themselves to be excellent innovators, taking things further with the development of ‘lighter-than-air platforms’ – balloons and related equipment, to you and me. Francis Hallé from the Laboratoire de Botanique Tropicale at Montpellier University took to a balloon in the mid-1980s in order to approach the canopy from above. His work in French Guiana was inspired by the use in Gabon of a tethered helium balloon by Marcel and Annette Hladick. Hallé went one further by using a small, purpose-built airship – a cigar-shaped balloon with propellers to aid manoeuvrability. “We suddenly had a mobile system that could move around the treetops; there was no other means of doing this,” says Mitchell. From this, two balloon-dependent features have developed: the radeau or raft, and the luge or sledge. The raft is a ‘floating’ platform, employed by French academics Dany Cleyet-Marrel and Laurent Pyot and is essentially an island in the treetops. Made of kevlar mesh netting and edged with inflated neoprene tubes, it rests on top of the canopy, allowing sampling (mostly of plants and insects) to take place at the edges of the platform, and can stay in position for several days. The luge, on the other hand, is an inflated hexagon similar to a traditional balloon basket but with a hole in the bottom covered with Kevlar mesh. Such techniques aren’t without their problems, however. “Balloons can cover larger areas, especially for collection purposes, but they are extremely expensive [the raft alone cost ¤122,000 (£86,000) in 2001], not very effective because you can only reach the tops...