Can living fig-tree bridges save lives in a changing climate?

By AditiVerma2193 (Own work) [CC BY-SA 4.0 (http://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons

In 1841, a young Scotsman called Henry Yule was exploring the Khasi Hills of north-east India when he came upon something no other European had ever reported. There, in that challenging landscape of thick rainforest and perilous gorges, was a most extraordinary structure — a living bridge formed from the roots of a gnarly old fig tree.

The tree’s roots had somehow reached more than 20 metres across a river and taken hold on the far side. Over time, they had thickened and interwoven to form a walkway, onto which Yule now had to step. One of the roots, which in places was thicker than his thigh, provided a handrail. Side roots had descended from it and merged into the walkway, making the whole structure strong and secure. Yule could cross with confidence.

The bridge was no miracle. Long before, human hands had guided the tree’s roots across the river, training them into a shape that could promise safe passage. Yule had assumed the bridge to be “unique, perhaps half accidental”, but he soon saw several more. Their architects were local Khasi people, whose attitudes towards time, the environment and their unborn descendants we are sorely lacking in our fast-warming world.

Fig tree bridge. Credit: Laurence Mitchell (https://eastofelveden.wordpress.com/2011/03/06/crossing-the-bridge/)

The Khasi Hills are in Meghalaya, an Indian state whose name means ‘land of the clouds’. The clouds cry often on this land, for nowhere else on Earth must people endure such heavy rainfall. Twelve metres of it falls in a typical year. After monsoon rains, the region’s rivers rise. The rush of water racing downstream renders steep gorges impassable, isolating villages and endangering lives. Yet people have lived in the Khasi Hills for at least 3200 years. For generations, they have overcome this extreme environment by harnessing the strong yet pliant roots of Ficus elastica, a fig species best known as the Indian rubber tree.

Fig roots are exceptional. They grow fast, long and strong. They can even rip apart bare lava and concrete. In many fig species, including Ficus elastica, the roots aren’t all underground. These figs produce aerial roots that flow down their trunks and drop from their branches. Their roots can merge and split and merge again, forming strong, mesh-like structures. Long ago, the Khasi people worked out how to get such fig roots to do their bidding.

It’s a practice still alive today. The Khasi and neighbouring Jaintia peoples have shaped fig roots into living ladders, whose rungs ease journeys up steep slopes. They have woven the roots into nets that hold banks of earth in place, preventing landslides and soil erosion. They have even forced fig roots to form a platform, from which to watch football games. But the masterworks of Khasi architecture are their bridges. Most — like one Yule sketched, below — form from the roots of two fig trees, one on either side of a river. The longest spans more than 50 metres, the oldest an estimated 500 years.

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Building these bridges involves first guiding slender fig roots through hollow trunks of betel palms, which support, nourish and protect the roots as they lengthen. Once the fig roots are long and strong, the bridge builders bind them to those of the opposing tree or embed them in the ground on the far side of the river. They shape secondary roots that grow from these mainstays into a net that will form a walkway. They use stones and soil to plug any gaps then wait for the roots to thicken and hold everything in place.

It can take 15-30 years before the bridge is strong enough to use. But in Khasi time this is an eye-blink. The Khasi people are investors in the future. People living there today benefit from the ingenuity and foresight of their ancestors and today’s bridge builders bequeath security to future generations. The fig tree bridges don’t only make commerce and romance possible between otherwise isolated villages. They also save lives. As the climate changes, this ancient approach to bioengineering has never been more relevant.

Meghalaya was already the wettest place in the world when Henry Yule explored its forested hills in 1841. Back then, the atmospheric concentration of carbon dioxide was 283 parts per million. Today it is more than 400. More carbon means warmer air, and as warmer air carries more moisture, this means more rain. The state government’s climate change action plan says rainfall has increased in most districts of Meghalaya in the past century, with the highest increase in the West Khasi Hills. It warns that as temperatures continue to rise, so will rainfall and the risk of floods and landslides.

To architect Sanjeev Shankar, these threats call for renewed attention to living bridges. In a research paper he presented in 2015, he warned that they are being replaced by “inappropriate solutions”. Quick-fix bamboo bridges buckle and break – they can’t withstand the monsoon rains. People have died as a result. Modern steel bridges corrode, their cables weaken and snap. And because repairs are rare, these bridges last just 40-50 years compared to hundreds for living bridges.

Shankar says the living fig bridges cost next to nothing and become stronger, more robust and resilient with time and use – unlike expensive, short-lived steel suspension bridges. Indeed, some of the bridges Henry Yule saw in the 1840s are still saving lives today. Shankar urges a revival of fig-tree bridge-building, and even foresees bridge that are strong enough for vehicles to cross.

The only downside is the time it takes the bridges to grow. But Shankar sees potential to blend the old with the new. Having seen how Khasi people have used fig roots to mend steel bridges, he envisages planned hybrid structures — steel bridges that fig trees envelop with their roots and make stronger. Shankar wonders if other fig species could perform this role in other countries, helping people adapt to the changing climate.

The question is, will there be time? It’s a question for us all, as climate change doesn’t respect the short-term thinking that tends to rule our lives. The Khasi people’s approach is instructive. To build living bridges, they invest time and effort knowing they might not personally benefit but that their children surely will. Such foresight, patience and selflessness is rare.

This post was first published by the Thomson Reuters Foundation and is reproduced here with permission.

IMAGE CREDITS: Top (Aditi Verma, via Wikimedia Commons); middle (Laurence Mitchell); bottom (Henry Yule, from Yule, H. (1844). “Notes on the Khasia Hills, and people”. Journal of the Asiatic Society of Bengal. 14 Part 2, Jul-Dec (152): 612–631).

My new book —published in the UK as Ladders to Heaven and in North America as Gods, Wasps and Stranglers tells how fig trees have shaped our world, influenced diverse cultures and can help us restore life to degraded rainforests.

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Why are so many strangler figs home to ghosts and goblins?

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No trees are home to a more motley mix of supernatural creatures than the strangler figs, whose eerie aerial roots are adept at seizing imaginations in their grip. Diverse cultures around the world say these trees shelter angels and fairies, gods and ancestral spirits, ghosts and other malevolent creatures.

There may be a biological basis to some of these beliefs. Strangler figs attract ghostly nocturnal animals such as leathery-winged bats and small primates with big eyes that reflect moonlight. In Indonesia and Malaysia, these trees are often home to small saucer-eyed primates called tarsiers (Tarsius tarsier) whose local names mean ‘spirit animal’ or ‘spirit monkey’.

Other denizens of strangler figs are decidedly less cuddly. In the folklore of the Philippines, they include giant tree demons called kapres, goblin-like duendes and the half-human, half-horse tikbalang.

On the Japanese island of Okinawa, folk tales feature impish red-haired spirits called kijimuna that live inside the hollows of strangler figs. These mischievous sprites love to play tricks on passing people, such as sitting on their chests so they can’t breathe.

In Australia, aboriginal stories warn of an altogether more fearsome fig-dweller, the yara-ma-yha-who. This manlike creature has bulging eyes and a gaping toothless maw. When hungry it will leap out of its fig tree onto an unsuspecting traveller. Its fingers and toes end in flattened discs, through which it sucks the blood of its victims.

These are just a few of the many supernatural beings that people across Africa, Asia, South America and the Pacific have said live in fig trees. As my new book Ladders to Heaven (US title: Gods, Wasps and Stranglers) explains, often these stories coincide with taboos against harming fig trees — in the image above, ghosts assail a Bengali man who made the mistake of chopping a branch from a sacred strangler fig.

Whether ancient people realised it or not, by protecting strangler figs, they were ensuring the survival of many other species of plants and animals upon which they depended. That’s because strangler figs are ecological linchpins. They produce figs year-round, sustaining a rich variety of birds and mammals that disperse the seeds of many other forest species. Without strangler figs many of these animal and plant species would simply go exinct.

So next time you see a strangler fig, fear not. The world would be a scarier place without them.

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Picture credit: Illustration by Warwick Goble from the 1912 illustrated edition of Folk-Tales of Bengal by Lal Behari Dey / Wikimedia Commons. Photo: A famous strangler fig called the Cathedral Fig in Queensland, Australia (James Niland / FlickrCreative Commons).

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The orangutan, the strangler fig and the photographer — a story of entwined lives

Orangutan climbing the pillar root of a strangler fig (Ficus stupenda)

Tim Laman / Wildlife Photographer of the Year

I’m thrilled for Tim Laman, who has just won the 2016 Wildlife Photographer of the Year award for this stunning shot of an orangutan climbing the pillar root of a strangler fig (Ficus stupenda) to feast on ripe figs.

There is a sweet irony to Laman’s winning photo. It was thanks to an image of an orangutan that Laman ever visited Indonesia, where he first became a fig biologist and later developed the skills that would enable him to take photos of life in the rainforest canopy.

Back in 1986, Laman had been at Harvard University studying for a PhD when he saw a poster advertising a research assistant’s job in Indonesian Borneo. The poster featured an image (below) from The Malay Archipelago by Alfred Russel Wallace, Laman’s future hero.

Laman got the job, put his studies on hold and travelled to Borneo, where he fell in love with the rainforest. His life tilted in a new direction. For the next few years, he studied  strangler figs — important plants whose figs feed orangutans and dozens of other wildlife species.

To understand these fascinating plants he had to climb the giant trees on which the stranglers grow. It was up there in the rainforest canopy that Tim found his true vocation — capturing phenomenal images of rare and endangered wildlife. Congratulations Tim!

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Notes:

I’m doubly grateful to Tim Laman. First, for his meticulous research on strangler figs, which helped me during my own doctoral research on these plants. Second, for the help he provided when I was researching my book about fig trees Ladders to Heaven / Gods, Wasps and Stranglers. Laman is the star of Chapter 7.

To see more of Laman’s photos, visit his Facebook and Instagram pages, or his website.

Wildlife Photographer of the Year is developed and produced by the  Natural History Museum, London. For more details of the awards, visit the website.

Full caption for Laman’s winning photo:

Entwined lives by Tim Laman – Winner, Wildlife Photographer of the Year 2016: 
A young male orangutan makes the 30-metre (100-foot) climb up the thickest root of the strangler fig that has entwined itself around a tree emerging high above the canopy. The backdrop is the rich rainforest of the Gunung Palung National Park, in West Kalimantan, one of the few protected orangutan strongholds in Indonesian Borneo. The orangutan has returned to feast on the crop of figs. He has a mental map of the likely fruiting trees in his huge range, and he has already feasted here. Tim knew he would return and, more important, that there was no way to reach the top – no route through the canopy – other than up the tree. But he had to do three days of climbing up and down himself, by rope, to place in position several GoPro cameras that he could trigger remotely to give him a chance of not only a wideangle view of the forest below but also a view of the orangutan’s face from above. This shot was the one he had long visualized, looking down on the orangutan within its forest home. GoPro HERO4 Black; 1/30 sec at f2.8; ISO 231.