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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‘I didn’t choose figs — They seduced me’

Howard Lovy, executive editor at US-based Foreword Reviews, recently published an interview with me about my new book. Published in the UK as Ladders to Heaven and in North America as Gods, Wasps and Stranglers the book tells how fig trees have shaped our world, influenced diverse cultures and can help us restore life to degraded rainforests. I am reproducing the interview here with Howard’s permission.

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HL: Let’s get this question out of the way first, since many in the U.S. don’t get it. You’ve attended United Nations climate change negotiations. You’ve devoted your career to studying and writing about nature. I’m sure you’ve also spoken to some very smart people. Can you, for the record, state whether climate change is real and man-made?

MS: Yes, man-made climate change is real. The mass of scientific findings made over the past three decades shows very clearly that human activities are raising the concentration of greenhouse gases in the atmosphere and that this is raising the global average temperature and changing the climate. 2016 is set to be the hottest year on record.

HL: Figs and wasps depend on one another for their existence. Not to be too obvious in our metaphors, but did you choose to focus on figs because of its wider implications for humans and nature?

MS: I didn’t choose figs—they seduced me. I spent three years studying dozens of wild fig species in Borneo and Papua New Guinea. I worked in forests where fig trees play a critical role in sustaining a large proportion of the wildlife and the thousands of plant species whose seeds these creatures disperse. The biology of fig trees was fascinating enough—shaped as it is by an 80-million-year-old partnership with tiny wasps. But when I also learned the many ways fig trees have influenced our own species, I became compelled to write their story.

The more I researched, the more these trees amazed me. I firmly believe everyone should know their story, not least because it is linked to every one of us in some way. It offers a powerful lens through which we can examine our own place in nature, as well as our future and our past.

HL: What is the most unusual, or surprising, role figs have played in altering the course of human history?

MS: Well, Queen Elizabeth II was asleep up a fig tree when she inherited the throne. The Buddha attained enlightenment whilst meditating beneath one. And without figs to power their bodies, the Egyptians might never have built the pyramids. In the colonial era, Britain used sacred fig trees as gallows to hang hundreds of Indian rebels. And in Kenya, rebels used a fig tree as a secret post office to plot against the British. Fig trees have played roles in the births of biology, of agriculture and of the first great civilizations. They feature in every major religion and have influenced diverse cultures all across the planet.

I’m most interested, however, in the possibility that fig trees played a role in our evolution, feeding our pre-human ancestors a year-round diet of energy rich figs—the perfect fuel for a large primate evolving a big and complex brain.

HL: You recently told The New Yorker that you used to spend time lying beneath a fig tree and recording its visitors. An amazing number of species would come and eat. Did that tell you anything about our own place in the ecosystem?

MS: A single strangler fig can produce as many as a million figs more than once a year, and at any time of the year. They are the pop-up restaurants of the rain forest and, year-round, they attract a great variety of birds and mammals.

Two things struck me as I watched these feasts unfold. First, I had no doubt that a fruiting fig tree would have often offered a lifeline to our earliest human ancestors, the first people, whose days would have focused largely on finding food. Second, I realized how fig trees are magnets for wildlife, and how the early humans would have used them as hunting grounds, just as hunters do today in forests across the tropics. As sources of both meat and figs, such trees would have been valuable resources to protect and respect.

It is little wonder then that all around the tropics, diverse cultures have woven fig trees into their stories and have often developed taboos against felling these trees.

HL: There are, very likely bits of mummified wasp in every fig we eat. How should we feel about this?

MS: While that is certainly true of the hundreds of wild fig species, we tend to eat figs of just one species: Ficus carica. This plant is among the first that people ever cultivated for food—several thousand years ago. Over that long history farmers bred some Ficus carica varieties that no longer need wasps to produce ripe figs. So, for those varieties, there’s no trace of a wasp. Great news for vegans!

Other Ficus carica varieties do need wasps to pollinate their flowers in order for them to develop seeds, then become sweet and ripe. But the wasps are so small and so few that you really won’t notice them. By the time you eat a fig, any dead wasps will have mostly broken down into nothingness. Rest assured, when you bite into a fig, any crunch comes from fig seeds not wasp corpses.

My 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.

Click here to read a summary and advance praise from Annie Proulx, Deborah Blum, Michael Pollan, Sy Montgomery, Fred Pearce, Simran Sethi and Thomas Lovejoy and others.

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Photo credit: A famous strangler fig called the Cathedral Fig in Queensland, Australia (James Niland / FlickrCreative Commons)

Chapter-by-chapter preview of my book Ladders to Heaven

Here is an outline of each chapter of Ladders to Heaven: How fig trees shaped our history, fed our imaginations and can enrich our future, the book I am crowdfunding through publisher Unbound. There’s a 10th chapter that I haven’t mentioned yet. That’s a secret for now.

If you like what you see, please considering reserving a copy. Everyone who does will have their name printed in each edition of the book. To watch a short video about the book, read a synopsis and summary, or to order a copy, visit the Unbound site.

Chapter 1: Trees of Life, Trees of Knowledge

I will show you how fig trees inspired the co-founder of the theory of evolution, how they feature in the creation myths of diverse religions and cultures, and how these two facts are connected.

Chapter 2: A Long Seduction

I will show you how people have revered one special fig species in Asia for more than 5000-years. You will meet the Buddha and a bloodthirsty dictator. I will tell the tale of a fig tree that has travelled thousands of kilometres and been made a king, has helped spread a philosophy of peace and had its flesh torn by hot bullets during a brutal massacre.

Chapter 3: Banyans and Botanical Monkeys

You hear how fig trees influence the founders of biology, more than 2300 years ago in Greece, and how Alexander the Great encountered a fig tree in India that was big enough to shelter thousands of his soldiers. I will tell the story of a 20th century fig biologist whose extraordinary drive to botanise had him labelled a traitor and a spy.

Chapter 4: Sex and Violence in the Hanging Gardens

You will find out how an 80-million year-old partnership between fig trees and tiny wasps will influence the fates of forests and wildlife across the tropics. This story is surely one of the most astounding in all of biology. It is one of the most important as well, for without these tiny creatures and their interactions with fig trees, the world as we know it would not exist.

Chapter 5: Struggles for Existence

I’ll show tell you the story of the ancient relationship between birds called rhinoceros hornbills and the giant fig trees whose seeds they disperse. Both partners face extreme challenges in their bid to survive and reproduce. Their solutions have knock-on effects on thousands of other species.

Chapter 6: Goodbye to the Gardeners, Hello to the Heat

I’ll take you to Borneo where I lived in a national park for 18 months studying dozens of wild fig species and the animals that disperse their seeds. I’ll explain how climate change, hunting and deforestation threaten the 80-million year long reign of the fig trees, and what this could mean for us.

Chapter 7: From Dependence to Domination

I’ll show you how fig trees played crucial roles in human evolution and cultural development, as sources of food, medicine and more. The figs were influencing our ancestors long before they descended from the trees. You will meet dinosaurs and ape-men, ancient royals and strange spirits, pharaohs and farmers. I will explain timeless wisdom of letting fig trees stand tall.

Chapter 7: The War of the Trees

I will explain the ecological and cultural reasons fig trees played many curious roles in the struggle for Kenyan independence. You will find out how fig trees connect a Nobel Peace Prize winner, a rum smuggler, Queen Elizabeth II, a prophet and the most wanted man in the British Empire.

Chapter 9: Once Destroyed, Forever Lost?

I’ll show you how fig trees could give yet provide us with their greatest gifts if we learn the lessons their biology can teach. I will tell you about a terrifying Time of Darkness, take you to volcanoes where fig trees have helped rebuild forests and share the story of a scientist with a vision of robots in rainforests.

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