‘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)

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If we cook these tiny wasps, we put the heat on hundreds of other species

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From the wings of tiny creatures hang the fates of hundreds of bird and mammal species, and perhaps even entire rainforests. They are fig wasps and they play a disproportionate role in the grand drama of life on Earth. They shape our own story too because of this. But new research warns that these insects could be “extremely vulnerable” to global warming.

This matters because each of the 750+ species of fig tree (Ficus species) relies utterly on particular species of fig wasp to pollinate its flowers. Without the fig wasps there would be no fig seeds to create the next generation of trees, and there would be no ripe figs for animals to eat.

In the case of any other group of trees this would not be such a big deal, but figs are special. Their pollinator wasps only live for about a day and each wasp species can only lay its eggs inside the flowers of its specific fig partner. So, to keep their pollinator species alive, each fig species needs to produce flowers and figs year-round. This means a year-round supply of food for birds and mammals, and helps to explain why figs feed more creatures than any other trees do (see A job for conservation’s keystone cops).

In the late 1990s, I set out to find out just how many animal species eat figs. The answer is an astounding 1,200-plus species, including ten per cent of all birds and six per cent of all mammals – see Who eats figs? Everybody). That’s the variety of life that stands to suffer in some way if fig-wasps disappear. Now, in a new study in the journal Biology Letters, Nanthinee Jevanandam of the National University of Singapore and colleagues provide a chilling insight into what a warmer world could mean for these wasps.

In a laboratory, they exposed the pollinators of four Ficus species to temperatures between 25°C and 38°C and to a various levels of humidity. The lifespan of all four species fell steadily as the temperature rose. By 36°C, the lifespan of three of the species had fallen to just two hours. In the wild this would give the wasps hardly any time to find a fig of the right species in which to pollinate and lay its eggs. It would hurt both wasp and fig species. This is the Achilles heel of a partnership that has existed for 80 million years. It is here that we might expect to see the relationship break down, with consequences for other species.

This has happened before. In the 1990s, fig-wasps in northern Borneo went locally extinct after a severe drought, and in Florida they disappeared when a hurricane wiped them out. In both cases, fig-wasp populations eventually bounced back — thanks to the fact they can disperse for tens of kilometres in the day or two they live. But a sustained temperature increase — like that which climate scientists predict will be a reality worldwide by the end of the century — is a different matter. As we turn up the global temperature we change the chemistry of life.

I asked Nanthinee whether she thought fig-wasps could adapt to a rise in temperature, either in their physiology or their behaviour — by flying at a cooler time of day for instance. “Fig wasps can produce up to 12 generations in a year in the aseasonal tropics, and so acclimation or genetic adaption is a possibility,” she said. “But more research has to be carried out to ascertain this. As to the possibility flying at different times, it is difficult to predict.”

The wasp species she and her colleagues studied came from distinct branches of the fig-wasp family tree, so they think their results will be relevant to hundreds of other fig-wasp species, the trees they pollinate and the animals that eat their figs. But these little wasps might have surprises in store for us yet. After all, they survived the mass extinction that saw off the dinosaurs, 65 million years ago. They might outlive us too.

Their story is a reminder that we are just new here, and that between our kisses, our fights and our smiles, we tend to stumble about breaking things before we know how they work.

Photo credit:
Valisia malayana fig-wasps at a fig of their host tree Ficus grossularioides (Nanthinee Jevanandam)

Related posts:
The humbling history of the tiny wasps that upset a Jurassic Park narrative.

Reference:
Jevanandam, N., Goh, A.G.R. & Corlett, R. 2013. Climate warming and the potential extinction of fig wasps, the obligate pollinators of figs. Biology Letters 9: X-X.  Published online March 20, 2013 doi: 10.1098/rsbl.2013.0041