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Limit global warming for fig tree, wasp survival: British biologist

Sep 9, 2017
New Delhi, If you want to see the wildlife in the tropics and subtropics, one of the best places to be is beneath a big fig tree. Many species of birds and mammals would go hungry if the fig trees disappear. And right now these trees are facing man-made threats.

By Vishal Gulati

These were the views of British biologist and writer Mike Shanahan, whose work focuses on rainforest ecology, climate change and related issues.

Every fig species depends on its own fig-wasp species (often just a single species, sometimes more) to pollinate its flowers, he explains about the fig and fig-wasp relationship for each other’s survival.

The fig-wasps in turn can only breed and reproduce inside the figs of their partner tree species. Each partner is utterly dependent on the other one.

“It is thanks to this 80-million-year-old relationship that the figs are available year round as the tiny pollinator wasps live for just a day or two and must always be able to find unripe fig in which to lay their eggs,” Shanahan told IANS in Cartagena, Colombia.

The fig trees (Ficus species) have been culturally important to people on the subcontinent for thousands of years.

According to Shanahan, in India, several species of fig trees have special cultural meaning and are important especially in Hinduism and Buddhism as well as to Jains and Sikhs and many local cultures.

They feature in creation myths and have strong associations with many different deities. This is especially true of India’s banyan and peepal trees.

The loss to fig trees -- which even germinates in rocky substrates that lack soil -- in turn leads to a threat to many bird and mammal species.

“If all the fig trees in the world disappeared today, many species of birds and mammals would go hungry. That’s because fig trees produce figs year-round and sustain these animals when other fruits are not available,” he explained.

Twenty years ago, when Shanahan researched the number of fig-eating animals, he found that at least 1,274 species of birds and mammals had been recorded eating figs.

“The true number is probably several hundred greater as I only found records for 260 of the 750 or so fig species,” he said.

His recently published maiden book has different titles in different markets.

They are “Gods, Wasps, and Stranglers: The Secret History and Redemptive Future of Fig Trees” and “Ladders to Heaven” in Britain.

The book talks about how fig trees have shaped humanity and the world about us because of their curious biology.

The biologist, whose doctoral research was in Sarawak, a Malaysian state on the island of Borneo, attributes the threat to the fig trees to deforestation -- and in urban areas to road-widening and other infrastructural development.

Fruit-eating animals are threatened by the loss of their forest habitat and by hunting. The bigger fruit-eating animals such as monkeys and other primates like flying foxes and birds like hornbills are particularly vulnerable.

Shanahan, who co-founded Internews’ Earth Journalism Network Climate Change Media Partnership to enable journalists to report on UN Climate Change Negotiations, said some biologists have shown the lifespan of fig-wasps falls dramatically as temperatures rise.

This means the fig-wasps would not have time to find figs of the right species in which to lay their eggs.

Other biologists point out that fig-wasps should be able to adapt to rising temperatures, by changing their physiology or flying at night instead of day, for instance.

“The truth is we don’t know. And if global warming does threaten the relationship between fig trees and fig wasps, we will probably find out too late. We need to limit global warming anyway, for so many reasons,” Shanahan said.

The 2015 Paris Agreement aims to limit average global warming to 2 degrees Celsius by cutting greenhouse gases from burning fossil fuels.

Can fig trees re-grow lost rainforests? He replied: “Yes.”

Researchers around the world are using fig trees to kick-start and accelerate rainforest regeneration in areas that have been logged or cleared for agriculture.

In Thailand, they are planting fig trees grown from seed in nurseries. So it is in Costa Rica where they are lopping off big branches from mature fig trees and planting them in the soil as “instant trees”.

He said there was also some evidence that strangler figs protect the trees on which they grow when cyclones strike. In Vanuatu in the Pacific Ocean, locals have used giant strangler figs as cyclone shelters for generations.

And in northeast India, people use fig trees to form living bridges over rivers and ravines, which save lives and connect villages during the monsoon rains.

“The fig tree bridges are astounding structures and some are thought to be hundreds of years old,” Shanahan added.

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