Figs, wolves and starfish: the regenerative power of keystone economics

“By themselves, the figs could build a forest,” wrote botanist E.J.H. Corner, after years of studying fig trees in the Singapore Botanical Gardens in the 1930s and 40s. Fifty years later, biologist Steve Elliott put this claim to the test in Thailand’s Doi Suthep-Pui National Park.

Following decades of land clearance for agriculture, one fifth of the park had become treeless, and locals were failing in their attempts to restore the lost forest. Elliott adopted the then groundbreaking ‘framework species approach’, planting ‘pioneer’ and ‘climax’ species all at once, aiming to accelerate the natural ecological ‘succession’.

Fig trees played a central role – of the eight best surviving tree species planted in the second phase of the reforestation, five were figs; and one fig species “produced figs almost continuously from the time of planting onwards,” where most other tree species took at least two and a half years before they bore fruit.¹

The result was spectacular. Within two years a new canopy had already begun to close, shading out weeds and covering the ground in rich leaf litter that encouraged new tree growth. Within 8 years the number of bird species populating the area had tripled and 73 other native tree species had sprung up, their seeds dispersed by the animals drawn into the new forest.

After 21 years the forest had reached maturity, storing almost as much carbon as an old-growth forest.² Australian biologist Nigel Tucker, who developed the framework species approach when restoring forests in Queensland, Australia, believes that, for effective reforestation, one in five of the tree species planted should be a fig.³

Read also: Hope from the ashes: unearthing ancient value in our forests

The magic figtree

The most famous tree in the world is a fig tree. The bodhi, a tree of the species ficus religiosa (meaning ‘sacred fig’), sheltered the Buddha for 49 consecutive days of meditation, at the end of which he is said to have achieved enlightenment. A direct descendant of that tree – the 2,500-year-old Mahabodhi tree – has become a place of pilgrimage for Buddhists the world over.

In the Abrahamic faiths, the first people on Earth made clothing from fig leaves; the ancient Greeks thought figs to be a gift from the gods; the Romans believed that Romulus and Remus, Rome’s founders, had been saved from drowning by the roots of a fig tree. For many indigenous communities the fig is the “world tree”, reaching up to the heavens and providing a conduit for God to communicate with his people. Other traditions believe that fig trees are gods themselves, or hold figs as symbols of divine sustenance.

Science now understands why these trees have been so long revered. The ficus (fig) is an unusual family. They are prodigious growers, with powerful roots that can crack rocks, stabilise soils and locate water even in dry seasons. Many of the more than 750 species “fruit” multiple times a year (figs are not, in fact, fruit, they are bundles of hidden flowers), providing food at times when other plants are barren. This makes them biodiversity magnets – all told, over 1,200 species of birds and mammals feed on figs, more than any other single fruit.⁴

But figs don’t dominate their environments. Instead, by attracting such a wide variety of seed-dispersing animals – who often arrive at the figs having first eaten the fruit of other trees many miles away – they give opportunity for other tree species to spread. In barren landscapes just a few fig trees can create an explosion of new plant and animal life. In 1986 Professor John Terborgh suggested that fig trees are so important to Peru’s Amazon basin that without them the entire ecosystem could collapse.⁵ According to Dr. Daniel Kissling, Associate Professor of Quantitative Biodiversity at the University of Amsterdam, fig trees are “keystone resources” on a “continental scale”.⁶

All animals are equal, but some are more equal than others

Nature has other keystones, too. In 1963, US ecologist Robert Paine began a multi-year experiment that would upend the field of environmental studies.⁷ From an ecologically diverse stretch of the intertidal zone at Makah Bay, Washington, Paine removed every starfish, a predator that feeds mostly on mussels and barnacles. Within a year, the total number of species in his 8-metre experimental area had fallen from 15 to 8; after a further 6 years the patch had become a monoculture of mussels.

Paine controlled his study by experimenting with the removal of other species – none had such a significant impact. Paine concluded that the starfish was a keystone species – by keeping the mussels in check, they provided room for others, and ensured a vibrant, diverse ecosystem. “All animals are equal,” he said, “but some are more equal than others.”

Ecosystem architects

A still more spectacular example of a keystone species in action can be seen in Yellowstone National Park, USA. In 1995, wolves were reintroduced to Yellowstone more than 50 years after they had been hunted to local extinction.⁸ While few in number (just 31 wolves were released, and even now the wolves total no more than 100)⁹ the wolves dramatically changed the character of the ecosystem. By creating what has been dubbed a ‘landscape of fear’, the elk and coyote population, who had previously roamed the park unchecked, were pushed to the fringes of the park.

With fewer elk around to eat saplings, and fewer coyotes to eat small, seed-dispersing mammals such as mice and ground-nesting birds, tree-life flourished. New growth of willow trees stabilised the banks of the Yellowstone River. Beavers returned – their numbers multiplied nine-fold in just 15 years – and their newly-built dams formed habitats for waterfowl, fish and amphibians. They recharged the water table and even changed the course of the Yellowstone River itself.

Like fig trees, it turns out, wolves are ecosystem architects on a grand scale.

Keystone economics

It pays to protect nature’s keystones. The cost of restoring the wolf population to Yellowstone National Park – an upfront spend of USD 30 million¹⁰ – has been paid off many times over; every year the states of Idaho, Montana and Wyoming receive USD 35 million in tourism income attributed solely to wolf-watching in Yellowstone Park.¹¹

Similar eco-tourism benefits have been seen in Costa Rica, often cited as the world’s most successful national reforestation project. There, figs are considered so valuable to forest restoration that “instant fig trees” (3.5 metre-long cuttings taken from already established trees) are planted in degraded areas in order to hasten ecosystem recovery.¹² Three million tourists visit Costa Rica each year, contributing USD 4 billion (8% of GDP) to the government coffers – more than 60% of visitors to the country say they visit for the unique environment and wildlife.¹³