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.
Valisia malayana fig-wasps at a fig of their host tree Ficus grossularioides (Nanthinee Jevanandam)
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
Global Witness has released footage that exposes the way elites have carved up and sold off the tropical forests of Sarawak in Malaysian Borneo, then siphoned away millions of dollars through illegal tax dodges. Global Witness filmed the footage in secret when one of its team posed as an investor who wanted to buy up land in Sarawak so he could set up oil palm plantations.
The main targets of the investigation are Tan Sri Abdul Taib Mahmud — who has been Sarawak’s Chief Minister for over 30 years and controls access to forests there — and members of his extended family.
“This film proves for the first time what has long been suspected — that the small elite around Chief Minister Taib are systematically abusing the region’s people and natural resources to line their own pockets,” said Tom Picken, Forest Team Leader at Global Witness, in a press release. “It shows exactly how they do it and it shows the utter contempt they hold for Malaysia’s laws, people and environment.”
In Sarawak, the website FZ.com caught up with the Chief Minister today and reported his response to the claims:
“Ok I saw the so called proof. Could it not be someone who tried to promote themselves to be an agent to get favours from me? It has nothing to do with me. I think it is a bit naughty of them.”
Taib is a master of public relations — as revealed in open letter that The Sarawak Report sent to British reality TV star Ben Fogle after he gushed good publicity about his recent trip to Sarawak. While it is clear that something “naughty” has indeed happened to Sarawak’s forests, Taib seems unconcerned by the latest salvo in an ongoing campaign against him.
Here’s the Global Witness video… The FZ.com interview follows:
Last year I brought you the story of Lambir Hills National Park, a Bornean forest in which I used to live and work, where hunting and other pressures have forced into extinction much of the biggest wildlife species (see The near empty forest that proves conservation is failing).
It describes how recent surveys had failed to find 20 percent of the park’s resident bird species and 22 percent of its mammal species. The forest is emptying fast. The losses include half of the park’s primate species and six out of seven hornbill species — all important dispersers of rainforest seeds. Sun bears and gibbons, bearded pigs and flying foxes all once called Lambir Hills home. Today it is hard to find an animal that weighs more than a kilogram in the national park.
Now researchers have shown what these extinctions mean for the forest itself. Rhett Harrison and colleagues tracked the fates of over 470,000 trees of more than 1,100 species for a 15-year period since intense hunting began there.
In a new study published in Ecology Letters, they have shown that the forest has changed markedly. There are far more trees now — the density of saplings increased by over 25 per cent between 1992 and 2008 — probably because there are fewer deer and other mammals to eat the young plants. But overall the diversity of trees has fallen. And compared to species that rely on gravity or wind to spread their seeds, there has been a relative decline in the number of new trees from species that depend on animals to disperse their seeds.
Species with animal-dispersed seeds — especially those with bigger seeds — are also more clustered than they were before hunting took off. This is probably because the loss of large fruit-eating animals means that seeds, on average, now travel shorter distances. There was no increase in clustering among species that need no animal assistance to spread their seeds.
The authors write: “Fruit that would formerly have been eaten by hornbills, gibbons or fruit pigeons, all of which are efficient long-distance seed dispersers, are now unlikely to be fed on by anything larger than a bulbul or a barbet”. For those of you who don’t know the birds of Borneo, members of the latter two types are both small enough to fit in a trouser pocket.
The researchers could draw their conclusions because Lambir is home to one of the world’s longest running forest studies. In 1992, scientists marked out a 52 hectare patch of the forest and then tagged, measured, mapped and identified every tree bigger than 1 cm diameter at breast height. In 1997, 2003 and 2008 they went back and repeated the exercise, each time taking several months to complete the task.
Their massive datasets, which track the identity and positions of around half a million trees every 5-6 years can animate the forest’s history. Like the photographs that form time-lapse videos, these periodic census snapshots reveal the patterns of life over time. The next census of the 52-hectare plot, which is due to take place soon, will add a critical fifth image that further refines the picture of a forest in flux.
The results are already striking but, as the authors note: “the full impacts of defaunation at Lambir are only likely to be realised over several plant generations.” So far, none of the species that depends on big animals to disperse its seeds has gone extinct. That’s just a matter of time.
Harrison, R. D. et al. 2013. Consequences of defaunation for a tropical tree community. Ecology Letters. Article first published online: 12 MAR 2013 DOI: 10.1111/ele.12102
Samuel Orr has been good enough to publish online this time-lapse video he shot from a house in a nature reserve near Bloomington, Indiana. He stitched it together from 40,000 images he took over a 15-month period. It’s a wild and beautiful place. On his website, Orr says: “I’d often look out the window and see turkeys, deer, flying squirrels, vultures, possums, huge orb weaving spiders, and a dizzying array of songbirds and woodpeckers.”
The result is a stunning portrait of the seasonal cycles that breathe life through every layer of the forest — and the soundscape is a rich as the view. Here Orr describes creatures we can hear.
“I tried to put in wildlife songs and calls appropriate to the season. For instance, the honking during what is late winter are Sandhill Cranes, which used a migratory flyway that passed directly overhead. Many of the calls were recorded on sight, others were from elsewhere in Indiana. Animals heard include migratory songbirds, spring peepers, tree frogs, cicadas (periodical and annual), turkeys, coyotes, elk, and wolves. While there are no wild wolves or elk native to Indiana anymore, but for hunting long ago they would still roam the surrounding hills. Maybe they’ll be back some day.”
You can read more about his work at Motionkicker.com
Take the keystone away from an arch and down will tumble the whole structure. Take a keystone species away and — so the concept goes — other species will go extinct too. In his excellent recent feature for Nature, Ed Yong explains how biologist Bob Paine came up with the concept while he studied starfish in the 1960s.
Paine’s keystone species concept “would go on to be applied to species from sea otters to wolves, grey whales and spotted bass” and — a group Ed missed from the list — wild fig trees, whose huge crops are available year-round and keep more animals alive than any other species.
For this reason, Ed’s article brought a blush to my cheeks. As I read it I recalled the time a journalist falsely quoted me, to suggest that I “came up with the idea of figs being a keystone”. Sixteen years later those words still make me wince, for they made it seem I had stolen another scientist’s idea. In fact it was Professor John Terborgh, then of Princeton University, who had been the first biologist to apply Paine’s keystone concept to fig trees.
The journalist had interviewed me in 1997 for The Reporter, a newsletter for staff and postgraduate students at the University of Leeds, because I had won a prize in the Daily Telegraph Young Science Writers competition with an article about fig trees. While I am certain Professors Terborgh and Paine never saw the piece, I remember well the horror I felt when I read the words the journalist had put into my mouth. The experience would guide me well in my own journalism years later.
Now, thanks to the memories Ed’s article has triggered, I’d like to set the record straight and also publicise a vast dataset that nearly got lost and which explains why figs are so special. I can trace its origins back through the work of both John Terborgh and Bob Paine.
Here too is the story I wrote that got The Reporter‘s journalist all worked up. Please forgive its naivety and clunky construction — it was my first ever attempt to write about science for a non-technical audience and it is clear to me today that I was still writing then as a scientist.
Some months later, on 18 February 1998, The Daily Telegraph published it with the title ‘Answering the distress call’. I prefer the title I submitted at the time — the one I have used for this blog post.
Figs: A job for conservation’s keystone cops
It is a myth that in tropical forests the bounty of nature’s larder is available year round to support fruit-eating animals. In reality, they may experience alternating episodes of feast and famine, with fig-eating potentially meaning the difference between life and death.
Many tropical fruit-bearing plants share seasonal fruiting patterns, with one or two peaks of ripening at the same time each year. Fig trees, though, can fruit at any time and, so, many sustain fruit-eaters through lean times. As well as providing for the vertebrates, figs may ensure the survival of more rarely fruiting species by maintaining animals which disperse their seeds. By attracting seed dispersing animals, figs may also be instrumental in the recolonisation of deforested areas, or volcanic islands.
Ecologists have described figs as keystone resources in tropical forests. Just as the removal of a keystone of an arch is quickly followed by its collapse, the loss of ecologically important keystone species may trigger a cascade of local extinction.
With more than 800 diverse species, fig plants exhibit great variety — including trees, climbers, shrubs, bushes, epiphytes and tree-stranglers. More so than any other wild tropical fruit, figs provide a large dietary contribution for a veritable Noah’s Ark of animal species. With varying colour, design and position, figs attract different types of vertebrates. The weird and wonderful mix of fig-eaters includes: fish, lizards, giant tortoises, birds, fruit bats, monkeys, rodents, bearded pigs, spectacled bears and the oddly-named olingos, kinkajous and binturongs.
Year-round fruiting is good news for the fruit-eaters, especially as fig trees produce superabundant crops (up to one million figs) and have only short intervals between fruiting episodes. The best documented of fruit shortages is the 1970-71 famine on Barro Colorado Island (BCI), Panama, where in the eight months from July 1970, fewer than 50 per cent of potentially productive plant species bore fruit. Intense hunger stress among fruit-eaters resulted in so many deaths that vultures could not cope with the supply of corpses. Starvation declined suddenly when figs came to the rescue — with peak fruiting in January and February 1971.
More recent research has identified a possible keystone role of figs in Peninsular Malaysia, Borneo and Peru’s Amazon basin where Princeton University’s John Terborgh suggests that loss of figs could lead to ecosystem’s collapse. However, at other sites in Gabon and India figs are apparently less important — being present at low densities and feeding only a small proportion of fruit-eaters. The importance of fig species evidently varies (to misquote George Orwell, “some figs are more equal than others”) either due to their distribution, density and crop size, or as a consequence of animals’ abilities to locate and utilise the fig resource.
Ecologists need to act as “keystone cops” to identify which fig species are disproportionately important in tropical forests with rollercoaster fruit economies. This requires exhaustive fieldwork, encompassing studies of fruiting patterns of figs and other species and behavioural studies of fruit-eating animals.
In Shakespeare’s Antony and Cleopatra, one of the queen’s attendants declares, “I loved long life better than figs.” Tropical fruit-eaters may be able to enjoy both, living longer through their love of figs. If some fig species are show to have keystone importance, their protection may be vital to tropical animal communities. This conservation goal is not too far out of reach as to be unrealistic.
In re-typing these words, I’m pleased to note how much I would write it differently today. I’m amazed too that I managed to wrote about figs being important to wildlife without mentioning the fig-wasps that are the reason for that — see The humbling history of the tiny wasps that upset a Jurassic Park narrative.
The article I wrote back in 1997 won me subscriptions to Nature and New Scientist. Later on it helped me secure funding for a PhD and get my first two jobs outside of academia. It was a real keystone in my career.
Like so many of the researchers Ed Yong highlighed in his Nature piece, I owe some words of thanks to Bob Paine, the man whose starfish throwing days set so many biological balls rolling. As Ed notes in his blog Paine is a keystone too.