Brilliant birds and the mystery of the mutating mangroves

twopics

As dusk falls in the Caroni Swamp on the west coast of Trinidad, hundreds of scarlet ibises fly in from their feeding grounds to roost in the mangrove trees that grow in the dark, brackish water. The birds settle in the trees like glowing embers.

For generations, local people hunted these birds for their meat and used their feathers for Carnival costumes. By the 1860s, colonial records warned that “a fierce war” had been waged on the ibis, and that it would soon be rare. Yet it is thanks to a hunter that the bird has a haven today.

In the 1930s, Simon Nanan started guiding fishermen and duck hunters into the maze of waterways in the Caroni Swamp – some 6000 hectares of marshes, mudflats and mangrove forest. Many of Nanan’s clients marvelled at the scarlet ibis, so he began offering tours to see the birds and these proved more popular than his hunting trips. And so, ecotourism in Trinidad was born.

In time, Nanan convinced the colonial authorities to create a sanctuary to protect the scarlet ibis. The bird now shares its umbrella of security with a rich variety of wildlife that includes silky anteaters, crab-eating raccoons, spectacled caimans and nearly 200 bird species. The Caroni Swamp also provides key services to local people. It protects the coastline from storm surges, provides a nursery for fish and shellfish, and supports a thriving tourism industry.

When Trinidad gained its independence in 1962, it made the scarlet ibis its national bird and banned hunting of the species. But old habits die hard and poaching has continued to the present day. Serving and eating the bird has apparently become a status symbol. In response, the government this week increased protection for the species.

Anyone caught harming, trading or possessing the species now faces a fine of 100,000 Trinidad and Tobago dollars (about US$15,000) and two years in prison. The penalties apply to possession of even a single feather. What few people realise is that those scarlet feathers have another story to tell.

In the late 1990s, researchers noticed harmful genetic mutations in mangrove trees in areas where the ibises roosted. They showed that the sediments beneath the trees had abnormally high levels of mercury, as did the feathers of the scarlet ibises — unlike those of some other birds in the swamp.

The researchers noted that, unlike the other birds, the scarlet ibises travelled to wetlands in Venezuela each year, where they fed on crustaceans and other animals. They concluded that mercury used by gold miners far inland had entered the country’s rivers and made its way into the food chain. Feeding on contaminated animals is what led the mercury to build up in the bodies of the scarlet ibises, they surmised.

Back in Trinidad, moulted feathers accumulating around the roost over decades appear to have polluted the sediments and resulted in the genetic mutations in the mangrove trees. This 20-year old scientific detective story takes on new relevance given the massive increase in mining and illegal use of mercury underway in Venezuela.

If Trinidad’s new penalties do not deter poachers and consumers of ibis meat, perhaps the risk of exposure to mercury will.

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Reference: Klekowski, E.J. et al. 1999. An association of mangrove mutation, scarlet ibis, and mercury contamination in Trinidad, West Indies. Environmental Pollution 105: 185-189. https://doi.org/10.1016/S0269-7491(99)00028-7

Photo credits: Bottom — Top left — Charles J Sharp / Wikimedia Commons; Top right — Fernando Flores / Creative Commons; Aaron Maizlish / Creative Commons

Sit down, chase some coral, then get up and act

Gulf_of_Eilat_(Red_Sea)_coral_reefs

If you’ve not yet seen the award-winning documentary Chasing Coral, I urge you to watch it as soon as you can. It is a powerful illustration of what we are doing to the planet and why we need to wake up and act. It is inspiring, illuminating and even funny in places.

Coral reefs sustain a quarter of all marine life and directly support the livelihoods of more than half a billion people. They are a source of medicines, such as cancer drug prostaglandin. And they protect coastal communities from storms because the skeletons they form create a living breakwater that constantly grows and rebuilds itself.

But corals are in big trouble. The biggest threat they face come from global warming. That’s because the oceans absorb most of the heat our greenhouse gas emissions are trapping in the atmosphere. As the seas warm, the corals eject the tiny plant cells that live within their tissues. Without the plant cells, the corals turn white — they ‘bleach’ — and then they die.

Chasing Coral follows a team on a quest to record the first ever footage of this process unfolding in real time. There’s a poignant moment in the film when team member Zack Rago is scuba diving on Australia’s Great Barrier Reef. He turns to the camera to show a note he has written with his underwater pen. It reads: “This is the hardest dive I’ve ever had to do.”

Rago, a self-identifying ‘coral nerd’, was stung by the effect of going into the sea each day for a month and seeing corals die from one day to the next, of seeing “flesh, living tissue, rotting away”. He was filming in 2016, the year in which 29 percent of the corals on the reef died. The following year another 22 percent perished.

Coral bleaching is now a worldwide phenomenon. At current rates of global warming, all of the world’s corals will be gone in 30 years, or as Ove Hoegh-Guldberg, Director of the Global Change Institute at the University of Queensland, puts it: “In our lifetime, on our watch”.

The film also follows Rago as he meets his childhood hero, Australian coral expert John ‘Charlie’ Veron, who has been diving on the Great Barrier Reef for 45 years. Veron tells Rago to never quit raising awareness of the threats to corals. “You have to keep at it,” he says. “Otherwise you’re not going to like yourself when you’re an old man. You’re going to like yourself much more if you can say, well, I sure tried to turn that around.”

I feel the same. I’ve been talking and writing about the damage we are doing to the planet for a long time now and I’m not going to stop. But sometimes it feels like nobody is listening, that everyone thinks someone else is going to solve these problems for them.

After the screening of Chasing Coral I saw yesterday, host Anjani Ganase of Wild Tobago and the Global Change Institute pointed out that people often ask what individuals can to do change anything. That’s the wrong way of thinking about it, she said. It is when we are vocal, when we come together that we can build a better future. “There’s no individual in this game,” she said. We are all in this together.

If you have Netflix you can watch Chasing Coral now. If not, you can get a free licence for a public screening.

Photo credit: Daviddarom / Wikimedia Commons

Scientists reveal yet another reason fig trees are titans of biodiversity

insectivores

Biologist David Mackay got a surprise when he began studying the birds visiting fig trees in his native Australia: While he expected to see plenty of species coming to eat the figs, he didn’t expect the insect eaters to outnumber them two-to-one.

Mackay already knew that figs feed more bird species than any other fruit. His research, published in June, would show that fig trees are disproportionately important for insect-eaters too. It adds to growing evidence that fig trees are titans of biodiversity with important roles to play in conservation.

What makes fig trees so crucial is their ancient relationship with tiny wasps. The trees depend on the wasps to pollinate their flowers, while the wasps can only breed and lay eggs inside their partner’s figs. Thanks to this partnership, figs are available year-round and have been called ‘keystone’ resources for fruit eaters. Mackay’s study is the first to show that fig-wasps emerging from figs before they ripen are also valuable year-round resources for a diverse variety of insect-eating birds.

Altogether, Mackay recorded 55 bird species visiting Ficus rubiginosa fig trees to feed on insects. They included ten species — such as the superb fairy-wren and the shining bronze-cuckoo —whose recent declines in numbers have concerned conservationists. Mackay and his colleagues say fig trees are “very likely” to be similarly important to insect-eating birds throughout tropical, subtropical, and temperate regions globally.

To support this view, Mackay points out that in just his study and two others in localised areas of India and Costa Rica, researchers have already identified more than a hundred insect-eating birds visiting fig trees. “The presence of avian insectivores in figs in these three continents strongly suggests their occurrence in figs is ubiquitous,” he says.

“I can hazard a wild guess that there are at least several hundred species of insectivorous birds that forage in fig trees worldwide,” Mackay told me. “This has important implications for the conservation of insectivores, many of which have suffered and continue to suffer declines in response to habitat loss and fragmentation.”

As Mackay points out, the number of fig-wasps emerging from figs on a single Ficus rubiginosa tree in just a few weeks could approach ten million. He adds that insect-eating bats would also relish fig-wasps, many of which fly at night. His study adds to a growing body of evidence that fig trees are centrepieces of vast food webs that include tens of thousands of species.

“I suspect fig trees could play an important role in conservation of declining insectivores as well as contributing to the conservation of other species in the wider communities they inhabit, including frugivores and the other plants that depend on them for seed dispersal,” Mackay said.

Increasingly, researchers and conservationists are turning to fig trees to boost rainforest regeneration by attracting seed-dispersers. Mackay said that using fig trees could also slow or even reverse declines of insect-eating birds: “If we don’t do these restoration projects with figs then we stand a chance of losing these birds altogether.”

This post was first published by Mongabay.com on 6 July 2018 and is reproduced here under a Creative Commons licence.

Read more about the ecological and cultural importance of fig trees in my book, published in the UK as Ladders to Heaven and in North America as Gods, Wasps and Stranglers.

Reference

Mackay, K.D., Gross, C.L. & Rossetto, M. 2018. Small populations of fig trees offer a keystone food resource and conservation benefits for declining insectivorous birds. Global Ecology and Conservation. Published online on 20 June 2018. https://doi.org/10.1016/j.gecco.2018.e00403

Photo credits

Left to right —  Superb fairy wren (Malurus cyaneus): Patrick_K59 / Wikimedia Commons; Eastern yellow robin (Eopsaltria australis): Graham Winterflood / Wikimedia Commons; Eastern spinebill (Acanthorhynchus tenuirostris): DavidFrancis34 / Wikimedia Commons

Religion + fig trees = a boost for biodiversity

Hanuman-temple-and-fig-tree-Ficus-religiosa-in-Bangalore-Anoop-Negi

A sacred fig tree at a Hindu temple in Bengaluru (Bangalore) – credit Anoop Negi

When Tarsh Thekaekara and Shruti Agarwal spotted a lone fig tree in sea of tea bushes in southern India, they knew it had to be special. The researchers were documenting sacred groves in tea plantations to see if they helped conserve wild species. They learned that the fig tree was all that remained of a grove consecrated by local Paniya people who, for generations, had convinced tea estate managers not to fell the tree.

As in many other countries, fig trees have been sacred species in India for thousands of years. Wherever they grow, figs are also key resources for wildlife. Thanks to their curious biology, they feed more bird and mammal species globally than any other fruit and so sustain the seed dispersers of thousands of other plant species. In India, and in many other countries, fig trees could play key roles in protecting biodiversity and regenerating lost forests — but policies to protect these trees are rare.

Writing in the Indian Express, Thekaekara and Agarwal tell how they returned to the lone fig tree and set up camera traps to find out what wildlife visited. They soon recorded monkeys, many bird species, civets and a species of flying squirrel. “As the figs ripened and fell to the ground, the place really came alive,” they write. “Porcupine, wild boar, barking deer, sambhar deer, bear and, even, an elephant! A leopard also walked by, probably feeling like she was missing the party, and to try to dine on a couple of fig-eaters!”

Thekaekara and Agarwal highlight the important ecological role the tree plays in a landscape dominated by tea bushes. “The irony is that even with this knowledge, there is no official protection for the tree,” they write, “and it could legally be cut if the correct permissions are sought.” They note that, across their study area, many sacred groves had been reduced to just a solitary tree — most commonly a fig tree.

In India’s urban areas too, the loss of wildlife-friendly trees is elevating the importance of surviving fig trees. In a new study, Harini Nagendra and colleagues documented 5504 trees at religious sites— 62 temples, churches and Hindu, Christian and Muslim cemeteries — in Bengaluru (Bangalore).

Compared with trees in the city’s parks and streets, the trees at religious sites were far more likely to be native species, which offer more to local biodiversity. As in the tea plantation, fig trees (Ficus species) are disproportionately important in urban areas as they feed so many birds and mammals, and at least one fig species was present at 71% of the religious sites the researchers surveyed.

“Fig trees play a critical role in supporting Bangalore’s threatened biodiversity,” says Nagendra. “Bangalore’s tree cover is extremely fragmented, and Ficus trees act as keystone species, improving canopy-to-canopy connectivity and supporting a wide range of species, including birds, butterflies, bees, bats, macaques, and even the endangered slender loris.”

The researchers found 286 individuals of just one fig species — the banyan, Ficus benghalensis — at the religious sites, where it was the fourth most common tree species. But in the city’s streets and parks, all species of fig trees were relatively rare. None ranked in the top ten species the researchers counted there. Nagendra and colleagues says the large numbers of Ficus trees in sacred sites “demonstrate a strong potential” for urban conservation.

“Unfortunately, there is no policy to promote the planting or fig trees, or to conserve them,” Nagendra told me. “Many Ficus trees in Bangalore are heritage trees, decades and even centuries old. Yet many are now under threat, their branches pruned, the bases concreted, or are cut down for road expansion projects.”

In fields and cities in India and all across the tropics, fig trees play key roles in sustaining wildlife. The ecological importance of these trees results from their 80-million-year old relationship with their pollinator wasps, and it helps explain why fig trees have become embedded in religions in many countries.

Over millennia, diverse cultures have protected fig trees but few societies today value them in the same way. Yet, with the right policies in place, these trees could help us to address 21st century challenges — from conserving biodiversity to restoring forest cover.

Tarsh Thekaekara is a biodiversity conservation researcher with The Shola Trust. Shruti Agarwal worked with The Shola Trust before joining the Centre for Science and Environment in Delhi. Harini Nagendra is a professor of sustainability at Azim Premji University, Bengaluru.

Related posts

The majesty and mystery of India’s sacred banyan trees

Why one fig tree in the middle of nowhere has a 24-hour armed guard

Fresh evidence of the power of fig trees to sustain wildlife and restore lost forests

Photo credit

A fig tree (Ficus religiosa) alongside a Hindu temple dedicated to the monkey god Hanuman in Bengaluru (Bangalore) — Anoop Negi (reproduced with permission). See Anoop Negi’s website for more images.

References

Jaganmohan, M. et al. 2018. Biodiversity in sacred urban spaces of Bengaluru, India. Urban Forestry & Urban Greening 32: 64-70. [Read online]

Thekaekara, T. & Agarwal, S. 2018. The Ficus in the Tea: The fight for the lonely atti maram (fig tree). The Indian Express. 22 April 2018. [Read online]

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