Image caption Kava is a popular drink across the South Pacific

It's a typically humid afternoon in Port Vila, the capital of Vanuatu, an island nation scattered across hundreds of miles of Pacific ocean.

The cicadas are loud, the mosquitoes are in search of a bite, and in a makeshift bar, a Ni-Vanuatu woman scoops muddy liquid into a small plastic bowl. The liquid in question is kava, which is a mixture of water and the crushed root of the kava plant.

"You have to drink it all in one go..... your mouth and tongue will start to go numb," explains Dr Vincent Lebot, a world-leading kava expert. Originally from France, he's lived in Vanuatu for decades. We ask what else will happen. "Not much," he chuckles.

There's a light above the bar's front gate, telling customers there's kava in the house. When the day's limited supply has run out, the light will be switched off.

The bar, or nakamal, is called Last Flight - thanks to its location behind the country's main airport. It's popular with workmen in overalls and heavy boots and has the atmosphere of a very quiet beer garden.

But there is no alcohol for sale here, just kava. Drinkers down it in one, sometimes swishing their mouths out with water to help cleanse the taste, and then they spit. Proponents say the drink reduces anxiety, helps with sleep, and can even leave users feeling mildly euphoric. Critics say it is dangerous, and it is banned in the European Union.

Image copyright Chris Morgan/ BBC Image caption Dr Vincent Lebot works for Vanuatu's agriculture ministry

"Kava is a very sacred drink across the Pacific," explains Dr Lebot. In Vanuatu, it was traditionally taken by chiefs at gatherings, during discussions of local affairs. It would be drunk out of a coconut shell. "Chiefs would drink it so they could communicate with their ancestors," he says.

But recently, its use has been democratised. Most families in Vanuatu are familiar with kava and grow it outside their homes. While it was once forbidden for women to drink it, today in the capital Port Vila, it's becoming more common, though some women in rural areas still steer clear.

Dr Lebot is hoping that the unusual tasting, sour, clay-coloured liquid might have global appeal, and could provide Vanuatu with a much needed revenue stream.

Kava exports have been tried before, but it didn't end as planned. Dr Lebot explains that kava is now restricted or banned in most EU countries, after extracts became briefly popular in supplement form, but were declared unsafe. Dr Lebot insists that when prepared properly, when the dried root is ground up into a paste and mixed with liquid, it is "perfectly safe".

He points to the kava bars that have recently popped up in some of New York's hippest neighbourhoods. So could it really have global appeal?

One of the issues facing Vanuatu, in its desire to professionalise the kava industry, is that farming of the plant is done on an ad-hoc basis.

Image copyright Chris Morgan/BBC Image caption Kava root is processed by hand by lots of independent growers

Dan McGarry, a Canadian who runs the local newspaper - and a kava fan - explains that in Pentecost Island, where much of the supply is grown, people have "little more than machetes" to cultivate the plant. He says that following a recent cyclone in neighbouring Fiji, demand for Vanuatu's supply has gone up and kava prices have increased.

"The popularity of kava has had quite the impact on the rural economies here," he says. "You have situations where locals are chartering planes to bring it down to Port Vila. You have people going to car dealerships with bundles of cash and buying brand new trucks."

But Mr McGarry says that this has also led to some intimidation and "cartel-like behaviour" as larger growers try to control the price.

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Anne Pakoa, a community leader in Vanuatu also has concerns. "You have situations where kava is destroying families. Women are drinking it too, and some of the kava bars have become hubs for prostitution. It causes lethargy, dry skin, and when people drink too much they can lose the use of their limbs while under the influence."

Ms Pakoa says that there are even instances where families have left children unattended to go and drink kava, and the family home has caught fire. "Kava causes problems now. Its use has gone from ceremonial to daily", she says.

With recent moves from the Australian government to loosen import restrictions on kava, many Vanuatu farms have started to ramp up production.

Image copyright Chris Morgan/BBC Image caption Nicole Paraliyu runs a kava farm, but says she has never tried the drink

Nicole Paraliyu shows us around the farm she manages, a large patch of reclaimed land, surrounded by dense rainforest. The farm used to produce mainly sandalwood, but has recently started growing a kava crop, too. Ms Paraliyu says farms like this have the potential to provide much needed income for the local population.

"People could stay on the islands rather than leaving to search for work overseas," she says.

We shelter from a tropical rainstorm near the farm's kava storeroom, packed with drying roots. There's a powerful smell, like an intense, musty ginger.

So, has she ever tried kava? "No, not once," she says, laughing.

Back at Dr Vincent's laboratory in the Ministry for Agriculture, he shows us rows of potions and extracts, and talks of the potential to harness some of the perceived anti-anxiety effects of the plant, and even the aspects which suppress appetites. The idea is to sell the crushed root as a powder that can be mixed with water and strained to make a drink.

Image caption Dr Vincent studies the various types of kava

"It's unfair that it is illegal in some parts of the world," he says. "Vanuatu can produce good kava, and it can be important for us. It's misunderstood."

Back at Last Flight Dan McGarry agrees. "It's hard to argue with the transformational impact it has had on the rural island economies. It can only really be regarded as a positive thing."