By Robin Pomeroy
TEMPIO PAUSANIA, Sardinia, Aug 6 (Reuters) - If you buy a bottle of wine with a metal screw-top or a plastic cork, you won't just be thumbing your nose at tradition. You may also be dooming the world's cork forests.
That is the view of environmentalists and cork producers who have joined forces to protect cork oaks -- and the unique habitat they provide -- from competition in the wine trade.
Alternative 'corks' are ever more common, as synthetic and aluminium wine closures have grabbed a 20 percent share of the market, up from just 2 percent in 2000, according to wine industry consultant Stephane Rein of Rein Consulting. He says that could increase to 35 percent by the end of the decade.
"Silicone corks are not a problem for quality wines, they'll always use cork," said Battista Giannottu, an agronomist who works with a consortium representing Sardinia's cork producers.
"But the mass market, which is 80 percent of the total, might (use synthetic corks). That's not just an economic problem but an environmental one."
The quercus suber, or cork oak, which grows on both the European and African sides of the Mediterranean, provides the raw material for practically all the 20 billion wine corks used every year.
The way cork is harvested -- shaved off the sides of trees like the way a sheep is shorn -- means forests continue to thrive as they give up their valuable bark.
In Sardinia, the only region in Italy that produces cork, the forests are a haven for wild boar, a species of hawk native to the island and Sardinian deer.
The highly endangered Iberian lynx roams the cork forests of Spain and Portugal, the global leader in cork production; in North Africa the forests provide a habitat for Barbary deer.
"Only experts can tell when it's ready," said Saverio Bacio, overseeing the harvest at a Sardinian government-owned forest.
His woodsmen work quickly, hacking at the bark before the summer heat causes the sap to glue it to the trees' sensitive inner core which, if left intact, will produce another thick layer of cork.
"You can tell if the weather, the temperature, is right for the bark to come away without bringing part of the core with it. It varies day by day, hour by hour."
A cork oak must be at least 30 years old before the first harvest and, even then, the gnarled, porous 'virgin cork' is not good enough to make wine closures. It will take another 10 years for the bark to grow back and be good enough to make corks.
That means a poor rate of return compared with other trees which might be planted in such areas, such as the fast-growing eucalyptus which competes with cork oaks for land.
"It isn't a tree which gives a lot of one thing -- it gives a little of a lot of things," said Nora Berrahmouni of WWF, an environmental group working to protect cork forest habitats.
The undergrowth is a patchwork of fragrant shrubs, including ones that produce the myrtle, a berry gathered to make Sardinia's liqueur Mirto -- an extra source of forest income.
LIKE A PIG
At the Molinas factory in Calangianus, a town that has thrived on the cork business, piles of harvested bark mature in the yard for the necessary year which allows its pores to close.
After that it is boiled in vats to make it more elastic and squeezed flat by giant steel presses. Once checked for the absence of fungus, it is cut into the shape of closures.
The natural terracotta colour of the cork is bleached to a 'cleaner' off-white demanded by most wineries.
"We say cork is like a pig, nothing is thrown away," said Michele Addis, quality control manager, straining his voice above the rumble of machinery.
More than 80 percent of the world's cork production is used for bottle closures. The rest is used for building materials and in items like fishing tackle and badminton shuttlecocks.
The best quality cork -- which is the least porous and has no cracks or flaws -- makes the best grade of stopper sold at a premium for wines made to be matured in the bottle.
Lower grades are used for cheaper wines: cork granules are agglomerated with a type of glue to make the dense champagne corks that must withstand the pressure of sparkling wine. Offcuts are glued to plastic discs to make the type of stoppers found in some sherry bottles.
As well as being cheaper alternatives, plastic and metal do not pose the same risk of "corking" the wine -- when a chemical called TCA is present in the stopper and gives the wine a "mouldy" odour.
But cork producers and environmentalists are fighting back. Aiming to cash in on the demand for 'green' products, they have started to produce corks certified 'environmentally friendly' under the Forest Stewardship Council (FSC) scheme, an 'eco-label' system already widespread for timber products.
Backers of the FSC scheme hope 'green' wine buyers will prefer a bottle with the FSC label. Cork makers hope it can guarantee their future by differentiating their traditional product from the upstarts.
"This could be a niche," said agronomist Giannottu. "Plastic and aluminium closures cannot compete against it."