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 production of cork
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.
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.
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.
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.