With over one-third of this country’s area covered with cork forests, it’s this little thing that holds the most value for Portugal’s economy.

Cork has long been a national treasure to an industry that employs some 20,000 people. But the emergence of metal screw-tops and plastic plugs is posing a threat to natural cork stoppers.

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As the global wine industry grew, consumers complained that cork producers had cut corners to meet the rising demand. Natural cork sometimes crumbled, or became tainted with a musty odor, spoiling the wine it was supposed to protect. So wine growers resorted to alternatives.

But Amorim, the world’s largest cork producer, says it’s cleaned up its act and has changed with the times.

“We now have an industry that's invested more in the last 10 to 15 years than in all the years before in terms of technology, but also in terms of mentality,” said Joana from Amorim Cork.

“There was a big change in thinking in how to approach things, especially in the closures industry. So there was a need to change and adapt to create a proximity with the supermarkets, with wine growers and everyone in the chain”.

Cork forests under threat – environmentalists

No trees are cut down to make cork. Instead, the spongy bark is stripped every nine years at harvest time. And with each harvest the average tree produces enough cork for 4,000 wine bottles.

However, if the trend for man-made bottle stoppers continues, the World Wildlife Fund estimates that up to three-quarters of the Mediterranean’s cork forests could be lost within ten years. These forests are home to some of Europe’s rarest wildlife.

Right now, environmentalists see the cork industry as an all-too-rare example of economics and ecology working in harmony.

“If you actually have an industry that supports an ecosystem where we have species of rare eagles, for instance, you have a way to protect this ecosystem,” explained Fransisco from Quercus Environmental.org. “If industry needs these materials, then it's involved in the whole process of maintaining that ecosystem”.

Environmental groups say plastic bottle stoppers are responsible for ten times more carbon emissions than their natural cork rivals, while metal screw caps produce 24 times more CO2.

So cork is good for the environment, the ecology and the economics of Portugal. And producers are pulling out all the stops to save the humble cork from extinction.