It was only when I moved to England that I realised wine bottles could have plastic stoppers or aluminium screw caps. Back in Portugal cork was always the natural choice.
The reason for the widespread use of cork stoppers in Portugal may be historic or economic, as the country produces over 50% of the cork harvested annually in the world. However, these days the preference for cork is also connected to sustainability, low carbon cost and biodiversity protection. Cork is a natural substance with amazing properties (buoyancy, elasticity and impermeability, to name a few) that make it ideal for use in wine bottles. It comes from the bark of cork oak trees which is sustainably extracted every nine years, the length of time required for the bare trunks to renew themselves after harvesting. The cork oak trees, endemic to the western Mediterranean, naturally sequester atmospheric carbon and can live for more than two centuries. It is therefore not hard to believe that the carbon cost associated to the production of cork stoppers is significantly lower than that linked to screw caps or plastic stoppers. But there is more to add to the list of environmental benefits of cork. As emphasised by WWF, choosing cork helps preserve the rich biodiversity of the western Mediterranean and reduces the risk of fire and desertification.
There is much environmental science (and more) to discuss over a glass of wine at your next dinner party. Just make sure the bottle has a cork stopper!