A really good article about cork and its impact on the environment in Food & Beverage International:

Cork trees can only be harvested every ten years, so to wind through miles of cork forests with the rustic orange shades of bare bark accenting the hues of the 100+ year old trees, means they have been just harvested. The white painted numbers on the bark indicates what year the tree was harvested. If you see the number 6 painted on the bark, that means it was harvested in 06 and should not be harvested again until 10 years later. The very fact of driving through miles of cork forest, with every tree having a number on it creates a feeling of confidence that the people of Portugal and the Iberian Peninsula use an ancient common sense to preserve and sustain their living off of the land.

I know cork gets a bad rap in some circles because corked bottles are more likely to have "corked" wine than screw top or plastic cork bottles. But, there is something satisfying about a cork. Not just the sound it makes being extracted from the bottle, but the connection with the earth, something that is such an important part of wine.