Every time we weigh up which bottle of wine to buy, we hold the fate of nightingales, rare black storks, secretive wild cats and one of the world's most remarkable trees in our hands. It has all to do with the stopper. If it is cork, it probably came from the bark of one of the ancient cork oak trees from the Montados, in the Alentejo region of Portugal. The cork oak is the only tree in the world whose bark can be periodically removed without killing it. But this tree is amazing in other ways. It survives in poor soil and searing heat, and provides not only nesting places for booted eagles but also space for some of Europe's rarest wildflowers.