Cork is the bark of the cork oak tree. The tree grows a thick layer of bark to protect itself from sun and small fires. Once every nine years, skilled workers carefully peel the outer bark off in big sheets, using a special axe. The tree is not harmed. Underneath, the trunk is bright red. Over the next nine years, the bark slowly grows back, ready to be peeled again.
A cork oak can live for 250 years. Most trees are peeled for the first time when they are about 25 years old. So one tree might give cork around 16 to 20 times in its lifetime, with nine years between each harvest. The workers paint the year on the trunk so they know when to come back.
Portugal has huge cork oak forests called montados, mostly in the south. Because the trees are never cut down, these forests are full of birds and animals. The very rare Iberian lynx, golden eagles, storks and wild boar all live in the montados.
Cork is amazing stuff. It is light, waterproof, fireproof and bouncy. It is also natural and grows back. Today, Portuguese scientists are using cork to make insoles for shoes, parts of space rockets, surfboards and even fabric for handbags. One renewable bark that does all of that.