Cork Oak (Quercus suber)
Growing to heights of 65 feet (20 meters), cork oak is a unique and valuable tree species. Unlike many other oak trees, cork oak is an evergreen and does not drop its leaves. The thick and knobbly dark grey bark which covers it is the portion known as “cork.”
During cork harvest, the tree remains standing while large sections of its outer bark -- the cork itself -- are cut and peeled from the tree. Cork oak is unique in its ability to regenerate its outer bark. After a tree reaches 25 years of age, it can be stripped of its cork once every 9 to 12 years without causing damage to the tree. A single cork oak, which lives up to 200 years, can be harvested over 16 times.
Cork oak is found through southwestern Europe and into northwestern Africa in Portugal, Spain, France, Italy, Algeria, Morocco and Tunisia. Portugal, which is home to the largest collection of cork oak trees, is also the world leader in cork production. Cork oaks are found in forest mosaics alongside other tree species, including a variety of other oaks, stone and maritime pines, and even wild olive trees. These lands are home to a great diversity of species. Plant diversity is higher here than in many other forest regions of the world, with almost 135 different plant species per square kilometer. The diversity extends to animal life, including some critically endangered species such as the Iberian lynx, Barbary deer and Iberian imperial eagle.
The cork oak faces many threats such as fire, deforestation, agricultural expansion, disease and climate change. Another threat: increased demand for alternative wine stoppers. As the market for cork decreases, fewer cork oak landscapes will be conserved and the species will be placed at greater risk.
Significance to Humans:
When forests are managed properly, cork oak can provide a sustainable and renewable timber product. Cork is primarily used as a stopper for wine bottles, but also functions as a closure for olive oil and other products. In addition, it’s used to create flooring, furniture and even footwear. Though it is lightweight and elastic, cork remains impermeable to gases and liquids -- the reason it has remained a popular liquid stopper since the times of Ancient Greece.
Cork oak also provides its ecosystem with several benefits. The trees help prevent soil erosion from wind and water, and increase the absorption rate of rainfall. The cork oak forests of the Mediterranean act as a barrier to the advancing process of desertification from North Africa. Furthermore, a harvested cork oak tree stores up to five times more carbon than an unharvested tree, since the tree utilizes additional carbon in the regeneration of its bark. Each year, cork oak forests account for 10 million tons of CO2 absoption.
Did You Know?
The Rainforest Alliance is working with cork producers throughout Spain and Portugal to help them achieve Forest Stewardship Council (FSC) certification. By meeting the comprehensive social and environmental standards required to achieve FSC certification, cork producers in the region are able to ensure the continued protection of their cork oak forests and provide for the families that depend on the cork harvest.
- The World Wildlife Fund: http://mediterranean.panda.org/about/forests/cork/
- The World Wildlife Fund: http://wwf.panda.org/what_we_do/endangered_species/cork_oak/
- Kew Royal Botanic Gardens: http://apps.kew.org/trees/?page_id=94
- Inset photo by Willamette Valley Vineyards