Cork Trees in Jeopardy

With great interest, I read your well-researched article on cork flooring in the January/February issue (Vol. 5, No. 1). As you concluded in the article, the harvest of commercial cork from the cork oak (

Quercus suber) tree is a relatively benign extraction that is one of nature’s best examples of a renewable, non-timber forest resource whose stewardship stretches back millennia.

As you mentioned in the article, the longevity and health of the oak is related to its thick, suberous bark which provides protection from droughts, fires, insects and disease. However, even this thick, protective bark could not prevent it from becoming the latest species to fall prey to one of the world’s most lethal plant diseases, the soil-dwelling fungus

Phytophthora cinnamomi (“cinnamomi” because it was originally isolated from the cinnamon tree on the island of Sumatra). The Fall 1994 issue of

Nature first reported that cork oaks are dying in the heart of their range.

P. cinnamomi attacks conifers, hardwoods and orchard trees—such as apricots, almonds and walnuts—characteristic of Mediterranean climates. In addition to causing root rot and death in many woody species and ornamentals, it was responsible for causing the devastating decline and dieback of

Eucalyptus marginata (jarrah) in western Australia. A related species,

P. lateralis, causes mortality of Port-Orford cedar on the Pacific Northwest coast of North America.

According to

Nature, the introduced fungus has spread so extensively there is little or no hope of stopping it with fungicides. Equipment used to remove the roots, such as bulldozer blades and tracks, is notorious for spreading the disease. Scientists are trying to breed resistant varieties but, unlike grape vines, this recovery will take decades or longer. The article further implicated global warming as a potential factor accelerating expansion worldwide because it spreads more rapidly through warmer soils.

How does this impact the use of cork products and sustainability of cork oak? According to the article, cork oaks throughout the range from Portugal to Spain to Morocco and Italy are being affected. If it is a rangewide decline, in which mortality exceeds re-establishment and growth, then it could signal the end of commercial cork production. However, this is unlikely because quarantine and control measures may slow down the rate of spread. Secondly, trees stressed from root rot probably should not be stripped for cork bark because this would cause an additional stress and may weaken the tree to the point of predisposing it to attack by insects or other fungal pathogens. Depending on recommended sanitation and salvage techniques, infected trees in disease-impact pockets may have to be removed to prevent the spread of the soil-borne fungus. The bark of dying trees or trees already in the spiral of decline could be harvested when the trees are cut for lumber or firewood.

Cork arboriculture has been in practice since the Roman legions came to Iberia. The cork orchards of “forests” are a prominent landscape feature in all the western Mediterranean countries, particularly Portugal. Loss of the cork oak will affect not only an age-old resource and tradition but forever alter the ancient landscapes of the region.

Yurij Bihun, Executive Director

Good Wood Alliance

Burlington, VT