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Cork and the cork oak system

M.C. Varela

Maria Carolina Varela is with the National Forest Research Station, Oeiras, Portugal.

An evaluation of the role and potential of cork oak (Quercus suber) and its products in the Mediterranean region, including consideration of a proposal to develop an identifiable imprint for products made from cork.

A well-managed stand of Quercus suber In Portugal. In the foreground, note the temporary fencing used to restrict animal grazing during cork harvesting

Cork-producing tree species in Europe cover more than 2 million ha and provide a source of livelihood for many thousands of people. Cork is a natural product and is currently produced using a sustainable, integrated system. This production system is at risk, however. New, artificial substitutes and aggressive marketing strategies threaten to displace cork from the market, and the outcome is likely to be hard times for producers, together with changes in land use and a shift to less ecologically friendly production systems. A possible solution could be a strategy based on the development of an identifiable, commercial imprint for products made from cork.

Cork from the outer bark of a Mediterranean oak, in addition to its familiar use as a bottle stopper, has various other uses - as insulation against sound and against temperature changes, cigarette tips, motor gaskets, flooring, insoles of shoes, etc. (Fuller. 1961).

Given the focus of this issue of Unasylva, i.e. Mediterranean forests, it may seem unnecessary to open an article on cork with a set of definitions. Yet, recently, the word "cork" has all too often been incorrectly used as synonym for "stopper". This fact is in no way inconsequential, as it immediately indicates the intricate link between the forest resource and a single, critical product.

Cork, or suber, is a vegetal product originated by the tissue phellogen, or cork cambium (Robbins. Weier and Stocking, 1958). Although it exists in limited quantities in many species, there is only one in which the quantity is such that its very name reflects this - Quercus suber, the cork oak (Font Quer, 1977).

Quercus suber, limited in natural range to the western part of the Mediterranean basin, is the only species allowing a sustained and economical production of cork. It is often said to occupy an area of some 2 million ha (cf. Natividade, 1950; Seigue, 1985), but its real area is not known, since up-to-date inventories are not available, particularly with regard to age distribution and the density of stands.

However, there is no doubt about the key role played by this species in Mediterranean economies. Direct economic benefits from cork exploitation, combined with activities carried out under cork canopies (cropping, grazing, hunting) and the ecological and social roles of the species, put the cork oak in a unique position. Moreover, the species range often coincides with areas in which other sources of income and employment are limited, on both the northern and southern sides of the Mediterranean basin, which further increases its importance.


In the wild, the cork oak is but one element of the Mediterranean maquis, sharing space with other tree species, including Quercus ilex, Q. faginea, Q. pyrenaica, Castanea sativa, etc., as well as an immensity of shrubs such as Arbutus unedo, Juniperus sp., Ulex sp., Cistus sp., aromatic essences, etc.

For many centuries, the Mediterranean maquis was used by rural populations primarily as a source of fuelwood, wood for agricultural tools, and tannins. Large areas of the maquis were cleared for crop and pasture land, and to distance wildlife from human settlements. Fire was the primary means used for carrying out this clearing (Silbert, 1978).

But in the second half of the seventeenth century, a French monk named Perignon disovered the special qualities of cork for wine sealing and a new era began for Quercus suber. Cork stoppers meant that wines could be efficiently stored for long periods of time and transported over great distances. This led to the development of the wine industry in a way that otherwise might never have been possible.

Harvesting cork from Quercus suber in Portugal

Slacked cork after harvest

The systematic use of cork for bottle stoppers led to management of the maquis in favour of Quercus suber over other species, and to the eventual transformation of large areas of the maquis into single-species stands.

This is not to suggest, however, that these stands were managed for a single product. Management of the stands to permit cork stripping (removal of the bark) requires thinning, shape pruning and understorey clearing. All of these lend themselves to financially valuable operations. For example, thinnings and prunings provide valuable fuelwood. The cultivation of fodder and other products under the trees and the grazing of animals there is a particularly efficient way of maintaining a clear understorey. Thus, over time, a cork oak agrosilvipastoral system has evolved.

Nonetheless, cork and, more specifically, stoppers are the driving force of the system. Stoppers alone represent more than 60 percent of the cork market. Therefore, if the market demand for cork stoppers were to decrease significantly, the entire system could collapse. Certainly, if this were to occur, the ecosystem could hardly be expected to return to the old maquis. Instead, it is much more likely that plantation species, for example Pinus spp. and eucalyptus, would replace the current system.

Is this a real risk? Unfortunately, yes. For many decades the cork sector has lived with a false sense of security and the belief of being in a market niche with no possible competition. This has led to an almost complete absence of activities aimed at the promotion of cork. At the same time, competitive substitutes have been rapidly developed and aggressively marketed by the plastics industries.

The substitutes market has intruded on the cork industry using two seemingly conflicting strategies. One is to produce a product that is as visually similar to cork as possible and even to use the word "cork" deliberately and incorrectly in the promotion of substitute products. The second is to make a flat denial of any connection with natural cork, a product that is unstable, unclean and difficult to manage.


A species may go into decline if its economic significance is menaced. Therefore, one of the most effective ways to save a threatened species is to revitalize economic interest in it (Turok et al., 1996). The economic exploitation of cork is vital for the maintenance of the cork oak system, and a key to "saving" the species is therefore to conduct effective promotional activities.

Faced with this scenario, in 1997 the FAO/Silva Mediterranea cork oak network launched the idea of a commercial imprint - a cork trademark -with the aim of promoting products made from cork. The short-term objectives of such an imprint would be:

i) to encourage consumers to prefer cork stoppers and other cork products to similar products made from substitute materials; and

ii) to develop a common strategy among cork oak-growing countries and within the commercial cork sector.

Over a longer time frame, the idea is to achieve certification of all cork products, and rigorous quality standards for various cork products, particularly for wine stoppers.

A natural stand of Quercus suber in Portugal

Cork has a number of intrinsic qualities that give it potential advantages in a promotional campaign of this nature. First and foremost, it is a natural product made from renewable resources following an environmentally friendly process that does not even require harvesting of the trees. A second aspect is the clear, demonstrated importance of the cork industry in maintaining the ecological stability of the fragile and threatened Mediterranean ecosystem. A third is the importance of the cork industry in terms of providing employment and income - in Portugal, for example, cork is the country's primary export product and probably the leading source of employment.

The decision on the actual design of the cork trademark is now being taken by an international committee.


Cork and the cork oak have occupied a key role in Mediterranean forest development. They can and should have a continuing role in the future. The appropriate promotion of cork through the development of an imprint could be an important element in ensuring this continuing role.


Font Quer, P. 1997. Dicionário de Botânica, 6th ed. Barcelona, Spain, Ed. Labor.

Fuller, H.J. 1961. The plant world, 3rd ed. New York, Holt, Rinehart & Winston.

Nativadade, J. 1950. Subericultura. Lisbon, DGSF.

Robbins, W., Weier, T. & Stocking, C. 1958. Botany, an introduction to plant science. New York, John Wiley.

Seigue, A. 1985. La forêt circumméditerranéenne et ses problems. Paris, GP Maisonneuve & Larose.

Silbert, A. 1978. Le Portugal méditerranéen à la fin de l'ancien régime. Lisbon, Inst. Nacional de Investigaçâo Cientifica.

Turok, J, Varela, M.C. & Hansen, C. 1997. Quercus suber Network. Report of the third and fourth meetings, 9-12 June 1996. Sassari, Sardinia, Italy, and 20-22 February 1997, Almoraima, Spain. Rome, IPGRI.

Turok, J., Erikson, G., Kleinschmit, J. & Canger, S. 1996. Noble Hardwoods Network. Report of the first meeting, 24-27 March 1996. Escherode, Germany and Rome, IPGRI.

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