Burma hold's 70 percent of the world's remaining teak forests. Teak (Tectona grandis) is one of the most valuable tropical timber species and occurs naturally only in India, Burma, northern Thailand, and north­western Laos. It is extensively used for shipbuilding, furniture, carving, and numerous other purposes. The properties of teak that make it so valuable are "light­ness with strength, stability, ease of working without cracking and splitting, resistance to termites, resistance to fungi, resistance to weather, and non-corrosive prop­erties". The physical and mechanical properties of teak are superior to other well-known temperate timber species, including ash, beech, oak, pine, and walnut. The systematic management of Burma's natural teak forests dates back to 1856. It was originally based on an exploitation-cum-cultural system known as taungya (shifting cultivation) forestry. Under this system, Karen planted teak alongside crops in their taungya; as the culti­vators moved to a new area after a couple of years, the process was repeated, and teak plantations were created. The scientific basis of this system was formalized as the Brandis Selection System, later known as the Burma Se­lection System. The system involves adoption of a 30­year felling cycle, prescription of exploitable sizes of trees, girdling (killing of teak trees in preparation for felling), thinning of congested teak stands, systematic se­lection of seed trees, removal of other trees interfering with the growth of young and old teak, enumeration of the trees left, carrying out of special sylvicultural opera­tions in bamboo flowering areas, and fixing annual yield based on the Brandis formula. For teak, the exploitable diameter limit varies with the type of forest. In good (moist) forest, the diameter limit at breast height is 73 centimeters (cm), and in poor (dry) forest, it is 63 cm. At the time of selection, teak trees down to a 29-cm diameter are recorded to serve as the basis for calculating future yields. Properly implemented, the Burma Selection System has proved successful at maintaining a high yield of top-quality timber with minimum environmental im­pacts in the mixed deciduous forests of central and northern Burma. Responsibility for the commercial exploitation of Burma's forests is vested in the Myanma Timber Enter­prise (MTE), formerly the State Timber Corporation. The Forest Policy "assigns the MTE an autonomous status so that it runs on a business enterprise basis with capability to make on-the-spot decisions" and "entrusts to the MTE the responsibility for only harvesting, marketing, and trade of forest products on [a] commission basis." The policy establishes the MTE as an enterprise wholly owned by, and financially accountable to, the SLORC and independent of the Forest Department. The MTE enjoys a monopoly on the production and trade of teak and other hardwoods. The MTE sells sawn teak at fixed prices , whereas teak logs are sold at monthly auctions, a system that allows the MTE to maximize its revenues. The MTE sells eight grades of teak. The top four grades are trimmed and inspected to ensure a straight grain, an absence of defects, and an even color and tex­ture; they are used to produce veneer. According to a teak trade specialist, logs of this quality have become quite rare because of a drastically shortened cutting cycle. Under the Burma Selection System, the forest was closed for 30 years. Today the loggers return in "a few years." Traditionally, logging in Burma has been carried out using elephants for both economic and practical reasons. Using elephants also minimizes environmental damage on steep slopes and erosion-prone terrain. The MTE is responsible for shipping the logs to port and for marketing them. In practice, however, the MTE operates independently of the department and determines its own cutting cycle and harvesting volume. The Forest Department is currently preparing a new working plan to meet the criteria and indicators for sus­tainable forest management set by the International Tropical Timber Organization, which Burma joined in 1993.