G.D. Piearce
Dr G.D. Piearce works with the Division of Forest Research in Kitwe. Zambia This article is based on a paper presented at the September 1985 meeting of the Commonwealth Forestry Association in Victoria British Columbia. Canada.
The decline of the Zambezi teak forests has proceeded slowly and steadily during this century. Only now is the international forestry community sensing that an irreplaceable resource could be lost if nothing is done. But what can be done? In this article, G.D. Piearce offers a number of solutions, some of them controversial. What is most necessary, he argues, is that action be started now and that funding be found.
ZAMBEZI TEAK a need for action now
· The indigenous mukusi or Baikiaea forests and woodlands found in the Kalahari Sands region of tropical Africa are today more aptly and conveniently termed the Zambezi teak forests. These forests have declined greatly in extent and condition during this century, almost entirely as a result of disturbance by man. What remains is still of considerable importance economically, scientifically and sociologically, but the extinction of these forests is imminent if intensive exploitation and devastating fires continue unchecked. Neither natural nor artificial regeneration has been able to keep pace with the rate of destruction over recent decades.
Various local, national and international initiatives have been proposed and are beginning to be implemented in Zambia to deal with the urgent needs for conservation, research and improved methods of management. A major constraint on this work is a critical shortage of investment funds at a time when there is increasing pressure for the forests themselves to be used to provide revenue for other development schemes. A critical factor will be the encouraging of active participation by local residents in forestry activities
One controversial contention is that natural regeneration offers the only logical and feasible approach to regeneration of the Zambezi teak forests.
Zambezi teak has now become the most popular name for the tree and timber that have been referred to in the past as African teak, Rhodesian teak, Zambian teak or Zambezi redwood. It is one of the finest heavy-duty timbers in the world. It is quite distinct botanically and structurally from the so-called true teak (Tectona grandis L.) native to Southeast Asia and widely planted as an exotic elsewhere in the tropics (Shikaputo, 1985), though its wood properties are similar.
Locally known as mukusi, Zambezi teak (Baikiaea plurijuga Harms) is a Caesalpinioid legume. Its natural distribution is restricted to the Kalahari Sands of southwestern Zambia and neighbouring parts of Angola, Botswana, Namibia and Zimbabwe. The best remaining stands of the unique forest type in which it occurs are in Zambia's Sesheke District, though a larger area of the western and southern provinces contains relict patches that are mostly occupied by Kalahari or Baikiaea woodland, a degraded form of Baikiaea forest (see Fanshawe, 1971; and Edmonds, 1976, for the most modern vegetation map). The Zambezi teak forests region is characterized by the presence of B. plurijuga as a principal element of the vegetation cover. Huckabay (1986) gives a concise overview of the species and the forests.
The significance of the Zambezi teak forests in Zambia is basically threefold. First, they are economically important because B. plurijuga and some of its associated species provide the country's most valuable commercial timbers. There is great pressure for the forests to be exploited to exhaustion for timber, both to supply Zambia and to earn foreign exchange.
Second, the forests are of considerable scientific, educational, and aesthetic value by virtue of the range of their flora and fauna. Their demise would reduce the region to an extension of the Kalahari Desert. Hence there is the increasing need for conservation of genotypes and the ecosystem for the benefit of future generations.
Third, sociologically, whereas such matters as commercial exploitation and conservation tend to be the main concerns of professional outsiders, those who actually live in the teak forest area are most directly aware of though somewhat ambivalent toward their natural environment. Perhaps more so than anywhere else in Zambia, local people depend on the forest for their personal welfare and livelihood. There are immediate needs for firewood and building materials, and forest industries are a major source of employment, offering a measure of prosperity and development. At the same time, with increasing population pressure, there is growing demand for agricultural land, which has led to a great deal of destruction under traditional systems of shifting cultivation.
Such conflicting factors have led to serious ecological disturbance of an intrinsically delicate ecosystem, and the balance since the turn of this century has been very much in favour of uncontrolled exploitation by man. The forests have been cut down much faster than they can regenerate. Positive intervention is required to reverse this trend, assuming it is not already too late.
The Zambezi teak forests were the subject of a conference held in Livingstone, Zambia, in March 1984, to discuss the many issues involved in maintaining these forests and perhaps restoring them to sustainable productivity. The alternative of resigning oneself to a "wasting asset" was unanimously opposed, and instead an integrated plan of action aimed at rehabilitation was formulated.
The present mood in Zambia is one of reserved optimism, a mood that should be shared by forest scientists and administrators abroad who were hitherto unfamiliar with the situation of the teak forests.
Incidentally to his more renowned pioneering achievements, the explorer David Livingstone first made the Zambezi teak forest region known to the outside world (1857). One of his companions on the great Zambezi expedition, John Kirk, was the first to collect botanical specimens of B. plurijuga, presumably in the vicinity of Sesheke in 1860, but the species was not named and described scientifically until 1903 (Brummitt, 1985), about the same time that commercial exploitation began.
TEAK AT SAWMILL IN THE 1940s the supply has diminished
As part of the grand scheme for a Cape-to-Cairo transport link, the railway line from the south reached the Victoria Falls in 1902, the bridge there was opened in 1905, and the railway had been extended to the copper belt of Northern Rhodesia (Zambia) when the first copper mine began production in 1910. The potential of Zambezi teak for use as surface and underground railway sleepers (ties) was soon realized.
Exploitation was first recorded in Southern Rhodesia (Zimbabwe) in 1908 (Judge, 1986), while in Northern Rhodesia the first sawmill began operating in Livingstone in 1911. The Livingstone forests were exhausted by the late 1920s, and forest operations moved westwards with the construction of the famous Mulobezi Railway, the longest privately owned railway line in the world (Calvert, 1986a).
Around this time, which saw the inception of Northern Rhodesia's Forest Department, organized forestry in the country was practically synonymous with exploitation of Zambezi teak. The earliest general accounts were published by Stevenson (1931) and Martin (1932, 1940), supplemented by Miller's (1939) paper on the Bechuanaland (Botswana) forests and woodlands.
It was Martin, the first forest officer to be posted to Barotseland (now Western Province) in 1931, who originated disciplined management of the Zambezi teak forests in Zambia. He was instrumental in preparing a number of licensing agreements regulating felling practices and in insisting upon fire protection measures and replanting work in concession areas. He drew up the Barotse Forest Orders of 1936, which were later adopted as the National Forest Laws and formed the basis of the Forest Act in force since 1973.
ZAMBEZI TEAK Baikiaea plurijuga inflorescence
In the early days of logging in the Zambezi teak forests, the minimum felling diameter was 45 cm and the maximum sizes available exceeded 100 cm. Nowadays much smaller stems are cut - from 25 to 54 cm in diameter - and very few larger ones are to be found. The figures speak for themselves of the degree to which Zambezi teak has declined.
Five sawmills are currently utilizing these forests in Zambia. Three are privately owned; the other two, at Mulobezi and Sesheke, are run by the parastatal company Zambezi sawmills, which is by far the largest concern. Recovery rates are quoted as being from 25 to 45 percent. Most of the production is from heartwood, and is converted to railway sleepers (ties) for the Zambia and Tazara Railways and the mining industry. A small proportion of mixed heartwood and sapwood is used for parquet flooring strips, which could become the principal export commodity.
Sales values over recent years have been in the region of zK 1.5 million (c. US$1 million) a year, 80 percent in the domestic market and 20 percent from exports. From royalties alone, the government accrued c. US$350000 during the period 1979-83.
MUTEMWA THICKET AMID TEAK a potential fire hazard
Commercial enterprises, however, account for only about 25 percent of the total timber removed, which in round figures is currently estimated at 500000 m3 annually. At least half this volume is used for domestic purposes. The remaining quarter is accounted for by agricultural land-clearing and destruction by forest fires.
Reserves of exploitable timber now are reckoned to stand at around 28 million m3. If recent trends continue, these forests will disappear within the next 50 years, and they are bound to become irretrievably diminished much sooner.
Mukusi is typically thin-barked, and therefore extremely sensitive to fire damage. Although the primary forests were not highly flammable, human-induced disturbances have rendered the present forests so. Following exploitation, logging residues and the herb and shrub species that colonize openings left after felling greatly increase fuel levels. Fires in these forests are almost invariably started by people.
The worst effects are seen after so-called late fires, which occur around September/October, at the end of the seven-month dry season. It is the hottest time of the year, and often windy. Such weather conditions, coupled with the tinder dryness of heavy accumulations of fuel, cause fires to be intense, with flames spreading up to 16 m per minute and reaching 15 m in height. The trees are at their most vulnerable to fire at this time, as they begin to break dormancy, and fruits and seeds are set for dispersal in anticipation of the rainy season. Even a single late fire in undisturbed forest, particularly if extensive damage to the canopy results, increases the subsequent fire danger by starting the process of deterioration of the overwood and promoting understorey growth. Thus the effects of repeated late fires are both severe and cumulative.
Though the nature of these forest fires was fully recognized and some control measures were introduced in the 1920s and 1930s, Martin (1940) reported that "the network of fire-damaged areas stretching throughout the average forest occupies from 20 to 50 percent of the total area'. And Wood (1985) quotes Watson's impression that half to two-thirds of the mukusi forests were destroyed by fire in the 30 years prior to 1950.
Fire protection activities were stepped up between 1945 and 1965, with the development of fire-break systems and boundary burning practices, and improvements in the organization of fire-detection and fire-fighting operations. Recently, fire protection has taken precedence over all other forestry work, but still an average of 1600 ha has been destroyed by late fires each year since 1965 (Zimba, 1986).
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FAO assists Zambia in creating genetic reserves Baikiaea plurijuga is one of the species listed by the FAO Panel of Experts on Forest Gene Resources as being in urgent need of attention. In the mid-1970s, FAO's Forestry Department assisted the Forestry Department of Zambia in the demarcation and establishment of two botanical reserves for the in situ conservation of this species. The reserves, established within the FAO/UNEP Project on Conservation of Forest Gene Resources, are located at Malavwe and Kataba in the Western Province of Zambia; they are 31.6 and 4.0 ha in size respectively. It is believed that they are the first reserves in the world to have been established with the specific objective of in situ conservation of intraspecific genetic variation of a woody species. To conserve the variation of the species completely, however, additional reserves would need to be established. Full botanical inventories have been carried out in the reserves, and some phenological/biological studies have subsequently been conducted in them with assistance from the Swedish International Development Authority. A full account of these reserves and other activities can be found in Report on the FAO/UNEP Project on Conservation of forest Gene Resources (FAO, Rome, 1985). Christel Palmberg |
The primary causes of recent forest fires have been uncontrolled fires started by cultivators, honey gatherers and hunters. Another factor is incendiarism arising from local disgruntlement. The latter category includes those who would prefer to use forested land for agriculture, and see destruction by fire as a means of achieving that end. With the population of the region likely to double in the next 30 years (Wood, 1986), there seems to be little prospect that such land-hungry attitudes will change unless an intensive education campaign is mounted.
Complete protection from fire is an impracticable ideal. In 1978, Zambia's policy changed to prescribed "early" burning. As a pre-suppression measure, this has two principal advantages: first, setting controlled fires at the beginning of the dry season, usually April/May, is an effective method of fuel reduction; and second, if properly conducted on an annual basis, it is essentially patch burning with low-intensity fire at a time when the trees are becoming dormant, so regeneration is not adversely affected.
However, there are practical difficulties in using fire as a silvicultural tool. A major limitation has always been the shortage, due to lack of adequate funds, of available labour, equipment and transport for large-scale early burning, back-up operations to maintain fire-breaks for access, and actual fire-fighting. A secondary issue concerns the skill required to carry out early burning successfully. As Calvert (1986b, 1986c) and others have emphasized, expertise is needed to gauge the optimum timing of the operation according to the conditions of the vegetation as a whole, the fuel layers and the weather.
Alternatives to early burning for fuel reduction have been proposed, such as systems of cattle grazing as practiced in Zimbabwe, but these are less applicable in Zambia in areas far from watering places. Here, given sufficient resources for the job, it would be technically possible to protect the remaining mukusi forests to a large extent from devastating late fires by early burning. But what to do about the greater area that has already been burnt out is another matter.
A severe late fire destroys the mukusi overwood entirely and the resultant "fire-hole" is rapidly colonized by undesirable thicket shrubs and scramblers, particularly Acacia ataxacantha DC., Dalbergia martinii F. White and several Combretum species. Collectively the thicket species are known as mutemwa, which is becoming increasingly predominant as a dense understorey in the mukusi forests, owing not only to fire but to other disturbances as well. In many places this vegetation is practically impenetrable, thereby increasing the fire danger even further. Moreover, the mutemwa poses major obstacles for mukusi regeneration.
Many interrelated ecological factors have aggravated the decline of the Zambezi teak forests in Zambia (Chisumpa, 1986; Malaya, 1986; Mbughi, 1986; Greenwood 1986). Mukusi does not coppice freely, so most regeneration is from seed, but the species faces great difficulties from the beginning. Flowering and fruiting of seed trees are erratic, with good seed crops being produced only once in three or four years. The ripening pods are a favourite food for monkeys and baboons, a troop of which can strip a tree in half an hour (Calvert, 1986d). Much of the seed that does reach the ground, especially when it is at the swollen and succulent pre-germination stage, is consumed by rodents and other small animals. Young seedlings are also attacked by these and larger mammals, notably antelopes such as the grey duiker (Sylvicapra grimmea L.), which browse leaves and stems and excavate roots. And the mutemwa markedly suppresses or prevents the growth of young plants because it competes intensely for light and moisture in addition to providing shelter for pest animals.
How then did these forests ever regenerate successfully? According to Mitchell's (1961) hypothesis, supported by Piearce (1979) and Lawton (1986), a crucial phenomenon has been the great reduction in the population of large mammals. By trampling, browsing and uprooting the mutemwa, burying mukusi seeds and providing manure, elephant and buffalo kept the mutemwa in check and facilitated regeneration of mukusi, which they find unpalatable. Hunting has been blamed for the decrease in numbers of these game animals, but a decimating outbreak of rinderpest disease in 1886 (Wood, 1986) may have been more significant.
If recent trends continue, these forests will disappear within the next 50 years.
The primary causes of recent forest fires have been uncontrolled fires started by cultivators, honey gatherers and hunters.
Later exploitation by man, and fires greatly reduced the stocking of mukusi seed trees over large areas, and allowed the mutemwa to become increasingly dominant, with a consequent increase in fire danger and in populations of the pest animals.
Thus the tangible problem of natural regeneration now is control of mutemwa. This can be achieved most successfully by the use of arboricides, particularly 2,4,5-T and Tordon, detailed prescriptions for the application of which have been worked out (Piearce, 1979). But because of uncertainties over their cost-effectiveness, and because using such chemicals is thought by many to be ecologically undesirable, their use on other than an experimental scale has not been sanctioned.
Lawton (1986) has proposed an alternative means of simulating the conditions under which mukusi probably regenerated originally. This involves mechanical clearance of mutemwa with heavy machinery, but again the cost factor deters implementation of such a scheme, even on a modest trial basis.
Attempts at artificial regeneration, by enrichment planting or establishment of trial plantations, have so far met with very little success (Malaya, 1986; Chitempa & Shingo, 1986). In the first place, land-clearing costs are increasing, and second, seeds are not always available in large quantities. Direct sowing is generally unsuccessful because of animal predation.
Seedlings are easy to raise in the nursery, where germination usually exceeds 90 percent, but they are difficult to transplant because the taproot grows very deeply from the outset, reaching 1.5 m after one year - though the shoot attains a height of only 15 cm over the first three years (Fanshawe, 1961; Endean, 1968; Högberg, 1986; Calvert, 1986b). The tap-root has to be severed before planting out, which renders the seedling vulnerable to drought stress, especially since rainfall in the region is notoriously unreliable. In some trials, the survival of transplanted seedlings has been as low as 10 percent after the first year, most losses being attributable to drought and duiker damage.
The best trial plot of mukusi in Zambia was established in the early 1960s, apparently by direct sowing but under circumstances that are by no means clear from existing records. It has been speculated that in those days the population of animal pests was manageably low, and that local rainfall may have been more favourable. It also seems that intensive management, possibly including the use of scarecrows and guards to deter animals, and watering of the seedlings, was practiced. Experience over recent years has taught that there is now no reasonable prospect of establishing mukusi in plantations with anything like that singular success of 20 years ago.
To the as yet unresolved silvicultural problems must be added the fundamental matter of the very slow growth rate of mukusi. Even under the best conditions, its rotation length (to reasonable timber size of 30 cm DBH) is estimated at 80 to 100 years - a formidable time to wait.
Commercial exploitation Twenty-two resolutions were passed at the conclusion of the Livingstone conference mentioned above. As regards commercial exploitation, the conference recommended reduction of the allowable cut and the level of sawmill waste so as to maximize the utilization of the timber that is felled; to restrict the uses of Zambezi teak to high-value (especially exportable) products; to encourage timber companies to participate in the management, protection and regeneration of the forests; and to develop the utilization of alternative and secondary species in order to maintain forest industries for redeployment of the present work-force.
Sawmillers have appreciated the need to limit wastage - although a 40 percent recovery is regarded as acceptable - and have requested assistance in this regard from the Forest Department's Division of Forest Products Research, which has carried out a preliminary feasibility study on charcoal production from sawmill residues (Musonda, 1986). There is also some interest in ideas to utilize waste for electricity generation, in a simple chipboard plant, and for briquetting of sawdust.
Promoting increased utilization of other timbers is the subject of long-term research and development proposals, for example involving further investigation of the commercial potential of the multipurpose tree mungongo, Ricinodendron rautanenii Schinz. (Duff, 1986), a species that is receiving particular attention from Zambia's National Council for Scientific Research. The Forest Department's Division of Forest Products Research has latterly initiated, with the Zambezi teak forests as a priority area, a countryside project on the suitability and durability of common timber species for rural construction, concentrating on prospective uses of lesser-known species in and around villages.
Meanwhile, virtually the only species other than B. plurijuga that is being exploited commercially is mukwa (Pterocarpus angolensis DC). But the sawmillers are anticipating greater use of mupumena (Entandrophragma caudatum [Sprague] Sprague); muzaule or Rhodesian copalwood (Guibourtia coleosperma [Berth.] J. Léon.); and m'wangura (Pterocarpus antunesii [Taub.] Harms), all characteristic secondary species in Baikiaea forests.
Research The conference also called for further research on the forest fauna, with special regard to the problem of the effects of larger animals on regeneration; on all silvicultural aspects of both natural and artificial regeneration; and on related matters of forest protection and tree improvement. There is also the underlying need to acquire up-to-date information on the present distribution and stocking of the major timber species by means of a thorough forest inventory, and to explore the use of satellite images to monitor change.
The problem of natural regeneration has been receiving renewed attention in Zambia. This may be especially important in view of Demeo's (1986) contention that natural regeneration offers the only logical and feasible approach to rehabilitation of the Zambezi teak forests. This became a controversial topic of discussion at the conference.
Although the alarmingly high rate of destruction of these forests is indisputable, the extent of what actually remains has not been fully quantified. Proposals for a national forest inventory were made several years ago, but since then lack of funds has held up their implementation.
Management In the management sphere, resolutions included giving priority to improving fire-protection practices by developing expertise in early burning and, in light of recent failures, suspension of attempts at large-scale reforestation until such time as the problems have been fully resolved by research.
It is largely the continuing, critical shortage of funds for fire protection (Zimba, 1986) that delays the implementation of a policy of extensive early burning, rather than insufficient experience and skills to carry it out. Possibilities for aerial ignition on a large scale using incendiary capsules merit further consideration, as does the setting up of a distinct and specialized fire protection unit.
Cooperation and extension In the fields of cooperation and extension, resolutions included strengthening present links between all organizations concerned with research and development in the Zambezi teak forests on a regional basis and intensifying efforts to promote public awareness of the value of these forests and local responsibility for their management and protection.
An important development within Zambia was the establishment in 1985 of a new Extension and Publicity Division of the Forest Department to foster active concern for and participation in forestry activities by local people and to discourage indiscriminate destruction of forests. This is a matter of vital importance in the conservation, management and protection of the teak forests (Banda, 1986; Matakala, 1986). Without the help of residents of the area, all other efforts aimed at rehabilitation will surely be in vain. The Zambezi Society, newly formed in Zimbabwe but liaising closely with conservationists in Zambia, will no doubt assist in this challenging field.
Funding In order to improve the availability of local funds for forestry work, the conference recommended an increase in the royalty rate for timber and the recycling of a reasonable proportion of government revenue derived from exploitation of the teak forests.
Present royalty rates for indigenous timbers cut in Zambia have remained unchanged for many years but are currently under review. Substantial increases are likely to be made. However, even if all government revenue were recycled to the teak forests it would still be inadequate to finance the rehabilitation programme, since the forests have long since passed the stage of being self-sustaining financially.
Thus, whether or not a revolving fund is instituted, regeneration work still needs to be heavily subsidized from external sources.
Conclusions Ultimately, the future of the Zambezi teak forests depends on a straightforward choice between short- and long-term gain: whether to merely use these forests to earn capital for other, seemingly more pressing, development needs, or to invest substantial resources now with little hope of financial return in the near future. It is impossible now to reap a net profit from the teak forests without hastening their disappearance.
In other words, the strong temptation to "cash in" this unique forest asset for, literally, several millions in much-needed convertible currency must be resisted, instead, somehow, millions in investment dollars must be attracted from other sources in order to spend them on ensuring the perpetual existence of these forests.
Note: The majority of references given below come from a single source, the forthcoming publication: Zambia Forest Department. 1986. G.D. Piearce, ed. The Zambezi teak forests. Proceedings of the First International Conference on the Teak Forests of Southern Africa, March 1984, Livingstone, Zambia. Hereinafter this publication is referred to simply as "ZTF".
BANDA, A.S. 1986, The role of forest extension in the protection and management of the Zambian Teak Forests. In ZTF, ch. 34.
BRUMMITT, R.K. 1986, A taxonomic perspective of the genus Baikiaea. In ZTF, ch. 6.
CALVERT, G.M. 1986a, The Zambesi Saw Mills railway, 1911 to 1964. In ZTF, ch. 47.
CALVERT, G.M. 1986b, The ecology and management of the Kalahari Sand Forest vegetation of south-western Zimbabwe. In ZTF, ch. 11.
CALVERT, G.M. 1986c, Fire effects in Baikiaea woodland, Gwaai Forest. In ZTF, ch. 25.
CALVERT, G.M. 1986d, Baikiaea regeneration and damaging agencies in Barotseland. In ZTF ch. 45.
CHISUMPA, S.M. 1986, Mukusi ecological associations and environmental effects. In ZTF, ch. 9.
CHITEMPA, T.T. & SHINGO, J. 1986, Research and management problems in the artificial regeneration of Zambezi teak. In ZTF, ch. 32.
DEMEO, T. 1986, The case for a natural regeneration system in managing the Zambezi teak forests. In ZTF, ch. 13.
DUFF, C.E. 1986, Mungongo - Ricinodendron rautanenii. In ZTF, ch. 40.
EDMONDS, A.C.R. 1976, Vegetation Map 1:500,000. Lusaka Zambia, Survey and Lands Department.
ENDEAN, F. 1968, The rooting habits of Baikiaea plurijuga, Pterocarpus antunesii and the main species forming the mutemwa. Manuscript report. Kitwe, Zambia, Division of Forest Research.
FANSHAWE, D.B. 1961, Baikiaea plurijuga Harms. Manuscript. Kitwe, Zambia, Division of Forest Research.
FANSHAWE, D.B. 1971, The vegetation of Zambia. Lusaka, Government Printer. Forest Research Bulletin 7.
GREENWOOD, D.E. 1986, Zambezi teak in Zambia. In ZTF, ch. 46.
HÖGBERG, P. 1986, Rooting habits and mycorrhizas of Baikiaea plurijuga. In ZTF, ch. 8.
HUCKABAY, J.D. 1986, The geography of Zambezi teak. In ZTF, ch. 2.
JUDGE, J.G. 1986, The teak forests of Zimbabwe. In ZTF, ch. 5.
LAWTON, R.M. 1986, How were the Zambezi teak forests established? In ZTF, ch. 39.
LIVINGSTONE, D. 1857, Missionary travels and researches in South Africa. London, John Murray.
MALAYA, F.M. 1986, A review of silvicultural research in the Zambian teak forests. In ZTF, ch. 13.
MARTIN, J.D. 1932, The mukushi (Baikiaea plurijuga Harms) forests of Northern Rhodesia. Annual Bulletin, 2: 71-76. Lusaka, Department of Agriculture.
MARTIN, J.D. 1940, The Baikiaea forests of Northern Rhodesia. Emp. For. J., 19: 8-18.
MATAKALA, P.W. 1986, Problems of forest extension work in the Zambian teak forests. In ZTF, ch. 35.
MBUGHI, R.J. 1986, The habitat and regeneration of Zambezi teak in Zambia. In ZTF, ch. 43.
MILLER, O.B. 1939, The mukushi forests of the Bechuanaland Protectorate. Emp. For. J., 18: 193-201.
MITCHELL, B.L. 1961, Ecological aspects of game control measures in African wilderness and forested areas. Kirkia, 1: 120-28.
MUSONDA, W.M. 1986, Fuelwood problems in the teak forests. In ZTF, ch. 44.
PIEARCE, G.D. The use of arboricides to control thicket species in the teak forests of Zambia. East Afr. Agric. For. J., 44 (4): 285-97.
SHIKAPUTO, C. 1986, Properties and end-uses of Zambezi teak. In ZTF, ch. 28.
STEVENSON, D. 1931, Some important native timbers. Annual Bulletin, 1: 45. Lusaka, Department of Agriculture.
WOOD, A.P. 1986, Man's impact upon the mukusi forests of Zambia with special reference to Sesheke District. In ZTF, ch. 3.
ZIMBA, S.C. 1986, Fire protection and related management problems in the Zambian teak forests. In ZTF, ch. 24.
