The regional timber trend studies published by FAO demonstrated, already in 1963, a trend towards a coming, greatly increased demand for forest products as a result of rapid increases in population and rising standards of living (Lanly and Allen 1991). Accordingly, the global forest plantation estate increased from 17.8 million hectares in 1980 and 43.6 million hectares in 1990, and to 187 million hectares in 2000. Of these, 39%, 36% and 48% in 1980,1990 and 2000, respectively, were established for industrial wood production. According to the global forest resources assessment 2000, forest plantations presently account for 5% of global forest cover and for less than 3% of the industrial forest plantation estate. However, in the year 2000 forest plantations were estimated to supply about 35% of global roundwood (FAO 1982, 1993, 2002, 2002b; Carle et al. 2002).
Provision of wood from natural forests, notably those in the tropics, is frequently not competitive, nor sustainable, in the long term. In many tropical countries there is therefore a rapid transition from natural to plantation forests for productive purposes. Plantation yields are often orders of magnitude higher than those of natural forests; for example, in Brazil, the mean annual increment expected for natural tropical forests is 0.5 m3-5 m3/ha/an, as compared to 35, 45, or up to 75 m3/ha/an in intensively managed plantations. In this country, plantations filled more than 70% of the national industrial roundwood needs in 1997, in spite of the fact that the natural forest area covered over 360 million hectares and plantation forests just 4.5 million hectares (Anon 2002d, FAO 2002b).
Other factors will also tip the balance in favour of plantations for wood production: the economies of scale based on location, and managerial and harvesting advantages of much higher concentrations of wood volume per unit area, increase enormously the relative financial efficiency of plantations. Moreover, and importantly over the last few years, forest plantations, while still needing to be managed in an environmentally sensitive manner, as noted by Leslie in a recent ITTO discussion paper prepared for the Global Environmental Facility, in many countries bear less of the environmental burden than natural forests, provided that they do not cause, an undue reduction in biodiversity values (Anon 2002d).
In establishing forest plantations, the choice of species and provenance, and their accurate matching to site and end use requirements, are essential for success. The need to do so is even more pronounced when non-native tree species are used, which often is the case in developing countries and in the tropics FAO 1958, 1958a; Mergen 1959).
The practical importance of systematic testing has been convincingly demonstrated. The international provenance trials of Eucalyptus camaldulensis, coordinated by FAO in the 1960s, were among the first of a number of such trials. At FAO, these went under the working name, Operation Camal. Experiments were established on 32 sites in 18 countries, and they showed that the potential gains in growth and yield which could be achieved by selection of the best-adapted provenances for prevailing environmental conditions, amounted to several hundred percent, with differences in growth between provenances ranging from 300% in northern Nigeria, to 800% in Israel (FAO 1977, 1979; Lacaze 1979). Spectacular provenance differences were also found in dry-zone Acacia and Prosopis species and provenances in a series of FAO coordinated trials in the 1980s and 1990s (FAO 1980; Palmberg 1981; Palmberg-Lerche 1993a, 1999).
In China, yields, following species and provenance selection and the introduction of better silvicultural methods, more than doubled; and rotation times decreased by 30%. In spite of increased costs of plantation establishment and management, the mean internal rate of return in the plantation schemes reviewed, using a 5% discount rate, was 35% (McKenney 1998). In the case of Acacia mangium, the productivity of large-scale plantations in Indonesia was doubled by use of better adapted provenances, as compared to yields obtained using as a starting point the relatively poor quality seed previously used. These stands were also of better quality in regard to stem straightness and branching (Midgley 1999).
A recent study of 45 reforestation projects in the tropics found that 95% of these were based on introduced species. Sixty percent of the projects carried out species trials in parallel with the reforestation activities. About 60% of these, in turn, gained additional information during the life span of the project which resulted in a change of species, and many more were incentivated to change the provenances originally used. Needless to say, timely species and provenance testing would have constituted a major economic saving in these cases (FAO 2002e).