1. INTRODUCTION

Forests are disappearing at a fast rate in many parts of the world. They are under constant pressure for commercial gain, community use, conversion to cash crops and to provide space for ever increasing human populations. In developing countries, it is estimated that forests are decreasing at a rate of 16.3 million hectares annually, of which 15.4 million hectares are in the tropics (FAO, 1995).

Tropical forests are particularly vulnerable to exploitation due to the combination of ecological complexity, sensitivity to disturbance and high demand for the wide range of goods and services and other opportunities for material gain that they provide. Zambia is estimated to be losing about 200 000-300 000 hectares of forests annually through licensed and unlicensed logging operations, charcoal production, shifting cultivation, late forest fires and establishment of illegal settlements in forest reserves. One of the consequences is loss of biodiversity and genetic resources of many tree species, which threatens their continued existence or their possible future use.

Forest genetic resources can be defined as the genetically heritable component within species variability that is of actual or potential use to mankind. Genetic resources occur in different forms and at different stages of genetic development covering reserves of plant species in their natural habitats, and those that are increasingly being used in man-made plantations and agroforestry systems. Thus, they include provenances selected in the wild, provenances and land races of species subject to extensive cultivation both inside and outside their natural range.

Conservation of genetic resources can therefore be explained as the actions and policies that ensure the continued availability and existence of needed genetic material. In the World Conservation Strategy of 1980 published by IUCN (World Conservation Union), UNEP (United Nations Environment Program) and WWF (World Wildlife Fund), the concept of genetic resource conservation is defined as "the management of human use of genetic resources so that they may yield the greatest sustainable benefit to present generations, while maintaining their potential to meet the needs and aspirations of future generations". The focus of gene resource conservation is thus on utilitarian values of evolution and human use. FAO (1989) states that the objectives of conserving forest genetic resources are to secure the ability of the forest tree species to adapt to environmental changes and to maintain the basis for improving production and other benefits of growing trees through future selection and breeding activities.

Burley (1993) gives three main reasons for the conservation of forest resources:

- maintenance of forest resources and life support systems;

- maintenance of genetic diversity which include taxa, species, populations, genotypes, genes or alleles and their frequencies;

- sustainable use of the resource for all its varied benefits which include industrial and indigenous consumptive products, social benefits, provision of standing capital, employment and general health and welfare.