For decades linkages between population, development and environment have been related to population growth which refers to the increase of population size without consideration of its internal dynamics, i.e. sex composition and age structure. It was the prime aim of the thesis to establish whether changes in population structure and age structure have any impact on the environmental changes, catchment forest in particular and the extended effects on catchment value and micro climatic change. Basing on the available quantitative data from the household survey and the qualitative data based on PRA discussions, it became apparent that both sex composition and age structure significantly influenced household members' involvement in activities related to both deforestation and those linked to conservation. A remarkable variation was noted in terms of involvement of males and females in specific activities that led to deforestation such as expansion of farms and firewood collecting. Males dealt with cutting of trees for firewood while females collected firewood from those trees cut by males. Male dominance was also clearly observed in conservation-related activities, particularly in tree planting. Sex and/or gender issues were noted to play a vital role in livelihood activities because sex differences and inequalities constitute social systems with consequences on environment changes. Individual's age also influenced one's involvement in livelihood activities. This based on biological capability for performing certain tasks and the socially assignment of duties and responsibilities, i.e. age-based division of labour and specialization which is part of culture. It is therefore imperative for demographic knowledge to be taken into account in the analysis of environmental changes. Gender based division of labour and specialization was the basis for differential involvement of household members in livelihood/development activities. It is argued that unless the key actors in deforestation and conservation are identified basing in the demographic characteristics no sustainable conservation may be attained. Even in the event of urging for participatory or joint forest management, like vast literature points out, a need to focus and target the key actors, by their demographic characteristics, becomes an indispensable and important aspect for attaining sustainable conservation. Poverty conditions that prevail in most developing countries, that limit availability of funds for broadbased extension service, would ensure its effective utilization of little financial resources available through adoption of a more focussed or targeted conservation strategy. Such scientifically planned extension interventions accrue from and are directed towards the identified environmentally significant population segments rather than the entire population. This is the essence of effectiveness and sustainability of conservation efforts based on demographic analysis of the in situ population. / Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2010.