Biodiversity is not exclusively a product of pristine natural processes but is also, to a considerable degree, caused by human activities. This is demonstrated by a detailed inspection of the use and classification of plants by the people of Nokopo village in the Finisterre Range of Papua New Guinea. Nokopo people recognise and value biodiversity on all its levels - genetic diversity, species diversity and diversity of ecosystems - and their activities enhance overall biodiversity. This can be partly explained by the usefulness biodiversity has to them, in terms of resource access and other utilitarian considerations. On the other hand, aesthetic concepts and values make a significant contribution. Both these intrinsically interwoven components - the utilitarian and the aesthetic component respectively - form the base for understanding the major role humans play in creating and maintaining biodiversity, the role of keystone species enhancing overall biodiversity in a given ecosystem.