Urban Ecology is introduced in an historical context, and an account is given of its development in concept and practice as a pioneering research venture in an international UN programme. The basic components of a paradigm for urban ecosystems are presented, ranging from the most quantifiable variables such as energy and materials flows, to the most intangible and unquantifiable such as psychosocial aspects. Examples of interdisciplinary, integrative and problem-oriented ecological research are given on urban systems, on urban/hinterland interrelationships and on nature and biological diversity in urban, periurban and industrial systems. Special emphasis is placed on the role, functions and benefits of nature in Cities, and on the need for ...