ECOLOGICAL PROCESSES AND SUSTAINABILITY

Ecology has developed from its position as an obscure science to being at the interface of science and public policy. The impact of mankind can be described in ecological terms relating to population size, ener gy use and non-renewability. Sustainable development needs to be addre ssed on the basis of knowledge of ecological processes which maintain the environment in a state of change; the processes need to be conserv ed, not maintained in any particular state. Recent advances in the und erstanding of ecological processes are reviewed to highlight the poten tial contribution of this knowledge to the development of a sustainabl e policy. At the level of the population the significance of consideri ng the extinction risks in the framework of spatio-temporal dynamics i s now established indicating opportunities for planning land use more precisely to sustain biodiversity. Whilst the maintenance of habitats is generally the key to the persistence of biodiversity, they must be viewed as ever-changing mosaics within which cycles of succession, bes t described by Markovian sets of probabilities, are occurring continua lly. The extent to which these probabilities are distorted will determ ine whether the ecosystem returns to the same system or moves to a nov el one. At the global level, biogeochemical cycles have a certain flex ibility in relation to fluxes and stocks, hence pollution must be defi ned by relating the flow rate of the substance to this flexibility, wh ich often permits the accommodation of anthropogenic perturbations. No n-sustainable processes can be defined in ecological terms, thus provi ding functional definitions of a sustainable policy and of sustainable development.