Moving from descriptive to predictive ecology

The science of ecology is undergoing many important shifts in emphasis and perspective which have important implications for its role in designing sus tainable farming systems. In particular, a shift has occurred from the equi librium paradigm to one which recognises the dynamic, non-equilibrium natur e of ecosystems. Allied to this is the recognition that ecosystems can occu r in any one of a number of alternative stable states, depending on the dis turbance and management history. An increased emphasis on spatial patchines s in ecosystems has also emerged as appropriate tools have emerged to analy se spatial mosaics. These features have led to a recognition that considera ble uncertainty is associated with the outcome of any particular ecosystem modification; hence predictive capacity is also low. Recent considerations of the interrelation between biodiversity and ecosystem function have also explored the questions of how many species need to be in a system to fulfil certain functions and confer resilience. We identify a set of steps that a re required for the development of an agricultural system based on mimickin g natural ecosystems. Central to this is identifying (1) the functions whic h are currently suboptimal in the agricultural system, and (2) the species which have key functional roles in the natural system, and then reaching de cisions as to the array of species needed to confer system function and res ilience.