Continuity and change in environmental systems: The case of shallow lake ecosystems

Traditional ideas concerning environmental management tend to be based upon simple relationships between cause and effect. Such approaches make the design of environmental management strategies fairly straigthforward: Once the cause of a problem has been identified, it is necessary only to address the cause and/or help the system to recover through some sort of attempt at restoration. In the case of shallow lake eutrophication, research in the 1960s and 1970s identified phosphorous as the key control on the trophic state of a lake and, hence, recommended reductions in the supply of phosphorous to lakes as the necessary remedial measure. However, subsequent research has illustrated that such measures were not always successful. This article reviews the science of shallow lake eutrophication to demonstrate the role of ecosystem-specific biological and chemical interactions in conditioning the response of lakes to remedial measures and, hence, shows how new ideas of complexity help us to understand the behaviour of lake ecosystems so that we can develop alternative environmental management strategies.