Fysisk restaurering av sjöar.

This report contains an overview on some of the most overarching kinds of anthropogenic degradations of lakes in the past and today, their effects on biological diversity, ecosystems and ecosystem services and possible physical restorations and counter-measurements.  The anthropogenic degradations raised in this report consists of, but is not limited to, water regulation of lakes, permanent lowering of lakes, eutrophication, lost lateral and longitudinal connectivity, and degradation of the shoreline and the riparian zones. The extent and present influences of these antropogenic disturbances of lake ecosystems in Sweden are presented and discussed.  In the first half of the report we discuss ecological and hydrological lake processes with emphasis on the functionality of habitat diversity and macrophytes. In the second half of the report we discuss restoration principles in general and present more detailed recommendations for each kind of disturbance.  Examples of performed restoration efforts are raised and discussed. Other than measures in eutrophicated lakes, there are very few scientific studies published on physical restoration of degraded lake ecosystems. We have therefore tried to discuss both published and unpublished as well as successful and unsuccessful examples from performed or ongoing restoration projects in Sweden. Unsuccessful attempts often depend on restoration efforts not being extensive enough. There are large knowledge gaps concerning the effects of lost habitat diversity in the riparian zone and in shallow water. Suggested restoration efforts here are directed towards mimicking the natural connectivity between land and water, adding habitat complexity through dead wood and restoring macrophytes.  Disturbances in lakes are often caused by multiple pressures and a holistic view is needed to assess attainable restoration goals and suitable and doable measurements to achieve these goals. Every lake, project and catchment is unique and may call for complex management planning. Despite the complexity of the problems, measures need not be difficult to perform.