The land use legacy effect: Including temporal context in understanding lake eutrophication

The effects of changing land cover on aquatic ecosystem functioning and ecosystem services poses many scientific questions, and is of critical importance to the conservation and effective restoration of these resources.  A fundamental challenge facing scientists is how to incorporate the impacts of previous land use (i.e., land use legacies) into our understanding of the effect of current land cover and land use. Prior research has shown that the present-day ecosystem characteristics are strongly related to historical landscapes. In this research, I investigate the role of land use legacies in understanding lake eutrophication. Changes in land use/cover over five time steps were quantified within buffer areas and compared to nutrient concentrations from 37 Michigan lakes. The relationship between time specific land use/cover and lake nutrient concentration was analyzed using principal components, multiple regression and classification and regression trees. Results show that past land use/cover increases explanatory power up to 49% over using current land/use/cover in isolation. Also, biogeochemical characteristics play a role in determining response-specific legacy effects. These results provide evidence for a land use legacy effect in lakes. Legacy effects should be incorporated when setting realistic management expectations for lake eutrophication mitigation.