| Large areas of boreal wetlands in Sweden have been artificially drained by ditching during the past centuries to increase timber production. For a significant part of these areas, no production increase has occurred. These areas has recently been suggested by governmental authorities as potential areas for restoration as a way to improve biodiversity and mitigate hydrological floods or droughts. In response to the extreme conditions that have occurred in recent years, culminating with the exceptionally warm and dry summer of 2018, the Swedish government recently allocated 200 mSEK over the next three years for wetland restoration (WR) to reduce the effect of both drought and flooding. However, limited information exists regarding the effects of WR on other types of ecosystem services such as water quality. One of the most emerging issues from a water quality perspective is the “brownification” of many surface waters across the northern hemisphere. The ongoing increase in water color caused by increasing dissolved organic carbon (DOC) and iron concentrations is of concern for multiple reasons but specifically problematic for the drinking water production in Sweden which heavily rely on surface water resources. In this context, WR is suggested as a strategy to improve water quality and potentially mitigate brownification. However, the scientific evidence for reduced DOC and water color by such WR efforts is scarce and the limited published literature show divergent results. In the worst case, large-scale restoration of wetlands could result in an acceleration of the brownification with unknown consequences for the drinking water supply. The proposed project aims to answer:
1) What are the effects of wetland restoration on the water quality of boreal surface waters?
2) Is wetland restoration an effective way to mitigate the brownification of boreal surface waters?
To answer these questions the proposed Phd project will include novel and detailed studies of water color related variables (DOC concentration and characteristics, iron concentration) in ground and stream water within a unique full-scale and replicated WR experiment. The WR experiment is a part of a newly established infrastructure for experimental forest practices called Trollberget, located in Västerbotten. The basic infrastructure is funded through the EU program GRIP for Life in conjunction with SLU and the Swedish Forest Agency. Within this infrastructure two wetland catchments will be restored during late summer 2020 by damming their outlets. Monitoring of ground and stream water will start prior to the operations and last for the full project period. The restored wetlands will be compared with two non-restored wetland catchments in order to detect any effects on water quality. The spatial dimension of the project will be explored by additional sampling (synoptic surveys) of restored and non-restored wetlands over large geographical regions of Sweden. The results will be fundamental for future management and conservation strategies of boreal wetlands and for keeping good quality of drinking water resources in Sweden. |