Determining the impacts of damming, water-level fluctuations, climate, and landscape changes in Voyageurs National Park and vicinity.

Abstract

In the past century, the border lakes in and near Voyageurs National Park have been subject to anthropogenic and natural stressors. These stressors include logging, damming, hydromanagement, human population growth, and climate change, which can be broadly categorized into three groups: land use, hydromanagement, and climate. In order to determine how these stressors have impacted the lakes, we developed a before-after control-impact paleolimnological study. Lakes included in the study were the dammed lakes of Namakan, Rainy, and Kabetogama, which are all in the Voyageurs National Park region, and undammed Lac La Croix, which is upgradient in protected wilderness lands. One sediment core was retrieved from each lake and analyzed for 210Pb inventory, loss-on-ignition, and diatoms. Multiple statistical analyses (species richness and turnover, cluster analysis, multivariate ordination, diatom-inferred water quality, and variance partitioning) were used to provide a more comprehensive picture of how these lakes were affected uniquely and interactively by the different stressors. Among the various stressors, land use generally explained the greatest amount of variance in diatom communities. Nevertheless, it is important to note that the interactive effects among land use, climate, and hydromanagement were also highly significant. Although hydromanagement is a primary source of concern in this region, multiple stressors and their interactions were identified as drivers of change in the diatom community and therefore must be considered in the management of the border lakes. The International Joint Commission who has been managing this system since 1940 has been mostly re-active in its decision making. However, in the late 1990s enough awareness was raised in regards to the deterioration of biological communities that they choose to modify the water-level rules in the border lakes. This step created a new decision-making process in this region; a move from being re-active to been pro-active. As part of this new rule change, the IJC required local agencies to evaluate the change in the rule curve. The ruling board located in the Rainy-Namakan System also has taken part in the new International Watershed Initiative which approaches the management of watersheds in an ecosystem approach. This step is extremely important as it promotes interactions between all stakeholders and therefore is able to fully integrate concerns in decision-making. Nevertheless, there are still concerns for the management of the resources in a sustainable way. Repeatedly, agencies in the region have raised concerns in the lack of funding from the IJC to maintain monitoring station. These stations are extremely important when making sustainable decisions especially during a time of unprecedented climate change. Thus, it is important that the IJC not only pro-active in its decision-making but also consider long-term sustainability.