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81 Landscape Change and Its Influences on Aquatic Habitats and Fisheries in the Great Lakes Basin Kevin Wehrly, Lizhu Wang, Dana Infante, Christine Joseph, Arthur Cooper, Les Stanfield, and Edward S. Rutherford The Laurentian Great Lakes are an economically and ecologically valuable resource. Thelakessupplywater for municipalities and industry, provide fishing and boating opportunities for residents and tourists, and serve as a key shipping route linking the agricultural, mining, and manufacturing centers of the basin to the world. The lakes also support a diverse array of aquatic life. Owing to their large spatial extent and geologic history, the Great Lakes exhibit considerable variation in climate and bathymetry that naturally maintains differences in temperature, water quality, and biological assemblages both within and among the lakes. Humans have altered Great Lakes ecosystems through exploitation and management of fish stocks, introduction of invasive species intentionally and unintentionally, and alteration of the landscape. Much of the management and research dealing with human impacts on the Great Lakes has primarily focused on fisheries issues in the pelagic zone and on impacts of invasive species. Comparatively little work has addressed landscape change and its influences on aquatic habitats and fisheries. The Laurentian Great Lakes, like other aquatic ecosystems, are strongly influenced by landscape characteristics. Broad-scale factors, such as climate and physiography, determine the cycling of water, sediment, and nutrients, which affect finer-scale habitat characteristics and, ultimately, the condition of biological communities. The natural landscape of the Great Lakes basin has been dramatically changed by human activities, and, as a consequence, the water quality and biota of the Great Lakes basin have also changed. Human activities vary across the basin, in terms of type, spatial extent, and ecological impact, largely as a function of natural landscape drivers. Viewing the Great Lakes from a landscape perspective is, therefore, critical to understanding the factors that structure the lakes, to understanding the impacts of landscape change, and to prioritizing conservation and management efforts in the Great Lakes basin. There is a growing recognition that a landscape perspective is needed to effectively manage and restore the Great Lakes (IJC 2006). Stakeholders have increasingly emphasized the need to evaluate and manage human landscape disturbances (Shear et al. 2005), and recent efforts have been made to better monitor and assess landscape condition and to quantify landscape impacts on Great Lakes ecosystems (Canada and the United States 2007; Danz et al. 2007; Niemi et al. 2007). Most of these efforts, however, have been focused on the U.S. portion of the basin, and a landscape perspective is not well integrated into Great Kevin Wehrly et al. 82 Lakes policy and management. Resource managers and policy makers may be slow to adopt a landscape perspective, because they are unfamiliar with the mechanistic linkages between the landscape and the Great Lakes ecosystem. This chapter increases awareness of these relationships with the hope of improving management and restoration of the Great Lakes. The chapter begins by describing the natural landscape of the Great Lakes basin as a template for landscape change and characterizing current land use patterns. It assesses and maps landscape disturbances on a watershed basis and maps the potential influence of landscape disturbance on nearshore and offshore areas throughout the entire Great Lakes basin. Finally, the chapter concludes by considering some of the factors that may influence the impacts of future landscape change. Landscape Changes in the Great Lakes Basin Patterns of Natural Landscape Features as a Template for Landscape Change The natural landscape of the Great Lakes basin is diverse, in terms of climate and physiography. This chapter defines physiography as both landform and land texture. Variation in climate and physiography is an important driver of native vegetation, the characteristics of lakes and streams, and human land use across the basin. Understanding the natural landscape is, therefore, important to understanding not only patterns of human activity, but also ecosystem sensitivity to landscape change and remediation. For example, because of their landscape setting, areas, such as Green Bay, Saginaw Bay, the western basin of Lake Erie, and Bay of Quinte, have naturally higher phosphorus concentrations (Chapra and Robertson 1977; Minns et al. 1986) and may be more responsive to increases or reductions in phosphorus loadings than other areas in the Great Lakes basin. CLIMATE The climate of the Great Lakes region varies spatially and seasonally, with longer growing seasons, warmer winter temperatures, and relatively less precipitation in the southern portion of the basin and shorter growing seasons, colder winter temperatures, and relatively more...

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