Numerous non-climate stressors already affect the Great Lakes, which may make the region more vulnerable to climate change. The cumulative effects of stressors, such as water withdrawals, pollution, and non-native or invasive species, reduce the overall resilience of natural systems. Examples of reducing non-climate stressors likely to interact with climate change include managing water withdrawals, reducing pollution, and reducing the presence and extent of invasive and nonnative species.

• Water Withdrawals
• Reducing Pollution
• Non-Native or Invasive Species

Water Withdrawals

Lake levels in the Great Lakes region are established through the “combined influence of precipitation (the primary source of natural water supply to the Great Lakes), upstream inflows, groundwater, surface water runoff, evaporation, diversions into and out of the system, consumptive use, dredging, and water level regulation.”²¹³ It has been estimated that less than one percent of the water within the basin can be renewed each year by precipitation, surface water runoff, and groundwater recharge.²¹⁴ Therefore, water withdrawals and diversions are major issues in the Great Lakes region. The Great Lakes-St. Lawrence River Basin Sustainable Water Resources Agreement and the Great Lakes-St. Lawrence River Basin Water Resources Compact are two frameworks created to protect the region’s water resources by limiting water diversions in both quantity and purpose (e.g., diversions to support enhancing public water supply are supported) and limiting water withdrawals through water conservation and regulatory programs.²¹⁵

Reducing Pollution

The Maumee River watershed in Ohio is the largest in the Great Lakes region; it suffers from multiple sources of pollution, including agricultural runoff, combined sewer overflows, and other non-point sources, which are causing harmful algal blooms and reducing fish populations in the river and Lake Erie. More intense and frequent storms expected with climate change will exacerbate these existing problems. Researchers at Ohio State University and Case Western Reserve University received funding to examine how land use practices in the watershed affect the water quality of Lake Erie and how people’s perceptions of the lake influence those practices. Project leads are conducting focus groups on people’s perceptions and behavior and developing decision-making models to identify upstream practices that can minimize agricultural runoff and resulting water quality degradation.²¹⁶ At the local level, the City of Milwaukee, Wisconsin, is employing swales and rain gardens to mitigate stormwater runoff in the hopes of reducing negative effects on water quality.²¹⁷

Non-Native or Invasive Species

Non-native/invasive species include plants and animals that have the potential to alter food webs, biodiversity, and ecosystem condition. Two projects in Michigan and Ohio are addressing invasive plant species. In 2009, the Huron Pines Resource Conservation and Development Council (Huron Pines) published the Northeast Michigan Coastal Stewardship Project report, which recommended that Huron Pines take the lead on addressing invasive species removal (e.g., phragmites australis) given that climate change could improve conditions for invasives in the future. Huron Pines has since developed a long-term, sustainable program for phragmites australis removal by creating a Cooperative Weed Management Area,²¹⁸ educating and engaging local government officials and property owners about invasive species removal, and developing an early detection and rapid response system.

The program has also enabled staff to discuss emergent wetland vegetation and climate change with landowners, which has led to many owners maintaining native wetland vegetation to increase the long-term resilience of Michigan’s coast.²¹⁹ In Ohio, managers of the Ottawa National Wildlife Refuge on Lake Erie are working with the Ohio Division of Wildlife to eradicate and minimize the spread of invasive species such as purple loosestrife and phragmites. Climate change is predicted to increase suitable habitat for these species, which threaten migrating birds and wildlife that depend on native vegetation and marshland habitat for survival. Local researchers are also aiding managers by creating visualization tools that show areas of “new” shoreline as a result of climate change, which will facilitate planning efforts.²²⁰

Pennsylvania Sea Grant conducted a project to examine the potential increase in habitat suitability for the introduction, distribution, and establishment of aquatic invasive species in a changing climate. Some studies estimate that increased temperatures will allow some species to expand their ranges. Project staff applied three climate scenarios in order to identify and prioritize species with the highest potential for range expansion; about 50 fish, plant, and invertebrate species not currently found in Pennsylvania were identified as potential invaders and four were identified as “high risk.” A framework was created to assist managers looking to develop proactive control and management techniques for addressing aquatic invasive species establishment.²²¹