Great Lakes

-- An Overview prepared by Peter Sousounis, Ph.D. (University of Michigan) and Patty Glick (National Wildlife Federation) --
 

Climate and changes in it – regardless of their cause – matter to people, communities and businesses. Global warming is likely to bring many changes to the nation. The United States as a whole is in a strong economic position to adapt to many of these changes, but adaptation is often expensive, not always possible or successful, and during transitions ecosystems, communities, and individuals could suffer. Moreover, national impact summaries disguise local dislocations and disruptions to the ways we live, work and recreate. Climate change adds a serious stress to our already threatened resources and treasured places. Overall impact statements also mask significant opportunities. To minimize the negative changes and make the most of the positive changes we need to take a close look at how climate change will affect each region. How will the Great Lakes region experience the effects of global warming? And how can we respond?

Summary
As the single largest source of surface fresh water in the world, the Great Lakes region supports a burgeoning economy in the US. While being the linchpin for drinking water, hydroelectric power, commercial shipping, and recreation, the region also houses an amazingly diverse array of plants and wildlife. With scenic lakeshores, unique wildlife, and diverse recreational opportunities drawing millions of tourists annually, problems such as urban sprawl, air and water pollution, and habitat fragmentation are already stressing ecosystems of the Great Lakes region. Global climate change looms as an additional threat on the region’s economy, population and wildlife by changing climate patterns and compounding the negative effects of current environmental problems.

Given the heavy pressure from development on the hundreds of miles of delicate lakeshore and ecosystems, the Great Lakes region is particularly susceptible to the effects of rapid global warming. According to the scenarios used in the National Assessment, scientists expect average temperatures in the Upper Great Lakes region to warm by 2 to 4°C, while precipitation could increase by 25 % by the end of the 21^st century. Despite this significant increase in precipitation, lake water levels are expected to fall by 1.5 to 8 feet by 2100 because of the higher temperatures, with serious implications for ecosystems and the economy. Although not necessarily due to global warming, the recent series of unusually warm years is already to blame for a drop of 3.5 feet in water levels for Lakes Huron, Michigan and Erie since 1997, and record low levels are expected later this summer. These lake-level declines from record high levels in the 1980s have caused concern among commercial shippers, hydroelectric companies, and recreational boaters.  Fewer cold air outbreaks and less lake-effect snow (especially around Lake Erie and Lake Ontario) may decrease annual snowfall significantly, a trend that has already been observed in the past few years. 
Although uncertainties remain, the research conducted through the National Assessment is an important first step in helping policymakers and residents understand the possible impacts of global warming on their region.  Identifying risks specific to the people and ecosystems of the Great Lakes will help them make better informed decisions about how to address the problem. 

Key Findings

Water Ecology
Aquatic ecosystems of the Great Lakes region support delicate, deeply interconnected webs of life which are highly adapted to the physical (and biochemical) characteristics and cycles of the lakes themselves. Climate computer models suggest that the waters of the Great Lakes will be warmer by the end of the 21^st century. In addition, models suggest that lengthening warm seasons will reduce the seasonal mixing that replenishes critical oxygen to biologically productive lake zones, possibly shrinking lake biomass productivity by around 20 %. This will include losses of zooplankton and phytoplankton that form the very base of aquatic food chains, and are critical to the survival of the many species of fish that live in the Great Lakes.

Changes in precipitation patterns may alter seasonal flow and volume patterns in streams and rivers feeding the Great Lakes. The National Assessment reiterates earlier findings that cold water stream habitats could be significantly altered by a warming climate, threatening cold-water species such as walleye and trout, and even some warm-water species such as smallmouth bass. Michigan, Wisconsin, Minnesota, New York and Pennsylvania may lose over half of their existing cold-water habitats, and those habitats may be wiped out completely in Ohio and Indiana as warmer temperature zones creep northward. 

Wetlands and Coastal Ecosystems
Climate change poses a significant threat to the remaining wetlands in the Great Lakes region, from the prairie potholes of Minnesota to the coastal marshes of northern Lake Huron. These delicate ecosystems are critical to declining migratory bird populations, providing food, breeding grounds, and resting stops along major migration routes. For example, Minnesota and Wisconsin may lose important duck habitat in prairie potholes. Already, the region has lost up to 60 % of its prairie pothole wetlands, and under dryer climate conditions, the size and number of those that remain could be further reduced. Additionally, at least 32 of the 36 species of fish in the Great Lakes are dependent on coastal wetlands for successful reproduction. Declines in water levels caused by climate change will reduce fishes’ access to the emergent vegetation of coastal marshes, which provide breeding habitat, shelter for young fish, and plenty of food in the form of vegetation and invertebrates. With only 50 % of original wetlands remaining in the Great Lakes region, and much of these areas already stressed by pollution and development, it is imperative that Great Lakes authorities take meaningful steps to preserve wetlands ecosystems under the compounding effects of climate change.

Forest Ecosystems and Bird Habitat
Forest ecosystems have contributed greatly to the prosperity and quality of life in the region as well as to cleaning its air and water, and the reduction of soil erosion. Their diversity has also provided important habitat to wildlife. If global warming occurs rather rapidly, both plants and animals are likely to face difficult challenges in adapting to changing conditions. Several species of trees may no longer be able to grow in the Great Lakes region as summers become too warm, including economically important species such as quaking aspen, yellow birch, jack pine, red pine and white pine. Both broadleaf and conifer forests are in danger of declining by as much as 50 to 70 % in the Upper Great Lakes region, although uncertainties in altered precipitation patterns make exact predictions impossible at this time. Other trees such as black walnut and black cherry may eventually migrate northward into the region. Although productivity may ultimately increase after an initial “dieback phenomenon,” current mixed forest communities could give way to grasslands, savanna, or hardwood forests consisting of more oak, elm, ash and pines. This will have serious implications for species dependent on very specific habitats, including the endangered Kirtland’s warbler, which breeds in the sandy jack pine barrens of Michigan.

Migratory birds are especially threatened by climate change in the Great Lakes. Michigan and Wisconsin – whose secluded woodlands provide preferred habitat for wood warblers – could each lose up to 32% of neotropical bird species. The assessment indicates that  67% of wood warbler species may be lost from Wisconsin, 61% from Michigan, and 52% from Minnesota, respectively. Changes in the distributions of upland game birds such as Northern pintails and mallards may also occur. 

Agriculture
Agriculture ranks among the most important economic activities in the Great Lakes region, accounting for more than $15 billion in annual cash receipts.  Livestock, including dairy, is the number one agricultural commodity group, comprising over half of the total.  Dairy production alone produces $5 billion in receipts.  Crop diversity is an important characteristic of agriculture in the region, at least in part reflecting the moderating influence of the Great Lakes on regional climate. Over 120 commodities are grown or raised in this region. 

The warmer and wetter climate across the region portrayed by the global climate models used in the assessment and the positive effects of CO2 enrichment suggest that future crop yields may be greater than historical yields.  Some crop yields may increase through 2050, but then decrease over time from 2051 to 2100, especially at western and southern locations. 

Quality of Life 
Heat waves in the Great Lakes region are still relatively rare but the climate models used in the assessment suggest significant increases in the number of days above 90° F.  Thus, a major quality of life issue in the region will be human health and well-being.  People who lack protection to high temperature extremes may suffer from heat stress, dehydration, respiratory distress, and occasionally heat stroke or cardiac malfunction. On the other hand, winters will be warmer, decreasing illness and mortality related to extreme cold.  Additionally, inter-annual variability may decrease – for example, cool summers may not occur as frequently as they do now.  Other impacts from short-term, extreme weather events such as floods, tornadoes, and blizzards may also increase in the region, particularly heavy precipitation events.

How can we prepare for the potential impacts of global warming?
 

The Great Lakes, especially their lake shores, are likely to bear a significant burden from the impacts of climate change. Climate scientists agree that further climate change is inevitable and will therefore require adaptation, although most scientists also think that the pace of climate change can be slowed by substantially reducing greenhouse gas emissions. This would give governments, businesses, and ecosystems around the world more time to respond and adapt to climate change as well as reduce the overall severity of climate change-related impacts, thereby buying "insurance" for an uncertain future.  Another way to buy insurance now is to incorporate climate change into all long-term decisions about natural resources, thereby providing greater resilience.

Water Resources and Ecology
The development of water conservation and regulation strategies robust enough for both high and low water levels would give Great Lakes water managers a more flexible, adaptive framework for decision-making. This would be aided by water management approaches that can deal with the lake level changes thought to be possible from climate change. 

If primary production in lakes declines as projected, stocking strategies may be required to rebuild stocks of native species that have survived in the lakes through centuries of post-glacial change. Appropriate public education programs to explain these changes could assist such efforts. 

Forests and Land Management
Possible adaptive strategies used within the forestry and land management communities include monitoring the health and productivity of forests as climate and other environmental parameters change; using land use planning and other tools (e.g., “sprawl” taxes) to minimize land use conflicts; facilitating the migrations of plant species as the most hospitable climate conditions shift north; and planting tree species that are better suited to a changed climate.  

Agriculture
Improvements in technology, the CO2 fertilization effect, and the use of adaptive farm management strategies can possibly mitigate some of the negative effects of climate change for the majority of farm operations in the Great Lakes region.  Additional adaptive farm strategies include: changes in crop selection to varieties currently used in more southern regions; changes in the timing of planting and harvesting; improved soil management to retain soil moisture and prevent soil erosion; and the development of new varieties of crops that are more adaptable to inter-annual variations of weather.

Quality of Life
Improved weather forecasting, information distribution, special assistance, and improving economic well-being will help at-risk populations to better cope with high temperature extremes.  Better insulation of homes against heat and cold, and other construction improvements, as well as preventing construction too close to lakeshores will help reduce some of the weather-related risks, especially those related to extreme heat, floods, and storms. Efforts to reduce air pollution at the source and timely health advisories for susceptible people, such as the elderly, will help reduce the impacts of air pollutants on health.   

Where do we go from here?

In order to improve regional climate change impact projections, further scientific progress is required. Several areas emerged over the course of the assessment efforts as particularly fruitful research areas for the Great Lakes region. For example, because managed land use accounts for as much as three-quarters of the land area of ecosystems such as grasslands in the Great Lakes, more information is needed on both the impacts that current land management has on the ability of vegetation communities to respond to global warming, and on how the dynamics of land use and management will interact with climate change.

Another area in need of better scientific understanding is public health: air pollution associated with respiratory disease has not been well studied in the Great Lakes region.  Air pollutants are but some of many factors involved in the etiology of respiratory diseases, and further study is needed to better understand the interactions with climate change.

Additional information

For more detailed information on the potential impacts of global warming on the Great Lakes region, several experts are available to answer your questions:

Dr. Peter Sousounis, University of Michigan
 Tel.: (734) 936-0488
Patty Glick, National Wildlife Federation
 Tel.: (202) 797-6898

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