All aquatic communities in the Chicago Wilderness region, including streams, rivers, inland lakes, ponds, and Lake Michigan, are likely to be impacted by the expected increase in water temperature and shift toward more extreme precipitation events. These impacts will manifest themselves in a variety of ways, with some affecting aquatic communities across the board and others tending to be more community-specific (Table 5). Just as the climate change impacts are expected to compound the existing threats to terrestrial communities, the same is likely to occur to the threats aquatic communities are facing, affecting both their water quality and quantity (Table 3).
Generally speaking, there are four main impacts likely to arise from increasing water temperature that probably will affect all aquatic communities in the Chicago Wilderness area. The first is that increasing water temperature may favor warmer-water fish and aquatic insect species over cooler-water species due to differences in competitive ability and/or thermal tolerance among natives. Increasing temperatures could affect changes in growth rates and associated development times, allowing some species to have multiple generations per year where they have only one under existing conditions. Secondly, warmer water temperatures may offer non-native species a better chance to establish themselves, increasing the stress on native plant and animal populations. Thirdly, increased water temperature could reduce availability of dissolved oxygen for organisms because warmer water holds less oxygen. Independently or collectively, these factors could lead to changes in our aquatic species assemblages, especially through the potential for a higher incidence of invasive species. The proportional composition of the assemblage could also change, whereby the same species are present but those with greater tolerances to warmer conditions become dominant. These would likely be species with more rapid growth and shorter life cycles (e.g., Chironomidae [midges], Culicidae [mosquitoes]). Lastly, warmer air and water temperatures increase the likelihood of changes in snow patterns (longer dry spells followed by large snow falls) reduced ice cover, earlier snowmelt and/or ice breakup, and earlier peaks in spring run-off, potentially shifting the timing and the volume of stream flows and influencing water levels. These conditions can also lead to pulses of cold or warm water that provide “thermal shocks” to fish in these streams. Hydrologic changes of this type play a role in determining species composition, especially among some groups of phytoplankton, such as diatoms (IPCC, 2002).
The projected increase in heavy precipitation events is also likely to affect aquatic communities as a whole. More extreme storm events may lead to more flooding and non-point source pollution due to greater runoff from urban/agricultural areas. Not only would this situation increase the number and the severity of summertime pollution episodes in our region, such as Combined Sewer Overflow (CSO’s), but it may cause extreme flow conditions that promote stream channel and lakeshore destabilization, leading to increased sedimentation and a loss of sensitive aquatic habitats (scouring). While invasive species, hydrologic change, and loss of native vegetation are common threats to both aquatic and terrestrial systems, aquatic communities are much more sensitive to sedimentation, toxic substances, and excess nutrients (Brönmark and Hansson, 2002).
Along with these broad impacts, it is likely that some climate change impacts may be community-specific. Below we outline three main aquatic community divisions in Chicago Wilderness and discuss the specific impacts they may be facing, as well as provide initial biodiversity adaptation strategies.
RIVERS AND STREAMS
Within Chicago Wilderness, streams and rivers are grouped into four size categories (headwater stream, low-order streams, mid-order streams, and large rivers) with additional subcategories defined by flow, gradient and substrate. Rivers are inherently dynamic systems that are constantly “adjusting” to changes in sediment and water inputs by migrating across the landscape and changing the depth, width, and sinuosity of their channels (Palmer, 2008). While these changes are part of a healthy river’s response to changes in the landscape and the climate regime, the rate at which water temperature and precipitation patterns are expected to change may be much faster than historical climate shifts, exceeding the ability of the biological communities in these streams and rivers to adapt (IPCC, 2007). The degree to which this aspect of climate change could impact rivers in Illinois, which are very dynamic systems accustomed to major and fast shifts due to flooding, will likely depend on the frequency of the flooding events and the human response to additional flooding. The latter issue highlights the need to anticipate ways to minimize the impacts of flooding on both humans and river systems, for example by restoring and reconnecting floodplains to rivers in order to reduce flood risk while increasing ecological services (Opperman et al., 2009).
(Maloney et al., 2008). However, differences in response times of macroinvertebrates and fish coupled with the temporal effect on several habitat variables highlight the need for longer-term studies. The expected changes to the timing, frequency, and duration of precipitation events, along with warm water temperature, will likely amplify the current threats to rivers and streams. As with terrestrial systems, climate change is likely to affect rivers and stream at the level of species as well as ecosystem function.
At the species level, environmental changes that affect attributes of streams and rivers closely associated with life history traits, such as flow regime, may lead to shifts in the abundance and/or distribution of species. For example, a rapidly altered river flow regime may render species unable to find suitable flow environments for feeding, reproducing, or surviving major flood events. Higher flows, due to more extreme storm events, may also result in a higher amount of suspended sediment and bedload transport and interfere with species’ ability to feed (Palmer et al., 2008). Another issue of great concern is the potential for sediment deposition to fill in interstitial spaces close to rivers. This could greatly reduce the availability of hyporheic habitat, or the narrow margins of land adjacent to river channels inhabited by riverine invertebrates (Palmer et al., 2008). Not only could this result in loss of habitat for insects and spawning areas for lithophilic fish, (i.e., fish species that lay their eggs on rocks; Pizzuto et al., 2008), but it may prove problematic for overall river ecology because the hyporheic zone provides a great deal of nutrient discharge crucial to biotic productivity in the river channel (Stanford and Ward, 1988). Whether deposition or net export of these sediments occurs will depend on the peak flows and size of the sediment moving into channels (Palmer et al., 2008). Export will occur when the amount of energy associated with the flowing water is large enough to move the particle (regardless of the size), whereas deposition occurs when there is not sufficient energy to move the particle. The characteristics of the existing discharge (flow), existing sediment load, and any new sediments moving into the channel associated with runoff (flow enhancement) will determine which of these process will occur at a specific time. Net deposition or export of sediment will depend on the relationship between the overall flow regime and sediment size distribution that makes up the stream channel and inputs from the adjoining landscape.
It is important to monitor sediment deposition and flow regime because particle size and hydraulic forces are both known to be major determinants of stream biodiversity (both in density and composition of algae, invertebrates, and fish). Failure to monitor and respond to these issues may result in excessive bottom erosion, which can decrease species diversity and lead to dominance by a few taxa (see Plants page, section 4.8) (Palmer, 2008; Allan, 2007). The key point here is that the monitoring program must be integrated into the management program so that monitoring results will be used to guide management (i.e., adaptive management).
Rivers and streams provide a variety of essential ecological processes, such as ensuring clean water for drinking and supporting wildlife, that will be influenced by warmer air and water temperatures and altered flow regimes. A major concern is that hotter summers with more extreme high temperature events and greater evaporation may disconnect flowing waters from their floodplains (Palmer, 2008), which could negatively affect the ability of species to disperse, as well as the energy flow and/or nutrient cycling of ecosystems. On the other hand, because primary production in streams is very sensitive to temperature and flow levels (Lowe and Pan, 1996; Hill, 1996), climate change could lead to an increase in food availability to herbivorous biota that may in turn support higher abundances, but also shift species composition. This shift in species composition of primary producers, associated with high levels of competition for nutrients, can also lead to a decrease in food supply as many nutrient fixing algae (especially blue green algae) are relatively unpalatable to herbivorous insects and fish. If this occurs stream assemblages may have less energy available for higher trophic levels, leading to trophic cascades or shifts in species dominance.
A great deal of uncertainty exists, however, about how ecological processes such as rates of nutrient processing will be influenced by climate change (see Palmer et al., 2008 for discussion) and few studies have been conducted to simultaneously examine the many interacting factors that are both subject to change in the future and known to influence ecological processes (Palmer et al., 2008). Another layer of complexity to consider is that within the Chicago Wilderness region few streams retain their original hydrologic regime, and much of the flow is effluent from human sources with flooding events dominated by Combined Sewer Overflows, suggesting the timing of flooding events is already atypical. Additionally, most streams in this area have been previously decoupled from their adjoining terrestrial habitats due to channelization or dredging. These aspects combined with the issue that effluents from sources such as power plants have already introduced unnatural temperature regimes to the system, makes it difficult to determine whether climate change effects will dwarf the existing changes, or be dwarfed by them.
Climate change can interact with existing threats in two main ways. First, it can exacerbate the impacts of current threats. For example, milder winters will create conditions that will be favorable to aquatic invasive species, increasing the magnitude of this stressor on aquatic systems (see Plants page, section 4.3). Additionally, choices made regarding how and where areas are developed and natural resources are utilized can in turn intensify the negative effects of climate change. Research has suggested that the land use change, particularly the clearing of native vegetation for urban and suburban developments, and excessive extractions of river water or groundwater that feed into streams and rivers will likely intensify the negative effects of climate change for rivers and streams (Allan, 2004; Nelson and Palmer, 2007). With the Greater Chicago region projected to experience a 25 percent increase in population growth and possibly a 55 percent increase in developed land by 2020 (SNAP, 1999), thereby increasing the stressors that amplify climate change impacts, it underscores the importance of integrating climate change adaptation strategies into current Chicago Wilderness river and stream management plans by developing a watershed plan that relies on green infrastructure.
Below are some initial strategies for biodiversity adaptation in streams and rivers under conditions of climate change drawn from the U.S. Climate Change Science Program (Palmer et al., 2008) and the Massachusetts Climate Change Adaptation Strategies Summary (2009):
Possible Biodiversity Adaptation Strategies for Rivers and Streams
Adapted from Glick et al. 2009*
- Increase monitoring capabilities in order to acquire adequate baseline information on water flows, water quality, and temperature, thus enabling river managers to prioritize actions and evaluate effectiveness;
- Strengthen collaborative relationships among federal, state, and local resource agencies and stakeholders to facilitate the implementation of adaptive river management strategies;
- Forge partnerships and develop mechanisms to ensure environmental flows (i.e., the amount of water needed in a watercourse to maintain healthy ecosystems) for rivers and streams in basins that experience water stress;
- Work with land use planners to minimize additional development on parcels of land adjacent to rivers and streams. Optimally, try to acquire floodplains and nearby lands that are not currently publicly owned or ensure they are placed in protected status. Recharge areas need to be included in these types of planning activities to provide baseflow to streams beyond that from effluent discharges;
- Remove in-stream barriers (dams and undersized culverts) and re-establish in-stream flows to restore aquatic habitats. This strategy should be well researched and designed to minimize the potential for the spread of invasives and disease vectors. Locations should be carefully and strategically selected to reflect areas that would benefit the most under both current as well as future conditions;
- Protect and conserve land including remaining critical cooler-water fish habitat areas, reconnect high quality habitats, protect belt-width-based river corridors (i.e., corridors defined by the lateral extent of the river meanders), and restore floodplains;
- Work with stakeholders to develop water conservation strategies to maintain stream flow because reductions to the base flow of a river may result in the river not being able to support the current native communities;
- Develop a list of possible new invasive species – what is out there and what are their chances of survival as the conditions change;
- Work with the agricultural community to discuss alternatives to the current ways that they use water for their crops and whether more efficient water systems exist, and reducing pesticides/insecticides and nutrients into the waterways;
- Get a better handle on human water consumption - increase water use efficiency and conservation*;
- Encourage greater use of seasonal and long-term projections for streamflows in water management decisions to more proactively protect and restore flows for fish habitat*;
- Promote biological diversity by managing for invasives and maintaining in-stream habitat diversity*;
- Restore riparian vegetation. Designing riparian restoration projects to endure stream flows of increased magnitude and variability will enhance long-term restoration success and improve the quality of the aquatic ecosystem*;
- Maintain natural flood regimes in places where they are still intact;
- Incorporate forward looking assessments and longer time horizons in water resource planning (e.g., CMAP's Water 2050 became a U.S. Environmental Protection Agency WaterSense Promotional Partner to promote water efficient fixtures such as high efficiency toilets and showerheads, also use of rain barrels for watering plants, grey water for flushing local ordinances for best management practices for lawn care);
- Discourage new development in floodplains*;
- Consider future climate changes when designing and building infrastructure (water control structures, drains, pumps, etc.);
- Guide growth and incentivize Smart Growth or low impact developments outside of floodplains;
- Improve storm water management;
- Select for more water efficient crops (e.g., peas, wheat etc. https://www.certifiedcropadviser.org/files/certifications/certified/education/self-study/exam-pdfs/184.pdf)
- Buffers should be encouraged along rivers and conservation easements can encourage them;
- Partner with NRCS to help promote the Best Management Practices for agriculture appropriate for the region and water supply, including less use of nutrients and pesticides;
LAKES AND PONDSBurkholder, 2001; Lévêque, 2001). The habitats that remain today have suffered loss of species diversity and ecological structure through introduced eutrophication, coupled with toxic pollution and the introduction of aggressive non-native species. Currently, the most severe threats to lakes are invasive species, nutrient loading, sedimentation, loss of native submerged and emergent vegetation, and management actions focused on only a narrow range of species (such as game fish).
Lakes and ponds are habitats of great human importance as they provide water for domestic, industrial and agricultural use, habitat to support an array of biodiversity, and food. In our region, glacial lakes are the most biologically diverse of the lake types. Species level biodiversity in freshwater lakes and ponds, as with other freshwater systems, is influenced by a number of factors, both abiotic (e.g., climatic factors, water chemistry, habitat heterogeneity, habitat size and isolation) and biotic (e.g., predation and competition) that operate at different spatial and temporal scales. Predation and competition are especially critical in determining species diversity and, perhaps more importantly, species composition, and thereby the function and dynamics of the whole system (Brönmark and Hansson, 2002). It’s possible that environmental disturbances due to climate change may result in reduced biodiversity due to either direct lethal effects on organisms or due to more complex interactions between different factors (Brönmark and Hansson, 2002).
There are several climate change impacts that may affect lakes and ponds in particular. For example, a drier environment may reduce the extent and duration of vernal ponds, which are essential to the survival and reproduction of many amphibian species. Additionally, warmer water temperatures may exacerbate the current problem of nutrient pollution and algae growth. The 2002 Intergovernmental Panel on Climate Change report on climate change and biodiversity cautions that increasing temperatures in deeper lakes could promote a longer stratified period that results in more areas low in dissolved oxygen. Reducing oxygen concentration, especially if exacerbated by eutrophication related to land-use practices, could lead to altered community structure in the form of fewer species. In more shallow water layers, higher temperatures could reduce the nutritional quality of edible phytoplankton, or possibly shift the composition of the phytoplankton community away from more nutritious species toward less nutritious species such as cyanobacteria and green algae (IPCC, 2002). Another impact from increased water temperatures may be higher microbial respiration rates, which could increase organic-matter decomposition rates and shorten the duration that detritus is available to invertebrates (IPCC, 2002). Finally, as water levels decline due to increasing rates of evaporation and greater pressure on water resources for human use, lakes may become disconnected from their bordering wetlands and negatively impact those species that rely on the interstitial areas for spawning (e.g., trout, salmon).
The State of our Chicago Wilderness Report Card points out that our lakes, like our rivers and streams, suffer from the effects of intense urbanization. Although some isolated glacial kettle lakes are in excellent condition, the majority of our region’s lakes remain in fair to poor condition. To minimize the extent of additional stress from climate change on our already vulnerable lake and pond communities, it will be imperative to integrate adaptive management strategies into our best management practices.
Possible Biodiversity Adaptation Strategies for Lakes and Ponds
- Since many of our lakes (and some ponds) are under multiple bottom ownership—meaning that the land beneath the waters is apportioned among various shoreline owners—it is imperative that partnerships and education are included in any long-term strategies, particularly with landowners;
- Develop education outreach for local entities and lake users, particularly for boat users because accidental transport by boats is one of the primary means for the introduction of invasive aquatic weeds and animals such as zebra mussels;
- Develop education for aquatic gardeners; many aquatic garden plants are semi-tropical, but may be able to survive or become invasive under conditions caused by climate change;
- Monitoring, particularly phytoplankton assemblies and invasive species, but also water quality. More intense storm events may lead to higher sedimentation rates, which will accelerate the eutrophication process. Monitoring of native fish and aquatic plant populations will be important as well, since many of these species are at their southern range here in the Chicago Wilderness;
- Guide growth and incentivize Smart Growth/low impact development to reduce nonpoint source pollution;
- Encourage water conservation; and
- Use native planting near/around lakes and ponds to help with runoff from communities.
Much of the shoreline in the Chicago Wilderness area has been filled for buildings, parks, and marinas, eliminating coastal wetlands. The wetlands that do remain, however, are some of the highest quality in the state of Illinois. Additional current threats to Lake Michigan include loss of coastal habitat connected to the lake along the lakeshore, habitat degradation along the lakeshore, reduced water quality due to invasive diseases for fish (e.g., viral hemorrhagic septicemia in fish) and toxins (e.g., Polychlorinated biphenyls, or PCBs, and mercury in fish), excessive fish harvesting, and changes in the food web (e.g., decreased populations of the shrimp-like amphipod Diporeia, an important food source for lake fish, may be related to the introduction of zebra mussels; invasives such as lamprey and the introduction of salmon, alewives, gobies, common carp, etc.). Futhermore, both quagga and zebra mussels are invasive species that are filter feeders, and they clarify the water and allow sunlight to penetrate deeper into the lake. Their fecal matter is nutrient rich and acts as a fertilizer, whereby increasing the growth of Cladophora algae and possibly playing a role in triggering the growth of Botulism.
As is the case with terrestrial and other aquatic systems, climate change is expected to exacerbate the current threats Lake Michigan faces, and affect the near shore waters and lakeshore in the Chicago Wilderness region. Great Lakes water usage is based on a legal compact between states, and the Supreme Court decree that governs Illinois’ withdrawals, which sets the framework and process for competition for water resources likely to increase over the next several decades due to population growth and lack of water conservation measures. Climate change may intensify this competition due to reduced winter ice cover and higher evaporation rates contributing to lower lake levels and increased ground water draw down, affecting both human resource needs and natural community ecology. For example, if H2O levels were reduced this could shift the location of near shore habitats and expose toxic sediments. Exposing certain toxins such as PCBs can cause them to become even more volatile. Reduced lake levels may additionally expose more nearshore areas to invasion by Phragmites, which can be especially threatening to the sand dunes and their unique species assemblage, or reed canary grass. While new habitats can emerge as a result of lower lake levels, often the native plants will not be able to establish themselves fast enough due to current problems with aggressive invasives along the shore.
Increasing water temperatures may impact Lake Michigan in several ways (see Plants page 4.1: Changes in frost dates; 4.2: Change in freeze-thaw cycles affect; 4.3: Milder winters). In particular, warmer water may favor invasive species like toxic Cyanobacteria algae, which can grow and bloom at faster rates in warmer water. Changes in water temperature can impact food webs, for example if the food web shifts in the phenology of important events in their life cycle, and these phenological shifts become out of phase (e.g., phytoplankton blooming, then zooplankton emergence from dormant forms…). Another major issue that warmer water temperatures could pose is the potential to exacerbate existing nutrient pollution and algae growth in freshwater lakes. Furthermore, coupling lower water levels with warmer water temperatures may accelerate the accumulation of mercury in the aquatic food chain, as it is more likely to convert into a more bio-available form. This is due to the fact that production of methyl mercury (the bio-available form) is strongly associated with factors that favor mercury methylating microbial communities, such as warmer sediment temperature and anoxic conditions (Foster et al. 2000). This effect would not be limited to Lake Michigan and would impact smaller lake and river systems as well. However, the scale of this issue would be greatest possibly in Lake Michigan.
A final point is that there is evidence from the upper Great Lakes region indicating surface water temperature may be increasing even faster than air temperatures. This situation is thought to be triggering a range of system-wide impacts such as higher wind and current speeds and longer periods of lake stratification in this region (Austin and Coleman, 2007, 2008; Desai et al., 2009; Dobiesz and Lester, 2009), and could potentially have far reaching effects to our region.
Possible Biodiversity Adaptation Strategies for Lakes Michigan
- Reduce water removal from Great Lakes;
- Reduce ground water removal and promote water conservation and efficiency;
- Reduce nutrient inflow into Lake Michigan;
- Utilize green infrastructure (wetlands, floodplains, bioswales, green roofs etc.) to capture water as it falls, which recharges groundwater for habitat and temperature modification, as well as prevents flash events that pour contaminants into the lake; and
- Develop restoration, and monitoring, standards that result and measure more resilient coastal habitats. For example we know that due to changes in lake levels, coastal restoration projects should be designed to include plants that do well under various lake level conditions.
Overall, the climate change impacts expected to exacerbate the greatest number of existing aquatic threats are 1) Increased storm intensity and/or frequency which may increase non-point source pollution of aquatic systems and wetlands and 2) Increased temperatures that may lead to drying wetlands and ephemeral streams, further isolating and fragmenting the remaining communities (Table 5). Both of these impacts are expected to amplify changes in hydrology. Additionally, increased storm intensity and frequency will likely increase flooding, and consequently erosion and sedimentation, while the drying of wetlands and ephemeral streams is expected amplify fragmentation and loss of structural diversity. By altering the timing, intensity, and duration of high and low flows in streams the conditions under which native biodiversity evolved will be changed, causing an additional stress on these communities irrespective of any changes in non-point source pollution or water temperature. Furthermore, of the existing threats to aquatic communities, hydrologic change is affected by the greatest number of climate change impacts (7 out of 12; Table 5), further compounding one of the most severe threats to aquatic communities in our region.
It is clear that climate adaptation for stormwater management will need to play a large role in securing the future health and continued functioning of our natural aquatic communities, just as it will be key in protecting our human health. According to the US EPA (2008), The Great Lakes Region’s 182 combined sewer systems, serving more than 40 million people, will see an average of 237 rainfall events per year that are too heavy for them to handle by mid-late century (2060–2099) if climate trends continue. To address this, and other climate change related issues, the Chicago Biodiversity and Stormwater expert workshop was convened in July 2009 in Chicago, IL. The workshop focused on climate adaptation planning and strategy development for biodiversity and stormwater management in the Chicago Wilderness region. Key findings from the workshop highlighted the need to modify our existing stormwater infrastructure, including the incorporation of natural communities, to help mitigate the expected increase in extreme storm events. One of the main themes that emerged was that we should be viewing stormwater as a useful resource, seeking as much water conservation and infiltration as possible, so that groundwater can be recharged, combined sewage overflows mitigated, and ecosystems maintained. A way to achieve to this goal, and many other terrestrial and aquatic climate change adaptation management strategies, is through Green Infrastructure, which will be discussed in the next section. Below we present research questions and initiatives for aquatic communities in general that will help us move forward and contribute to climate change adaptation management.
Research Questions/Initiatives for Aquatic Communities
- Which species, both native and introduced, are most affected by expected changes in water temperature both positively and negatively?
- Model combined sewage overflows in response to a range of extreme precipitation events.
- Understand ecological effects of altered flow regime, so we can figure out what are the crucial factors to attempt to influence.
- How will different temperature regimes affect nutrient cycling?
- The current water budget was developed for monitoring diversion limits. What is the water budget we need for sustaining biodiversity? How can environmental flows be incorporated into existing and future water budgeting efforts?
- What are the aquatic food web needs for spawning in the near shore, shore, wetlands, rivers, streams, reservoirs and reef lakes? How can they be protected?
- In Toronto, they have begun building artificial spawning structures into piers and other structures. Is this working? Is it worth the expense?